Original Article

Behavioral Ecology and Sociobiology

, Volume 61, Issue 3, pp 449-454

First online:

Search costs influence the spatial distribution, but not the level, of extra-pair mating in tree swallows

  • Peter O. DunnAffiliated withDepartment of Biological Sciences, University of Wisconsin-Milwaukee Email author 
  • , Linda A. WhittinghamAffiliated withDepartment of Biological Sciences, University of Wisconsin-Milwaukee

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


Costs of searching for a mate are an important component of models of sexual selection, yet they have rarely been examined in wild populations of vertebrates. In this paper, we report an experiment in which we handicapped female tree swallows by clipping some flight feathers. This manipulation increased the costs of flight and searching for extra-pair mates. Despite these costs, handicapped females had the same level of extra-pair mating (percentage of extra-pair young, percentage of broods with extra-pair young, and the number of extra-pair sires per brood) as control females. However, handicapped females were more likely to have young sired by extra-pair males that lived closer to her nest than control females. This change in the distribution of extra-pair mating was most likely due to female choice rather than male coercion, and it suggests that extra-pair mating has significant benefits to females. One important implication of our study is that ecological and social factors that influence search costs could affect the spatial distribution of extra-pair sires and, consequently, the intensity of sexual selection. These effects may have been overlooked in previous studies that did not identify extra-pair sires.


Mate choice Tachycineta bicolor Extra-pair paternity Sexual selection Handicapping