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Natural selection is a central tenet of evolutionary theory, yet the estimation of the direction and intensity of selection remains problematic. Here, we assess the strength of selection on the early expression of a secondary sexual ornament, bill colour, in male European blackbirds (Turdus merula) using 5 years of capture-mark-recapture (CMR) data. The best-fitting model consisted of a quadratic relationship between survival rate and bill colour, indicating stabilizing natural selection on the early expression of a secondary sexual trait. There was no evidence for sexual selection acting on bill colour in the first year. We suggest that the consideration of early selection and the adoption of refined statistical methods may reveal patterns of selection in the wild that have, as yet, remained undetected.

Original publication

DOI

10.1111/j.1420-9101.2004.00756.x

Type

Journal article

Journal

J Evol Biol

Publication Date

09/2004

Volume

17

Pages

1152 - 1156

Keywords

Age Factors, Animals, Beak, Birds, Europe, Models, Genetic, Pigmentation, Regression Analysis, Reproduction, Selection, Genetic, Sex Characteristics, Sexual Behavior, Animal