Conspecific recognition of the chatter-call by parasitic Molothrus bonariensis nestlings

IGNACIO CRUDELE; FIORINI VD; REBOREDA JC

Virtual

Conferencia; North American Ornithological Conference; 2020

The password hypothesis states that conspecific recog- nition in brood parasites develops when a young par- asite encounters a unique species-specific signal that triggers the learning of other aspects of the producer of the signal. For cowbirds (Molothrus sp.), the chatter- call has been proposed to act as a password for species recognition. The aim of this work was to evaluate if Shiny Cowbird (M. bonariensis) nestlings recognize conspecific chatter-calls. Field work was carried out during October-February 2018-2019 and 2019-2020 at Reserve ?El Destino?, Buenos Aires, Argentina. We tested Shiny Cowbird nestlings, reared by Chalk- browed Mockingbirds (Mimus saturninus) and House Wrens (Troglodytes aedon) and host nestlings as con- trol species. Six-day-old nestlings were removed from the nest and we presented randomly the following treat- ments: 1) chatter-calls, 2) host-vocalizations, 3) non- host-vocalizations. Each treatment lasted one minute and they were interspersed with 5-minute silences. Sev- enty seven % of cowbird nestlings reared by mock- ingbirds (32/42) and 73% of those reared by wrens (19/26) begged during the chatter-call, without differ- ences between them (GLM, p=0.8). Shiny cowbird nestlings reared by either mockingbirds or wrens re- sponded more to conspecific chatter-calls than to het- erospecific calls of mockingbirds (0%) or wrens (25%, GLMM, p=0.001). Mockingbird nestlings (N=26) did not beg during treatments. Forty five % of wren nestlings (10/22) begged during host-vocalizations and 27 % during chatter-call (GLMM, p=0.002). None of the three species begged during non-host-vocalization. Our results indicate that there is an innate specific recognition of Shiny Cowbird nestlings of the chatter- calls and support the password hypothesis.