Utilization of wetlands by ardeids in Starling Inlet, Hong Kong: A year-round study and a comparison between the census and flight-line methods

Habitat use by ardeids in Starling Inlet, Hong Kong, was assessed be walkin g a fired 6 kin route, two or three times a month, during low tide between August 1997 and August 1998. A total of 36 surveys were made, with a mean c ount of 452 individuals per survey (S.E. +/- 128). Eight species of ardeids and two species of bitterns were recorded. In the winter, non-breeding sea son, the dominant species was the Great Egret (Casmerodius albus), while in the summer (breeding season) it was the Black-crowned Night Heron (Nyctico rax nycticorax). Shallow coastal waters and mudflats were the most importan t habitats at low tide for Great and Little Egrets (Egretta garzetta), and Grey Herons (Ardea cinerea), while fishponds were the most important for Bl ack-crowned Night Herons. A freshwater marsh was used mainly by Cattle Egre ts (Bubulcus ibis) and Intermediate Egrets (Mesophoyx intermedia). During t he 1998 breeding season, a comparison was made between the census and a fli ght-line methods in evaluating ardeid habitat use. Both methods gave simila r results for habitat use by Great and Little Egrets, but the census method underestimated the use of mangrove habitats by Black-crowned Night Herons and missed the Else of wet grassland habitats outside the inlet by Cattle E grets. We suggest that the census method is more efficient for assessing th e use of particular open habitats, while the flight-line method is more acc urate for investigating overall use of a landscape during the breeding seas on.