Do ornaments, arrival date, and sperm size influence mating and paternity success in the collared flycatcher?

Males advertise their intrinsic parental and/or genetic qualities by the size of secondary sexual ornaments. Moreover, they compete with one another for the best territory and males who arrive first at the breeding ground usually have an advantage in this competition. Females may consider multiple male qualities simultaneously and prefer the one most important for their fitness in the current context. They can further improve their fitness by selecting the best care-giver as their social mate and engaging in an extra-pair copulation with a genetically superior male. In such cases, sperm competition arises in the female reproductive tract and its outcome may be affected by the sperm morphology of both the social and extra-pair male. Here, we tested these ideas in the collared flycatcher (Ficedula albicollis), a species with context-dependent choice of social partners and frequent extra-pair paternity. We recorded male arrival to breeding sites, manipulated their forehead patches, and measured sperm size. In contrast to a previous study in a Swedish population, males with enlarged patches were nonsignificantly less successful late in the season while no such difference was found early in the season. Besides this tendential seasonal interaction, arrival date did not affect mating and paternity success or male fitness, and the same was true for sperm size. These results suggest different benefits of male ornamentation and female mate choice between populations and call for more replicated research within and between species.