Extra-pair paternity in the boreal, socially monogamous Grey-headed Chickadee (Poecile cinctus)

Abstract

Extra-pairmatingisacommonalternativereproductivestrategyamongsociallymonogamous bird species, but empirical data on the genetic mating systems of most species are still lacking. Here we present the first parentage study in the Grey-headed Chickadee (Poecile cinctus), a socially monogamous passerine breeding at low densities in the borealregionofthePalaearcticandNearctic.InapopulationinnortheasternNorwaysampled acrosssix years,theprobabilityfor abrood to contain atleastoneextra-pair offspring was 37.5% (95% CI: 17.9–62.3%; total N = 16) and on average 16.7% (95% CI: 6.9– 35.0%; total N = 120) of nestlings per brood were sired extra-pair.