Abstract
Habitat selection, foraging behaviour and prey items of five species of herons were studied at an estuary in Chiba Prefecture, central Japan. The two largest species, the Grey Heron Ardea cinerea and the Great White Egret Egretta alba modesta fed mainly on the tidal flat and in the river. The three smaller species, the Intermediate Egret E.intermedia, the Little Egret E.garzetta and the Cattle Egret Bubulcus ibis fed mainly on farmland. The Great White Egret and Little Egret were habitat generalists using all types of habitat, whilst the three other species seemed to be habitat specialists. Grey Herons fed only in large bodies of water; Cattle Egrets were highly terrestrial feeders; Intermediate Egrets preferred farmlands or wet habitats but avoided both large bodies of water and dry habitats. The primary foraging behaviour of Grey Herons was Standing by which method they captured large prey. Great White Egrets adopted a Walking Slowly method as well as Standing, and they took significantly smaller prey than Grey Herons. Intermediate Egrets adopted mainly Walking Slowly, Standing and slow foraging behaviours, in contrast to Little Egrets that used Walking Quickly and very active foraging behaviours. Cattle Egrets foraged mainly by Walking Slowly, but also adopted active foraging behaviours. In their feeding ecology, the Grey Heron, Intermediate Egret and Little Egret in Japan seemed to be, respectively, ecological counterparts to the Great Blue Heron A.herodias, Little Blue Heron E. caerulea and Snowy Egret E.thula in North America. Recent population declines of the Intermediate Egret may be related to deterioration of the farmland habitats upon which this species depends.
