Habitat structure and breeding biology of the Cattle Egret, Bubulcus ibis,in a colony of the Soummam Valley (Petite Kabylie, Algeria)

The Cattle Egret, Bubulcus ibis, is a new breeding bird in the Soummam Vall ey region (Petite Kabylie, Algeria). The location of each of 511 nests was determined in relation to the chronology in time of colony site occupation. This allowed an assessment to be made of preferential nest site selection. The regular monitoring of 58 marked nests provided data on reproductive pa rameters. The nesting season lasted from the end of March to the end of July. The mea n clutch size (2.77 +/- 0.56, N = 64), the mean fledging success (1.69 +/- 0.87, N = 64) and the breeding success (57.3 %) are low compared to other b reeding areas in the Mediterranean. Losses of eggs and chicks were due main ly to high winds (Sirocco). The first Cattle Egrets arriving at the colony in March selected the highes t trees, and the highest nest supports close to the trunk. With new arrival s during the course of the season, a gradual decrease was observed in the h eight of the nests which were progressively built away from the trunk. This selective behaviour is a new aspect observed during nesting of Cattle Egre ts.