IADIZA   20886
INSTITUTO ARGENTINO DE INVESTIGACIONES DE LAS ZONAS ARIDAS
Unidad Ejecutora - UE
artículos
Título:
Function of egg punctures by Shiny Cowbirds in parasitized and non-parasitized Creamy-bellied Thrush nests
Autor/es:
ASTIÉ, ANDREA ALEJANDRA; REBOREDA, JUAN CARLOS
Revista:
JOURNAL OF FIELD ORNITHOLOGY
Editorial:
Wiley-Blackwell
Referencias:
Año: 2009 p. 336 - 343
ISSN:
0273-8570
Resumen:
Avian brood parasites usually remove or puncture host eggs. Several hypotheses have been proposed for explaining the function of these behaviors. Removing or puncturing host eggs may enhance the efficiency of incubation of cowbird eggs (incubation efficiency hypothesis) or reduce competition for food between cowbird and host chicks in parasitized nests (competition reduction hypothesis), and, in non-parasitized nests, may force hosts to re-nest and provide cowbirds new opportunities for parasitism when nests are too advanced to be parasitized (nest predation hypothesis). Puncturing eggs may also allow cowbirds to assess the development of host eggs and use this information to decide whether to parasitize a nest (test incubation hypothesis). , During the 1999-2002 breeding seasons, we tested these hypotheses using a population of  Creamy-bellied Thrushes (Turdus amaurochalinus) in Argentina that was heavily parasitized by Shiny Cowbirds (Molothrus bonariensis). We found that puncturing host eggs did not increase the efficiency of incubation of cowbird eggs, but did increase the survival of cowbird chicks. Punctures were more frequent in parasitized than in non-parasitized nests and its intensity was similar in both groups. The proportion of punctures associated with parasitism decreased as incubation progressed. However, 40% of punctures during egg laying and early incubation were not associated with parasitism. Our results indicate that punctures in parasitized nests benefit Shiny Cowbirds by reducing competition between cowbird and host chicks. In non-parasitized nests, our results do not support the "nest predation hypothesis" and are partially consistent with the "test incubation hypothesis", suggesting that there may be other factors that influence egg-puncturing behavior in non-parasitized nests.