Dietary composition of cattle egrets (Bubulcus ibis) in the central Free State

Abstract

Analysis of 152 stomach samples of adult cattle egrets (Bubulcus ibis) collected over a period of five years in the central Free State showed this species to be mainly insectivorous. The Insecta, occuring in almost all stomach samples, are represented by prey items from 13 orders of which the Orthoptera, followed by the Coleoptera, Isoptera, Diptera and Lepidoptera, showed the highest frequency of occurrence. Amongst the non-insect invertebrates, the Araneae and Solifugae occured most frequently. Based on dry mass the Orthoptera and Isoptera constitute by far the most important components. Prey items of vertebrates combined represent only ca. 10% of the diet. Overall, the stomach contents of 75 chicks correspond with that of the adults, except that vertebrates make a significant contribution to the diet during the first week of the nesting phase. In general cattle egrets can be considered opportunistic feeders that concentrate on easily obtainable food sources which become sporadically available (partly because of their regular association with mammalian hosts).