Adaptaciones y contraadaptaciones entre el Tordo Pico Corto (Molothrus rufoaxillaris) y el Tordo Músico (Agelaioides badius).

DE MÁRSICO, M.C.; REBOREDA, J.C.

El Hornero

Asociación Ornitológica del Plata

Lugar: Buenos Aires; Año: 2014 vol. 29 p. 1 - 12

0073-3407

Avian obligate brood parasites exploit the parental care of individuals of other species (hosts) that rear the parasitic offspring at the expense of their own reproductive success. The costs of parasitism select for antiparasitic defences in host populations (i.e. adaptations that reduce the impact of parasitism). This, in turn, may favour counteradaptations in the parasite population, leading to a coevolutionary arms race between parasite and host. In this study we review the reciprocal adaptations between a specialist brood parasite, the Screaming Cowbird (Molothrus rufoaxillaris), and its primary host, the Bay-winged Cowbird (Agelaioides badius). The defences of the Bay-winged Cowbird include the rejection of parasitic females, a little predictable egg-laying behaviour, the rejection of whole ?superparasitized? clutches, and discrimination against juveniles that do not resemble their own. These defences are partially countered by the Screaming Cowbird through an elusive behaviour and rapid egg-laying, a close monitoring of host nesting activities and the evolution of visual and vocal mimicry of host young in the parasite juveniles. These results suggest an escalated arms race between the Screaming Cowbird and the Bay-winged Cowbird through the entire nesting cycle. Future studies of the interactions between these species before, during and after parasitism might improve the understanding of host-parasite coevolutionary processes and the evolution of specialization in host use in brood parasitic birds.