Nestlings of brood-parasitic Screaming Cowbirds can manipulate host parental behavior by vocally resembling host young

URSINO, C.A.; DE MÁRSICO, M.C.; GLOAG, R.; REBOREDA, J.C.

New York

Congreso; 15th Conference of the International Society of Behavioral Ecologyth Conference of the International Society of Behavioral Ecology; 2014

International Society of Behavioral Ecology

Young brood-parasitic birds can manipulate host parental behavior via their begging call structure by mimicking acoustic signals of host young or exploiting host?s sensorial biases for non-specific acoustic features (e.g. rapid call rates). The former alternative is expected if hosts rely on species-specific acoustic cues to discriminate against alien young. We studied the role of begging call structure of two brood parasites, the specialist screaming cowbird (Molothrus rufoaxillaris) and the generalist shiny cowbird (M. bonariensis) in stimulating nest provisioning in a shared host, the baywing (Agelaioides badius). Screaming cowbird, but not shiny cowbird, nestlings match the begging call structure of baywings?. We conducted a playback experiment at 6-7 days post-hatch in 25 baywing nests. Each nest received four 40-min sessions, preceded by a 20-min interval of no broadcast: 1) screaming cowbird calls, 2) shiny cowbird calls, 3) baywing calls, and 4) no broadcast (control). Call rate and amplitude were standardized and session orders were rotated among nests. We recorded the number of feeding visits made to the nest by adult baywings during each session. Baywings increased nest provisioning rates in response to baywing and screaming cowbird calls compared to shiny cowbird calls and no-broadcast sessions, but provisioning rates did not differ between baywing and screaming cowbird calls, and between shiny cowbird calls and nobroadcast sessions. These results strongly suggest that baywings cue on species-specific acoustic signals to adjust parental investment, and that screaming cowbird nestlings may manipulate host parental behavior by resembling the begging call structure of host young.