Distribution of Colonies and Roosts and Feeding Dispersal of the Little and Cattle Egrets (Egretta garzetta and Bubukus ibis) in Nara Basin, Japan

(1) The distribution of colonies and roosts and the daytime feeding dispersal of Little and Cattle egrets, Egretta garzetta and Bubulcus ibis, were investigated in Nara Basin, Honshu, Japan, from August 1976 to September 1977. (2) In our study area Little egrets (about 1, 200 individuals), Cattle Egrets (about 670 individuals) and Night Herons (not counted) bred and roosted in one colony. (3) The farthest feeding point from the colony where we observed in daytime was 25.6 km for Cattle Egrets and 27.0 km for Little Egrets. (4) Within a radius of 5 km of the colony, 45.7%(285 individuals) of feeding individuals of Little and Cattle Egrets were distributed. (5) Little Egrets appeared to feed solitarily along rivers. In contrast, Cattle Egrets fed communally in cultivated fields. (6) In winter almost all Cattle Egrets left the study area for migration. Little Egrets roosted at 6 roosts including the colony. (7) The total number of Little Egrets counted at these 6 roosts was about 1, 400 individuals. (8) In winter, 65.3% (810 individuals) of feeding Little Egrets were distributed within a radius of 5 km of 4 roosts. (9) The method of estimation of the total number of Little and Cattle egrets in Nara Basin, the difference of feeding dispersal between the two species and factors influencing on breakup of the colony and roost in non-breeding season were discussed.