During June–September 2007, we searched bird nests for evidence of parasitism by brown-headed cowbirds (Molothrus ater) and we tested response of the avian community to taxidermy mounts of a brown-headed cowbird in a tropical deciduous forest in the Chamela-Cuixmala Biosphere Reserve in western Mexico. Of 46 nests found (black-capped gnatcatcher Polioptila nigriceps, 2; red-breasted chat Granatellus venustus, 1; blue bunting Cyanocompsa parellina, 1; orange-breasted bunting Passerina leclancherii, 1; rufous-backed thrush Turdus rufopalliatus, 1; yellow-green vireo Vireo flavoviridis, 39), only one was parasitized (nest of a black-capped gnatcatcher). Experimental responses to taxidermy mounts suggested that yellow-green vireos may have had previous contact with cowbirds. We conclude that in the Chamela-Cuixmala Biosphere Reserve, parasitism by brown-headed and bronzed cowbirds (Molothrus aeneus) remains low, or even absent for some species, as on the yellow-green vireo, but this situation could change in the near future because significant developments for the tourism industry are planned adjacent to the reserve; that could create new habitat and sources of food for cowbirds.