Evidence of innate vocal mimicry of host young by the brood-parasitic screaming cowbird.

ROJAS RIPARI, JUAN MANUEL; URSINO, CYNTHIA A.; REBOREDA, JUAN C.; DE MÁRSICO, MARÍA C.

Nueva Jersey

Congreso; 51th Animal Behavior Society Meeting; 2014

Animal Behavior Society

Young of obligate avian brood parasites, in order to obtain adequate levels of parental care, must tune their begging into the host?s existing parent-offspring communication system. The host-specialist screaming cowbird (Molothrus rufoaxillaris) possesses begging calls that resemble those of its primary host, the baywing (Agelaioides badius). We studied whether such vocal resemblance develops innately in screaming cowbird chicks. First, we examined the differences in begging call structure (min, max and peak frequency, frequency bandwidth and call duration) between 8-9 days-old baywing chicks and screaming cowbird chicks that were either reared by baywings or experimentally cross fostered as eggs to a non-host species (Mimus saturninus). Then, we tested the function of parasite?s begging calls using a playback experiment at baywing nests. A discriminant function analysis correctly classified 73, 91 and 83% of cases in each group, respectively. Hosts responded similarly to broadcasts of begging calls of conspecifics and those of screaming cowbirds reared by baywings or M. saturninus. Our results strongly suggest a genetic basis for host-specific vocal mimicry in screaming cowbirds.