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 pre dation. However, few empirical measures of these costs exist. We exami ned whether nestling begging calls could attract predators to nests by comparing predation rates at artificial nests with and without playba cks of tree swallow begging calls. Nests were baited with quail eggs a nd placed in pairs on time ground or in modified nest-boxes. Nests wit h playbacks of begging calls were depredated before control nests sign ificantly more often in both the ground and nest-box trials, suggestin g that predators may use begging calls to locate nests. These results suggest that the risk of nest predation may be increased because of ca lling by nestlings and provide further support fur the assumption that conspicuous begging is costly in terms of predation.