Male tail streamer length predicts fertilization success in the North American barn swallow (Hirundo rustica erythrogaster) |
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Authors: | Oddmund Kleven Frode Jacobsen Rasa Izadnegahdar Raleigh J Robertson Jan T Lifjeld |
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Institution: | (1) Natural History Museum, University of Oslo, P.O. Box 1172, Blindern, 0318 Oslo, Norway;(2) Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada |
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Abstract: | In socially monogamous species, extra-pair paternity has the potential to increase the variance in male reproductive success,
thereby affecting the opportunity for sexual selection on male extravagant ornamentation. In the European barn swallow (Hirundo rustica rustica), the tail streamer length is a sexually selected male ornament and an honest indicator of viability. The North American
barn swallow (Hirundo rustica erythrogaster) also shows sexual dimorphism in tail streamer length, but whether this trait holds the same signalling function in this
subspecies is a controversial issue, and the available literature is presently scarce. Here, we present data on paternity
in the North American barn swallow, including a complete sampling of extra-pair sires in four colonies. We analysed how extra-pair
paternity affected the variance in male fertilization success and examined whether male tail streamer (i.e. the outermost
tail feather) length correlated with fertilization success (n=86 males). Extra-pair paternity constituted 31% of all offspring and significantly increased the variance in male fertilization
success. The number of offspring sired by extra-pair males accounted for almost half of the total variance in male fertilization
success. Males with naturally long tail streamers had a higher fertilization success than males with shorter tail streamers,
and this pattern was mainly caused by a higher extra-pair success for males with long tail streamers. Males with long tail
streamers also paired with early breeding females in prime body condition. These results are consistent with the idea that
there is directional sexual selection on male tail streamer length, possibly mediated through male extra-pair mating success
or the timing of breeding onset. |
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Keywords: | Extra-pair paternity Opportunity for sexual selection Tail streamer length Hirundo rustica |
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