Extra-pair paternity in relation to regional and local climate in an Arctic-breeding passerine

Reproductive processes are affected by local and regional climate variation. Birds breeding in the Arctic may experience strong energetic constraints, which will affect their reproductive output. Recent research has emphasized the importance of extra-pair copulation as a means of improving reproductive output. In this paper, we explore ecological and climatic determinants that may explain variation in extra-pair paternity (EPP) in an arctic-breeding passerine, the snow bunting Plectrophenax nivalis. EPP occurred in 10.8 % of the young and 20.9 % of the broods sampled from 1999 to 2003. We found that the proportion of extra-pair young in a nest was positively related to the body size and age of the social male and weakly negatively related to the local average minimum temperature prior to the onset of egg laying. These results suggest that older and larger males lost a larger share of paternity than smaller and younger males, and that the relative loss of paternity decreased with cold weather during the female’s fertile period. Large and old males spend less time mate guarding compared to small and young males and may allocate more time towards extra-pair forays, and thus lose more paternity in their own nest. Climatic conditions most likely constrain the total energy budget with less energy available for extra-pair activity in cold weather.