Laying site fidelity and consistent egg phenotype of individual brood parasitic females of Shiny Cowbird revealed by genetic analysis of chick relatedness

DE LA COLINA, M. A.; HAUBER, M. E.; STRAUSBERGER, B.; REBOREDA, J. C.; MAHLER, B.

Perth, Australia

Congreso; 13th International Behavioral Ecology Congress; 2010

ISBE

It is well established that the shiny cowbird (Molothrus bonariensis) is a host-generalist brood parasite. However, little is known about individuals’ strategies regarding host- and space-use and the resulting consequences on social behaviors and egg morphology. We aimed to determine individual host-use within a breeding season through molecular analyses of parasitic offspring sampled across host nests, and tested assumptions of prior work, in this and other generalist avian parasites, that individual females lay a constant egg-type, by analyzing egg morphology and color pattern. Seven polymorphic microsatellite DNA markers were applied to calculate relatedness coefficients among cowbird eggs collected from nests of three host species. Of 61 analyzed eggs, we inferred 11 mothers of 34 offspring, with two to six eggs assigned to each female. Laying periods lasted up to 71 days. Shiny cowbirds used one ore more host species in spatial proximity and, in some cases, parasitized the same nests to lay multiple eggs. Background colors were similar for a given female, but maculation showed high variability in some cases. These results are consistent with the hypothesis of individually generalist strategy of shiny cowbirds and suggest future work on spacing patterns and territoriality in this brood parasite.