Do mimetic screaming cowbirds (Molothrus rufoaxillaris) show a reduced begging display compared to generalist shiny cowbirds (Molothrus bonariensis) when parasitizing a shared host?

SHARP, EMILY; DE MÁRSICO, MARÍA C.; REBOREDA, JUAN C.; URSINO, CYNTHIA A.

virtual

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

Avian brood parasites show a more exaggerated begging display than host chicks in order to overcome the kin-selective tendency for host parents to ignore unfamiliar chicks. We studied how evolved similarities between parasites and host chicks affects the begging intensity of chicks in Grayish Baywing (Agelaioides badius) nests, which experience parasitism by the specialist Screaming Cowbird (Molothrus rufoaxillaris) as well as the generalist Shiny Cowbird (Molothrus bonariensis). Screaming Cowbirds have evolved to visually and aurally resemble Baywing chicks, which might help them overcome the barrier of kin selection in the host parents’ food provisioning decisions. We filmed 25 nests at 4 and 8 days post-hatching, with chick groups consisting of all host chicks (n = 13), host chicks with one specialist parasite (n = 13), and host chicks with one generalist parasite (n = 11) , coding for begging frequency and intensity. We hypothesize that specialist parasites will still beg more frequently and intensely than host chicks, but will show reduced begging compared to the generalist parasites due to the similarities in specialist appearance and call structure to those of the hosts.