Social learning and the significance of mixed-species flocks of chickadees (Parus spp.)

Abstract

The experiments described in this paper show that two species of chickadees learn from one another about the location and nature of potential feeding places when they are foraging together in mixed flocks in large aviaries. In the first experiment, I show that when an individual of one species finds a single food item, members of the other species modify their foraging behavior over the next few seconds so that they put more effort into searching near the site of the find. This applies to both species. Further, members of both species modify their foraging behavior when a bird of the other species searches in a place unsuccessfully. This response to an unsuccessful search is similar to, but weaker than, the response to a food find. The second experiment shows that when the two species are trained to forage in different positions in the experimental trees, they converge in their foraging behavior when they are put in mixed flocks, This is a result of copying. The third experiment shows that individuals of both species are more likely to discover a completely new foraging place if they are in the presence of an experienced bird of the other species.I discuss these results in relation to theories on the adaptive significance of flocking, and conclude that learning about potential feeding places from other species is an important function of mixed flocks, at least for some species. This does not exclude the possibility of other functions of mixed flocks.