No evidence for effects of breeding density and male removal on extrapair paternity in the Pied Flycatcher

Molecular methods have brought new insight to the study of mating patterns. Extrapair fertilizations (EPF) have proven to be widespread among bird spe cies irrespective of social relationships. Ecological factors, such as bree ding density and synchrony, have been suggested as contributors to variatio n in EPF rates. Absence of a male during the female fertile period may also increase the probability of EPFs. In this study, we examined experimentall y whether breeding density and male absence before egg-laying influence the EPF rate in pied Flycatchers (Ficedula hypoleuca). DNA fingerprinting reve aled that 4.4% (10/225) of nestlings were the result of EPFs and 7.0% (3/43 ) of broods included at least one offspring sired by a male other than that attending the nest. We did not find any evidence of higher EFF rate with h igher breeding density as stated by the density hypothesis. Contrary to exp ectation, EPFs were more frequent, though not quite statistically significa ntly, at low breeding density: all three EPF nests were found in low-breedi ng-density areas. There was no evidence that EPF rate was affected by a 4 h male removal. In all cases of EPE an old female was mated with a yearling male, which suggests that older females mated with browner yearling males m ay have adjusted their initial mate choice through EPCs to acquire indirect genetic benefits. Pied Flycatcher females may be constrained to accept a m ate of lower than preferred quality, especially at low breeding density, du e to the cost of searching for alternative males.