Foraging Habitat Preferences of Herons and Egrets

Abstract

We investigated the foraging habitat preferences of herons and egrets in an agricultural area in Asan city, Chungcheongnam-do, Korea. In the study area, rice fields were the most abundant habitat type (86.8%) and total suitable feeding habitat was greater in the northern area (59.0%) than the southern area (22.5%) of the colony. Most feeding herons and egrets were located in the northern area of the colony. The number of feeding individuals in a given area was related to the available feeding area (Pearson correlation, r=0.773, p< 0.001 for field habitats; r=0.901, p< 0.001 for freshwater habitats). Feeding habitat preferences differed among species. Grey herons ( Ardea cinerea ), great egrets ( Egretta alba ), and black-crowned night herons ( Nycticorax nycticorax ) used reservoirs and ditches. However, intermediate egrets ( E. intermedia ) and cattle egrets ( Bubulcus ibis ) were dependent on rice fields. The little egret ( E. garzetta ) was a habitat generalist using all types of habitats. The two largest species, grey herons and great egrets, fed at deeper site than little egrets and foraged in deeper sites in reservoirs than in ditches ( χ 2 -test, χ 2 3=26.6 and p< 0.001 for grey herons, χ 2 3 =17.5 and p< 0.001 for great egrets). All species displayed seasonal changes in feeding habitat use and these changes were related with changes in availability of feeding habitats.