Species diversity and ecological release in Caribbean land bird faunas

Communities of breeding, non-raptorial land birds were studied in nine major habitat types (secondary grassland and scrub, young and old secondary forest, mature lowland forest, cloud forest, mangroves, savanna, residential land) in each of five Caribbean areas (Panama, Trinidad, Jamaica, St. Lucia, St. Kitts). In each habitat, the frequency of occurrence of individual species was determined in ten 20-min observation periods. Foliage height profiles were determined for all areas except St. Kitts. Data on frequency of occurrence were converted to indices of absolute abundance. Ecological release, involving both increase in the average number of habitats occupied per species and increase in within-habitat abundance, was extensive, and complete density compensation or overcompensation occurred in Jamaica, St. Lucia, and St. Kitts. Dropout of species along the species diversity gradient from Panama to St. Kitts appeared to be random with respect to generic or familial status. Habitat distribution appeared to shift from-being strongly influenced by interspecific relations in Panama to being largely independent of such influence in St. Kitts.