Phenotype-dependent selection of juvenile urban Feral Pigeons Columba livia

Abstract

Capsule We suggest the existence of colour-based selection processes on juvenile Feral Pigeons in an urban environment. Aims To investigate whether the colour or pattern of a fledgling affects its probability of survival to adulthood. Methods We determined the frequency of colour morphs of young and adult birds on 20 days in 1996 by recording the coloration in a population of Feral Pigeons in Vienna, Austria. Results Over 57% of the Feral Pigeons were of colorations also shown by wild Rock Pigeons with almost 30% Blue Bars and 27.5% Blue Checkers. We found significant differences in colour morph frequencies between juvenile and adult Feral Pigeons. In comparison to the reference ‘wild type’, Blue Bar, pigeons with the T-Pattern and the additional factors Spread and Bronze showed a significant increase in frequency with age. In contrast, birds with the pattern Checker decreased in frequency between juvenile and adult ages in an urban environment. The increase in frequency of individuals with the Bronze factor was not observed in pigeons with the T-Pattern. Conclusions A potential positive additive effect on survival of Bronze and Checkers could explain the high frequency of Checkers (31.5%) in the population. We propose that the observed changes in plumage morph frequencies are associated with selection episodes taking place between fledging and independence.