Relatedness among chicks indicates laying site fidelity and constant egg coloration in Shiny Cowbird females

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

Perth

Congreso; 13th International Society of Behavioral Ecology Congress; 2010

It is well established that the shiny cowbird (Molothrus bonariensis) is a host-generalist brood parasite. However, little is known on individual parasitism strategies. The aim of this study was to determine host use by individual shiny cowbird females within a single breeding season through molecular analyses of offspring found in host nests. We used seven polymorphic microsatellite DNA markers to calculate relatedness coefficients (r) among cowbird eggs collected from nests of three host species. We assigned full-sibship to pairs of eggs with r = 0.5. We also tested the "constant egg-type hypothesis" by analyzing egg morphology and color pattern. Of 61 analyzed eggs, we inferred 11 mothers of 34 offspring, with two to six eggs assigned to each female. Our results showed that females tend to use closely located nests (K-S, D=0.41; p