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F
of the
FLORIDA STATE MUSEUM
Biological Sciences
Volume 19
1975
Number 5
ECOLOGICAL ANALYSIS OF THE CAYMAN ISLAND AVIFAUNA
cv "
DAVID W. JOHNSTON
UNIVERSITY OF FLORIDA
GAINESVILLE
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ECOLOGICAL ANALYSIS OF THE
CAYMAN ISLAND AVIFAUNA
DAVID W. JOHNSTON1
SYNOPSIS: Ecological studies of the avifauna carried out over the past eight years
in the three Cayman Islands of the Caribbean Sea revealed the presence of 151
species, mostly transients. Grand Cayman has 39 species of breeding birds (26
terrestrial), Little Cayman 29 (17 terrestrial), and Cayman Brac 30 (20 terrestrial).
Each island also supports an additional 40 North American migrants in winter.
Seasonal occurrences and relative abundances of birds are described, particularly for
seven upland ecological formations in which the greatest breeding species diversities
k-- occur in logwood-thatch palm-red birch and limestone forests. In one sere, from
pastureland through limestone forest, bird species diversity and total abundance in-
crease with age of the community. High species diversity and density in the lime-
stone forest are associated with some semblance of stratification but more so with a
greater number of feeding niches. For the most part, the land birds breed in May
r- and June at the onset of a rainy season.
In the past 30-40 years, two bird species have become extinct on Grand Cayman,
whereas two others have at least attempted colonization. The problems of inter-
island distributional patterns are discussed in an attempt to explain the presence and
absence of different species on different islands. No evidence was found to support
the idea that the absence of one species on an island permitted another one on that
same island to broaden its ecological niche; rather, the absence of woodpeckers, a
tanager, flycatcher, dove, finch, and others on the two small islands strongly sug-
gests vacant niches on those islands.
Competition for environmental resources among the resident terrestrial birds was
analyzed, especially between congeners and between species of similar ecologies.
The four (or five) sympatric dove and pigeon species are separated chiefly by
habitat and food differences; the two woodpeckers by food; four flycatchers by com-
binations of bill size, habitat, feeding height, and food type; the vireos by body
size and bill size; and two Dendroica warblers by habitat and feeding height.
With the exception of the scarce Barn Owl, no significant vertebrate predators
on birds occur on these islands. The largely ornithophagous owl probably repre-
sents the greatest single biological control of the avifauna.
C
1 The author is a Professor of Zoology, University of Florida, Gainesville, Florida
32611. Manuscript accepted 26 April 1974.
JOHNSTON, DAVID W. 1975. Ecological Analysis of the Cayman Island Avifauna.
Bull. Florida State Mus., Biol. Sci., Vol. 19, No. 5, pp. 235-300.
236 BULLETIN FLORIDA STATE MUSEUM Vol. 19, No. 5
S., 0 ..
Feeding ecologies, habitat distribution, and taxon cycles are specified, where
known, for all the resident terrestrial species. Taxon cycles appear to be similar to
those of other insular avifaunas, despite the absence of montane refugia on the Cay-
mans. Species in Stage I (evidently the recent colonizers) are more common in
early seral stages ("marginal habitats"), whereas the endemic subspecies (Stage IV)
are more abundant in the mature forests. Because of the relatively large number
of available habitats, Grand Cayman has 3.8 habitats per species, an exceptionally
high figure when compared with mainland and other insular populations. This value
plus other data indicate a remarkable generalization for the Cayman Island birds.
The large number of wintering species appears to influence the residents very
little because the wintering forms usually occupy feeding niches different from the
residents. It is suggested that the winter is characterized by an abundant food
supply (chiefly insects) that is incompletely exploited by the resident avifauna.
TABLE 01 CONTENTS
INTRODUCTION 236
ACKNOWLEID)IENTS .. 237
GENERAL DES(I OPTION OF THE ILANI)S AND THEIR A\vI.-NA . 238
ECOLOGICAL FORMATIONS .. 243
AVIF NAI. DISTRIlBITION IN TIE ECOLOGIK AL FORMiATIONS 253
PoP Il. VIoN DENSITIES ON C \Y\1\N BRA 259
BIRD POPU.ATIONS \N]) UI, \NI) SE(xCNI)D PL \NT SUcC(:ESSION. 261
BLEEDING SEASONS .... 265
INTER-ISIL AN DISTBit TIONALI, PATTERNS 268
IMMhall.I lIION S\NO EXTaIN( LION 272
COMPETITION FO()I ENVIRONMENTAL RESOt Il CES AMONI THE RESIDENT
TErHIESTRI \x, AV I -\ N \ 275
PREDATION \NI) POPI L \TION CONTROL 281
A GENERiL ASSESSMENT OF FEEDING Ec(OLOG(IES ANI) H \liITI
DISTRIBnUTIONS 283
T \xoN CYCLES. 283
HABITAT DISTBIBUTIONS OF INSL LAR \ND MAINLAND) BIRD POPULATIONS 288
THE WINTER ATANA .A.. . 291
LITERATURE CITED ... ..293
APPENDIX I: S('IENTIFI( AN) CON\ON NAMES OF BIRDS APPEARIN(.
IN TEXT 296
APPENDIX II: SCIENTIFIC I\N COMMON NAMES OF PLANTS AI'PEAIN(,
IN TEXT 298
APPENIX III: STORM (II CONTENTS OF C \YlM N ISLAN BIRDS 299
INTRODUCTION
Despite the recent burgeoning of interest in island biogeography, few
complete ecological investigations have been conducted on insular forms
of virtually any taxon level. Theoretical treatments of insular population
biology (e.g., MacArthur and Wilson 1967) necessarily relied heavily
upon many literature sources in the construction of species-area curves,
extinction-immigration curves, and other ecological models. This is not
meant to imply that such derived models are necessarily incorrect or in-
adequate, but simply to underscore the need for more raw data on island
JOHNSTON: CAYMAN ISLAND AVIFAUNA
populations so that ecological models and generalizations might be more
rigorously tested, amended, or even rejected. Since complete data for
avian insular populations are particularly sparse, scattered in the litera-
ture, and often incomplete, the ecological model-builder or synthesizer
must consult a multitude of scientific papers by different authors, each
using different techniques and reporting usually single ecological param-
eters from widely different islands. For the entire complex of West
Indian Islands, not one island has yet been subjected to a thorough, com-
prehensive investigation of its avifauna, despite the distributional survey
by Bond (1971) and the general assessments of taxon cycles by Ricklefs
and Cox (1972).
Accordingly, this report is an assemblage of published data, several
years of personal field experience and collecting, and a thorough analysis
of as many ecological parameters as possible for a single insular avifauna,
namely that of the three small isolated Cayman Islands. Attention is
focused on "standard" ecological parameters such as population densities,
competitive interactions, food and feeding behavior, reproductive cycles,
predation and other population controls, habitat and stratal distribution,
and secondary succession. Even this comprehensive report, which cor-
roborates and augments ideas from other insular studies, is admittedly
incomplete in one important aspect-the impact on resident bird popula-
tions by a large contingent of North American birds that overwinter in
these islands.
ACKNOWLEDGMENTS
Through the years a number of organizations have provided financial support for
these investigations. They include a Biomedical Institutional Support Grant from the
Division of Sponsored Research of the University of Florida, the Bradley Fisk Fund,
the American Philosophical Society (Johnson Fund, Penrose Fund), and National
Science Foundation (GB-2114). Partial subsidy for publication came from the
Bradley Fisk Fund and the Division of Biological Sciences, University of Florida.
Assistance in field observations and collections came from Jon C. Barlow, Charles
H. Blake, Donald W. Buden, Alexander Cruz, Erma J. Fisk, and Albert Schwartz.
David May made the insect identifications and Albert Laessle most of the fruit and
seed identifications. Walter Auffenberg, Pierce Brodkorb, and Ronald Pine kindly
assisted in the identification of vertebrate prey items. I am particularly indebted to
Alexander Cruz, Daniel Simberloff, Carmine Lanciani, and Robert Ricklefs for spirited
and helpful discussions that shed much insight on ecological problems concerning
insular avifaunas. C. D. Hutchings, Chief Agricultural officer, and R. F. Pocock,
Chief of Police of the Cayman Islands, were both cooperative in many ways espe-
cially in the collecting of birds. Finally, of inestimable value has been the lifelong
field experiences of the islands' principal naturalist, Ira Thompson.
BULLETIN FLORIDA STATE MUSEUM
GENERAL DESCRIPTION OF THE ISLANDS AND THEIR AVIFAUNA
The three Cayman Islands (Grand Cayman, Little Cayman, Cayman
Brac) lie in the northwestern Caribbean Sea where, as a group, their
remote position is rather extreme among the many West Indian islands.
Grand Cayman (1920'N,8120'W) is approximately 290 km (180 mi.)
south of Cuba, about the same distance northwest of Jamaica, and 480
km northeast of Honduras, the nearest point in Central America. Cay-
man Brac (19043'N,79050'W) is 89 km east of Grand Cayman and 8 km
east of Little Cayman. These three limestone islands are of similar
geological structure and represent the projecting peaks of the ancient
submarine Cayman Ridge extending from near British Honduras to Cuba
(Richards 1955). Steep-sided submarine slopes occur around the islands,
with a 100-fathom line lying only a few hundred meters offshore. Bart-
lett Deep, a 6,200 m trench, is found just south of Grand Cayman.
Further indications of the isolation of these islands are the many well-
marked animal species and subspecies that have been described from
them, including birds (Johnston et al. 1971), insects (Clench, H. 1964),
mollusks (Clench, W. 1964), and reptiles (Grant 1940).
These islands are typically low and flat. Much of Grand Cayman
(185 km2) is less than five meters in elevation, although an east-west
forested ridge on its north side reaches 20 m in places. Low-lying la-
goons and inland swamps abound (Fig. 1). Chiefly because of a beauti-
ful beach of coral sand on its western side, most of the human popula-
81I20 81"10
WEST BAY NOR
19'20 R an
RR
GEORGETOWNlt EAST END
Va LIMESTONE FOREST SCALE
EE3 MANGROVE FOREST ,
SPOND 3KM
FIGURE 1.-Map of Grand Cayman showing general distribution of major forest types
and ponds. P= pasturelands/clearings; R= residential areas.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
tions are currently on that portion of the island, namely at Georgetown
or West Bay or between the two. (In the early 1970s, however, an
extensive construction "program" was rapidly expanding eastward and
progressively engulfing formerly untouched natural communities.) Ex-
cept along the western "seven-mile beach" a typical coral reef fringes
the island. A honey-combed bluff limestone formation, often with an
intermittent ridge and swale effect, characterizes the central, eastern,
and southern parts of the island, whereas "ironshore" formation is espe-
cially prominent adjacent to the shoreline (Doran 1954). Pockets and
crevices in the underlying rock frequently include a reddish soil formed
by erosion of the original limestone.
Topographically and geologically, Little Cayman (24 km2) resembles
Grand Cayman (cf. Fig. 1 and Fig. 2), except that relatively few places
on the smaller island are over 4 m in elevation and the highest point is
only 14 m. The few human inhabitants, largely clustered at the south-
west end, have disturbed Little Cayman very little. A recently con-
structed road nearly encircling the island's shoreline forebodes "develop-
ment."
Cayman Brac (31 km2) differs physiographically much from the
other two islands, chiefly by the presence of an ascending (west to east)
plateau with bluffs that reach 43 m at the island's eastern end. Abutting
both the north and south sides are bluffs (Figs. 3 and 4). Closely asso-
ciated with the existence of the high bluffs is a marked reduction in la-
goons and mangrove swamp forests on Cayman Brac. The human popu-
1943'
1940O
M2 LIMESTONE FOREST SCALE
El MANGROVE FOREST
POND IKM
80005' 8000'
FIGURE 2.-Map of Little Cayman. Legend as in Figure 1.
BULLETIN FLORIDA STATE MUSEUM
S LIMESTONE FOREST
EI MANGROVE FOREST SCALE
- POND I KM
rr7 BLUFF
19o45
19*41
79*50',
FIGURE 3.-Map of Cayman Brac. Legend as in Figure 1.
FIGURE 4.-Precipitous bluff on east end of Cayman Brac; sole breeding sites of Sula
leucogaster and Phaethon lepturus in the Cayman Islands.
lation of a few hundred persons is now chiefly restricted to the north
coast and western tip, although coconut plantations were once common
on both coasts. Largely because of their relative inaccessibility, the bluff
or limestone forests in the central highlands of the island have been little
disturbed, except for scattered, small cultivations of vegetable crops.
79045'
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
The climate of the Cayman Islands is characterized by mild to hot
temperatures and a distinct dry season. A weather station maintained
at Owen Roberts airfield on Grand Cayman provided the temperature
and rainfall data in Table 1. From the data supplied by the weather
station personnel, the mean annual high temperature was calculated to
be 30C. Seasonal fluctuations in temperature are not extreme. On the
other hand, both rainfall (annual mean of 154.9 cm) and prevailing
winds do change seasonally. From May to October the prevailing winds
are easterly, but through the winter months they tend to be from
the northeast or northwest. A dry season extends from November
through April, and periods of drought are frequent at other times. De-
spite an annual wet season during the summer and autumn months, the
islands' low relief, desiccating winds, shallow soils, and porosity of the
limestone formation preclude the humid, tropical, luxuriant vegetation
characteristic of many West Indian islands. In fact, much of the natural
upland vegetation (see later discussion), including the introduced
species, takes the form of low xerophytic scrub, many of the plants pos-
sessing sharp spines and small leaves. Occasional autumnal hurricanes
buffet the islands, and their effects may be quite severe, as was the hurri-
cane of October 1944.
TABLE 1.-TEMPERATURE AND RAINFALL MEASUREMENTS AT OWEN ROBERTS AIR-
FIELD, GRAND CAYMAN, 1957-1970.
Mean temperatures (C) Mean rainfall (cm)
maximum minimum
mean extreme mean extreme
January 28 32 21 13 4.39
February 28 31 21 11 3.30
March 29 32 21 13 1.57
April 30 32 21 15 4.52
May 30 33 22 14 19.25
June 31 34 24 21 23.93
July 32 33 24 21 15.06
August 32 33 23 22 15.82
September 31 33 23 20 21.16
October 30 32 23 21 27.25
November 29 31 22 15 12.70
December 28 30 22 14 7.11
Through 1971, 151 species of birds had been recorded from the Cay-
S mans (Johnston et al. 1971). Most of these are North American migrants
either in-transit or overwintering in the islands. A breakdown of the
avifauna is as follows:
BULLETIN FLORIDA STATE MUSEUM
Grand Cayman Little Cayman Cayman Brac
185 km2 24 km2 31 km2
known or suspected
breeding species:
a. aquatic 13 12 10
b. terrestrial 26 17 20
total 39 29 30
These data fall within the expected ranges on a species-area curve deter-
mined by Ricklefs and Cox (1972) for small West Indian islands.
Species numbers (12-47) for the small (18-658 km2) satellite islands off
Hispaniola also generally conform to this species-area curve (Schwartz
1969).
Bond (1934: 345) believed that "Grand Cayman has received most of
its bird life from Jamaica and Cuba, whereas Little Cayman and Cayman
Brac have derived theirs from Cuba alone . ." Certainly the breeding
terrestrial avifauna of Grand Cayman has many species in common with
Cuba or Jamaica. But of the two smaller islands only one species
(Mimocichla rubripes), which is restricted to Cayman Brac, has affinities
with Cuban birds, whereas the remaining 18 species on the smaller
islands have affinities with forms occurring in both Cuba and Jamaica.
Furthermore, the Grand Cayman avifauna includes more species related
to the Cuban avifauna than do the smaller islands.
The extent to which the origins of all the Cayman Island avifauna
can be assessed accurately will always be speculative, partly because
such an evaluation would depend upon the taxonomic level under con-
sideration. For example, most biogeographers consider the family Paru-
lidae to be of North American origin (Mengel 1964), but Dendroica
petechia eoa, the Cayman Island form, also occurs on Jamaica. So, did
this Yellow Warbler reach the Caymans from North America (perhaps
via Cuba) and then spread to Jamaica, or follow the opposite route, or
neither one? We really do not know the answer to this and related
questions. It is nevertheless possible to assess affinities of avifaunas in
a general way, as Bond (1934, 1966a) has attempted, and one would
have to agree with Bond that by and large the Cayman Island avifauna
probably originated chiefly from Central American elements. In this
group, I would include the Columbidae, Cuculidae, Vireonidae, Coere-
bidae, Icteridae, and some Fringillidae. On the other hand, the closest
relatives to the Caymanian Amazona, Mimocichla, Colaptes, Centurus,
and Melopyrrha are presently Cuban. Contributions from Jamaica de-
pend partly upon one's viewpoint but quite likely these include Chor-
deiles minor, most or all of the four species of Tyrannidae, Dendroica
petechia, and perhaps Spindalis and Quiscalus.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
My own field work and collections on these islands were initiated in
1965 and have continued intermittently for eight years, covering all sea-
sons and all three islands, although most of the data were taken on Grand
Cayman. Additional valuable field notes, specimens, bird stomachs, and
other experiences on the islands in the past decade have been kindly
shared with me by Albert Schwartz, Erma J. Fisk, Alexander Cruz,
Ronald Pulliam, Jon C. Barlow, and Donald W. Buden.
ECOLOGICAL FORMATIONS
So that the distribution of the avifauna can be analyzed generally,
major ecological formations for the islands are proposed, defined, and de-
lineated here. Fundamental to the definition of the formations are major
and minor plant associations, distinctive topographic features, and perti-
nent geologic, edaphic, and hydrologic conditions. These ecological for-
mations are similar to, if not identical with, some of the major plant
communities described by Asprey and Robbins (1953) from Jamaica.
