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Extra-Pair Mating System of a Synchronously Breeding Tropical Songbird
Bridget J. M. Stutchbury, Eugene S. Morton and Walter H. Piper
Journal of Avian Biology
Vol. 29, No. 1 (Mar., 1998), pp. 72-78
Stable URL: http://www.jstor.org/stable/3677343
Page Count: 7
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Extra-pair matings are now recognized as a fundamental component of avian mating systems. However, in tropical regions where breeding is typically asynchronous socially monogamous species appear to have low sperm competition and few extra-pair matings. We predicted that if breeding synchrony promotes the evolution of extra-pair matings, then tropical species that breed synchronously, like the Clay-colored Robin Turdus grayi, should have abundant extra-pair young (EPY). Breeding began relatively abruptly during the dry season (Feb-Mar) in this non-migratory species, with a mean of 25% of females fertile on a given day. Overall, 53% of females produced EPY, and 38% of nestlings were EPY. Males have a long and conspicuous dawn chorus, which could be a result of intense male-male competition for extra-pair matings. Male songs are individually recognizable and males vary greatly in song output. Male song output declined significantly from the pre-nesting stage through the incubation stage, as would be expected if song is important in mate choice. Our results support the idea that breeding synchrony favors extra-pair matings, however further studies of tropical songbirds are needed to fully explore how ecology is tied to extra-pair mating systems.
Journal of Avian Biology © 1998 Nordic Society Oikos