Risk of predation and foraging sites of individuals in mixed-species tit flocks

Abstract

Abstract. Foraging sites of individual willow tits, Parus montanus, and crested tits, P. cristatus, on spruce were studied in a winter when the risk of predation from pygmy owls, Glaucidium passerinum, was high and in a winter when it was low. Mixed-species flocks consisted of two crested tits (a pair) and three to six willow tits. The risk of predation from owls is likely to be highest on the most exterior tree parts. Female crested tits foraged further out on the branches than other individuals when predation risk was low, but foraged in the safer sites close to the tree trunk when the risk was high. Male crested tits retained both their relative distance to the trunk and their relative foraging height irrespective of the risk of predation. Dominant adult willow tits foraged more on the outer parts of branches than subdominant willow tits when predation risk was low. Under high predation risk adult willow tits of both sexes foraged closer to the trunk and also moved to the lower parts of the tree. First year willow tits retained the same distance from the tree trunk irrespective of predation risk, but preferred the lower parts of the tree under high risk of predation. Female crested tits and adult female willow tits changed their relative distance to the trunk more than any other individual in the flock. Dominant males may protect their mates from both other flock members and owls in winter in particular when risk of predation is high.