Abstract
Over a three year study the Cattle Egret's mean clutch size was 3.6 eggs and 81% of nests with eggs produced one or more fledglings. Breeding success averaged 2.1 chicks to fledgling stage, and between 1.5 and 1 8 fledged per nesting pair. These data illustrate the breeding performance of a population in an expansion phase of its history. The determinants of growth of immigrant Cattle Egret populations are sought in a comparison of its breeding parameters in different lands. A significant reduction in clutch size occurred after about two‐thirds of clutches had been laid each year. One‐year‐old birds nesting for the first time are implicated in this reduction.