Abstract
The Grey Heron Ardea cinerea and the Great Egret A. alba are assumed to have competitive relationship for food resource because of their overlapped feeding habitats. We observed their feeding behaviours in rice paddy fields in central Honshu, Japan. The main diets of both species were pond snails Sinotaia quadrata histrica and weather loach Misgurnus anguillicaudatus, suggesting competition for foods between the herons. Although the frequencies of peck trials and successful pecks were higher in Great Egrets than in Grey Herons, food intake had a tendency to be greater in Grey Herons than in Great Egrets. This inverse result must be caused by the higher proportion of small pond snails in Great Egret diets. Great Egrets frequently peck and obtain smaller foods, and Grey Herons use infrequent chance to obtain larger foods, which may relax the competition in food between the species.
