MATE CHOICE ON MULTIPLE CUES, DECISION RULES AND SAMPLING STRATEGIES IN FEMALE PIED FLYCATCHERS

The mate sampling behaviour and mate choice of 125 individually marked female pied flycatchers, Ficedula hypoleuca, was recorded with video cameras. Females visited on average 3.1 males within a period of less than 1 day. Females had independent preferences for unmated males, bri ghtly coloured males and males with nestboxes that had small entrance holes; 77-86% of the females chose a male that was the best one among the males sampled in relation to at least one of these factors. When h aving a choice only on mating status 91% of the females made a correct choice; corresponding values fbr plumage colour and nest site quality were 64% and 73%, respectively. Females made 'mistakes' more often wh en differences between males were small, at least regarding plumage co lour. When given simultaneous choices on two cues, females gave priori ty to the cue with the largest differences between males. Females retu rned to some males before rejecting them and these males tended to hav e brighter plumage or better nestboxes than males that were visited on ly once. The final choice of mate was not related to the order in the sequence of males visited, suggesting that many females used a pool-co mparison strategy. However, about one third of the females visited onl y one male, and one third sampled males in a way conforming to thresho ld or sequential comparison strategies as well as a pool-comparison st rategy. The temporal pattern of female visits suggested that they eith er sampled males at once and then settled, or that they visited one ma le repeatedly and made occasional visits to other males, often after a long period of residency. Twenty-eight females (22%) made visits to o ther males after they had settled (he. started nest building) with one male, and this resulted in mate switching in seven cases (6% of all f emales). These results show that females compare and choose mates on t he basis of at least three different cues, and that most females are a ble to pick out the best or one of the best males among those sampled. However, females sample few males, probably because of competition be tween females for a mate, so that they must sometimes accept dull or m ated males, or males with poor-quality nest sites. Limited choice redu ces the strength of sexual selection even when female preferences are strong. This may help explain why plumage colour variation and polygyn y exist in the pied flycatcher.