Strategies of dynamic plumage colour change : a field experiment to test costs of intermediate coloration

许多脊椎动物的雄性表现出两性异形，并在性内选择的选择压力下进化出雄性特有的性状。在鸟类中，许多鸟类具有性二色性，它们的雄性有明亮的羽毛。然而，一些鸟类的年轻雄性并不具有明显的外观，看起来与雌性非常相似。换句话说，年轻的雄性具有“中等亮度”。年轻雄性的暗淡羽毛可能有特定的好处和成本，这与那些明亮羽毛的雄性不同。本研究旨在探讨蓝尾跗线雀的暗羽对其生长发育的影响。进行了一项现场实验：两种类型的特殊填充模型，一个明亮的蓝色男性模型和一个沉闷的模型，提出了领域业主的红腹知更鸟。土地所有者对每种模式表现出不同的反应。因此，红腹知更鸟的羽色可能具有雄-雄相互作用的地位信号。

Males of many vertebrates show sexual dimorphism and male-specific traits evolved by selection pressure of intra-sexual selection. In avian species, many birds have sexual dichromatism and their males have bright plumages. However, young males of some avian species do not possess conspicuous appearances and appear quite similar to females. In other words, young males have "intermediate brightness". The young male's dull plumage may have specific benefit and cost, which are different compared to those males of bright plumages. This study focused on the effect of the dull plumages in the Tarsiger cyanurus. A field experiment was performed: two types of special stuffed models, a bright blue male model and a dull model, were presented to territory owners of bushrobins. Territory owners showed different responses to each models. In conclusions, plumage colours of the bushrobin may have a status signal for male-male interaction.