DAILY ACTIVITY AND INTAKE RATE PATTERNS OF WINTERING COMMON CRANES Grus grus

Abstract

Daily activity patterns ofwintering CommonCranes Crusgrus were studied at Gallocanta, NE Spain, and related with changes in foraging site, distance to roost and flocking behaviour. Per cent time spent feeding, feeding bout length, and food intake rate showed two peaks, in early morning and late afternoon. Vigilance, preening and other activities followed an in­ verse pattern, peaking at midday, when birds usually gathered at drinking sites. The feeding habitat and location, and the flock size changed between the morning and the evening foraging peaks. During the morning cranes showed a higher locomotor activity, foraging in smaller flocks, at higher dis­ tances from the roost, and on grounds with higher food availability. On the contrary, during the afternoon birds showed lower locomotor activity, aggre­ gated in larger flocks, and foraged closer to the roost, on grounds with lower food availability. We explain these daily changes as a consequence of the risk-sensitive foraging behaviour of the cranes. Birds shifted from a risk­ prone foraging with higher intake rate in the morning to a risk-averse one with lower intake rate in the evening.