Patterns of use of communal roosts by avian brood parasites

ROMINA C. SCARDAMAGLIA; ALEX KACELNIK; JUAN C. REBOREDA

Exeter

Congreso; International Society for Behavioral Ecology 2016 Conference; 2016

International Society for Behavioural Ecology

We analysed temporal and spatial roosting patterns by radio-tagged males and females of two avian brood parasites: the generalist shiny cowbird (Molothrus bonariensis) and the specialist screaming cowbird (M. rufoaxillaris). Screaming cowbirds are socially monogamous, while shiny cowbirds are not. The tags served to determine roost locations, dawn departure times and parasitic events. Females of both species used mainly a communal roost near their diurnal home ranges, which was maintained throughout the breeding season. Males of screaming, but not shiny cowbirds shared the females? communal roost. Male shiny cowbirds were rarely found in the area at night. Females left the roost both before and after sunrise, but parasitized hosts almost exclusively before sunrise. This is consistent with the hypothesis that females only leave the roost in the dark on days when they are ready to lay, and attack either previously located suitable host nests or nests located by following informed conspecifics.