The foraging behaviors of the Eastern Great Egret and the Little Egret were studied along a tidal river, the Umi River, Fukuoka City. Interspecific and seasonal differences in the behavior of the two species were derived from a combination of morphological characters and prey availability. Morphological characters were presumed to influence foraging site selection, and each species adopted foraging methods that were best suited to the most abundant prey in their chosen sites. The foraging methods adopted by each egret species were affected by prey characteristics, especially prey mobility. Seasonal differences in egret foraging behavior resulted from seasonal changes in prey availability at each foraging site.