Foraging flights of nesting Egrets and herons at a Hong Kong Egretry, South China

Observations of the foraging flights of nesting Great Egrets (Casmerodius a lbus), Little Egrets (Egretta garzetta), Black-crowned Night Herons (Nyctic orax nycticorax) and Cattle Egrets (Bubulcus ibis) in 1997 and 1998 from th e A Chau Egretry in Starling Inlet, Hong Kong, China, showed that shallow c oastal waters were the major feeding habitat of Great and Little egrets, wh ose habitat use greatly overlapped. Black-crowned Night Herons, the dominan t breeders in the colony, preferred mangroves and fishponds, while Cattle E grets made most use of freshwater marsh and abandoned paddy fields. Cattle Egrets showed the highest use of feeding habitats outside the Inlet. In bot h years, Cattle Egrets made the longest median flights at both high and low tides. Black-crowned Night Herons made the shortest flights at high tide i n both years while Great Egrets and Black-crowned Night Herons flew the sho rtest distance at low tide in 1997 and 1998, respectively. In both years, G reat and Little egrets flew farther at high tide, when nearby shallow water s were too deep for feeding. Foraging flight distances varied significantly between years only for Cattle Egrets. More Black-crowned Night Herons and Cattle Egrets were involved in group flights. The feeding habitats in Starl ing inlet supported far more breeding ardeids than expected for their area, probably because of their high productivity. The short foraging flight dis tances of Black-crowned Night Herons may reduce foraging costs and help exp lain the dominance of this species in the colony. Conservation of all wetla nd feeding habitats in Starling Inlet will be necessary to maintain the pre sent size and diversity of nesting ardeid populations.