Rejection of brood-parasitic shiny cowbird Molothrus bonariensis nestlings by the firewood-gatherer Anumbius annumbi?
Article first published online: 8 NOV 2011
© 2011 The Authors
Journal of Avian Biology
Volume 42, Issue 5, pages 463–467, September 2011
How to Cite
Delhey, K., Carrizo, M., Verniere, L., Mahler, B. and Peters, A. (2011), Rejection of brood-parasitic shiny cowbird Molothrus bonariensis nestlings by the firewood-gatherer Anumbius annumbi?. Journal of Avian Biology, 42: 463–467. doi: 10.1111/j.1600-048X.2011.05439.x
- Issue published online: 8 NOV 2011
- Article first published online: 8 NOV 2011
- Paper received 10 February 2011; manuscript accepted 5 July 2011
Costs imposed by brood parasitic birds exert strong selection on their hosts to avoid parasitism. While egg rejection is a common defence, nestling rejection is rarer and less well understood. Theoretical models suggest that among non-evicting parasites such as cowbirds nestling rejection can only evolve when levels of parasitism are high. Here we describe a possible case of early rejection of cowbird nestlings, by an infrequently parasitised host, the firewood-gatherer Anumbius annumbi. Firewood-gatherers accepted most shiny cowbird Molothrus bonariensis eggs despite clear differences in coloration. Cowbird eggs usually hatched 4–5 d before host eggs. All parasitic nestlings died within 48 h, and hosts continued their breeding attempts. Nestling death was most likely due to neglect since little food was found in the stomach of dead nestlings. Feeding neglect could be due to differences in visual or acoustic appearance between host and parasite hatchlings. Alternatively, hosts may refrain from feeding nestlings that hatch too early compared to their normal incubation time. At the moment our data do not allow distinction between active nestling recognition or cowbird nestling failure due to the unsuitability of the firewood-gatherer as a host (i.e. too long incubation). Experiments are needed to tease these alternatives apart.