Hoarding Sites in Mixed Flocks of Willow and Crested Tits

Abstract

We studied the possibility that interspecific kleptoparasitism restricts the choice of hoarding sites in mixed flocks of the Willow Tit Parus montanus and the Crested Tit P. cristatus. In coniferous forests of Central Finland both species hoard seeds, and we observed the locations where the birds of five different flocks cached sunflower seeds provided by us. Overlaps in the hoarding niches were smaller than overlaps in the foraging niches in all study flocks. The reduction in the overlap of hoarding sites was due to Crested Tits hoarding relatively many seeds in the outer parts of spruce branches and Willow Tits hoarding many seeds on the trunk and the thickest branches. Both species tended to avoid the locations in which the other species forages, suggesting that the risk of interspecific kleptoparasitism influences the selection of hoarding sites in mixed species tit flocks.