Implied for each formation are those general and specific niche require-
ments essential to the successful occurrence of each of its avifaunal com-
ponents, including food and other trophic relationships, available nesting
and feeding sites, and protective cover. In addition to the plant com-
munity analyses by Asprey and Robbins (1953), other reports have
proven valuable in the definitions of these formations, namely those by
Doran (1954) and Richards (1955) on geology, and Swabey and Lewis
(1946) on forestry.
In evaluating insular avifaunas it is sometimes useful and desirable to
include a "marine littoral element," essentially pelagic birds depending
upon offshore waters for food and the island for breeding sites. Although
this contingent is not considered here as a distinct, important ecologic
formation, it is emphasized that at least four species of birds breeding
on the Cayman Islands would be considered pelagic during the non-
breeding season-Phaethon lepturus, Sula leucogaster, S. sula, and Fre-
gata magnificens.
FRINGING REEFS AND LAGOONS.-For the most part the three islands
possess fringing coral reefs that enclose shallow lagoons or sounds (Fig.
5), although on Cayman Brac the reefs are limited to the southwestern
tip. The reefs, usually 30 to 100 m offshore, typically vary from about
0.5 m below sea level to about 0.3 m above. Water in the enclosed la-
goons may be 3 m or more deep but is usually less than 1 m deep. De-
spite the incessant pounding of surf on the reefs and water depth of the
lagoons, both are visited periodically for food by some herons, egrets, and
terns, plus an occasional shorebird, especially at low tide.
BULLETIN FLORIDA STATE MUSEUM
0. "
FIGURE 5.-Typical fringing reef:, lagoon, and sand-coral beach, Grand Cayman.
A distinctive feature of Grand Cayman is its immense North Sound
(Fig. 1), embracing some 64 km2 and partially separated from the open
sea to the north by a broken reef and shoals. The greatest depth of the
sound (near its center) is only about 6 m; much of its shallow floor
abounds in turtle grass (Thalassia testudinum). Although the boundary
of the North Sound with land is not always clear-cut, nonetheless much
of its periphery is composed of red mangroves (Rhizophora mangle),
with occasional mangrove islands in the sound. The sound and its fring-
ing red mangroves are not generally used by aquatic birds, but at least
one island (Booby Cay) is a well-known heron rookery, whereas other
small mangrove islands provide temporary roosting sites for frigate birds,
herons, and egrets.
SAND-CORAL BEACH.-The coastlines of the islands are composed of
coral cobbles, sandy beaches, or steep bluffs. The beaches are best de-
veloped for about 5 km on the western end of Grand Cayman, a popular
resort area. Steep bluffs (6-30 m) dropping off into deep water are best
developed along the northeast coast of Grand Cayman and at the eastern
end of Cayman Brac.
The sand-coral beach formation (Fig. 5) consists of blown coral sand
and well-rounded coral fragments piled up and worn by winds, waves,
storms, and hurricanes. This formation, some 3-10 m wide, has little
covering vegetation, but some pioneer plants grow on it including
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
Sesuvium portulacastrum, Ipomea sp., and Sporobolus virginicus. On the
landward side the sand-coral beach formation is continuous in many
places with a rugged, irregular shore platform termed "ironshore." It
slopes gradually to a height of 4-5 m, may extend inland some 10-50 m,
and also possesses sparse or no vegetation, except in certain areas where
woody thickets of Caesalpinia bonduc have developed.
SEA GRAPE-ALMOND WOODLAND.-This coastal vegetation formation
is characteristic of the West Indies ("strand woodland" of Asprey and
Robbins). From the "ironshore" or, where it is absent or poorly de-
veloped, from the sand-coral beach formation, the gradually ascending
beach ridge supports a distinctive plant community dominated by Cocco-
loba uvifera, Terminalia catappa, Thespesia populnea, Casuarina equiseti-
folia, Chrysobalanus icaco, Tournefortia gnaphalodes, and other salt-
resistant shrubs and forbs (Fig. 6). Commonly the trees are wind-
pruned, desiccated in appearance, and no more than 5 m tall. On Grand
Cayman, at least, this arboreal community usually does not exceed 30 m
in width, but it does extend as a distinctive coastal band nearly around
each of the islands. It has offered shade and sheltered sites for human
habitations for many generations.
MANGROVE SwAMPS.-Extensive areas of Grand Cayman and Little
Cayman are covered with mangrove or buttonwood swamps (see Figs. 1
FIcURE 6.-Sea grape-almond woodland with Australian pines behind beach on
Grand Cayman.
1975
BULLETIN FLORIDA STATE MUSEUM
and 2). In wetter and more saline places, as around North Sound,
Rhizophora mangle predominates (Fig. 7), but farther inland at some-
what drier sites (at least seasonally) other mangroves (Laguncularia
racemosa and Avicennia nitidca) combine to form a thick-canopied forest
(Fig. 8). At even drier sites, buttonwood (Conocarpus erectus) and
mahogany (Swietenia mahagoni) dominate this formation. On the in-
terior eastern side of North Sound these mangrove swamps attain their
greatest development; the trees often reaching heights of 18-20 m. As
will be demonstrated later, these swamps are important communities for
wintering birds.
FIGURE 7.-Red (foreground) and black (background) mangroves beside North
Sound, Grand Cayman.
PASTURES AND CULTIVATED AREAS.-Characteristically, for many years
the Caymanian people have depended upon small cultivations for staples
such as yam, cassava, potato, papaya, and bananas. Small cultivated
areas, hewn and burned out of the limestone forests, are chiefly at inland
sites, such as at the interior eastern end of Grand Cayman and on the
bluff of Cayman Brac where pockets of red earth support the meager
crops. Formerly coconuts (Cocos nucifera) were extensively cultivated,
especially at coastal sites on Little Cayman and Cayman Brac, but a bud-
rot disease has virtually eliminated the once flourishing coconut industry.
The "bush" has also been traditionally cleared for pastures especially
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
FIGURE 8.-Black and white mangrove forest, Grand Cayman.
on Grand Cayman (Figs. 9 and 10). Important introduced grasses of
these pastures are Guinea grass (Panicum maximum) and Seymour grass
(Andropogon metusus), and there are also scattered shrubs, such as
Comocladia dentata and trees such as Bursera simaruba, Roystonea sp.,
and Mangifera indica. Maintenance of the pastures (i.e., the arresting of
natural secondary succession to a woody community) is effected chiefly
by sporadic man-made fires. These small, scattered fires are important,
though not essential, ingredients in stirring up insects for anis, egrets,
and swallows.
LOcwoOD FOREST OR SCRUB WOODLAND.-Pastures and other cleared
areas, if not maintained as such, quickly revert to a woody community
with the invasion of a variety of plants (Fig. 11). The latter include
maiden plum, red birch, and especially the introduced logwood (Haema-
toxylon campechianum). Open and, later, dense stands of nearly pure
logwood develop and are common on Grand Cayman on drier upland
sites (Fig. 12). Local people often refer to the dense logwood as "scrub
woodland." These stands, depending upon their age and other variables
(soil and water), frequently include in later stages thatch palm (Thrinax
argentea) and red birch, the combination woodland averaging about 6 m
in height and forming a nearly impenetrable forest (Fig. 13). This
formation is restricted to Grand Cayman and is most frequent in the
middle section of the island.
BULLETIN FLORIDA STATE MUSEUM
FIGURE 9.-Partially cleared pastureland with scattered trees, Grand Cayman.
FIGURE 10.-Inland clearing for cassava, potato, and other vegetables with dense
limestone forest in background, Grand Cayman.
Vol. 19, No. 5
1975 JOHNSTON: CAYMAN ISLAND AVIFAUNA 249
-iA
FIGURE 11.-Early logwood succession, Grand Cayman. Note interspersed grassy
plots.
Ilk.
FIGURE 12.-Pure logwood forest (5 m high), Grand Cayman.
r -a
ah
BULLETIN FLORIDA STATE MUSEUM
FIGURE 13.-Dense logwood-thatch palm-red birch forest (8 m high), Grand Cay-
man.
LIMESTONE FOREST.-Originally, this type of forest must have cov-
ered most of the drier upland portions of Grand Cayman (Swabey
and Lewis 1946), especially on the northern and eastern sections where
limestone ridges are common. These ridges, oriented in an east-west
direction, commonly reach heights of 2-8 m, typically possess jagged
honey-combed rocks, and are difficult to traverse except for a very few
trails. With some red soil deposited, especially in intervening swales,
the limestone ridges support a dense hardwood forest (Fig. 14), which
has been selectively cut over as a source of lumber and other wood
products for many years. The larger mahogany trees, in particular, have
been removed, but even today this type of forest contains Hippomane
mancinella, Clusia flava, Cedrela odorata, Bursera simaruba, Eugenia sp.,
Ficus populnea, and other hardwoods. Swabey and Lewis (1946) list
some 30 species of trees as characteristic of this forest. The forest on
Grand Cayman may reach a height of 14 m. Apparently the limestone
forest formation on the Cayman Islands is of the same structure as that
described for the wet limestone forest of Jamaica by Asprey and Robbins
(1953).
The bluff limestone forest on Cayman Brac (Fig. 15) is of the same
general character, except that mahogany is absent and cedar abounds due
to the well-drained terrain. Agave americana is a conspicuous plant of
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
FIGURE 14.-Interior of dense limestone forest, Grand Cayman.
FIGURE 15.-Bluff limestone forest, Cayman Brac.
BULLETIN FLORIDA STATE MUSEUM
these bluffs. On Little Cayman the limestone forest of the inland sites
is lower in height (6 m or less) and appears to be denser, with a greater
frequency of mahogany and Cereus cacti.
INLAND LAGOONS AND PoNDs.-Although no streams occur on these
islands, to some degree all of them possess brackish lagoons (Fig. 16)
just behind the coastal ridges. Farther inland on Grand Cayman and
Little Cayman in lowlands are rain-fed ponds, chiefly brackish in nature
and surrounded by mudflats or mangroves. These ponds are breeding
sites for the abundant mosquito populations, but also support small fish
(chiefly Limia caymanensis and Gambusia p. puncticulata) and crabs
available to the piscivorous avifauna. Except for one large lagoon and
a few ponds in mangrove swamps on the southwestern portion, Cayman
Brac with its large central bluff is devoid of standing water.
TOWN AND HOUSE SiTEs.-Where the native vegetation has been
cleared for houses, an important and distinctive ecological community
has developed. House sites, for example, include clearings for small
gardens, cultivated flowers and introduced shrubs, fruit-bearing trees,
scattered shade trees, and ruderal areas (Fig. 17). The spread-out towns
of Georgetown and West Bay on Grand Cayman are typical of this com-
munity with its introduced plants, which are attractive to certain bird
species. Particularly attractive to birds are flowers of Bougainvillea
glabra, Delonix regia, and Nerium oleander and fruits of Coccoloba
FIGURE 16.-Inland lagoon and mudflats with fringing mangroves, Little Cayman.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
FIGURE 17.-Typical roadside and house-site habitat, Cayman Brac.
uvifera, Bursera simaruba, Mangifera indica, Carica papaya, Psidium
guajava, and Manilkara zapoda. Included in this formation is the so-
called "roadside community" which contains powerlines, poles, and fence
lines. Because there is currently a small resident human population on
Little Cayman (about 20), this ecological formation is virtually absent
from that island.
AVIFAUNAL DISTRIBUTION
IN THE ECOLOGICAL FORMATIONS
The impenetrability of most of the wooded formations on the Cayman
Islands, the exceedingly rough and uneven terrain, and the absence of
trails for accurately measuring distances made it possible to obtain
precise quantitative measures of the terrestrial avifauna, except in unusual
instances (see census data presented later). Thus, traditional techniques
for measuring bird population densities, such as a transect-count or the
territory-mapping technique, could not be employed in these investiga-
tions. A semi-quantitative method was devised, however, to provide rela-
tive indices of abundances of species populations. The method was used
on all three islands, although most of the censuses were taken on Grand
Cayman. Ten censuses, each of about two hours duration in early morn-
ing hours, were taken in representatives of each of the major ecological
formations during the months) indicated in the accompanying tables.
1975
BULLETIN FLORIDA STATE MUSEUM
After a count was made of all individual birds recorded during each
census, relative scores were derived as follows:
U (uncommon)-5-20 individuals/20 hr.
FC (fairly common)-20-100 individuals/20 hr.
C (common)-100-300 individuals/20 hr.
VC (very common)-300 individuals/20 hr.
Excluded from the following summary tables are the rare or accidental
species, that is, those observed less than five times in the total counts.
As a rule, bird species diversity is a positive function of vegetational
complexity (MacArthur, Recher, and Cody 1966). Foliage height diver-
sity is believed to be a good and reasonably accurate indicator of bird
species diversity, particularly for tropical avifaunas. In the Cayman Is-
lands, however, use of vegetation as an indicator was impractical for two
major reasons: (1) with the exception of some limestone and inland man-
grove forests, a given habitat studied for its avifaunal composition usually
did not exceed 5 m in height; and (2) the honey-combed limestone
terrain with its exceedingly dense vegetation (often impenetrable and
thorny) precluded attempts to accurately measure vegetational strata
and the organisms occurring in presumed strata. Rather, as will be in-
dicated later, attention was given to average relative feeding heights of
only potential competitors, especially congeners.
BIRDS OF FRINGING REEFS, LAGOONS, AND SAND-CORAL BEACH.-Table
2 summarizes the relative abundances of birds in this formation. It is
important to note that few species are ever common here. Thalasseus
maximus is the most common year-around inhabitant of the reef-lagoon-
beach area where fish are plentiful in the shallow waters. Actually, no
birds breed in this formation in the Cayman Islands; the summer occur-
rences of Phaethon lepturus, Sula leucogaster, S. sula, and Fregata mag-
nificens represent birds feeding or flying over from nest-sites on nearby
bluffs or lagoons farther inland. Otherwise, most of the 18 species in
Table 2 are either migrants or winter residents that feed on the marine
fauna (chiefly invertebrates and small fishes) found in this formation.
Forms such as Florida caerulea and Hydranassa tricolor breed elsewhere
on the islands and make only occasional visits to the beach area.
Of all the ecological formations studied here, this one has the lowest
bird species diversity (10 in summer, 13 in winter) and the smallest
populations.
BIRDS OF SEA GRAPE-ALMOND WOODLAND.-As stated earlier, this
formation forms a belt around most of the islands and is an important
woody, terrestrial community for birds because it provides (a) suitable
nesting sites for 5-7 species, (b) a dependable food supply, and (c) at
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 2.-BIRDS OF FRINGING REEFS, LAGOONS, AND SAND-CORAL BEACH.
Island: GC GC LC CB
Species Date: December Apr-June August June-Aug
Phaethon lepturus C
Sula leucogaster U C
Sula sula VC
Fregata magnificens U FC VC FC
Ardea herodias U
Florida caerulea U U U
Hydranassa tricolor U
Pandion haliaetus U U
Squatarola squatarola FC U U U
Arenaria interpres FC U U U
Actitis macularia U U
Tringa solitaria U
Catoptrophorus semipalmatus U U
Larus atricilla FC U
Sterna hirundo FC
Thalasseus maximus C C
Ceryle al!con U
Hirundo rustica C
Total species 13 10 7 5
least a temporary first landfall for migrants. Three breeding forms
(Elaenia martinica, Dendroica petechia, and Coereba flaveola) are com-
mon there throughout the year (Table 3). The very interesting Nycta-
nassa violacea, known locally as "crabcatcher," stalks small land crabs
(chiefly Gecarcinus lateralis and Cardiosoma guanhumi) on the ground
among the Coccoloba and Terminalia trees. Fruits of these and other
trees are important seasonal dietary items of Columba leucocephala and
both of the Zenaida species. In winter this formation supports at least
10 additional species of North American migrants, for the most part
foliage-gleaning warblers (Parulidae).
BIRDS OF MANGROVE SWAMPS.-Although mangrove swamps differ
floristically according to the dominant plant species (Rhizophora mangle
or Laguncularia racemosa and Avicennia nitida or Conocarpus erectus),
as a whole this formation teems with bird life, especially in the winter
(Table 4). Noticeably high concentrations of North American warblers
(12 species) utilize mangrove swamps in the winter months (see later
analysis of the winter avifauna). Field observations of a non-quantita-
tive nature suggest that insect food supplies also peak at this season.
Even during the breeding season 10 bird species regularly inhabit this
formation, with Dendroica petechia being exceptionally common at all
seasons.
BIRDS OF PASTURES AND CULTIVATED AREAs.-Pastures, grasslands, and
cultivated fields are well-known for'relatively low densities of breeding
BULLETIN FLORIDA STATE MUSEUM
TABLE 3.--BIRDS OF SEA GRAPE-ALMOND WOODLAND.
Island: GC GC GC LC CB
Species Date: December June August August June-Aug.
Nyctanassa violacea
Columba leucocephala
Zenaida aurita
Zenaida asiatica
Columbina passerina
Coccyzus minor
Coccyzus americanus
Colaptes auratus
Centurus superciliaris
Sphyrapicus various
Tyrannus dominicensis
Tyrannus caudifasciatus
Myiarchus stolidus
Elaenia martinica
Mimus polyglottos
Mimocichla plumbea
Vireo altiloquus
Vireo magister
Mniotilta varia
Parula americana
Dendroica petechia
Dendroica tigrina
Dendroica caerulescens
Dendroica fusca
Dendroica palmarum
Geothlypis trichas
Setophaga ruticilla
Coereba flaveola
Quiscalus niger
Passerina cyanea
Melopyrrha nigra
Total Species
* known or suspected breeders
U U U
U U
U
FCO
U
U U
FC*
C Co
VC* VCO
FCO U*
U
U
VC* VC
VCO
C FC*
7 10
7
birds in North America (Johnston and Odum 1956), and census data
from the Cayman Islands are not an exception to this rule (Table 5).
Only six species were found breeding in this formation. Some of these
birds required nesting sites in low trees and shrubs at the edge of or in a
partially cleared pasture. During the nonbreeding season an additional
10 species occurred at times in this formation, none of them (except
Ardeola ibis) ever recorded as common.
