Effects of body size and sex on foraging territoriality of the Little Egret (Egretta garzetta) in Japan

I studied the characteristics of foraging territoriality in the Little Egret (Egretta garzetta) and effects of body size and sex on territoriality. Sixty-eight birds were captured and sexed, and foraging behavior (usage of area, defense rate, and foraging efficiency) of 26 birds identified by color bands was observed in detail for 3 years. I categorized territoriality within the foraging area into three types according to the birds' exclusiveness and attachment to the area: high exclusiveness and strong attachment to the same area for along period, moderate exclusiveness and attachment, and minimal exclusiveness and attachment. Body size was largest and feeding efficiency was highest in the first type. I propose a model that predicts a relationship between body size and defense rate to explain the behavior of egrets.