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

CECILIA DE MÁRSICO; ROCÍO PRIETO; ROMINA C SCARDAMAGLIA; JUAN C REBOREDA

Congreso; Animal Behavior Society 2021 Virtual Meeting; 2021

In avian brood parasites, juveniles need to locate and recognize their conspecifics to continue their life cycle after being raised by individuals of another species. However, little is known about the mechanisms and cues involved in this critical stage of their lives. One possible mechanism is that adult females 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. In birds, one of the main communication channels is the acoustic one; therefore, if facilitation does exist, adult females are expected to be able to recognize and respond positively to the vocalizations of juveniles of their own species. To test whether adult females of Shiny Cowbird (Molothrus bonariensis) and Screaming Cowbird (M. rufoaxillaris) are able to recognize conspecific juveniles based on acoustic signals, we carried out two experiments: one in semi-captivity and one in the field. In both cases, three types of playbacks were presented sequentially and in random order 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 neither between playback types or sexes for any of the three measured response variables: duration of the response, latency to approach the speaker and number of interactions with the speaker. In the field experiment, no conspecifics approached the playback area. In all cases, the recruited individuals were the hosts of the species whose playback was being played. Our results do not support the facilitation hypothesis and suggest that adult females of Shiny Cowbird and Screaming Cowbird are not capable of recognizing conspecific juveniles through acoustic signals, at least not through the type of signals used in these experiments.