|| 要旨トップ | 目次 |||日本生態学会第63回全国大会 (2016年3月、仙台) 講演要旨
一般講演（ポスター発表） P2-285 (Poster presentation)
Breeding birds search for food nearby their nests or colony sites. So previous studies on colonial birds often showed that the density of foraging individuals around their breeding colony decreased as the distance from their colony increased. Here we report a contradicting distribution of foraging egrets against the above expectation. Long lasting egret Colony A in Ibaraki Prefecture, Japan, was suddenly abandoned in 2010 without any explicit reasons. Colony B had been established 11 km away from Colony A in 2006, and egrets belonged to Colony A were believed to join in Colony B since 2010. Colony B is the nearest colony around Colony A. Distributions of foraging egrets were recorded on paddies within a radius of their usual foraging range (10 km) around Colony A from 2009 to 2015. The total number of foraging egrets on the paddies remarkably decreased since 2010, but paddies around Colony A, that is located more than 15 km from Colony B, were consecutively used by egrets until 2015. Thus, egrets do not always forage near their colony, and foraging sites located far from the colony can be used frequently. Individuals with good foraging experience around Colony A in 2009 may exhibit site fidelity, and thus the same profile of egret distribution had been persisted as if Colony A was still alive.