The diets of Malaysian swiftlets

Four species of swiftlet (Aves: Apodidae), two of which produce 'edible nests', occur sympatrically in Malaysia. Food boluses were analysed to investigate (1) diet differences and resource partitioning among the four species and (2) the influence of habitat on the diet of the Glossy Swiftlet Collocalia esculenta. Hymenoptera and diptera were the most abundant prey in all diets. Black-nest Swiftlets Aerodramus maximus were extremely selective; 89% of the items taken were hymenoptera, of which 97% were flying ants. White-nest Swiftlets A. fuciphagus and Mossy-nest Swiftlets A. salanganus took more than twice as many prey items as either of the other species. Their diets were taxonomically diverse and differed only in the average prey size taken, Mossy-nest Swiftlets taking the larger prey. Glossy Swiftlets took a higher proportion of coleoptera than did the other species. For the habitat comparisons, diptera were the main constituents of the Glossy Swiftlet diet in an urban habitat (71% of total prey items), whereas hymenoptera predominated in forest habitat (42% of total prey items). The results suggest that diet separation occurs among the four species of Malaysian swiftlet, in relation to both species and habitat. The implications of potentially habitat-driven dietary changes are discussed for the edible-nest swiftlets.