Is there vocal recognition of conspecific juveniles by adults in two avian brood parasites?

PRIETO, ROCÍO; DE MÁRSICO, MARÍA C.; REBOREDA, JUAN C.; SCARDAMAGLIA, ROMINA C.

virtual

Congreso; 58th Annual Conference of the Animal Behavior Society; 2021

Juveniles of interspecific avian brood parasites need to locate and recognize conspecifics to continue their life cycle after being reared by individuals of another species. However, little is known about the recognition mechanisms and cues involved in this critical stage of their lives. One possible mechanism is that adult parasites facilitate the early socialization of juveniles by interacting with them. During those interactions, the juveniles could learn and/or reinforce the necessary cues to recognize conspecifics. Since acoustic communication is one of the main channels used by birds, if facilitation by adult avian brood parasites does exist, adult cowbirds should recognize and respond positively (i.e., approaching) to playbacks of vocalizations of conspecific juveniles. We experimentally tested whether adult shiny (Molothrus bonariensis) and screaming (M. rufoaxillaris) cowbirds respond positively towards acoustic signals of conspecific juveniles using two playback experiments, one conducted in semi-captivity and the other in the field. In both cases, we presented sequentially and in random order three types of playbacks to adult males and females of both cowbird species: vocalizations of shiny cowbird juveniles, vocalizations of screaming cowbird juveniles, and white noise as a control. The vocalizations corresponded to begging calls of birds between 13 and 20 days of age. In the experiment in semi-captivity, no significant differences were found between treatments. In the field experiment, no conspecifics approached the playback area, although hosts of the species whose playback was played were recruited. In conclusion, our results do not support the facilitation hypothesis and indicate that adult shiny and screaming cowbirds do not respond positively to acoustic signals of conspecific juveniles, at least not to the type of signals used in our experiments.