Female mate preferences and subsequent resistance to copulation in the mallard

In the majority of socially monogamous bird species, femalessolicit or accept copulations from males other than their partner.Females may gain direct benefits from extrapair males, suchas greater access to resources, or indirect genetic benefitsthat will influence the future success of their offspring. However,one group of birds appears to be the exception to this generalrule; in the wildfowl (Anseriformes), all extrapair copulationsappear to be resisted by females. It has been suggested thatresistance behavior may be a strategy to allow females a greaterchoice of mates, either at the precopulatory level (to promotechoice of copulation partner) and/or the postcopulatory level(to promote multiple mating to increase their choice of sperm).This paper examines the function of female resistance behaviorin one of the dabbling ducks, the mallard (Anas platyrhynchos).Observations on a marked population of wild mallard and experimentswith captive birds found that although females showed a strongpreference for particular males that are the first to molt intotheir breeding plumage, male attractiveness did not influencefemale responses to pair or extrapair copulation attempts. Femaleresistance decreased the likelihood that copulation attemptswould end in successful insemination. The findings did not supportthe hypothesis that females resist copulations to promote femalechoice and the reasons why waterfowl may benefit from avoidingall extrapair copulations are discussed.