EXPERIMENTAL MATE SWITCHING IN PIED FLYCATCHERS - MALE COPULATORY ACCESS AND FERTILIZATION SUCCESS

By making female birds pair successively with different males, and ana lysing the paternity of the eggs laid? it is possible to examine how a male's success in obtaining fertilizations is determined by the timin g of his copulatory access to the female. Such an experiment is report ed here with pied flycatchers, Ficedula hypoleuca. Mate switching was induced at different stages within the female's fertile period by remo ving the resident male. The paternity of the clutch was analysed by mi crosatellite DNA typing. Removed males had full paternity in the clutc h if they were removed as late as after the second egg was laid (day 1 ), and they lost all paternity if they were removed more than 1 day be fore the first egg was fertilized (less than day - 2). Male switching during the period day - 2 to day 1 always resulted in mixed paternity in the clutch. Males that were paired to the female for only a few (1- 3) days during this period achieved on average more than one fertiliza tion per access day, with a peak on day -1. Thus, assuming that the ti ming of observed pair bonds reflects the timing of each male's copulat ory access to the female, the first eggs in the laying sequence were f ertilized by inseminations occurring shortly before the time of fertil ization, whereas the last eggs were fertilized by inseminations taking place several days prior to their fertilization. Our documentation of the most important period for copulatory access has some important im plications for understanding sexual behaviour in this species. (C) 199 7 The Association for the Study of Animal Behaviour.