More secluded places for extra-pair copulations in the great grey shrike Lanius excubitor

Abstract

Summary Extra-pair copulations (EPCs) are prominent features of avian mating systems. EPCs can be costly for both sexes, especially if extra-pair encounters are discovered by a social partner. The threat of extra-pair fertilization of the social partner could potentially result in physical punishment, reduced parental investment or divorce. In order to reduce the costs of EPCs, natural selection may favour behaviour that reduces the likelihood of detection of EPC by a social partner. Moreover, habitat structure may influence the efficiency of male paternity guards and, therefore, the possibilities of seeking and obtaining EPCs. We tested this hypothesis with the great grey shrike Lanius excubitor, a socially monogamous passerine bird, living in semi-open landscapes. We have found that 1) extra-pair and within-pair copulations (WPCs) occurred in different places, and 2) individuals of both sexes chose more secret places for extra-pair than for within-pair copulations.