RESPONSES OF POTENTIAL HOST SPECIES TO SIMULATED BRONZED COWBIRD PARASITISM AT TWO SITES IN COSTA RICA

Abstract

To assign responses of acceptance and rejection of potential hosts to parasitism by the Bronzed Cowbird (Molothrus aeneus), in Costa Rica, 110 egg manipulations were performed at nests of 17 species, from which 10 responses, by three species, were scored as ejections (Pitangus sulphuratus, Cyclarhis juganensis, Turdus grayi) and nests were deserted by three species (Zonotrichia capensis, Arremenops conirostris, Piranga bidentata). None of the artificial eggs removed from nests at which they were accepted exhibited peck marks that would indicate attempted ejection. Additional experiments are necessary to determine whether mixed responses of acceptance and rejection by individuals of the same species is more common in tropical environments.