Begging and the risk of predation in nestling birds

Theoretical models of the evolution of begging in nestling passerines assume that begging is costly, either energetically or in terms of predation. However, few empirical measures of these costs exist. We examined whether nestling begging calls could attract predators to nests by comparing predation rates at artificial nests with and without playbacks of tree swallow begging calls. Nests were baited with quail eggs and placed in pairs on the ground or in modified nest-boxes. Nests with playbacks of begging calls were depredated before control nests significantly more often in both the ground and nest-box trials, suggesting that predators may use begging calls to locate nests. These results suggest that the risk of nest predation may be increased because of calling by nestlings and provide further support for the assumption that conspicuous begging is costly in terms of predation.