Genetic Monogamy despite frequent extra-pair Copulations in “strictly monogamous” wild Jackdaws

“Monogamy” refers to different components of pair exclusiveness: the social pair, sexual partners, and the genetic outcome of sexual encounters. Avian monogamy is usually defined socially or genetically, while quantifications of sexual behavior remain scarce. Jackdaws (Corvus monedula) are considered a rare example of strict monogamy in songbirds, with lifelong pair bonds and little genetic evidence for extra-pair offspring. Yet jackdaw copulations, although accompanied by loud copulation calls, are rarely observed, since they occur visually concealed inside nest cavities. Using full-day nest-box video surveillance and on-bird acoustic bio-logging, we directly observed jackdaw sexual behavior and compared it to the corresponding genetic outcome obtained via molecular parentage analysis. In the video-observed nests, we found genetic monogamy, but frequently detected forced extra-pair sexual behavior, accompanied by characteristic male copulation calls. We thus challenge the long-held not...