BIRDS OF LOGWOOD FORESTS.-The dense logwood forests of Grand
Cayman support 10 breeding species (Table 6), some of these being
common or very common (Vireo magister, Dendroica vitellina, Coereba
flaveola, and Quiscalus niger). As in other terrestrial formations dis-
cussed here, a significant number of migrant species (12) regularly in-
habit this formation in the winter.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 4.--BRDS OF MANGROVE SWAMPS.1
Island: GC GC GC LC CB
Species Date: December June August August June-Aug.
Butorides virescens FC
Gallinula chloropus
Columba leucocephala C
Zenaida asiatica
Ceryle alcyon U
Colaptes auratus FC
Centurus superciliaris U
Tyrannus caudifasciatus FC
Myiarchus stolidus FC
Elaenia martinica U
Polioptila caerulea U
Vireo crassirostris U
Vireo magister FC
Mniotilta caria U
Parula americana C
Dendroica petechia VC
Dendroica tigrina U
Dendroica caerulescens FC
Dendroica virens U
Dendroica dominica U
Dendroica discolor U
Dendroica palmarum C
Seiurus aurocapillus U
Seiurus noveboracensis U
Geothlypis trichas U
Setophaga ruticilla C
Coereba flaceola FC
Spindalis zena
Quiscalus niger C
Total Species 26
* known or suspected breeders
1 exclusive of roosting herons and egrets
Co C Co VC*
FC* FC
VC* VC VC* VC*
BIRDS OF LOGWOOD-THATCH PALM-RED BIRCH FORESTS.-As plant
species diversity increases from a logwood forest to this formation, so do
the breeding and wintering bird populations (Table 7). Probably the
Haematoxylon-Thrinax-Bursera formation contains a greater food diver-
sity and more strata and feeding niches to support the avifaunal complex.
This formation contains, among other forms, two breeding species of
doves, two woodpeckers, three flycatchers, two vireos, and two warblers.
Partitioning of food resources by these pairs will be discussed in a later
section. Again, a significant invasion by wintering warblers is character-
istic of this formation.
BIRDS OF LIMESTONE FORESTs.-As a whole, the limestone forests of
the Cayman Islands support a relatively great variety of breeding birds
(Table 8). For all three islands, 17 bird species breed in this formation;
1975
BULLETIN FLORIDA STATE MUSEUM
TABLE 5.-BIRDS OF PASTURES AND CULTIVATED AREAS.
Island: GC GC LC CB
Species Date: December Apr-May August June-August
Ardeola ibis C C FC U
Circus cyaneus U
Falco columbarius U
Falco sparverius U
Zenaida asiatica FC FC U
Columbina passerina FC FC* C* U*
Amazona leucocephala U U U
Coccyzus minor U U
Crotophaga ani C C* FC* FCO
Chordeiles minor UO U*
Tyrannus dominicensis C* U0
Mimus polyglottos C CO FC* U0
Dendroica palmarum VC
Quiscalus niger FC FC U
Dolichonyx oryzivorus U
Tiaris olivacea FC FC* U* U*
Passerina cyanea U
Melopyrrha nigra U
Passerculus sandwichensis U
Ammodramus savannarum U
Total Species 16 9 7 8
* known or suspected breeders 5 5 6
this represents 63 percent of the breeding terrestrial avifauna for the
islands. Furthermore, during the breeding season the total population
in this formation exceeds that of any other formation on the islands, with
the exception of the town-house site-roadside formation. In winter, the
limestone forests clearly do not attract as high a contingency of North
American migrants as do the logwood, logwood-thatch palm-red birch,
and mangrove forests. This may be partially explained by the so-called
"irregularity principle," as discussed by Willis (1966), namely the
tendency for migrants in the tropics to avoid extensive forests but to
favor "irregular" or "peripheral" habitats, such as montane forests or iso-
lated areas or those disturbed by man.
BIRDS OF INLAND LAGOONS AND PoNDS.-In winter and spring migra-
tion periods, a large variety of birds is attracted to this formation (Table
9). This is due to (1) the abundant food supply (small fish, crustaceans,
etc.) and (2) varying water depths that can accommodate both small
wading birds, such as sandpipers, and birds feeding in deeper waters,
such as occasional diving ducks. The low but dense mangroves sur-
rounding such ponds provide nesting sites for herons and egrets.
BIRDS OF TowNs, HOUSE SITES, AND ROADSIDES.-Areas subjected to
human disturbance generally possess such a great variety of plant species
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 6.-BIRDS OF PURE LOGWOOD FORESTS.
Grand Cayman
Species December June
Zenaida asiatica FC
Colaptes auratus U U*
Centurus superciliaris U
Tyrannus caudifasciatus C
Myiarchus stolidus U*
Elaenia martinica U U
Mimus polyglottos FC FC*
Dumetella carolinensis C
Vireo crassirostris U FC*
Vireo magister C C*
Mniotilta varia U
Helmitheros vermivorus U
Parula americana FC
Dendroica petechia U U*
Dendroica tigrina U
Dendroica caerulescens U
Dendroica vitellina C VCO
Dendroica palmarum VC
Seiurus aurocapillus U
Seiurus noveboracensis U
Geothlypis trichas C
Setophaga ruticilla U
Coereba flaveola C VC*
Quiscalus niger U C*
Tiaris olivacca U0
Melopyrrha nigra U
Total Species 24 10
known or suspected breeders 10
for nest sites and foods that birds are equally attracted. It is not sur-
prising, therefore, to note the high number of bird species and their
abundances found here (Table 10). Considering breeding birds alone,
this formation supports the greatest species diversity and populations
of all the terrestrial ecological formations on the Cayman Islands. Al-
though this formation is relatively high in wintering migrants, these
birds reach higher populations in other formations (for example, man-
grove swamps and logwood forests). The avian population data from
this disturbed formation, therefore, do not necessarily conform to the
irregularity principle" mentioned above.
POPULATION DENSITIES ON CAYMAN BRAC
A large area physically suitable for precise quantitative evaluation of
bird populations was difficult to find on these islands. Such an area,
however, was located at one relatively undisturbed site on Cayman Brac.
1975
BULLETIN FLORIDA STATE MUSEUM
TABLE 7.-BIRDS OF LOGWOOD-THATCH PALM-RED BIRCH FOREST.
Grand Cayman
Species December Apr-May August
Columba leucocephala U U
Zenaida aurita U U*
Zenaida asiatica U U* U
Colaptes auratus FC U* U
Centurus superciliaris U FC* FC
Tyrannus caudifasciatus FC* FC
Myiarchus stolidus U FC* ,U
Elaenia martinica C VCO C
Dumetella carolinensis C
Vireo crassirostris FC FC* FC
Vireo magister FC FC* U
Mniotilta varia U
Helmitheros vermivorus U
Parula americana FC
Dendroica petechia U U* U
Dendroica tigrina U
Dendroica discolor FC
Dendroica vitellina VC VC' VC
Dendroica palmarum C
Seiurus aurocapillus U
Geothlypis trichas C
Setophaga ruticilla U
Coereba flaveola VC C* C
Spindalis zena U0
Quiscalus niger C FC* FC
Tiaris olivacea U
Melopyrrha nigra FC U*
Total Species 25 15 13
known or suspected breeders 15
One side of a road contained 2.4 acres of limestone bluff forest and the
other side, 4.8 acres of a scrubby woodland (not a logwood forest, how-
ever), including some house sites (Table 11). The limestone forest
contained seven bird species, virtually the same species composition as
observed in censuses of limestone forests at inland sites (Table 8) on this
island. Furthermore, with the exception of Columba leucocephala, there
is good agreement between the density figures in Table 11 and the
relative abundance scores in Table 8. Both methods revealed high popu-
lations of Elaenia martinica, Coereba flaveola, and Dendroica vitellina,
with lower values for Zenaida asiatica and the two vireos. The "scrub
woodland" census showed high numbers of Coereba flaveola, Dendroica
vitellina, Elaenia martinica, and Tiaris olivacea. The presence of Tiaris,
Mimus polyglottos, Columbina passerina, and Ardeola ibis indicates a
disturbed community from which the native trees and shrubs have been
partially cleared, resulting in grassy or bare areas utilized by and essential
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 8.-BIRDS OF LIMESTONE FORESTS.
Island: GC GC GC LC CB
Species Date: December Apr-May August August June-Aug
Columba leucocephala
Zenaida aurita
Zenaida asiatica
Columbina passerina
Leptotila jamaicensis
Amazona leucocephala
Coccyzus minor
Ty!to alba
Colaptes auratus
Centurus supcrciliaris
Tyrannus dominicensis
Tyrannus caudifasciatus
A!Myiarchus stolidus
Elacnia martinica
Dumetella carolinensis
Mimocichla plumbea
Vireo crassirostris
Vireo altiloquus
Vireo magister
Mniotilta varia
Parula americana
Dendroica petechia
Dendroica virens
Dendroica citellina
Setophaga ruticilla
Cocreba flaveola
Spindalis zena
Quiscalus niger
Melopyrrha nigra
Total Species
U* FC FC* FC*
U U0
FC*
U
C FC*
C FC*
FC*
VC VC*
U U
FC U0
C CO
U
U
U
U
C FC*
U U
VC VC*
U FC*
U*
C FC*
15 21
FC*
C U
U*
U
U
U
VC* VC*
U
U0
U6 FC*
C C* FC*
10 11
* known or suspected breeders
7 8
to the feeding behavioral patterns of these four species. The avifaunal
composition of this "scrub woodland" census is most closely comparable
to that of the relative abundances for towns, house sites, and roadsides in
Table 10.
BID POPULATIONS AND UPLAND
SECONDARY PLANT SUCCESSION
Although detailed studies of secondary plant succession have not been
carried out in the Cayman Islands, apparently some of the major ecologi-
cal formations (plant communities) discussed above should be considered
as climax: sea grape-almond woodland, mangrove forests, and limestone
forest. (Some of the relatively dry buttonwood areas may not be cli-
max.) At any rate, all the evidence from these islands, and chiefly from
BULLETIN FLORIDA STATE MUSEUM
TABLE 9.-BIRDS OF INLAND LAGOONS AND PONDS.
Islan
Dat
Species
Podilymbus podiceps
Butorides virescens
Florida caerulea
Ardeola ibis
Casmerodius albus
Egretta thula
Hydranassa tricolor
Plegadis falcinellus
Dendrocygna arborea
Anas discors
Anas americana
Aythya affinis
Porphyrula martinica
Gallinula chloropus
Fulica americana
Charadrius semipalmatus
Charadrius wilsonia
Squatarola squatarola
Arenaria interpres
Himantopus himantopus
Capella gallinago
Actitis macularia
Tringa solitaria
Tringa melanoleuca
Tringa flavipes
Catoptrophorus
semipalmatus
Calidris canutus
Calidris pusilla
Crocethia alba
Limnodromus griseus
Larus atricilla
Sterna hirundo
Sterna albifrons
Ceryle alcyon
Riparia riparia
Hirundo rustica
Petrochelidon pyrrhonota
Stelgidopteryx ruficollis
Total Species
* known or suspected breeders
d: GC
e: Dec.
C
U
FC
U
U
VC
FC
U
U
VC
U
U
VC
VC
GC
Apr-May
U*
FC*
FC*
U*
CC
Aug.
U
U
FC* C FC*
VC* VC FC*
U* U U*
CB
June-Aug.
U*
U*
U*
U*
U*
U*
U
U
C Co U*
U*
U
U
FC
U C
C CO U*
U U
U U U
U U
FC
U
FC U* C*
U
VC
U
U
26 23
10
11 14
10
Grand Cayman, points to one conspicuous
ture or cultivated field to logwood forest
birch forest to a climax limestone forest.
secondary sere-from a pas-
to logwood-thatch palm-red
The time involved in each
seral stage is unknown and is obviously subject to local variations, es-
pecially edaphic influences and drainage patterns, but certainly rever-
sion of pastureland to logwood forest probably occurs within a few years
--
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 10.-BIRDS OF TOWNS, HOUSE SITES, AND ROADSIDES.
Island: GC GC GC CB
Species Date: December Apr-May August June-August
Ardeola ibis
Falco sparcerius"*
Columba letcocephala
Zenaida aurita
Zenaida asiatica
Columbina passerina
Crotophaga ani
Colaptes auratus
Centurus superciliaris
Sphyrapicus various
T!urannuis domninicensis
Tyrannus caudifasciatus
Afiiarchus stolidus
Elacnia martinica
Hirundo rustica**
Mim us polyglottos
Diumetella carolinensis
Mimocichla plhmbeac
Vireo crassirostris
Vireo nmagister
Dendroica ipctchia
Dendroica citellina
Dendroica palnarum
Coercba flaveola
Spindalis zena
Quiscalus niger
Dolichonyx oryzicorus**
Tiaris olivacea
Passerina cyanea
Melopyrrha nigra
Passerculus sandwichensis"*
Total Species
* known or suspected breeders 19 10
"* species typical of roadside only
because the seedlings of Haematoxylon are fast-growing.
By selecting representatives of these seral stages, it is then possible
to assess the progression of the attendant avifaunal populations, espe-
cially during the breeding season (Table 12). As might be expected
from similar analyses of secondary succession and bird populations on
the North American mainland (Johnston and Odum 1956), with ad-
vancing ecological age and increasing complexity of the plant communi-
ties, there is a concomitant increase in breeding bird composition, at
least through the subclimax (logwood-thatch palm-red birch) formation.
Similarly, total density figures show an increase. On the other hand, if
one considers the wintering populations (inclusive incidentally, of the
C FC*
FC*
U*
FC*
VC VC"
FC FC*
FC
BULLETIN FLORIDA STATE MUSEUM
TABLE 11.-ROADSIDE CENSUSES ON CAYMAN BRAC.O
Limestone Bluff Forest Scrub Woodland"*
Species (2.4 acres) (4.8 acres)
Elaenia martinica 60"** 16
Mimus polyglottos 0 4
Coereba flaveola 44 28
Mimocichla plumbea 0 6
Vireo crassirostris 4 6
Vireo altiloquus 6 0
Dendroica vitellina 12 24
Tiaris olivacea 0 16
Tyrannus dominicensis 0 6
Columbina passerina 0 2
Zenaida asiatica 8 4
Coccyzus minor 4 0
Ardeola ibis 0 2
Average number of birds seen per five 1-hour censuses in late June 1970
** Included three house sites and yards
"" All density figures are converted to a 10-acre basis
TABLE 12.-BIRDS OF PROBABLE SUCCESSIONAL STAGES ON GRAND CAYMAN.
Pastures and Logwood Logwood- Limestone
Breeding Species Cultivated Areas Forest Palm-Birch Forest
Columbina passerina FC
Crotophaga ani C
Chordeiles minor U
Mimus polyglottos C FC
Tiaris olivacea FC U
Dendroica petechia U U
Vireo crassirostris FC FC U
Colaptes auratus U U FC
Vireo magister C FC C
Dendroica vitellina VC VC FC
Coereba flaveola VC C VC
Quiscalus niger C FC U
Myiarchus stolidus U FC FC
Zenaida asiatica U
Tyrannus caudifasciatus FC
Zenaida aurita U U
Centurus superciliaris FC FC
Elaenia martinica VC VC
Spindalis zena U FC
Melopyrrha nigra U FC
Amazona leucocephala FC
Columba leucocephala U
Leptotila jamaicensis U
Total breeding species 5 10 15 15
Abundance index* 11 22 29 30
Total wintering species 16 24 25 15
Abundance index 30 42 47 32
*Obtained by summations of equivalent values: U= 1, FC=2, C= 3, VC=4.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
resident breeding complement) separately, it is apparent that the climax
limestone forest does not support the densest population in this sere. An
explanation for the relative decrease in winter in this climax formation
may be found in part in the "irregularity principle" cited earlier (Willis
1966). Perhaps, in turn primary productivity is higher annually in the
subclimax logwood-thatch palm-red birch formation than in the limestone
forest.
Note should also be made of the changing proportions between seral
stages of uncommon and fairly common species to the common and very
common ones. In early seral stages common and very common species
represent 66 percent of the birds, but in the subclimax and climax stages
these classes comprise only 25 percent of the breeding avifauna. Con-
versely, in the climax seral stage the proportion of uncommon and fairly
common species increases. A completely satifactory explanation of this
phenomenon cannot be provided at the present time, but several factors
are influential. First, in both the subclimax and climax stages, there is
an obvious increase in niches available to the avifauna, the niches mark-
edly influenced by increasing tree species diversity and attendant strati-
fication of the foliage. Second, among the species found only in the
limestone forest and yet ranked only as uncommon or fairly common are
Amazona leucocephala, Columba leucocephala, and Leptotila jamaicensis.
All these birds are large in body size and from numerous field observa-
tions appear to have large home ranges. Thus, on a unit area basis each
of these species would maintain lower densities than smaller birds with
smaller territories. Finally, a factor undoubtedly influencing the habitat
distribution of these three species is food. All are frugivores and on
Grand Cayman their preferred fruiting trees during the breeding season
are most abundant in the limestone forests (see Appendix III).
BREEDING SEASONS
Breeding seasons of tropical and equatorial birds have received the
attention of biologists especially interested in elucidating causative factors
underlying the seasonality. There is a dearth of published information
for insular avifaunas, so the present data from the Cayman Islands
should be of value despite their geographic location north of the equator.
Few concerted efforts have been made by any single investigator to
obtain quantitative breeding data for any species on these islands, al-
though such long-term efforts would certainly be rewarding for the anal-
ysis and interpretation of annual population fluctuations, natality, mor-
tality, and population controlling mechanisms. Indeed, it is a sad com-
mentary that no one ever recorded breeding data for the extinct Grand
1975
BULLETIN FLORIDA STATE MUSEUM
Cayman Thrush (Mimocichla ravida), although the species was observed
and collected by ornithologists over a span of some 50 years. Contem-
porary data on breeding seasons of birds of the Cayman Islands are
summarized in Table 13, the data having been derived from the scanty
literature, from my own experiences, and those of Donald W. Buden who
spent five continuous months on Grand Cayman in the spring of 1970.
