The foraging ecology of Egrets in rice fields in southern New South Wales,Australia

Numbers of wading birds are declining throughout the Murray-Darling Basin i n Australia, and the loss of wetland habitats to agriculture is the most li kely cause. This study describes the foraging of egrets in irrigated rice f ields that occur extensively in areas of former wetlands. Tadpoles were the main prey of Great and Intermediate Egrets (Ardea alba and A. intermedia), with insects important secondary prey. Insects were the main prey of Cattl e Egrets (A. ibis). Prey capture rates for Great and Intermediate Egrets de clined by around 40% between November and January as the rice plants grew f roth seediing to mature stages. Cattle Egret prey capture rates did not dec line. The abundance of tadpoles and most aquatic insects in the rice fields declined significantly between November and February. All three egret spec ies laid eggs mainly during December and had young in the nest during Janua ry arid February. Thus the declining profitability of rice fields as foragi ng sites coincided with the maximum demand for food by the birds to rear th eir voting. Rice fields may not be an adequate substitute for natural wetla nds for Great and Intermediate Egrets.