Foraging behaviour of Nuthatches(Sitta europaea) in relation to the presence of mates and mixed flocks

Abstract

Nuthatches (Sitta europaea) usually forage in pairs outside the breeding season. I investigated whether foraging site selection in winter (tree species, height, substrate size) differed between sexes and whether this difference was related to the presence of mixed-species flocks. Foraging sites of pair members foraging together were highly correlated. In the rare cases when each used different tree species, males foraged significantly more often on the preferred oak trees than females. Males foraged significantly lower than females in some territories, but not in others. The reasons for this significant variation between pairs remains unexplained. Males also foraged lower than females in the company of mixed flocks. These differences are probably better explained as avoidance of the dominant male by the subordinate female, rather than specialization in resource use to avoid competition.