A number of features in Table 13 merit special mention. Sula leuco-
gaster shows a bimodal breeding season, a characteristic of this species
well-known from several previous reports on other islands (Schreiber and
Ashmole 1970). Tyto alba, although not studied in detail throughout the
year, clearly shows some peak of breeding activity in mid-winter. Mimus
polyglottos, from fragmentary observations and reports, has a protracted
breeding period in the spring. Coereba flaveola apparently breeds in
every month of the year.
The annual breeding cycles of land birds on the Cayman Islands con-
form generally to Immelmann's description (1971: 348-9): "Most birds
of regions with a regular change between one long dry and one long wet
season per year . breed around the rainy season with only a few spe-
cialists laying during the dry period." In Table 13, it is evident that peak
breeding on the Caymans is in May and June; in each of these months 54
percent of the land birds are breeding and, for June, 55 percent of all
the breeding species. By referring to Table 1, it can be seen that this
peak in breeding activity coincides with the onset of the wet season.
Tentatively, then, it would appear that rainfall is an important proximate
factor in regulating breeding, a conclusion similarly reached by Snow and
Snow (1964) for Trinidad. Obviously, the wet season (May-October)
is the period in which resident birds should reach their highest annual
population densities and should make their greatest demands on food
resources. Quantification of food resources was not made in this study,
but it is quite likely that the wet season is a time of maximum food
availability. The quantitative report by Dingle and Khamala (1972: 220)
at African localities is relevant here: "Most savanna and dry country
birds breed during the long rains; this breeding is correlated with a major
increase in the availability of insect food." (On the other hand, as
discussed later, the dry winter months must also be a season of abundant
foods, especially small insects, to support the influx of North American
migrants, many of which glean insects from leaf surfaces in the mangrove
and limestone forests.)
The "specialists laying during the dry period" (Immelmann 1971)
should more properly be called generalists in this sense, especially if they
breed during both dry and wet seasons. Among the Cayman avifauna in
this category are Crotophaga ani, Tyto alba, Coereba flaveola, and prob-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 13.-BREEDING TIMES OF BIRDS ON THE THREE CAYMAN ISLANDS.*
Species J F
Podilymbus podiceps
Phaethon lepturus
Sula leucogaster
Sula sula
Fregata magnificens
Florida caerulea
Ardeola ibis
Hydranassa tricolor
Nyctanassa violacea
Gallinula chloropus
Fulica americana
Himantopus himantopus
Catoptrophorus
semipalmatus
Sterna albifrons
Columba leucocephala
Zenaida aurita
Amazona leucocephala
Coccyzus minor
Crotophaga ani
Tyto alba
Chordeiles minor
Colaptes auratus
Centurus superciliaris
Tyrannus dominicensis
Tyrannus caudifasciatus
Myiarchus stolidus N
Elaenia martinica
Mimus polyglottos ? ?
Mimocichla plumbea
Vireo crassirostris
Vireo magister
Dendroica petechia
Dendroica citellina
Coereba flaveola N N
Spindalis zena
Quiscalus niger
Tiaris olivacea
Melopyrrha nigra
Totals (N and/or Y) 1+ 2+
"includes all breeding species for wh
and/or dependent young (Y).
M A M J J A S O N D
Y
Y Y
Y Y
N NY
N
NY NY
N N Y
Y
Y Y
Y
Y Y
N N N
N N
N
? ? N
N
N N N N N
NY
N N N
Y Y
8+ 11- 15 21 8 4 1 1 2 5
ich data are available, based upon nests (N)
1975
BULLETIN FLORIDA STATE MUSEUM
ably Mimus polyglottos. Crotophaga is obviously an omnivore (see Ap-
pendix III), Tyto preys on birds and rodents, and Coereba is chiefly a
nectarivore. Considering the small populations of Tyto on these islands,
an apparently adequate food supply, and the absence of a competitor,
the breeding season of this owl should not a priori be restricted by either
a wet or dry season. Crotophaga is more abundant, occurring in scat-
tered but small and discrete groups in many ecological formations; be-
cause of its omnivorous habits, it too would hardly be restricted in
breeding by wet or dry seasons. Perhaps a similar argument could be
made for Mimus, but less is known of this species' annual cycle. Coereba
is an interesting case, because throughout its range in the Caribbean re-
gion it is renowned for a protracted breeding season. In the absence of
hummingbirds (at least for the Cayman Islands) this Bananaquit can
utilize a unique food resource (nectar and tiny insects) to support a
large and widespread population at all seasons.
INTER-ISLAND DISTRIBUTIONAL PATTERNS
Archipelagos are renowned for their interrupted distributional pat-
terns among the avifauna. In this context, examples are found in indi-
vidual species of Galapagos finches (Geospizidae) and Hawaiian honey-
creepers (Drepaniidae). However, patterns above the family level, al-
though often well known for a given archipelago, have largely been over-
looked in the literature, and since the Cayman Island avifauna contains
conspicuous examples of distributional "anomalies," an analysis of these
distributional patterns is discussed here and summarized in Table 14.
One is faced, of course, with the obvious question-why is species A
restricted to a given Cayman island and yet species B, whether a con-
gener or not, occurs on all three islands? At the outset, several basic
premises must be recalled and at least temporarily accepted: (1) the
three Cayman islands are of a similar geological age; (2) with relatively
minor exceptions (introduced logwood and its scattered stands limited to
Grand Cayman), ecological formations or habitat structures appear to be
identical, or nearly so, among the three islands (see previous discussion);
(3) the three islands are each approximately the same distances from
both Cuba and Jamaica, the potential if not actual sources of most of the
avifauna; (4) Grand Cayman has a much greater land area than the
smaller islands, and certainly the areal expanse of each ecological forma-
tion is far greater on the larger island; and (5) there is no evidence that
hurricane tracks or wind or water currents are extraordinarily restricted
to any one of the islands.
Pertinent to these disjunct distributions are the statements by White-
head and Jones (1969: 176): ". . if one assumes that the rate of move-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
TABLE 14.-SOME INTER-ISLAND BREEDING DISTRIBUTIONAL PATTERNS.
Species Grand Cayman Little Cayman Cayman Brac
Phaethon lepturus breeds
Sula leucogaster + breeds
Sula sula breeds
Fregata magnificens + breeds +
Dendrocygna arborea breeds breeds
Columba leucocephala breeds + breeds
Leptotila jamaicensis breeds
Amazona leucocephala breeds + breeds
Colaptes auratus breeds
Centurus superciliaris breeds
Myiarchus stolidus breeds
Mimocichla plumbea + breeds
Vireo altiloquus + breeds breeds
Vireo magister breeds
Spindalis zena breeds
Quiscalus niger breeds breeds +
Melopyrrha nigra breeds
Totals = 17 11 5 6
Breeding endemic on 7 2 3
only one island
+ = present, but contemporary breeding unconfirmed
ment of propagules . across a given segment of ocean surface is es-
sentially constant through time, it follows that larger islands will intercept
a larger number of disseminules per unit time." On this basis one would
expect Grand Cayman to support a larger resident avifauna (39 species)
than the two smaller islands (Cayman Brac 30, Little Cayman 29). This
is only a partial explanation, however, because habitat areal expanse
and standing water with its concomitant mangrove swamps are also
important factors supporting a diversity of bird life.
With these ideas in mind, we can initiate an analysis of the inter-
esting, interrupted distributional patterns as summarized in Table 14.
Phaethon lepturus and Sula leucogaster prefer or require for breeding
the high bluffs occurring only on Cayman Brac. Sula sula and Fregata
magnificens currently maintain a moderate-sized breeding colony in the
landward mangrove fringe of a large shallow lagoon on Little Cayman.
The physiognomy of this lagoon site appears similar to those on Grand
Cayman, but these birds have not bred on Grand Cayman, at least in
historical times. Perhaps quite local prevailing winds and the lack of
human disturbances are primary factors in the restricted breeding distri-
butions of these two species on Little Cayman. Dendrocygna arborea
is evidently confined as a breeding bird to Grand Cayman and Little
Cayman where mangrove swamps and ponds are common (cf. Figs. 1, 2,
1975
BULLETIN FLORIDA STATE MUSEUM
3); breeding of this species has not been confirmed for Cayman Brac,
an island where open water and mangrove swamps are quite limited.
Columba leucocephala and Amazona leucocephala evidently do not
currently breed on Little Cayman, although both species are at least
moderately common on the other two islands. Longtime human residents
of Little Cayman report that both of these species breed on Cayman Brac
and that small flocks of each undertake daily round-trip flights to Little
Cayman for feeding purposes only. Leptotila jamaicensis, a large ground-
feeding dove, is a species with one of the most restricted ranges of all
the Cayman Island avifauna, being found only in the remote inland lime-
stone forests of Grand Cayman. Why it does not occur on the other two
islands is unknown. Quiscalus niger, a ubiquitous and conspicuous resi-
dent of both Grand Cayman and Little Cayman, is virtually unknown
on Cayman Brac. Small groups sometimes fly back and forth between
the two smaller islands (8 km) but there is presently no rational expla-
nation for its absence as a breeding bird on Cayman Brac.
The eight remaining species in Table 14 present puzzling distribu-
tional patterns among the three islands. Why are Colaptes, Centurus,
Myiarchus, Vireo magister, Spindalis, and Melopyrrha all restricted to
Grand Cayman? Why does not Mimocichla plumbea occur permanently
on Grand Cayman and Little Cayman, the latter only 8 km from Cayman
Brac? Apparently, favorable habitats for this species would be the same
for all three islands. One is tempted to explain these patterns by sug-
gesting that the original successfully breeding pair(s) reached only one
island (usually the largest) from the source population. In subsequent
times, perhaps fortuitously, propagules have failed to reach the other
islands, and the populations now established on the single island became
sedentary. This could be the explanation for these eight species. Is it
probable, however, that of the four forms with definite Cuban affinities
(Colaptes, Centurus, Melopyrrha, and Mimocichla), all but the latter one
should colonize only Grand Cayman?
In reviewing all these distributional patterns, I am inclined to support
a chance-colonization hypothesis for a number of reasons. In the first
place, preferred ecological formations on Cayman Brac, for example, ap-
pear to be potentially suitable to all these terrestrial species currently
restricted to Grand Cayman, and it is likely that they simply never
reached the other islands. Alternatively, populations could have become
extinct. Second, two species (Zenaida asiatica and Mimus polyglottos)
have within quite recent years spread from island to island and now
maintain breeding populations on islands where each was absent as
recently as 25 years ago. Third, Mimocichla plumbea has been recorded
as a vagrant on Grand Cayman (Johnston 1969) where an unmated fe-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
male, previously unrecorded from this island, even constructed unsuccess-
ful nests in at least two successive years. The point is that with the pos-
sible exception of the congeneric vireos in which competitive exclusion
may be an important limiting factor (see discussion beyond), most if not
all of the terrestrial birds currently restricted to a single island could
probably successfully colonize any of the other islands (contra Bond
1934: 345-346). Perhaps the sedentary habits of species now restricted
to Grand Cayman and the distance (97 km) to the other islands have
served as barriers to their dispersal to the smaller islands. This latter
point, emphasizing a "poor" immigration rate of birds such as wood-
peckers, is in substantial agreement with the views of Ricklefs and Cox
(1972: 215).
Among the most curious distributional features of the Cayman Island
avifauna is the absence of resident hummingbirds. This fact is especially
anomalous when it is recalled that (1) every other major island and land
mass east, west, and north of the Caymans all have several resident hum-
mingbird species (Moynihan 1968; Bond 1971), (2) hurricane paths in
the past argue for the possibility of widespread dissemination of birds in
the Caribbean region, and (3) occasional hummingbirds are known to
migrate through Grand Cayman (Johnston et al. 1971). Collectively,
these points tend to negate an hypothesis that hummingbirds could not
or have not reached the islands in the past. The problem is, I believe,
whether or not conditions are currently favorable for their existence in
the islands. The absence of breeding hummingbirds is related to two
factors, a dependable food supply and the possible role of potential
competitors.
As pointed out elsewhere in this paper, the small size, low relief,
desiccating winds, sparse soils, and porous limestone base of the Caymans
preclude the support of luxuriant tropical vegetation, despite the mod-
erately heavy, though seasonal, rainfall. The extensive expanses of lime-
stone and mangrove forests of the Caymans (Figs. 1, 2, 3) are not
characterized by the diversity, distribution, or abundance of flowering
trees and shrubs that one finds elsewhere in the West Indies. Although
quantitative support cannot be marshalled for this statement on plant
diversity and distribution for the Cayman Islands, it is obvious that most
of the favorite hummingbird nectar-bearing plants of Jamaica (Hibiscus,
Bougainvillea, Nerium, Tamarindus, Psidium and many others) are at
best limited chiefly to scattered and relatively sparse house sites on the
Caymans. Thus, I believe that even if potentially immigrant humming-
birds did currently find their way to the Caymans, a dependable food
supply would not be available.
Another consideration in the lack of hummingbirds is the possibility of
BULLETIN FLORIDA STATE MUSEUM
competition specifically with the ubiquitous Bananaquit (Coereba fla-
veola). Throughout the rest of the West Indies and Central America
where hummingbirds and Coereba are sympatric, there is much evidence
that hummingbirds dominate Coereba at food sources (see, for example,
Wetmore 1927). Furthermore, hummingbirds and these bananaquits
generally feed in different fashions, though often utilizing the same food
source simultaneously. None of these features suggest that competition
does or would play a significant role in explaining the absence of hum-
mingbirds on the Caymans.
Intriguing questions on niche breadth, occupancy, and vacancy are
invoked by these inter-island distributional patterns. Characteristic
timber-probing woodpeckers (Colaptes and Centurus) are absent from
the two smaller islands. For these woodpeckers island size and habitat
diversity are important limiting factors. Three species that are frugi-
vorous in low trees or on or near the ground surface on Grand Cayman
are Leptotila, Spindalis, and Melopyrrha. Are these feeding niches
simply vacant on the smaller islands? They probably are, but not
enough is known of comparative feeding behaviors of species with
similar feeding patterns where a competitor is absent. For example, it
is possible, though not documented, that Elaenia has a broader feeding
niche on Cayman Brac (both qualitatively and quantitatively) than on
Grand Cayman, where it undoubtedly competes with Spindalis, Melo-
pyrrha, and other species for small fruits. Similarly, the absence of the
foliage-gleaning insectivorous Myiarchus on the two small islands might
release potential competitors (Vireo, Dendroica) to the extent that their
feeding behavior patterns are broadened on Little Cayman and Cayman
Brac. These and related points certainly merit future intensive studies.
IMMIGRATION AND EXTINCTION
An equilibrium model for the number of species on an island was de-
veloped by MacArthur and Wilson (1967), who predicted that the num-
ber of species on an island is determined by a balance between
immigration and extinction rates. Our current knowledge of the Cayman
Island avifauna provides some concrete examples in support of this
model, despite the fact that few bird species and a relatively short period
of time are involved. There is sufficient evidence, for example, that
two birds (Mimocichla ravida and Icterus leucopteryx bairdi) are now
extinct on Grand Cayman, where formerly (1900-1916) both were mod-
erately common and were last observed in the 1930s (Johnston et al. 1971).
Unfortunately, no precise information is available on the causes of their
extinction, whether by hurricanes, partial habitat destruction, human dis-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
turbance, or a combination thereof. Another thrush, Mimocichla plumbea
rubripes, became extinct on Swan Island, possibly because of forest de-
struction (Paynter 1956). Both species on Grand Cayman, incidentally,
were undoubtedly in Stage IV of a taxon cycle because, among other
characteristics, each was highly restricted in habitat distribution, the
thrush probably to limestone forests and the oriole to sites on the north-
ern coast. (I. 1. leucopteryx is still common on Jamaica as is 1. 1.
lawrencii on St. Andrews Is.) Conversely, the White-winged Dove
(Zenaida asiatica) has invaded all three Cayman Islands since about
1935 and is now a well-established and common resident, especially in
more peripheral habitats of the islands. A spurious attempt at coloniza-
tion by an unmated female Mimocichla plumbea on Grand Cayman was
earlier documented by Johnston (1969). If one can include this last
occurrence as a bona fide instance of immigration, then within the last
40 years Grand Cayman alone has experienced two instances of avian
extinction and two of immigration. Even if one considers the Mimocichla
incident as being an unsuccessful immigration, the data still fit the Mac-
Arthur-Wilson model for a small island where the probability of extinc-
tion increases with decreasing island size.
Immigration and extinction are not well documented for birds on the
smaller islands (Cayman Brac and Little Cayman), chiefly because few
ornithologists have carefully studied the birds of these islands until re-
cently (Johnston et al. 1971). The interrupted distribution of certain
species on these islands is both curious and unexplained (see Table 14),
especially since histories underlying the current distributional patterns are
largely unknown, and little information is available on food, habitat, and
other ecological factors. Evidently Anmazona leucocephala does not
presently breed on Little Cayman (if it ever did, despite old specimens
and observations to the contrary), but small flocks regularly fly over
from Cayman Brac during the day to feed on ripe fruits. Conversely,
the older ornithological records indicate that Quiscalus niger was once
common on Little Cayman and Cayman Brac; today, small flocks fly
from Little Cayman to Cayman Brac to spend the day feeding, but
evidently this grackle does not now breed on Cayman Brac. Minmo-
cichla plumbea is moderately common at least on the lowland perimeter
of Cayman Brac (Table 11); yet it has never been recorded from nearby
Little Cayman but has attempted to breed on Grand Cayman.
