SEARCH

SEARCH BY CITATION

A qualitative survey of the terrestrial bird community (sixty-five species) and a quantitative analysis of the five-diurnal raptor assemblage were earned out on 33 islands of the oceanic Andaman archipelago in the Bay of Bengal Among seven geographical parameters, island area was the main determinant of species richness for both the whole bird community and each category of species associated with four habitat types Species richness decreased most markedly with island size in the smallest islands and in open habitat species The rarest forest species were the most extinction prone with decreasing island size Specific habitat selection was the most prominent ecological correlate of inter island species distribution Observed species distribution patterns did not fit the random species placement or equprobable occurrence hypotheses

Raptors were primarily forest species, two of them restricted to forest interior, two more tolerant of fragmentation and one naturally associated with mangroves Unexpectedly, the two rarest and most area sensitive raptors were the two smallest species with a strong active flight, whereas the most abundant and widespread species was the most forest interior and endemic taxon Both raptor species richness, species frequency of occurrence and abundance indices decreased with island area, which was consistently the most significant determinant of every species' occurrence and abundance There was a significant correlation between abundance or frequency of occurrence of every raptor species and the proportion of their preferred habitat type No relationship was found between habitat niche breadth or local abundance of any species and their distribution range among islands The hypothesis of random composition of species assemblages on islands was not supported because of species specific habitat selection Any evidence of interspecific competitive exclusion was limited to the striking habitat segregation of the two congeneric serpent eagles A metapopulation structure was suggested by small population distribution patterns, observed sea crossing and the circumstances of an apparent extinction