Extra-pair young despite strong pair bonds in the European Nuthatch (Sitta europaea)

Abstract

We choose the European Nuthatch (Sitta europaea), an extremely socially monogamous passerine species, to investigate the breeding biology and frequency of extra-pair activities of females. Breeding individuals live in strong pair bonds for their total life and defend their territory all year round. As a consequence of these narrow social bonds, nuthatches have to date been considered extremely sexually monogamous. Our genetic study, however, reveals a minimum of 10% of extra-pair young in 188 chicks from 32 broods in populations of southwestern Germany. Independently of the habitat type (high via low quality), most of extra-pair sires are identified as neighbouring territory holders. © Dt. Ornithologen-Gesellschaft e.V. 2005.