As late as 1956, the Mockingbird (Mimus polyglottos) was unknown
from both Little Cayman and Cayman Brac (Bond 1956), even though
the species has been a common resident of ruderal and roadside habitats
on Grand Cayman at least since the earliest days of ornithological in-
vestigations in 1886. By 1956 Mockingbirds were reported on Cayman
BULLETIN FLORIDA STATE MUSEUM
Brac by C. H. Blake (Bond 1958), and the species became well estab-
lished on that island around "inhabitated areas" by 1966 (Harvey, in
Bond 1967). Harvey also noted the species on Little Cayman in the same
year. In the summer of 1971, I recorded nine well-spaced individuals
on Little Cayman during two hours of observation along 8 km of that
island's newly constructed perimeter road. It is apparent that construc-
tion of this road has created open habitats preferred by this species.
The mockingbird probably immigrated to the two smaller islands from
Grand Cayman where it continues to increase in number, probably in
response to continued clearing of mangrove swamps and logwood forests,
thus increasing its preferred habitat.
As discussed elsewhere in this paper, the distribution of the genus
Vireo on these islands is curious, because V. crassirostris occurs on all
three islands with either V. magister (Grand Cayman) or V. altiloquus
(Little Cayman and Cayman Brac). No more than two species of Vireo
are sympatric on a given island. Bond (1966b) mentioned a single old
record of two V. altiloquus on Grand Cayman that probably represented
vagrants.
The fragmentary data available on the ecology of Mimocichla ravida
(English 1916) and Icterus leucopteryx on Grand Cayman conform to
Mayr's (1965) belief that small population sizes and probable genetic
uniformity have made such populations exceptionally vulnerable to the
smallest environmental change. This is another way of invoking genetic
drift as a contributing factor in the extinction of these two forms on
Grand Cayman. Both existed in quite restricted habitats (thus reducing
gene flow), and their population densities in any one year probably never
exceeded 100 breeding pairs. In these small populations, by genetic drift
some alleles favored by selection could have been lost and less favored
ones, perhaps lethals, could have increased in frequencies. These birds
might not have been able to adapt to ensuing environmental changes.
As stated before, the nature of that change, or changes, is unknown, but
possibilities would include some habitat disturbance or hurricane effects.
Furthermore, each of these small Cayman Islands appears to exemplify
Mayr's statement (1965: 1587) ". . that the smaller the island the lower
the percentage of endemic species . ." In fact, plotting data from these
small islands on Mayr's figure 2, the linear relationship between double
logarithmic plottings for island area on percent of endemic species would
become curvilinear, the line extrapolating to zero endemic species with an
island area of approximately 70 square miles or less. According to this
interpretation, none of the Cayman Islands should have any endemic
species, and currently they do not.
In the first analysis of the birds of these islands, Cory (1886) de-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
scribed 13 new species from Grand Cayman alone, and subsequently,
three other species were recognized by early systematists from the other
two islands (for a list, see Johnston et al. 1971). Later taxonomists (e.g.,
Ridgway and Friedmann 1901-1950) synonymized all of these other West
Indian forms, except for Mimocichla ravida. Consequently, a modern
treatment (Johnston et al. 1971) recognized no current endemic species
from the islands, but 16 endemic subspecies. This latter figure appears
to be high for small West Indian islands and suggests a relatively long
period of isolation for the resident avifauna, with little or no recent im-
migration.
A similar example of insular equilibrium between extinction and im-
migration is Diamond's (1969) analysis of the Channel Islands of Cali-
fornia. Those islands lie from 8 to 61 miles from the mainland. Be-
tween 1917 and 1968 from 17-62 percent of the breeding bird species
disappeared, but an approximately equal number of new immigrants
became established.
COMPETITION FOR ENVIRONMENTAL RESOURCES
AMONG THE RESIDENT TERRESTRIAL AVIFAUNA
Ecological isolating mechanisms, the avoidance of competition, and
related phenomena in birds have been discussed by numerous investi-
gators and were summarized recently by Lack (1971). The thesis of
Lack and others is that contemporary bird species can coexist in the same
area only if they differ in some ecological factorss. If an investigator
interested in sympatric forms (genera, species) A and B looks long and
hard enough, presumably he will discover that their coexistence is made
possible by differences in habitat, food, feeding methods, stratification,
or the like, because the only other alternatives are competitive exclusion
or extinction (i.e., coexisting species will have different ecological
niches). Theoretically, at least, the more niches available in a given
community, the more species of birds that can actually or potentially
coexist in that community. Interesting cases are those of insular birds
with quite similar niches; these have been the subject of intensive studies
among the closely related resident Cayman Island birds.
A morphological indication of reduced interspecific competition be-
tween closely related birds is difference in bill size, which, in turn, pre-
sumably reflects differences in food particle size and hence partitioning
of food resources. Grant (1968, 1969), for example, demonstrated that
sympatric congeneric species of birds on islands differ in bill length and
avoid competition by feeding in different habitats or by having different
feeding habits. Schoener (1965), in developing this theme quantitatively,
1975
BULLETIN FLORIDA STATE MUSEUM
suggested that a character difference (ratio of larger to smaller bill
length) greater than 1.14 was typical of sympatric congeneric insular
birds. Congeners with such bill length differences would reduce com-
petition by selecting different-sized food particles. Of the five congeneric
pairs of birds on the Cayman Islands, two have a bill character difference
less than 1.14: Dendroica petechia-D. vitellina (1.01) and Tyrannus
dominicensis-T. caudifasciatus (1.02) (bill measurements taken chiefly
from Ridgway 1901-1950). In the two Dendroica species stomach anal-
yses revealed few qualitative differences in food choices (see discussion
beyond and Appendix III); competition between these forms is avoided
primarily by differences in habitat choice as well as feeding heights. The
Tyrannus species, although possessing similar bill lengths, (1) take dif-
ferent foods, (2) are found in different habitats, and (3) obviously feed
in different fashions. Bill size differences are, therefore, not always the
most important means of avoiding competition in all the Cayman Island
congeners. As will be discussed later in this paper, congeners and other
closely related forms clearly have evolved a spectrum of mechanisms that
in various combinations facilitates coexistence. It should be noted that
in the relatively short time that birds have been studied on these islands,
there is no assurance that competition is not causing a gradual exclusion
of one species or a slow transition into a new ecologic niche for another.
DOVES AND PIGEONS (COLUMBIDAE).-A nearly linear relationship
exists between island size and number of species of Columbidae in the
West Indies (A. Cruz, pers. comm.). Island size is not necessarily the
prime factor, however, because certainly habitat diversity and distance
to the source population are of major importance. The largest West
Indian islands support the highest numbers of species of Columbidae
(Jamaica 10, Cuba 11, Hispaniola 10), but these islands also have greater
relief and habitat diversities than are found on more xeric, flatter West
Indian islands, such as the Caymans. Furthermore, on no island are the
several dove and pigeon populations and densities necessarily the same;
Columba inornata and Geotrygon passerina of Jamaica are both relatively
rare, as compared with the common Columbina passerina and Columba
leucocephala on that island. Relative population densities of the doves
and pigeons on the Cayman Islands seem to be, in decreasing order of
abundance: Zenaida asiatica, Columba leucocephala, Columbina pas-
serina, Z. aurita, and Leptotila jamaicensis (the latter restricted to Grand
Cayman). Thus in terms of a given island, it is ecologically misleading
merely to enumerate species without also considering relative or absolute
abundances and habitat diversity.
The question posed here is: how can each of the Cayman Islands sup-
port its complement of four or five species of columbids? Or, how do
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
these columbids partition resources so as to permit (1) sympatry on the
island and (2) syntopy in given ecological formations? It is initially
important to admit the paucity of information on their breeding habits,
seasonality of breeding (see Table 13), and feeding behavior. Never-
theless, from the available information summarized in Table 15, it ap-
pears that the columbid species partition resources in two principal
fashions-by habitat selection and by food type. As breeding birds, no
more than three species are found in a given ecological formation (Tables
3-10). All these species are basically frugivorous and, for the syntopic
species, limited stomach analyses (see Appendix III) do not indicate
any marked interspecific differences in food habits.
TABLE 15.-NICHE CHARACTERISTICS OF DOVES AND PIGEONS ON GRAND CAYMAN.
1 Leptotila jamaicensis 1
BS
2 Columba leucocephala FH 2
(H),BL BS,BL
3 Zenaida aurita FT FH,FT
4 ..BL,H (BS) BL,(BS)
4 Zenaida asiatica FT? FT? FT?
BS,BL BS,BL BS,BL BS,BL
5 Columbina passerina H, FT H,FH FT (H),FH
FT FT
Key: BS (body size), BL (bill length), H (habitat), FH (feeding height), FT
(food type). A symbol in parentheses indicates that the difference is poorly
developed.
WOODPECKERS (PICIDAE).-The two resident woodpeckers (Colaptes
auratus and Centurus superciliaris) of Grand Cayman were earlier be-
lieved to be ecologically separated, chiefly on the basis of habitat, with
Colaptes supposedly being a bird of the mangrove swamps and Centurus
most common around human habitations (Johnston 1970). Subsequent
intensified study by Alex Cruz and me showed, however, that these species
were not necessarily separated by habitat differences. As seen earlier
in the distribution analyses of birds in the various ecological formations
(Tables 3-10), clearly both woodpeckers occur together in most of these
wooded formations, although Colaptes predominates in mangrove
swamps. Overall, the differences in habitat choice between these two
woodpeckers are only of minor importance (Table 16).
The principal niche differences between these species are in feeding
methods and food type. Colaptes is essentially a probing and drilling
1975
BULLETIN FLORIDA STATE MUSEUM
TABLE 16.-NICHE CHARACTERISTICS OF CLOSELY RELATED RESIDENT BIRDS OF THE
CAYMAN ISLANDS.
body bill feeding feeding food**
size length habitat height methods type
Colaptes auratus1 2 2 1 3* 4*
Centurus superciliaris (
Tyrannus dominicensis 1 1
Tyrannus caudifasciatus 1 1 4 4 4 3
Elaenia martinica 3 4 1 4 4 4
Myiarchus stolidus 1 4
Vireo magister 2 2 ? 2
Vireo crassirostris C 4 4 2 2 2
Vireo altiloquus LC 4 4 2 2 ? ?
CB
Dendroica petechia 2 1 4 4 1 1
Dendroica vitellina
* Differences: (4) strongly developed, (3) moderately well developed, (2) poorly
developed, (1) absent or negligible.
** Based chiefly upon percent differences in animal and vegetable material and not
upon different species of animals or plant materials consumed.
woodpecker, whereas Centurus spends much of its time in gleaning
arthropods (especially in bromeliads) and taking small fruits. Analyses
of stomach contents indicate differences in foraging techniques. From
Appendix III it can be seen that 19 Colaptes fed heavily (97% of the
diet) on arthropods, mostly on ants and termites. Although Centurus
has a diet high in insects (56% ), especially beetles, approximately one-
half of its diet is fruit. In fact, the frequent occurrences of this wood-
pecker at house sites are closely connected to the fruit-bearing trees,
especially papaya, cultivated there. Of interest also are the "herptiles"
taken by Centurus, the Hyla most likely captured by probing into brome-
liads.
FLYCATCHERS (TYRANNIDAE).-Of all the closely related birds on the
Cayman Islands, the four resident species of Tyrannidae possess the most
interesting sets of ecological isolating features. No two species-pairs
have evolved precisely the same mechanisms, which are based on dif-
ferences in habitat choice, feeding height, feeding methods, and food
types (Table 16). Of particular significance is the fact that one of these
"flycatchers," Elaenia martinica, is chiefly a frugivore (Appendix III),
and as such does not compete with the other three insectivorous tyran-
nids. Also, Tyrannus caudifasciatus consumes both lizards and frogs, a
predatory habit not shared with the other tyrannids. Elaenia martinica
is one of the most widespread and abundant members of the resident
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
avifauna (Tables 3-10) and is also extremely belligerent both intra- and
interspecifically. In the hundreds of interspecific behavioral encounters
I observed, it appeared that Elaenia was always dominant. Among the
four species, within-habitat feeding strata clearly differed from species
to species (Figure 18); in no case did two species spend more than about
20 percent of the time feeding at the same stratum, and even when they
did, each selected different foods.
In summary, the tyrannids provide a classic case of the partitioning
of environmental resources such that coexistence of four resident forms
is possible on Grand Cayman. Elaenia is chiefly a frugivore, whereas
the others are chiefly insectivorous; Tyrannus dominicensis is a large
insectivore feeding at tree-top levels in open sites around towns and
100-
Z 75-
LaJ
LUJ
LL
Ld
5o-
LL
0
I--
25-
W
Q0-
0-
FIGURE 18.-Feeding
I I I I
0-Im 1-3m 3-6m >-6m
heights and percentages of time feeding for flycatchers.
0-0 Elaenia GC
A- Elaenia CB
0*- Myiarchus GC
A Tyrannus dominicensis CB
1975
BULLETIN FLORIDA STATE MUSEUM
houses; T. caudifasciatus is common in wooded formations where it
consumes large insects and small vertebrates; Myiarchus is an inter-
mediate-sized woodland and "edge" species that is more generalized in
food habits (insectivorous and frugivorous) than the other species.
VIREOS (VIHEONIDAE).-The three resident vireos of the Caymans
proved difficult to analyze for interspecific ecological differences, and the
present summary should be considered tentative. As is true elsewhere in
the distribution of the genus Vireo where sympatry and/or syntopy are
evident, the usual case is the presence of an arboreal member of the
subgenus Vireosylva and a thicket-inhabiting member of the subgenus
Vireo (Hamilton 1962). Presumably these stratal and perhaps other
differences effectively minimize interspecific competition.
Over the years of observations on Grand Cayman, however, it be-
came apparent that V. crassirostris, although the only vireo inhabiting
thickets and shrubby fields, coexisted with V. magister in early logwood
successional stages. A similar relationship existed between V. crassirostris
and V. altiloquus on the other two islands. Indeed, through the seral
stages into a climax limestone forest formation, both forms could be
found. Frequently both species were observed or collected in the same
strata between 3 and 5 m. As a rule, V. crassirostris was most frequently
encountered below about 4 m, whereas both V. magister and V. altiloquus
tended to prefer foraging positions from 5 to 15 m.
The relatively large number of stomachs examined (11 for V. crass-
irostris and 9 for V. magister) and taken at the same season revealed
food differences that (1) reinforce feeding strata differences and (2)
provide the key to avoidance of interspecific competition (see Appendix
III). V. crassirostris consumes a higher percentage (77%) of animal
food than V. magister (51% ). Probably the species of Coleoptera or
other taxa mutually eaten by both vireos were in fact different, although
the insect fragments found in their stomachs could not be identified be-
low the family level.
Thus, the two vireo-pairings on these islands showed closer ecolog-
ical niche characteristics than the other closely related resident avifauna,
and should certainly be subjected to a more detailed scrutiny.
WOOD WARBLERS (PARULIDAE).-The two resident warblers (Den-
droica petechia and D. vitellina) were initially believed to be habitat
restricted, with D. petechia being a mangrove swamp species and D.
vitellina occurring principally in thickets, shrubland, and early logwood
forests. Further observations showed that habitat separation was not
complete because D. petechia is now known to be more widespread,
occurring as a breeding bird in six of the upland ecological formations
(Tables 3-10). On the other hand, D. vitellina is found in only four of
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
these. Attention must be given to the relative population densities of
each species in each formation: where petechia is very common (sea
grape-almond woodland and mangrove swamps), D. vitellina is absent;
where D. vitellina is fairly or very common logwoodd, logwood-thatch
palm-red birch, and limestone forests), D. petechia is at best uncommon.
To some extent then, these species are segregated by habitat.
Feeding heights of these warblers are also important, D. vitellina
choosing the lower strata up to about 3 m, and D. petechia usually oc-
curring from 3 m upwards. At present no available data support an
hypothesis that the two species either have different foraging habits or
select different foods.
PREDATION AND POPULATION CONTROL
Of special importance for the bird populations of the Cayman Islands
is the obvious paucity of vertebrate predators. Grant (1940) docu-
mented systematics of the herpetofauna but devoted little attention to
their biological features. He did note (p. 49), however, that the colubrid
snake Alsophis angulifer is "diurnal, active, feeds on lizards, frogs, birds
S. .Lewis took a number of specimens in the tops of trees, one over 30
feet off the ground . [where they were feeding on] Hylas." On Cay-
man Brac a specimen of this snake, reported by Grant (p. 50), had a
honeycreeper in its stomach. In my several years of observing and col-
lecting on these islands, I never encountered an Alsophis pursuing birds
or with a bird in its stomach, nor did any of the local people indicate an
ornithophagous habit for this species. Still, Grant does provide some
evidence that the snake at least occasionally preys on birds. The abun-
dant Anolis lizards, especially A. conspersus, might prey on birds' eggs
(there is no concrete evidence) because elsewhere in the West Indies
Anolis occasionally eats eggs of honeycreepers (Biaggi 1955). No mam-
malian carnivores occur on the Caymans. Both Mus musculus and Rattus
(mostly R. rattus but some R. norvegicus) are found, but they are only
locally abundant. Specimens of these mammals have been collected or
observed chiefly in areas of human habitation and not in the "wilder"
portions of the islands.
A conspicuous hiatus in the avifaunal trophic structure is a diurnal
predator. In winter an occasional hawk (Circus cyaneus, Falco sparver-
ius and F. columbarius) does visit the islands (Johnston et al. 1971).
The food habits of these predatory birds in the Caymans are unknown,
although elsewhere birds do constitute some portion of their diets. But
even if they did prey on an occasional (or more) land bird in winter,
the small numbers and infrequent occurrences of these hawks would
1975
BULLETIN FLORIDA STATE MUSEUM
tend to minimize their predation pressure on the avifauna. On the other
hand, the resident Barn Owl (Tyto alba) has been shown recently to
be a potent predator on birds (Johnston 1972), even though its numbers
are low. The regurgitated pellets of these owls taken from five widely
scattered sites on Grand Cayman, and quite likely representative of five
different individuals, revealed a high proportion of avian remains among
their prey, ranging in size from a medium-sized egret (Egretta) to a
honeycreeper (Coereba). Furthermore, the prey items included at least
eight genera of the resident birds. These data suggest that of the actual
or potential vertebrate predators on the avifauna only Tyto alba is espe-
cially important, and I suspect this predator represents the greatest single
biological control of the resident avifauna.
