Behavioral Ecology and Sociobiology

, Volume 41, Issue 5, pp 353-360

First online:

Extra-pair paternity and tail ornamentation in the barn swallow Hirundo rustica

  • A. P. MøllerAffiliated withLaboratoire d'Ecologie, CNRS URA 258, Université Pierre et Marie Curie, Bât. A, 7ème Étage, 7 Quai St. Bernard, Case 237, F-75252 Paris Cedex 05, France Tel.: + 33 1 44 27 36 89; Fax.: + 33 1 44 27 35 16; e-mail: AMOLLER@SNV.JUSSIEU.FR
  • , H. TegelströmAffiliated withDepartment of Genetics, Uppsala University, Box 7003, S-750 07 Uppsala, Sweden

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Females of socially monogamous species may copulate with attractive non-mates to obtain access to the genes of such males, and a preference for attractive copulation partners may result in sexual selection. Extra-pair copulations are common in the socially monogamous barn swallow Hirundorustica, and a 2-year study of paternity using multi-locus DNA fingerprinting demonstrated that 33% of 63 broods and 28% of 261 offspring were sired by extra-pair males. The frequency of extra-pair offspring within broods was highly skewed with the majority of all broods having either no extra-pair offspring or only extra-pair offspring. Individual pairs were consistent in their frequency of extra-pair paternity among broods, and the repeatability of extra-pair paternity of multiple broods of the same female was statistically significant. The proportion of extra-pair offspring was negatively related to the tail length of the male attending the nest. Behavioural observations showed that extra-pair fertilizations were more likely in broods raised by females that had been observed to engage in extra-pair copulations. The frequency of extra-pair offspring was unrelated to the intensity of two male paternity guards, mate guarding and the rate of intra-pair copulations. In an analysis of extra-pair paternity and male parental care in different broods of the same male, male barn swallows fed their offspring relatively less frequently if the brood contained more extra-pair offspring. Therefore, female barn swallows pursue extra-pair copulations with attractive males, which may result in sexual selection, even though extra-pair paternity is costly for females due to the reduction of paternal care by their social mates.

Key words DNA fingerprinting Paternal care Paternity guards Repeatability Sexual selection