你所看到的红胁蓝尾鸲“妹妹”说不定是个汉子？！！

       没错，你所看到的红胁蓝尾鸲妹妹说不定是个汉子。由于红胁蓝尾鸲具有"延迟羽毛成熟(delayed plumage maturation)"的现象，所以你看到的长得雌鸟模样的个体，没准儿是只雄性个体。延迟羽毛成熟一般指鸟类的雄性个体在他们具有繁殖能力的时候（特别是在第一年繁殖的时候），仍然保持类似雌鸟的暗淡的羽毛的现象。这种现象在许多雀形目和非雀形目鸟类都存在，所以以后通过羽色来判断某些鸟类的性别可要小心了。

      我们多年在河南董寨国家级保护区的调查中，发现这里越冬的“妹妹”模样的红胁蓝尾鸲占绝大多数(> 85%)，这让我们怀疑该越冬种群的种群性比可能是偏雌的。为了检验我们的猜测，我们用分子生物学手段鉴定了几年冬季环志所收集的红胁蓝尾鸲的血液样品，结果发现大部分（约70%）的“妹妹”实际上都是年轻的小伙子，而且这个红胁蓝尾鸲冬季越冬种群的性比是显著偏雄的。所以，不管你是在董寨，还是在北京或者其它地方，见到红胁蓝尾鸲“妹妹”，可不要轻易断言他是妹妹了！

       该研究工作发表在老牌杂志《Journal of Natural History》上，链接如下http://www.tandfonline.com/doi/full/10.1080/00222933.2015.1105318#abstract

      Abstract The sex ratio of a population is an important demographic parameter, but compared to 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 (ca. 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 genetic method is a more appropriate way for sexing 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.