Chick-a-dee call variation in Carolina chickadees and recruiting flockmates to food

The "chick-a-dee" call of many Paridae species (titmice, tits, and chickadees) is structurally complex and functions in social cohesion. Studies with different Parid species suggest that variation in the note composition of calls relates to a wide variety of contexts. An earlier study with Carolina chickadees (Poecile carolinensis), the focal species of the present study, found that receivers responded differently to playback calls differing in note composition in feeding contexts. Here, we addressed whether signalers actually produce calls differing in note composition in feeding contexts and whether those calls might serve a recruitment function. In a first study, we found that the first chickadee to take seed from a feeding station produced calls with a greater number of D notes before the second chickadee arrived to take seed, compared with after the second chickadee arrived to take seed. This suggests that calls with a large number of D notes might serve a general recruitment function. We tested this idea in a second study, using playbacks of calls containing a large number of D notes or a small number of D notes at different sites. We found that the latency for a first chickadee to come into a site and take seed was shorter for playback variants containing a large number of D notes. Thus, in Carolina chickadees, chick-a-dee calls containing a large number of D notes may function to recruit other flock members to a discovered food source. Copyright 2009, Oxford University Press.