THE CHOICE OF HOST SPECIES IS INDEPENDENT OF NEST AVAILABILITY IN THE BROOD PARASITIC SHINY COWBIRD

DE LA COLINA, M. A.; STRAUSBERGER, B.; HAUBER, M. E.; REBOREDA, J.C.; POMPILIO, L.; MAHLER, B.

Nueva York

Congreso; XV Congress of the International Society for Behavioral Ecology; 2014

ISBE

The Shiny Cowbird Molothrus bonariensis is an obligate brood parasite that parasitizes an extreme range of hosts, including more than 200 species. Due to its high mobility, little is known about the reproductive behavior of this parasite at the individual level. Some works suggested that female laying preferences could be flexible and related to the availability of the hosts. The aim of this work was to study individual strategies of parasitic females in host nest choice.  We tested the ?availability hypothesis? using microsatellite analysis of cowbird eggs and chicks found in nests of the two most frequent hosts, the Chalk-browed Mockingbird Mimus saturninus and the House Wren Troglodytes aedon. By reconstructing full sibling groups, we inferred the laying behavior of 26 females a posteriori. We found that some females had a clear preference for mockingbird nests while other used house wren nests, even when nests of both species were available; few females also used the alternative host simultaneously at low frequency. These findings suggest that host nest choice was not related to nest availability. Use of alternative hosts might be a consequence of imprinting errors, social learning, or active choice. This process improves parasitism success in this cowbird species by increasing the probability of using new hosts.