Mate Choice On Multiple Cues, Decision Rules and Sampling Strategies in Female Pied Flycatchers

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Abstract
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, brightly 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 having a choice only on mating status 91 % of the females made a correct choice; corresponding values for plumage colour and nest site quality were 64% and 73%, respectively. Females made 'mistakes' more often when differences between males were small, at least regarding plumage colour. When given simultaneous choices on two cues, females gave priority to the cue with the largest differences between males. Females returned to some males before rejecting them and these males tended to have brighter plumage or better nestboxes than males that were visited only 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-comparison strategy. However, about one third of the females visited only one male, and one third sampled males in a way conforming to threshold or sequential comparison strategies as well as a pool-comparison strategy. The temporal pattern of female visits suggested that they either sampled males at once and then settled, or that they visited one male repeatedly and made occasional visits to other males, often after a long period of residency. Twenty-eight females (22%) made visits to other males after they had settled (i.e. started nest building) with one male, and this resulted in mate switching in seven cases (6% of all females). These results show that females compare and choose mates on the basis of at least three different cues, and that most females are able to pick out the best or one of the best males among those sampled. However, females sample few males, probably because of competition between females for a mate, so that they must sometimes accept dull or mated males, or males with poor-quality nest sites. Limited choice reduces the strength of sexual selection even when female preferences are strong. This may help explain why plumage colour variation and polygyny exist in the pied flycatcher.