FOOD-HABITS OF 4 SPECIES OF WADING BIRDS (ARDEIDAE) IN A TROPICAL MANGROVE SWAMP

The food habits of wading birds in the tropics are poorly known, parti cularly in coastal systems. We documented the food habits of Tricolore d Herons (Egretta tricolor), Great Egrets (Ardea alba), Snowy Egrets ( E. thula) and Little Blue Herons (E. caerulea), and assessed the degre e of similarity among their diets in a mangrove swamp in southwestern Puerto Rico. Thirty-five birds were collected during the winters of 19 94 and 1995 to examine their stomach contents. Eleven prey groups, com prised of 7 families of fish, 2 genera of crustacea (Xiphocaris, Uca) a lizard (Anolis spp.) and one group of insecta (i.e., Orthoptera), we re identified. Great and Snowy Egrets fed mainly on shrimps (Xiphocari s spp.) and guppies (Poecilia spp.),while Little Blue Herons fed exclu sively on Fiddler crabs (Uca spp.), and Tricolored Herons fed mainly o n guppies (Poecilia spp.) and snooks (Centropomus spp.). Three dietary groups were identified on the basis of a percentage overlap index. Sn owy and Great Egrets exhibited the highest degree of dietary overlap ( 54%) owing to their high consumption of shrimps. Fish contributed to t he intermediate overlap values (22-24%) among Tricolored Herons and Sn owy and Great Egrets. Little Blue Herons overlapped the least (i.e., < 1%) with Tricolored Herons and Great Egrets, and not at all with Snow y Egrets. Our data underscored the ability of wading birds to prey upo n a variety of resources across their range. This capability is advant ageous when exploiting coastal systems which might exhibit spatio-temp oral fluctuations in prey availability.