Male incubation in barn swallows: the influence of nest temperature and sexual selection
Publishing year: 1992
Document type: Journal article
Publisher: Cooper Ornithological Society
Male Barn Swallows (Hirundo rustica) help their mates to incubate in North America but not in Europe. In this study, conducted at four colonies in southeastern Canada, males contributed an average of 9% of the total amount of incubation during daylight hours. The total percent of time that eggs were incubated (nest attentiveness) by both sexes declined through the day, largely due to a response to increasing temperature. The nest attentiveness of both males and females was negatively correlated with nest temperature (i.e., air temperature near the nest) but not consistently with weather. In general a male seemed to incubate more when his help was needed-early in the day when the female had to recover energy lost during nighttime incubation and late in the incubation period when females should have been most stressed energetically. We found no evidence that male nest attentiveness was affected by their expected opportunity to obtain extra-pair copulations - neither differences in male attractiveness due to tail-length manipulation (shortening or elonption) nor changes in the operational sex ratio affected the male's relative share of incubation duties. Using DNA fingerprinting, we also found that the male contribution was not affected by his paternity in the brood. Since colony size and the mating system of this species appear to be similar in both North America and Europe, the intensity of sexual selection should not differ substantially between these populations. Instead we suggest that nest temperature or feeding conditions are the most likely factors influencing the differences in male incubation behavior between European and North American populations.
- ISSN: 0010-5422
E-mail: henrik [dot] smith [at] biol [dot] lu [dot] se
Sölvegatan 37, Lund