Host use by Shiny Cowbirds in different bigeographic regions of Argentina

REBOREDA, J.C.; CHOMNALEZ, M.; DI GIACOMO, A.G.; MAHLER, B.

Portland, USA

Congreso; 126th Stated Meeting of the American Ornithologists' Union; 2008

We analyzed host use by Shiny Cowbirds (Molothrus bonariensis) at four sites of Argentina corresponding to three biogeographic regions: Pampa grasslands, Espinal shrublands and Chaco woodlands. For each site we determined: frequency of parasitism in available hosts; association between frequency of parasitism and host´s body size, nest type, and genetic distance between host and parasite; and if frequency of parasitism in same hosts was similar at different sites. In all sites few hosts were parasitized at high frequencies (>50%), and the majority of potential hosts were not parasitized or parasitized at low frequencies (