Parent-offspring recognition in tree swallows, Tachyeineta bicolor

Parent-offspring recognition appears to be highly developed in species in which the risk of misdirecting care is high (e.g. colonial species). Some of the best evidence for this relationship comes from comparative work on swallows of the family Hirundinidae. Using methods followed in earlier studies, we determined whether parent-offspring recognition occurs in the tree swallow, Tachycineta bicolor, a non-colonial species closely related to the highly colonial bank swallow, Riparia riparia, and the solitary rough-winged swallow, Stelgidopteryx ruficollis. Parents did not discriminate between playbacks of the calls of their own versus non-related nestlings. However, older nestlings called more in response to playback of parental calls than non-parental calls, suggesting that they recognized their own parents. Despite significant individual variation in parental and nestling calls, variation in tree swallow nestling calls was lower than analogous calls in the bank swallow. Our results provide further support for a positive relationship between recognition, individual variation in call structure and coloniality.