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 a long 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.