The ubiquitous hermit and land crabs are clearly potential scavengers
or predators of any terrestrial animal life. Only the Nighthawk (Chor-
deiles minor) is a consistent ground-nesting bird on the Caymans, how-
ever, and because this species is scarce and breeds only in bare fields
where crabs are also scarce, it appears highly unlikely that even this
bird, its eggs, or young would be preyed upon by the crabs. Interest-
ingly, where land crabs are most abundant on the islands (rocky barren
roadsides and limestone forests), no ground-nesting birds are known,
unless it is a very occasional dove (Columbina passerina or Zenaida
aurita).
The widespread and abundant Coereba flaveola is conspicuous
throughout the Caymans and elsewhere in its range. In most West In-
dian island avifaunas, it is the most abundant terrestrial resident species.
Controlling mechanisms for this species were documented by Gross
(1958) and include bird predators (Quiscalus, Crotophaga) as well as
ants and lizards. In the absence of concrete evidence, we can only as-
sume that similar predators prey on Coereba in the Cayman Islands.
Coereba is an occasional victim of the uncommon Barn Owl (Appendix
III).
The extent to which other biological and physical factors exercise
any control on population size of birds is as yet unassessed. For example,
for the Caymanian avifauna no quantitative data are available on annual
population fluctuations, clutch size, hatching success, fledging success, or,
indeed, natality rate for any bird species especially in comparison with
other insular or mainland populations. Two species are increasing in
numbers and range in the Caymans, Mimus polyglottos and Zenaida
asiatica. Conversely, the only documented recent losses there are of
Mimocichla ravida and Icterus leucopteryx bairdi; causative factors bear-
ing on their extinctions have been discussed in an earlier section.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
A GENERAL ASSESSMENT OF FEEDING ECOLOGIES AND
HABITAT DISTRIBUTIONS
It is instructive now to generalize and summarize data on feeding
ecologies or feeding niches of the resident terrestrial avifauna. As shown
in Table 17, most of the bird species (57% ) are arboreal foragers, either
on arthropods or fruits. Furthermore, with the expected exception of
pastures and cultivated areas, these same species are each widely dis-
tributed in the seven upland formations and have comparable frequency
of occurrence and relative abundance therein. Conversely, ground-feed-
ing forms (21'i ) are relatively less common as a whole in the Caymans
and are virtually restricted to the non-forested formations. The latter
distribution strongly suggests the scarcity of insects and seeds on the
ground in the several forest formations. Indeed, ground cover is notice-
ably scarce in the several forest formations due to a combination of
factors (edaphic karst topography, light penetration). The relatively
high proportion of arboreal insectivores and frugivores, augmented by
the timber-probing and -gleaning woodpeckers would be expected on
islands, such as the Caymans, where forest formations of several types
predominate in areal extent (see Figs. 1-3).
Bird species diversity is a known function of habitat or plant species
diversity. Although plant species diversity was not determined quantita-
tively in the present study, it is nonetheless empirically true that in the
comparisons of avifaunal compositions of the several ecological forma-
tions, bird species diversity does attain its peak in those forest formations
with the greatest plant diversity. Complexity of floristic composition
(presence of many codominant trees vs. one or two dominants, height of
vegetation, some semblance of stratification, etc.) may be sequentially
arranged in descending order (number of bird species in parentheses)
as follows: towns and house sites (20), limestone forests (17), logwood-
thatch palm-red birch forest (15), sea grape-almond woodland (16),
mangrove swamps (11), pure logwood forests (11), and pastures and
cultivated areas (11). A relationship between number of terrestrial bird
species and habitat complexity is implied by these data.
TAXON CYCLES
A subject of recent interest to some island biogeographers is that of
taxon cycles, and for the West Indian avifauna these have been explored
generally and in detail by Ricklefs and Cox (1972). Whether an anal-
ysis of taxon cycles for individual small islands or archipelagos is mean-
ingful (see Ricklefs 1970, for Jamaica) is a moot point because of great
areal and relief differences in large island groupings, but an attempt at
TABLE 17.-FEEDING ECOLOGIES AND HABITAT DISTRIBUTIONS OF RESIDENT TERRESTRIAL SPECIES ON GRAND CAYMAN.
Total Pastures Towns Sea Logwood-
Species & and Grape- Pure Thatch Palm- Lime-
Feeding Avail- Cultivated House Almond Logwood Red Birch stone Mangrove
Ecology able Areas sites Woodland Forests Forest Forests Swamps
Predator on vertebrates 1 1 1
Aerial Insectivore 2 1(3)* 1(1) 1(1)
Foliage feeding-nectar 1 1(4) 1(4) 1(4) 1(3) 1(4) 1(3)
Foliage feeding-arthropods 8 2(3) 6(10) 4(8) 6(14) 7(15) 7(11) 4(10)
(chiefly insects)
Foliage feeding-fruits/seeds 8 2(3) 5(11) 5(11) 1(1) 5(8) 7(13) 4(7)
Timber probing-insects 2 2(2) 2(2) 1(1) 2(3) 2(4) 2(2)
Ground feeding-arthropods 3 3(9) 2(6) 1(1) 1(2)
(chiefly insects)
Ground feeding-
other invertebrates 1 1(1)
Ground feeding-seeds 2 2(4) 2(5) 1(1) 1(1)
*Figure in parentheses= sum of number of species X total abundance scores (see footnote of Table 18)
JOHNSTON: CAYMAN ISLAND AVIFAUNA
such an analysis for the three Cayman Islands has been undertaken, a
summary of which appears in Table 18. There appears, first of all, to be
only a weak correlation between feeding ecology and early stages of the
taxon cycle, namely that the presumed recent colonizers (Stage I) are
mainly either frugivores or omnivores. On the other hand, other char-
acteristically frugivorous birds, plus some insectivores, have also been
classified as Stage IV forms. As a rule, specific feeding ecology cannot
be closely correlated with a stage in the taxon cycle, at least for the
Cayman Island avifauna. There is, unfortunately, no available informa-
tion on food habits of Mimocichla ravida and Icterus leucopteryx, the
two recently extinct birds from these islands, although it is certainly true
that if this study had been made 40 or more years ago, both of these
birds would have been in Stage IV using the criteria of Ricklefs (1970).
Both were known, for example, to be quite restricted in habitat prefer-
ences and areal distribution on Grand Cayman.
Some problems arise in subjectively assigning a given bird species to
a given stage in the taxon cycle, especially as regards Stage IV. Ricklefs
(1970: 475) gives this definition: "The last stage of the cycle, before
going extinct or recycling, is the endemic population. As the cycle pro-
gresses, populations move from marginal coastal habitats into more
central and montane habitats." Similarly, Ricklefs and Cox (1972: 195)
note: "Finally, descendant populations, often subspecifically or specifi-
cally distinct, are restricted to small refugia." The problems in diagnosing
taxon cycle stages for the Cayman Island avifauna condense to two major
points. First, as described previously, these islands have neither montane
habitats nor discreet small refugia, unless in the latter case one considers
the mature, more-or-less inland limestone forests. Second, these three
islands currently have no endemic species of birds, but, according to
Bond (1956) and Johnston et al. (1971), do contain 13 species with
endemic subspecies. It is of interest to recall that earlier taxonomists
(for example, Cory 1886) regarded seven of these as distinct species.
Based upon the contemporary belief that these (see Table 18) are all
well-marked, distinct subspecies, endemic to one or more of the three
islands, I am tentatively assigning the 13 forms to Stage IV in the taxon
cycle. Their occurrences on the individual islands were outlined earlier
by Johnston et al. (1971).
Taxon cycles for the Caymanian avifauna may be compared, albeit
with some qualification, with those of Jamaican birds (Ricklefs 1970) and
Solomon Island birds (Greenslade 1968). Although the Cayman Islands
currently contain no endemic species, Jamaica does have 26 such species,
many of which (a) occur in the interior montane forests and (b) are in
Stage IV. Ricklefs (1970) gave 14 as the number of Stage IV endemics,
1975
BULLETIN FLORIDA STATE MUSEUM
TABLE 18.-FEEDING ECOLOGIES, STAGES IN TAXON CYCLE, AND ABUNDANCE OF
RESIDENT TERRESTRIAL SPECIES.
Feeding Stage in Totalt Average No. of
Species Ecologyf Taxon Cycle Abundance Abundance habitats
Columba leucocephala FF I 8 2.0 4
Zenaida aurita FF I 4 1.3 3
Zenaida asiatica FF(?) I 6 3.0 3
Columbina passerina GS II 5 2.5 2
Leptotila jamaicensis FF IV 1 1.0 1
Amazona leucocephala FF IV 2 2.0 1
Coccyzus minor FI,GI(?) II 2 1.0 2
Crotophaga ani GI,GV,GS I 6 3.0 2
Chordeiles minor AI I 1 1.0 1
Colaptes auratus TPI,FF IV 8 1.3 6
Centurus superciliaris TPI,FF,TV IV 5 1.7 3
Tyrannus dominicensis AI I 7 2.3 3
Tyrannus caudifasciatus FI,TV,FF IV 4 1.3 3
Myiarchus stolidus FI,FF III 8 1.6 5
Elaenia martinica FF,FI IV 17 3.4 5
Mimus polyglottos GI,GO,GS I 10 2.5 4
Mimocichla plumbea unknown IV 2 2.0 1
Vireo crassirostris FI,FF II 6 1.5 4
Vireo altiloquus unknown I 2 2.0 1
Vireo magister FI,FF IV 12 2.4 5
Dendroica petechia FI II 10 2.0 5
Dendroica vitellina FI,FF IV 12 3.0 4
Coereba flaveola FN,FI IV 22 3.7 6
Spindalis zena FF IV 5 1.7 3
Quiscalus niger FI,TV,FF IV 13 2.2 6
Tiaris olivacea GS II 5 1.7 3
Melophyrrha nigra FF,FI IV 5 1.7 3
f Adapted from Salt (1953, 1957) and Orians (1969): AI, aerial insectivore; PV,
predator on vertebrates; PI, predator on invertebrates; FN, foliage feeding on
nectar; FI, foliage feeding on insects and spiders; FF, foliage feeding on fruits
(and/or seeds); TPI, timber probing for insects; TV, timber gleaning for verte-
brates; GV, ground feeding on vertebrates; GI, ground feeding on insects and
spiders; GO, ground feeding on other invertebrates (crustacea, mollusks); GS,
ground feeding on seeds. When two or more feeding ecologies are given for a
bird, the predominant type is listed first.
SScored by conversion of U (uncommon)= 1, FC (fairly common)=2, C (com-
mon) =3, VC (very common)=4. See individual census tables for each habitat
concerned.
Seven habitats available during breeding season.
Stage of Taxon Cycle
I II III IV
Number of species and subspecies 8 5 1 13
Mean number of habitats occupied 2.6 3.2 5.0 3.6
Mean total abundance 5.5 5.6 8.0 8.4
Mean of the average local abundance 2.1 1.7 1.6 2.1
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
but his censuses did not include the endemic columbids, parrots, cuckoos,
and hummingbirds. Ricklefs' 14 Stage IV forms, as compared with the
Caymanian 13, were less widespread in habitat occupancy and less
abundant than Stage I types. The converse is true for the Cayman birds
(Table 18). Probably these differences are at least partially explicable
in terms of the likelihood that the Jamaican avifauna is older than that
of the Cayman Islands, has available well-developed refugia in the
montane forests, and occupies a much larger island with greater relief and
habitat diversity.
An interesting ecological question is whether or not immigrating and
hence colonizing species on islands are found chiefly in "marginal habi-
tats." Because so many factors potentially determine the success of
colonization (competition, adaptability of the propagule, niche avail-
ability, etc.), it is important to speculate on, or document, an ecological
habitat that fits the needs of most immigrating forms. Another way of
examining this problem is to assess the habitat distribution of species in
Stage I of a taxon cycle. Do they, indeed, "occupy marginal habitats
at the center of their expansion . [and] exhibit 'ecological release'
on small islands due to lack of competition" (Ricklefs 1970)? For Solo-
mon Island birds, Greenslade (1968) concluded that "the habitats of the
species suggest that expansion occurs mainly in coastal situations while
the rest of the cycle involves a shift to lowland rain-forest and, increas-
ingly in the final stage, to montane forest."
The Cayman Islands have neither rain forests nor montane forests.
In terms of secondary succession they do have fields and pastures, early
logwood forests, logwood-thatch palm-birch forests, and a (presumed)
climax limestone forest. If one can equate the fields and pastures (many
of which are at least near the coast) with marginal or coastal habitats
as used by Greenslade, Ricklefs, and others, then the distribution of
breeding birds of each taxon cycle stage in this and later successional
stages should provide answers to the questions posed above. From data
in Tables 12, 17, and 18 it can be determined that 50% of the Stage I
birds breed in the fields and pastures and the other 50% occur in the
later forested seral stages. All of the Stage II birds are restricted to
early seral stages, and at least 757 of the Stage IV types are in the
later seral stages. Thus even in the absence of montane forest refugia
on the Cayman Islands, the ecological distributions of the resident
avifauna partially support the idea that the most recent colonizing species
are found primarily in so-called marginal habitats, and the "older" en-
demics are more characteristic of interior forests.
On the other hand, colonization of these islands has yet a different
facet. What considerations should be given to the presently forest-
1975
BULLETIN FLORIDA STATE MUSEUM
adapted Stage IV species such as the Centurus woodpecker, Amazona
parrot, and vireos? At the time that each form invaded these islands,
did each undergo a taxon cycle beginning in a marginal habitat and
ultimately become associated with the mature limestone forest? Con-
temporary data do not support such a possibility. Rather David Lack
(in litt.) appears to have a more plausible explanation to the effect that
potential colonists on nearby islands would have to be best adapted to
conditions on the Cayman Islands. For example, the Amazona parrot
on the Caymans is especially characteristic of limestone forests (Table
8); on Cuba its conspecific is found in remote woodlands from mountains
to sea level. Elaenia martinica, so widespread and abundant in the
Caymans, is adapted to arid lowland woodlands elsewhere in the Carib-
bean region. Mimocichla plumbea of Cayman Brac, Cuba, and Hispani-
ola is a bird of forested regions, plantations, and gardens. These and
other examples strongly support the contention that colonization of new
islands is not necessarily restricted to Stage I species but could be suc-
cessful for species in any taxon cycle stage, provided they were pre-
adapted to and could find suitable ecological conditions on a new island.
HABITAT DISTRIBUTIONS OF INSULAR AND MAINLAND
BIRD POPULATIONS
The extent to which breeding bird species occupy all habitats avail-
able to them has been discussed at least in part by MacArthur and
Wilson (1967, Chap. 5). Clearly, some combination of competition,
predators, immigration, vegetational complexity, and other factors play
significant roles in restricting bird species to given habitats. In some
insular avifaunas that have been investigated intensively (e.g., those of
Puerto Rico) individual bird species have undergone an ecological ex-
pansion into many habitats, whereas species in the Panamanian tropical
forests are much more restricted to a small number of habitats. As a rule,
if an avifauna can specifically occupy all or most of the habitats avail-
able, it can be described as eurytypic or "generalized;" if the species
occupies only a small number of available habitats, it can be considered
stenotypic or "specialized."
Some interesting figures emerge from the habitat distribution of the
Grand Cayman avifauna. Considering seven upland terrestrial forma-
tions (Tables 3-10), the distributions of the 24 species occurring therein
(exclusive of the wide-ranging Barn Owl and Nighthawk) are as follows:
1 species, in only 1 formation
5 species, in only 2 formations
5 species, in only 3 formations
5 species, in only 4 formations
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
3 species, in only 5 formations
4 species, in only 6 formations
1 species, in all 7 formations
By extrapolation one arrives at an average figure of 3.9 habitats per spe-
cies. Data for mainland populations (Fig. 19) are in sharp contrast; for
example in Georgia the figure is 1.6 habitats per species (Johnston and
Odum 1956) and for Panama about 1.3 (MacArthur et al. 1966). On
Puerto Rico the value is 2.5 (Recher 1970) and Jamaica 2.9 (Ricklefs
1970). For Grand Cayman the relatively large number of habitats oc-
cupied by each species indicates either reduced interspecific competition
per se, the evolution of mechanisms to avoid competition, or both.
These properties are discussed at length in the previous section on com-
petition.
To exemplify these features more generally, a number of published
breeding censuses from typical island and mainland populations have
been reviewed with respect to number of available habitats occupied by
the species. This assessment is graphically summarized in Figure 19.
In regions where relatively few habitats are available (three or four),
mainland bird populations tend to be specialized, and as more habitats
become available (five or six), the mainland populations tend to become
even more specialized. Large islands, such as Puerto Rico and Jamaica,
include bird populations that are intermediate between the extremes of
generalization and specialization. On small islands (including Grand
Cayman) the bird populations reach peaks in generalization. Grand
Cayman is unique in this feature by having the highest known value of
mean number of habitats per species, namely 3.9.
Lack concluded (1969: 207) that ". . the small numbers of resident
bird species on islands are due . to ecological limitations, to which
the islands' birds are often specially adapted, and which enable fewer
species with broader niches to exclude a greater number of specialists."
If I interpret this sentence correctly and if "ecological limitations" are
chiefly those of habitat diversification, then the graphic presentation of
Figure 19 supports his contention only for small islands. In fact, with
respect to number of habitats occupied by each species, the larger islands
of Puerto Rico and Jamaica, with their large number of available habitats,
resemble the mainland populations. Grand Cayman, Bermuda, and St.
