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.