Cooperatively breeding white-winged choughs use recruitment calls selectively in food-associated contexts

Abstract

Many social animals produce vocalizations to attract others to food, with diverse benefits including improved foraging success, reduced predation risk and access to social and reproductive rewards. In some species, the production of such calls varies based on food divisibility, but little is known about the significance of divisibility in food-sharing behaviour. White-winged choughs, Corcorax melanorhamphos , are highly social, cooperatively breeding birds with a diverse vocal repertoire. Using a combination of natural observations and field experiments, we investigated whether chough ‘peep’ calls function in recruitment to food and explored effects of food divisibility on peep calling. We found that peep calls were produced by adults upon discovering high-quality food, and such calls were acoustically distinct from foraging contact calls. Furthermore, choughs gave more peep calls when presented with divisible rather than whole food, and this was associated with a lower tendency to monopolize the food. Both adult and juvenile group members responded to playback of peep calls by looking towards and approaching playback, indicating peep calls function in recruitment to food. Field observations revealed that choughs produced peep calls during group travel and following predator alarms as well as during foraging; we suggest peep calls also function in recruitment in such nonfeeding contexts. Our findings confirm that choughs produce vocalizations to advertise food to groupmates, although they are less likely to call when food is easily defended and challenging to share. Such calls likely allow choughs to gain inclusive fitness and group augmentation benefits by enhancing the foraging success of their groupmates, and represent another aspect of their highly cooperative social system.