John each tend to have (fewer?) species with "broader niches." The
extent to which such ecological generalization might "exclude a greater
number of specialists" is certainly undemonstrable from present evidence.
Another, yet different, approach to this subject is Simberloff's species/
genera ratios (1970). Similar S/G values for large and small islands
would indicate, for example, that competition is at least as intense on the
1975
PR JA
A A
Mich. Me.
0 0
CR Al.
00
Ga. Al. E
CD A
N.C. Ga. SJ
OOA
I I I I I
O I 2 3 4
MEAN NUMBER HABITATS/SPECIES
FIGURE 19.-Habitat distributions of insular and mainland bird populations. Pa.=
Panama (MacArthur, Recher, and Cody 1966); PR=Puerto Rico (Recher 1970);
JA= Jamaica (Ricklefs 1970); Mich.=Michigan (Kendeigh 1948); Me.=Maine
(Stewart and Aldrich 1952); CR= Costa Rica (Orians 1970); Al.= Alaska (Kessel
and Cade 1958, Williamson et al. 1966); Ga.= Georgia (Johnston and Odum 1956);
B=Bermuda (Crowell 1962); N.C.=North Carolina (Odum 1950); SJ=St. John
(Robertson 1962).
JOHNSTON: CAYMAN ISLAND AVIFAUNA
small islands. Therefore, based on comparative data for the Caymans
(Grand Cayman=1.18, Little Cayman=1.25, Cayman Brac=1.27) and
those of Cuba (S/G=1.26) competition is of about equal intensity on
the Caymans and Cuba. As Simberloff indicated, small islands can sup-
port many similar species, and insular avifaunas will likely contain species
that occupy more habitats because of less competition within habitats.
THE WINTER AVIFAUNA
Influences of the many North American migrant birds on a resident
tropical avifauna have not been widely investigated (but see, for example,
Eaton 1953 and Willis 1966). Despite intensive studies by a few in-
vestigators, most of the major questions remain unanswered or poorly
documented. Thus the interrelationships permitting coexistence between
migrants and residents require close scrutiny, but on a protracted basis
in the field. On the Cayman Islands a detailed investigation was not
undertaken, but a number of general and interesting ecological features
have been at least partially elucidated.
As indicated elsewhere in this paper, the resident terrestrial avifauna
of all the Caymans includes some 27 species; in winter at least an addi-
tional 20 reasonably common species also occur. Some 10 other species
are currently known from three or fewer winter records (c.f. Johnston
et al. 1971), but in time some of these forms might prove to be more
common. For the most part the wintering birds occur in loose mixed-
species flocks (especially parulid warblers), a habit also reported for
Cuba (Eaton 1953) and Puerto Rico (Recher 1970). Whether any in-
dividuals are sedentary and maintain winter territories remains unproven
for the Cayman Islands, but observations of at least the Seiurus warblers
suggest this to be the case. The 20 wintering species are found on the
islands mainly in the wooded ecological formations-logwood and lime-
stone forests, mangrove swamps, and the sea grape-almond woodland.
Some of these birds occur in smaller numbers in the town-and-house site
formation, whereas the two wintering sparrows (Passerculus sandwich-
ensis and Ammodramus savannarum) are both restricted to pastures
and grassy fields. In the wooded formations an observer is immediately
impressed by the quantitative predominance of the North American
migrants. In Table 4, for example, note that the terrestrial migrant
species outnumber the breeding residents by 13:8 in mangrove swamps.
From these data and field observations, some immediate questions arise.
What ecological features permit coexistence between migrants and resi-
dents? What role does seasonal availability of food play? How do
1975
BULLETIN FLORIDA STATE MUSEUM
the two groups, corporately and individually, partition food resources?
To what extent is behavior (territoriality, if it exists, and aggression)
important in these syntopic relationships?
In the first place, the augmentation of a rather depauperate resident
population in the mangrove swamps by wintering migrants strongly
suggests two things: (1) during the breeding season there are probably
unoccupied feeding niches or limited food resources in mangrove swamps,
assuming that (2) a reasonably constant annual food supply is available.
No data have been assembled on food resources; however, it may be
noted, by way of example, that in mangrove swamps foliage-gleaning
insectivores are represented in summer by one resident (Dendroica
petechia), whereas in winter D. caerulescens, Parula americana, Seto-
phaga ruticilla, and others also occur. (Multispecific warbler flocks in
winter are well known from other Caribbean islands, such as Puerto Rico
[see Recher 1970: E-78].) This winter increase of the avifauna at a
single trophic level strongly suggests an abundant insect food supply dur-
ing that season. Furthermore, in the mangrove swamps a number of
feeding niches are filled only in winter-trunk and branch-gleaning for
small insects (by Mniotilta varia), aerial-feeding small insectivores
(Setophaga ruticilla, Polioptila caerulea), ground-feeding insectivores
(Seiurus noveboracensis and S. aurocapillus). Possibly insects are less
abundant in these swamps in summer than in winter, but I suspect there
is a high annual insect population that is simply underexploited by the
resident birds in summer. In other words, some feeding niches are un-
filled during the summer. Similar arguments might be made, inciden-
tally, for the other ecological formations.
Competition for food, at least in the form of overt aggressive pur-
suits, does not appear to be very evident between the residents and mi-
grants. The reason for this is at least partially explained by the fact that
feeding ecologies of residents and migrants are generally dissimilar. The
resident insular birds such as doves, woodpeckers, cuckoos, the parrot,
flycatchers, and the bananaquit, have virtually no competitors among the
wintering migrant birds. When active pursuits were observed, they were
infrequent, of short durations, and appeared to involve intraspecific ac-
tions among the residents (such as two Dendroica petechia) or interspe-
cific and intraspecific actions among the migrant warblers or other species.
(Chases were often so rapid that neither bird could be positively identi-
fied.) Also central, localized feeding (fruiting) trees so characteristic of
other tropical forests are apparently not an important ecological com-
ponent in any of the Cayman Island formations; hence, competition at
such a localized site is virtually nonexistent.
In summary, it appears that the large number of wintering birds in-
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
fluence the resident species very little, chiefly because the wintering
forms usually occupy different feeding niches than the residents. That
is, migrants rely upon a food resource not fully exploited by the residents,
a feature previously noted in tropical regions by Morel and Bourliere
(1962) and Willis (1966). On the other hand, migrants in the Caymans
do not necessarily favor secondary habitats or disturbed areas; hence,
they do not conform to the "irregularity principle" of Willis (1966)
except with reference to a supposed abundant winter food supply.
Nevertheless, the wintering birds, many of which are insectivorous, prob-
ably do play a significant trophic role in controlling insect populations.
LITERATURE CITED
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23(4): 359-412.
Biaggi, V., Jr. 1955. The Puerto Rican Honeycreeper (Reinita) Cocreba flaceola
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Bond, J. 1934. The distribution and origin of the West Indian avifauna. Proc.
Amer. Phil. Soc., 73(5): 341-349.
1956. Check-list of birds of the West Indies. Acad. Nat. Sci. Phil.,
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1958. Third supplement to the check-list of birds of the West Indies
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1966a. Affinities of the Antillean avifauna. Carib. J. Sci., 6(3-4):
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1967. Twelfth supplement to the check-list of birds of the West
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1971. Birds of the West Indies. Collins, London. 256 pp.
Borror, D. J. and D. M. DeLong. 1964. An introduction to the study of insects.
Iolt, Rinehart, and Winston, New York. 819 pp.
Clench, H. K. 1964. Remarks on the relationships of the Butterflies (excluding
Skippers) of the Cayman Islands. Occ. Pap. Mollusks, Mus. Comp. Zool.,
2(31): 381-382.
Clench, W. J. 1964. Land and freshwater Mollusca of the Cayman Islands, West
Indies. Occ. Pap. Mollusks, Mus. Comp. Zool., 2(31): 345-380.
Cory, C. B. 1886. Descriptions of thirteen new species of birds from the island of
Grand Cayman. Auk, 3: 497-501.
Crowell, K. L. 1962. Reduced interspecific competition among the birds of Ber-
muda. Ecology, 43: 75-88.
Diamond, J. M. 1969. Avifaunal equilibria and species turnover rates on the
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Dingle, H. and C. P. M. Khamala. 1972. Seasonal changes in insect abundances
and biomass in an East African grassland with reference to breeding and mi-
gration in birds. Ardea, 59: 216-221.
Doran, E., Jr. 1954. Land forms of Grand Cayman Island, British West Indies.
Texas J. Sci., 6(4): 360-377.
Eaton, S. W. 1953. Wood warblers wintering in Cuba. Wilson Bull., 65(3): 169-
174.
English, T. M. S. 1916. Notes on some birds of Grand Cayman, W. I. Ibis, (Ser.
10), 4: 17-35.
1975
BULLETIN FLORIDA STATE MUSEUM
Grant, C. 1940. The herpetology of the Cayman Islands. Bull. Inst. Jamaica, Sci.
Series, No. 2: 1-65.
Grant, P. R. 1968. Bill size, body size and the ecological adaptations of bird
species to competitive situations on islands. Syst. Zool., 17(3): 319-333.
1969. Colonization of islands by ecologically dissimilar species of
birds. Can. J. Zool., 47(1): 41-43.
Greenslade, P. J. M. 1968. Island patterns in the Solomon Islands bird fauna.
Evol., 22: 751-761.
Gross, A. O. 1958. Life history of the Bananaquit of Tobago Island. Wilson
Bull., 70(3): 257-279.
Hamilton, T. H. 1962. Species relationships and adaptations for sympatry in the
avian genus Vireo. Condor, 64: 40-68.
Immelmann, K. 1971. Ecological aspects of periodic reproduction. Ch. 8 in Avian
Biol., Vol. I, ed. by D. S. Farner and J. R. King. Acad. Press, New York, pp.
341-389.
Johnston, D. W. 1969. The thrushes of Grand Cayman Island, B. W. I. Condor,
71(2): 120-128.
1970. Niche relationships in some West Indian woodpeckers. Year
Book of the Amer. Phil. Soc., 1970: 323-324.
1972. Food of the Barn Owl on Grand Cayman, B. W. I. Quart. J.
Fla. Acad. Sci., 35: 171-172.
Johnston, D. W., C. H. Blake, and D. W. Buden. 1971. Avifauna of the Cayman
Islands. Quart. J. Fla. Acad. Sci., 34: 145-156.
Johnston, D. W. and E. P. Odum. 1956. Breeding bird populations in relation to
plant succession on the Piedmont of Georgia. Ecology, 37(1): 50-62.
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Michigan. Ecology, 29(1): 101-104.
Kessel, B. and T. J. Cade. 1958. Birds of the Colville River, northern Alaska. Bio.
Pap. Univ. Alaska, No. 2: 83 pp.
Lack, D. 1969. The numbers of bird species on islands. Bird Study, 16: 193-209.
S1971. Ecological isolation in birds. Harvard Univ. Press, Cambridge,
Mass., 404 pp.
Long, R. W. and O. Lakela. 1971. A flora of tropical Florida. Univ. Miami Press,
Coral Gables, Fla., 962 pp.
MacArthur, R. H., H. F. Recher, and M. Cody. 1966. On the relation between
habitat selection and species diversity. Amer. Nat., 100(913): 319-332.
MacArthur, R. H. and E. O. Wilson. 1967. The theory of island biogeography.
Princeton Univ. Press, Princeton, N. J., 203 pp.
Mayr, E. 1965. Avifauna: turnover on islands. Science, 150(3703): 1587-1588.
Mengel, R. M. 1964. The probable history of species formation in some northern
Wood Warblers (Parulidae). Living Bird, 3rd annual: 9-43.
Morel, G. and F. Bourliere. 1962. Relations e6ologiques des avifaunas s6dentaire
et migratrice dans une savane sah6lienne du bas S6negal. La Terre et al Vie,
4: 371-393.
Moynihan, M. 1968. The "Coerebini": a group of marginal areas, habitats, and
habits. Amer. Nat., 102(928): 573-581.
Odum, E. P. 1950. Bird populations of the Highlands (North Carolina) Plateau in
relation to succession and avian invasion. Ecology, 31(4): 587-605.
Orians, G. H. 1970. The number of bird species in some tropical forests. Ecology,
50(5): 783-801.
Paynter, R. A., Jr. 1956. Birds of the Swan Islands. Wilson Bull., 68(2): 103-110.
Recher, H. F. 1970. Population density and seasonal changes of the avifauna in a
tropical forest before and after gamma irradiation. In Odum, H. T., A tropical
rain forest. U. S. Atomic Energy Comm., E 69-E 86.
Richards, H. G. 1955. The geological history of the Cayman Islands. Notulae
Naturae, No. 284: 1-11.
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
Ricklefs, R. E. 1970. Stage of taxon cycle and distribution of birds on Jamaica,
Greater Antilles. Evol., 24(2): 475-477.
Ricklefs, R. E. and G. W. Cox. 1972. Taxon cycles in the West Indian avifauna.
Amer. Nat., 106: 195-219.
Ridgway, R. (and H. Friedmann). 1901-1950. The birds of North and Middle
America. 11 parts. U. S. National Museum, Washington.
Robertson, W. B., Jr. 1962. Observations on the birds of St. John, Virgin Islands.
Auk, 79: 44-76.
Salt, G. W. 1953. An ecological analysis of three California avifaunas. Condor,
55: 258-273.
1957. An analysis of avifaunas in the Teton Mts. and Jackson Hole,
Wyoming. Condor, 59: 373-393.
Schoener, T. W. 1965. The evolution of bill size differences among sympatric
congeneric species of birds. Evol., 19: 189-213.
Schreiber, R. W. and N. P. Ashmole. 1970. Sea-bird breeding seasons on Christmas
Island, Pacific Ocean. Ibis, 112: 363-394.
Schwartz, A. 1969. Land birds of Isla Saona, Republica Dominicana. Quart. J.
Fla. Acad. Sci., 32(4): 291-306.
Simberloff, D. S. 1970. Taxonomic diversity of island biotas. Evol., 24(1): 23-47.
Snow, D. W. and B. K. Snow. 1964. Breeding seasons and annual cycles of Trini-
dad land-birds. Zoologica, 49: 1-39.
Stewart, R. E. and J. W. Aldrich. 1952. Ecological studies of breeding bird popula-
tions in northern Maine. Ecology, 33(2): 226-238.
Swabey, C. and C. B. Lewis. 1946. Forestry in the Cayman Islands. Development
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Wetmore, A. 1927. The birds of Porto Rico and the Virgin Islands. N. Y. Acad.
Sci., 9(4): 109-598.
Whitehead, D. R. and C. E. Jones. 1969. Small Islands and the equilibrium theory
of insular biogeography. Evol., 23(1): 171-179.
Williamson, F. S. L., M. C. Thompson, and J. Q. Hines. 1966. Avifaunal investi-
gations. Chap. 18 in Environment of the Cape Thompson region, Alaska. (N.
J. Wilimovsky, Ed.) U. S. Atomic Energy Comm., 437-480.
Willis, E. 0. 1966. The role of migrant birds at swarms of army ants. Living Bird,
5th annual: 187-231.
BULLETIN FLORIDA STATE MUSEUM
APPENDIX I: SCIENTIFIC AND COMMON NAMES
OF BIRDS APPEARING IN TEXT1
Podilymbus podiceps (Linnaeus). Pied-billed Grebe.
Phaethon lepturus Daudin. White-tailed Tropicbird.
Sula leucogaster leucogaster (Boddaert). Brown Booby.
Sula sula sula (Linnaeus). Red-footed Booby.
Fregata magnificens Mathews. Magnificent Frigatebird.
Ardea herodias Linnaeus. Great Blue Helon.
Butorides virescens maculatus (Boddaert). Green Heron.
Florida caerulea (Linnaeus). Little Blue Heron.
Ardeola ibis ibis (Linnaeus). Cattle Egret.
Casmerodius albus (Linnaeus). Common Egret.
Egretta thula (Molina). Snowy Egret.
Hydranassa tricolor ruficollis (Gosse). Louisiana Heron.
Nyctanassa violacea (Linnaeus). Yellow-crowned Night Heron.
Plegadis falcinellus (Linnaeus). Glossy Ibis.
Dendrocygna arborea (Linnaeus). West Indian Tree Duck.
Anas discors Linnaeus. Blue-winged Teal.
Anas americana (Gmelin). American Widgeon.
Aytlhya affinis (Eyton). Lesser Scaup.
Circus cyaneus (Linnaeus). Marsh Hawk.
Pandion haliaetus (Linnaeus). Osprey.
Falco columbarius Linnaeus. Pigeon Hawk.
Falco sparverius Linnaeus. Sparrow Hawk.
Porphyrula martinica (Linnaeus). Purple Gallinule.
Gallinula chloropus cerceris Bangs. Common Gallinule.
Fulica americana Gmelin. American Coot.
Charadrius semipalmatus Bonaparte. Semipalmated Plover.
Charadrius wilsonia Ord. Wilson's Plover.
Charadrius vociferus Linnaeus. Killdeer.
Squatarola squatarola (Linnaeus). Black-bellied Plover.
Arenaria interpres morinella (Linnaeus). Ruddy Turnstone.
Himantopus himantopus (Miiller). Black-necked Stilt.
Capella gallinago Linnaeus. Common Snipe.
Actitis macularia (Linnaeus). Spotted Sandpiper.
Tringa solitaria Wilson. Solitary Sandpiper.
Tringa melanoleuca (Gnelin). Greater Yellowlegs.
Tringa flavipes (Gmelin). Lesser Yellowlegs.
Catoptrophorus semipalmatus semipalmatus (Gmelin). Willet.
Calidris canutus (Linnaeus). Knot.
Crocethia alba (Pallas). Sanderling.
Limnodromus griseus hendersoni (Gmelin). Short-billed Dowitcher.
Larus atricilla Linnaeus. Laughing Gull.
