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Li J.,Beijing Forestry University | Li J.,Beijing Normal University | Zhang Z.,Beijing Normal University | Wang Y.,Beijing Normal University | And 6 more authors.
Journal of Natural History

The sex ratio of a population is an important demographic parameter, but compared with breeding populations, the sex ratios of avian winter populations have received relatively little attention. The orange-flanked bush-robin (Tarsiger cyanurus) is a migratory species whose plumage is sexually dimorphic with delayed plumage maturation wherein first-year males show female-like plumage. We investigated the sex ratio of an orange-flanked bush-robin population wintering in Dongzhai National Nature Reserve located in central China. The results show that most (> 85%) orange-flanked bush-robins of this population have female-like plumage, implying that the population sex ratio might be female-biased. However, genetic analysis revealed that most (c. 70%) individuals with female-like plumage were males, resulting in a significantly male-biased population sex ratio. Among the individuals with female-like plumage, the males were found to have significantly longer wings and tails than females, but the accuracy of a discriminant analysis employing the two morphological traits to sex them was low. The results suggest that a genetic method is a more appropriate way to sex those orange-flanked bush-robins with female-like plumage and more importantly, one needs to be cautious when using the morphology of individuals to infer the sex ratio of a population for species like orange-flanked bush-robins. © 2015 Taylor & Francis Source

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