Delhey Kaspar, Peters Anne, Kempenaers Bart
Max Planck Institute for Ornithology, PO Box 1564, D-82305 Seewiesen, Germany.
Am Nat. 2007 Jan;169 Suppl 1:S145-58. doi: 10.1086/510095.
Colorful plumages are conspicuous social signals in birds, and the expression of these colors often reflects the quality of their bearers. Since mature feathers are dead structures, plumage color is often considered a static signal that does not change after molt. Feathers, however, can and do deteriorate between molts, and birds need to invest heavily in plumage maintenance. Here we argue that this need for preserving plumage condition and hence signaling content might have given rise to a novel type of sexual signal: cosmetic coloration. Cosmetic coloration occurs when the substances used for plumage maintenance change the color of the feathers, thereby becoming a signal themselves. Our review of cosmetic coloration in birds demonstrates that it is more widespread than currently realized, occurring in at least 13 bird families. Cosmetics have varied origins: they can be produced by the bird itself (uropygial and skin secretions, feather powder) or obtained from the environment (soil, iron oxide). Intraspecific patterns of cosmetic use (sex, age, and seasonal dimorphism) suggest that in many cases it may act as a sexual signal. However, more information is required on function, mechanisms, and costs to understand the evolution of cosmetic coloration and to confirm its signaling role.
色彩斑斓的羽毛是鸟类显著的社会信号，这些颜色的表达往往反映了其拥有者的品质。由于成熟的羽毛是无生命的结构，羽毛颜色通常被视为一种静态信号，换羽后不会改变。然而，羽毛在换羽期间会磨损，鸟类需要在羽毛维护上投入大量精力。在此，我们认为这种保持羽毛状态从而维持信号内容的需求可能催生了一种新型的性信号：修饰性色彩。当用于羽毛维护的物质改变羽毛颜色，从而自身成为一种信号时，修饰性色彩就会出现。我们对鸟类修饰性色彩的综述表明，它比目前所认识到的更为普遍，至少在13个鸟类家族中存在。用于修饰的物质来源多样：它们可以由鸟类自身产生（尾脂腺和皮肤分泌物、羽粉），也可以从环境中获取（土壤、氧化铁）。修饰性色彩在种内的使用模式（性别、年龄和季节性二态性）表明，在许多情况下它可能作为一种性信号。然而，需要更多关于功能、机制和成本的信息，以了解修饰性色彩的进化并确认其信号作用。
