American Barn

While female mate choice is well established, mutual choice may play a larger role in mate selection than currently recognized. Assortative mating is a common form of nonrandom mating in animals that can result from mutual choice. However, few studies address assortative patterns beyond the social pair, potentially overlooking assortativity in the mating pair and in the social environment that shapes reproductive decisions. We asked whether North American barn swallows (Hirundo rustica erythrogaster) breeding in a large colony form pairs, mate (through both within-pair and extra-pair fertilizations), and interact assortatively by ventral plumage color, wing length, and age. Social interactions were tracked using proximity loggers, which recorded close contact between tagged individuals when birds were mating and laying eggs. Barn swallows paired and mated assortatively by their ventral plumage color; however, the assortative patterns in mating pairs were not as strong as they were in social pairs. Barn swallows also interacted assortatively, associating more often with individuals of both sexes who had similar phenotypes relative to the other birds in the colony. Finally, older males and females with darker ventral plumage achieved the highest reproductive success. Investigation of assortative behavior beyond the level of the social pair provides a more complete understanding of mate choice and suggests a mechanism that may maintain the large variation in ventral plumage color in North American barn swallows.

Across diverse taxa, morphological traits mediate social interactions and mate selection. Physiological constraints on signal elaboration have been widely documented, but the potential for trait display to influence physiological state remains poorly understood. We tested for the presence of causal links between ventral plumage colour-a trait known to covary with reproductive performance-and physiological measures in female North American barn swallows, Hirundo rustica erythrogaster. Naturally darker swallows have lower levels of plasma oxidative damage. Females manipulated to display darker ventral plumage during reproduction rapidly decreased oxidative damage, adopting the physiological state of naturally darker individuals. These results support the presence of a social mechanism that links static plumage traits with the physiological state of their bearer during trait advertisement, long after the completion of signal development.

Method for simulative reproduction, verification and technical adaptation as part of biological kinematics studies

In this study conducted in southeastern Ontario, Canada, we manipulated the length of outer tail feathers (streamers) of male barn swallows (Hirundo rustica) shortly after they returned to four small breeding colonies in the spring. Both streamers on most males in these colonies were experimentally either lengthened or shortened by 20 mm and as a result 10 randomly chosen males of each category had their streamer lengths manipulated before the fertile period of their mate. Males with elongated streamers had a significantly shorter pre-laying period (from arrival until first egg date) than those with shortened streamers and we interpret this as indicating that they obtained their mates more rapidly. Females mated to elongated males had significantly longer tails and laid their first egg significantly earlier than those mated to shortened males; no other indices of reproductive success differed between these two experimental groups. These results provide some support for previous work suggesting that females prefer males with longer streamers and thus that streamer length in this species is under the influence of sexual selection. We also found that males with longer natural streamers were significantly more likely to break them and that males were much more likely to break their streamers than were females. Since males participate in incubation in North America but not in Europe, we suggest that the aerodynamic disadvantages of streamer breakage that result from incubation attentiveness are at least partly responsible for the shorter streamer length of males in North America.

No evidence of paternal genetic contribution to nestling cell-mediated immunity in the North American barn swallow