MALE PHILOPATRY CONFERS A MATING ADVANTAGE IN THE MIGRATORY COLLARED FLYCATCHER, FICEDULA-ALBICOLLIS

The potential benefits of philopatry versus dispersal were investigate d in yearling males of the migratory collared flycatcher on the island of Gotland, Sweden. Data on mating success from 4 years showed that p hilopatric males (i.e. hatched in the nestbox plot) mated more quickly after arrival than immigrant males and were less likely to remain unm ated. Among mated males, however, there was no significant difference in reproductive success between philopatric and immigrant males. Data on nestbox preferences gathered from 8 years revealed that philopatric males on average chose higher-ranked boxes than immigrant males. Male mating success was associated with the preference score of the nestbo x, suggesting that the observed mating advantage of philopatric males was probably a consequence of the higher quality of their nest site. I t is suggested that prior local experience facilitates nest site selec tion in philopatric birds when high search costs force individuals to choose between a small number of alternative sites. Dispersal may part ly be a consequence of prohibitively high time costs of searching and finding the way back home. Male-biased philopatry in the collared flyc atcher may then be a result of a sex-difference in the time costs of s earching for and assessing alternative sites.