Loyal as a Robin: low frequency of extra-pair paternity in a European Robin Erithacus rubecula population in the natural forest of Białowieża National Park (Poland)

The European Robin is a common Eurasian bird but little is known about its extra-pair paternity (EPP), mainly due to its secretive behaviour during the breeding season, but we found a low frequency of EPP in natural forest. To reveal the level of EPP among European Robins in natural forest conditions. The study was conducted in 2018–2019 during the European Robin’s breeding season in the Białowieża National Park (north-eastern Poland). Genetic material was obtained from 70 European Robin families. Genotypes of social parents were compared with those of nestlings to assess the occurrence of EPP and identify extra-pair males. To analyse the EPP frequency, microsatellite genotyping was used. We found evidence of EPP in 5.7% of nests, with 5.1% of nestlings being the offspring of extra-pair males. The European Robin showed a low frequency of EPP under natural forest conditions, in contrast to results from studies of many other socially monogamous passerines.