Sterna hirundo hirundo Linnaeus. Common Tern.
Sterna albifrons antillarum (Lesson). Least Tern.
Thalasseus maximus maximus (Boddaert). Royal Tern.
Columba leucocephala Linnaeus. White-crowned Pigeon.
Zenaida aurita zenaida (Bonaparte). Zenaida Dove.
Zenaida asiatica (Linnaeus). White-winged Dove.
Columbina passerina insularis (Ridgway). Ground Dove.
Leptotila jamaicensis collaris (Cory). White-bellied iDove.
Amazona leucocephala Linnaeus. Cuban Parrot.
Coccyzus minor (Gmelin). Mangrove Cuckoo.
Coccyzus americanus amcricanus (Linnaeus). Yellow-billed Cuckoo.
1 Nomenclature from Johnston et al. (1971).
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
Crotophaga ani Linnaeus. Smooth-billed Ani.
Tyto alba furcata (Temminck). Barn Owl.
Chordeiles minor (Forster). Nighthawk.
Chaetura pelagica (Linnaeus). Chimney Swift.
Archilochus colubris (Linnaeus). Ruby-throated Hummingbird.
Ceryle alcyon (Linnaeus). Belted Kingfisher.
Colaptes auratus gundlachi Cory. Flicker.
Centurus superciliaris caymanensis Cory. West Indian Red-bellied Woodpecker.
Sphyrapicus various (Linnaeus). Yellow-bellied Sapsucker.
Tyrannus tyrannus (Linnaeus). Eastern Kingbird.
Tyrannus dominicensis dominicensis (Gmelin). Gray Kingbird.
Tyrannus caudifasciatus caymanensis (Nicoll). Loggerhead Kingbird.
Myiarchus stolidus sagrae (Gundlach). Stolid Flycatcher.
Contopus virens (Linnaeus). Wood Pewee.
Elaenia martinica caymanensis Berlepsch. Caribbean Elaenia.
Progne subis subis (Linnaeus). Purple Martin.
Progne dominicensis (Gmelin). Martin.
Riparia riparia (Linnaeus). Bank Swallow.
Stelgidopteryx ruficollis (Vieillot). Rough-winged Swallow.
Hirundo rustica erythrogastcr Boddaert. Barn Swallow.
Petrochelidon pyrrhonota (Vieillot). Cliff Swallow.
Petrochelidon fulva (Vieillot). Cave Swallow.
Mimus polyglottos orpheus (Linnaeus). Mockingbird.
Dumetella carolinensis (Linnaeus). Catbird.
Mimocichla plumbea coryi Sharpe. Red-legged Thrush.
Mimocichla ravida Cory. Grand Cayman Thrush.
Polioptila caerulea caerulea (Linnaeus). Blue-gray Gnatcatcher.
Vireo crassirostris crassirostris (Bryant). Thick-billed Vireo.
Vireo griseus (Boddaert). White-eyed Vireo.
Virco altiloquus (Vieillot). Black-whiskered Vireo.
Vireo magister caymanensis Cory. Yucatan Vireo.
Mniotilta caria (Linnaeus). Black-and-white Warbler.
Helmitheros vermicorus (Gmelin). Worm-eating Warbler.
Parula americana (Linnaeus). Parula Warbler.
Dendroica petechia eoa (Gosse). Yellow Warbler.
Dendroica tigrina (Gmelin). Cape May Warbler.
Dendroica caerulescens caerulescens (Gmelin). Black-throated Blue Warbler.
Dendroica sirens (Gmelin). Black-throated Green Warbler.
Dendroica dominica dominica (Linnaeus). Yellow-throated Warbler.
Dendroica discolor discolor (Vieillot). Prairie Warbler.
Dendroica vitellina Cory. Vitelline Warbler.
Dendroica palmarum palmarum (Gmelin). Palm Warbler.
Seiurus aurocapillus (Linnaeus). Ovenbird.
Seiurus noceboracensis notabilis Ridgway. Northern Waterthrush.
Geothlypis trichas (Linnaeus). Common Yellowthroat.
Setophaga ruticilla (Linnaeus). Redstart.
Coereba flaveola sharpei (Cory). Bananaquit.
Spindalis zena salvini Cory. Stripe-headed Tanager.
Quiscalus niger (Boddaert). Greater Antillean Grackle.
Icterus leucopteryx bairdi Cory. Jamaican Oriole.
Dolichonyx oryzivorus (Linnaeus). Bobolink.
Tiaris olivacea olivacea (Linnaeus). Yellow-faced Grassquit.
Passerina cyanea (Linnaeus). Indigo Bunting.
Melopyrrha nigra taylori Hartert. Cuban Bullfinch.
Passerculus sandwichensis savanna (Wilson). Savannah Sparrow.
Ammodramus savannarum (Gmelin). Grasshopper Sparrow.
BULLETIN FLORIDA STATE MUSEUM
APPENDIX II: SCIENTIFIC AND COMMON NAMES
OF PLANTS APPEARING IN TEXT1
Thalassia testudinum Koenig and Sims. Turtle Grass.
Sporobolus virginicus (L.) Kunth. Dropseed.
Panicum maximum Jacq. Guinea Grass.
Andropogon metusus L. Seymour Grass.
Cocos nucifera L. Coconut Palm.
Thrinax argentea L. Thatch Palm.
Agave americana L. Century Plant.
MAisa sp. L. Banana.
Casuarina equisetifolia Forst. Australian Pine.
Ficus populnea Willd. Fig.
Coccoloba uvifera (L.) L. Sea Grape.
Bougainvillea glabra Choisy. Bougainvillea.
Sesuvium portulacastrum (L.) L. Sea Purslane.
Prunus myrtifolia L. West Indian Cherry.
Chrysobalanus icaco L. Coco Plum.
Haematoxylon campechianum L. Logwood.
Tamarindus indica L. Tamarind.
Caesalpinia bonduc Roxb. Cockspur.
Delonix regia (Bojer) Raf. Royal Poinciana.
Bursera simaruba (L.) Sarg. Gumbo Limbo or Red Birch.
Cedrela odorata L. Cedar.
Swietenia mahagoni (L.) Jacq. West Indian Mahogany.
Hippomane mancinella L. Manchineel.
Ceratiola sp. Michx. Rosemary.
Mangifera indica L. Mango.
Comocladia dentata Jacq. Maiden Plum.
Muntingia calabura L. Strawberry Tree.
Thespesia populnea (L.) Seaside Mahoe.
Hibiscus sp. L. Hibiscus.
Clusia flava Jacq. Balsam.
Passiflora sp. L. Passionflower.
Carica papaya L. Papaya.
Cereus (L.) Mill. Cactus.
Rhizophora mangle L. Red Mangrove.
Conocarpus erecta L. Buttonwood.
Terminalia catappa L. Almond.
Laguncularia racemosa Gaertn. F. White Mangrove.
Calyptranthes pallens Griseb. Pale Lidflower.
Psidium guajava L. Guava.
Eugenia sp. L. "Strawberry".
Myrtus sp. L. Stopper.
Ardisia escallonioides Schlecht & Cham. Marlberry.
Manilkara zapoda (L.) Naseberry.
Nerium oleander L. Oleander.
Ipomoea sp. L. Morning Glory.
Tournefortia gnaphalodes (L.) B. Br. Sea Lavender.
Avicennia nitida Jacq. Black Mangrove.
Cirsium sp. Mill. Thistle.
1Nomenclature from Swabey and Lewis (1946), Asprey and Robbins (1953), or
Long and Lakela (1971).
Vol. 19, No. 5
JOHNSTON: CAYMAN ISLAND AVIFAUNA
APPENDIX III: STOMACH CONTENTS OF
CAYMAN ISLAND BIRDS
The birds utilized in these analyses were collected in either April or August,
chiefly from Grand Cayman. The numbers in parentheses represent the numbers of
bird stomachs examined, A= animal food, V=plant food, and an asterisk (*) in-
dicates a predominant food item. When more than one stomach was examined, the
percentages for A and V are mean values. Nomenclature for the insect items follows
that of Borror and DeLong (1964) and for plant foods, that of Asprey and Bobbins
(1953) or Long and Lakela (1971).
Butorides virescens (2). A, 100%7 Isopoda; Odonata, Libellulidae; Orthoptera,
Acrididae, Cyrtacanthacridinae; Hemiptera, Belostomatidae, Belostoma (?)*; Co-
leoptera, Carabidae*, Dytiscidae.
Porzana carolina (1). V, 100%. Sedge seeds.
Columba leucocephala (1). V, 100%. Elaeocarpaceae, Muntingia*.
Zenaida aurita (1). V, 100%. Cyperaceae, Scleria', Rhynchospora*; Poaceae,
Panicum; legumes; Empetraceae, Ceratiola; Myrtaceae, Eugenia; Asteraceae,
Cirsium.
Columbina passerina (2). V, 100%. Cyperaceae, Scleria*; Commelinaceae, Com-
melina*; Asteraceae, Cirsium.
Leptotila jamaicensis (1). V, 100%. Cyperaceae, Scleria; Convolvulaceae, Ipomoea;
legumes; Elaeocarpaceae, Muntingia; Rosaceae, Prunus; Empetraceae, Ceratiola.
Amazona leucocephala (2). V, 100%r. Caricaceae, Carica.
Crotophaga ani (3). A, 87%/; V, 13%. Arachnida, Araneida; Orthoptera, Acrididae,
Cyrtacanthacridinae; Odonata, Coenagrionidae(?), Aeshnidae(?); Lepidoptera,
Noctuidae, Nymphalidae(?); Coleoptera, Scarahaeidae, Chrysomelidae(?), Cur-
culionidae*, Tenebrionidae; Homoptera, Cicadellidae; Hemiptera, Pentatomidae,
Coreidae(?), Scutelleridae*, Chelysoma; Diptera head; Hymenoptera, Vespidae3.
Vertebrate: Anolis conspersus.
Sedge seeds; Passifloraceae, Passiflora.
Tyto alba (ca. 50 pellets). Invertebrate- Paguridae, Coenobita cylpeatus, Coleoptera;
Reptilia- Aristelliger praesignis; Aves-Egretta thula, Centurus superciliaris,
Elaenia martinica, Mimus polyglottos, Dumetella carolinensis, Dendroica sp.?,
Coereba flaveola, Quiscalus niger, Melopyrrha nigra; Mammalia-Rattus rattus*,
R. norvegicus, Mus musculus*, Brachyphylla nana, Artibeus jamaicensis.
Colaptes auratus (19). A, 97%; V, 3%. Arachnida, Araneida; Coleoptera, Cer-
ambycidae, Bostrichidae(?); Hymenoptera, Formicidae, Formica*; Isoptera,
Rhinotermitidae*.
Unidentified fruit fragments.
Centurus superciliaris (16). A, 56%; V, 44%. Arachnida, Araneida, Seytodes
fusca; Orthoptera, Cryllidae, Acrididae*; Coleoptera, Curculionidae, Otior-
hynchinae, Tenebrionidae; Hymenoptera, Formicidae, Vespidae(?).
Hyla septentrionalis, Sphaerodactylus lewisi.
Moraceae, Ficus; Caricaceae, Carica*.
Tyrannus dominicensis (1). A, 100%. Homoptera, Cicadidae*.
Tyrannus caudifasciatus (5). A, 96%; V, 4%. Orthroptera, Gryllidae; Coleoptera,
Curculionidae*, Carabidae, Buprestidae, Polycesta; Hymenoptera, Vespidae,
Vespula(?), Formicidae, Myrmicinae. Hyla septentrionalis, Anolis conspersus*.
Burseraceae, Bursera simaruba; Passifloraceae, Passiflora.
Myiarchus stolidus (4). A, 89%; V, 11%. Arachnida, Araneida; Orthoptera,
Gryllidae; Lepidoptera; Coleoptera, Cerambycidae*, Oedemeridae*; Hemiptera,
Scutelleridae, Chelysoma(?)*; Hymenoptera, Tiphiidae(?), Andrenidae, Colleti-
dae, Colletes, Vespidae(?).
Burseraceae, Bursera simaruba; unidentified seeds.
1975
BULLETIN FLORIDA STATE MUSEUM
Elaenia martinica (9). A, 6%; V, 94%. Coleoptera, Curculionidae; Homoptera,
Flatidae.
Moraceae, Ficus*; Burseraceae, Bursera simaruba; Passifloraceae, Passiflora; many
unidentified seeds*.
Mimus polyglottos (1). A, 87%; V, 13%. Crustacea, crab parts, Isopoda; Cole-
optera, Scarabaeidae, Dyscinetus(?); Hemiptera, Pentatomidae: Hymenoptera,
Formicidae, Solenopsis.
Unidentified seeds.
Vireo crassirostris (11). A, 77%; V, 23%. Arachnida, Araneida*; Orthoptera; Lepi-
doptera larva*, Microlepidoptera, Geometridae; Neuroptera, Chrysopidae; Cole-
optera*, Curculionidae*, Oedemeridae, Cerambycidae*, Staphylinidae(?), Ela-
teridae(?), Chrysomelidae; Hymenoptera, Formicidae, Vespidae; Hemiptera,
Pentatomidae, Phymatidae.
Burseraceae, Bursera simaruba; many unidentifiable seeds.
Vireo magister (9). A, 51%,; V, 49%. Arachnida, Araneida; Orthoptera, Gryllidae;
Lepidoptera larvae*, Geometridae; Neuroptera, Chrysopidae; Coleoptera*, Ten-
ebrionidae, Chrysomelidae, Curculionidae*, Cerambycidae, Scarabaeidae(?);
Oedemeridae; Hemiptera, Pentatomidae; Homoptera, Flatidae; Homoptera leg;
Hymenoptera, Ichneumonidae, Formicidae, Cryptocerus.
Burseraceae, Bursera simaruba; many unidentified seeds.
Dendroica petechia (3). A, 100%. Coleoptera*, Curculionidae, Oedemeridae*;
Hymenoptera, Formicidae.
Dendroica vitellina (7). A, 97%; V, 3%. Arachnida, Araneida*; Lepidoptera
larvae; Orthoptera, Gryllidae(?); Coleoptera, Curculionidae*; Homoptera*,
Aphidae, Fulgoridae*, Ceropidae; Diptera, Muscidae; Hymenoptera, Formi-
cidae.
Few unidentified seeds.
Coereba flaveola (6). A, 50%; V, 50%. Lepidoptera larvae*; Coleoptera, Chry-
somelidae, Chalticinae, Curculionidae; Homoptera, Cercopidae(?); Hymenoptera,
Chalcidoidea.
Unidentified flower parts.
Spindalis zena (4). V, 100%. Myrsinaceae, Ardisia; many unidentified seeds.
Quiscalus niger (8). A, 87%; V, 13%. Arachnida, Araneida; Orthoptera, Tetrigi-
dae, Gryllidae(?), Blattidae; Lepidoptera, Noctuidae; Coleoptera, Carabidae*,
Oedemeridae, Curculionidae*, Alleculidae; Homoptera, Cicadidae; Hemiptera,
Pentatomidae, Scutelleridae(?); Hymenoptera, Formicidae; Diptera, Culicidae
(?).
Hyla septentrionalis*, Anolis conspersus".
Moraceae, Ficus; unidentified seeds and plant fragments.
Tiaris olivacea (3). V, 100%. Poaceae, Panicum*; many unidentified seeds.
Melopyrrha nigra (4). A, 39%; V, 61%. Lepidoptera larvae*; Coleoptera*;
Chrysomelidae (?).
Unidentified seeds.
Vol. 19, No. 5
VC. I ?
Contributions to the BULLETIN OF THE FLORIDA STATE MUSEUM, BI-
OLOGICAL SCIENCES SERIES, may be in any field of biology. Manuscripts deal-
ing with natural history of systematic problems involving the southeastern United
States or the New World tropics are solicited especially. Manuscripts should be of C,, CL(
medium length-circa 35 to 200 pages (10,500-16,000 words). Examination for
suitability is made by an Editorial Board.'
The BULLETIN is distributed worldwide through institutional subscriptions and
exchanges. It is considered the responsibility of the author to distribute his paper
to all interested individuals. To aid in this the authors) receives(s) 50 copies free,
and he may purchase additional separates at cost if ordered when page proof is re-
turned. The author is also responsible for any charges incurred for alterations made
by him on galley or page proofs. The Museum will send an invoice to the author
for this amount upon completion of publication.
PREPARATION OF MANUSCRIPT
Contributors should consult recent numbers of the BULLETIN for preferred style
and format. Highly recommended as a guide is the CBE Style Manual, 3rd Edition,
1972 (Washington, D.C., Amer. Inst. Biol. Sci.).
MSS must be submitted in duplicate (please no onionskin) and satisfy the following
minimal requirements: They should be typewritten, double-spaced (especially tables,
figure captions, and "Literature Cited"), on one side of numbered sheets of standard
(8-1/2x11 in.) bond paper, with at least one-inch margins all around. Tables
(which should be unruled) and figure legends should be typed on separate sheets.
All illustrations are referred to as figures. They must comply with the following
standards: Photographs should be sharp, with good contrast, and printed on glossy
paper. Drawings should be made with dense black waterproof ink on quality paper
or illustration board. All illustrations should have a cover sheet. All lettering will
be medium weight, sans-serif type (e.g. Futura Medium, News Gothic) in cutout,
dry transfer or lettering guide letters. Make allowance so that after reduction no
lowercase letter will be less than 1 mm high (2 mm is preferred) nor any capital
letter greater than 5 mm high. The maximum size for illustrations is 8-5/8x14 in.
(twice typepage size); illustrations should not be less than typepage width (4-5/16
in.). Designate the top of each illustration and identify on the back with soft
pencil by author's name, MS title, and figure number.
Manuscripts and all editorial matters should be addressed to:
Managing Editor of the BULLETIN
Florida State Museum
Museum Road
University of Florida
Gainesville FL 32611
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