Daily activity and intake rate patterns of wintering Common Cranes

Daily activity patterns of wintering Common Cranes Grus grus were studied at Gallocanta, NE Spain, and related with changes in foraging site, distance to roost and flocking behavior. 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 inverse 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 distances from the roost, and on grounds with higher food availability. On the contrary, during the afternoon birds showed lower locomotor activity, aggregated 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 behavior of the cranes. Birds shifted from a riskprone foraging with higher intake rate in the morning to a risk-averse one with lower intake rate in the evening.

Alonso JC. & Alonso J.A., ARDEA 80 (3): 343-351.