Data from: Do trace metals influence visual signals? Effects of trace metals on iridescent and melanic feather colouration in the feral pigeon

Trace metals are chemical pollutants of prime concern nowadays given their implication in several human diseases and their noxious effects on wildlife. Previous studies demonstrated their negative (e.g. lead, cadmium) or positive (e.g. zinc) effects on body condition, immunity and reproductive success in birds. Because of their effects on bird condition, trace metals are likely to influence the production of condition-dependent plumage colours, that may be used in mate choice. In the feral pigeon Columba livia, we investigated iridescent colouration in response to lead and zinc experimental (i.e. metal supplementation in standardized conditions) and natural exposure (i.e. metal concentrations in feathers of wild urban pigeons), and melanic feather colouration in response to experimental lead and zinc exposure. Both studies (i.e. experimental and correlative) consistently showed that lead exposure decreased iridescent neck feather brightness independently of colour morph. Moreover, lead, when provided alone, decreased melanic feather reflectance in the middle wavelengths while zinc supplementation increased melanic feather reflectance in the violet-wavelength. In conclusion, our study suggests that the colouration of iridescent and melanic feathers depends on the exposure to pollutants. Whether trace metal exposure affected the ability of birds to produce melanin pigments, to grow the microstructural feather elements required for maximum colour display, or to cope with bacteria that degrade feather microstuctures remains unclear. Future studies should investigate whether these metal-induced modifications of plumage colouration affect behaviours involved in sexual selection.痕量金属（trace metals）如今已成为首要关注的化学污染物，因其与多种人类疾病存在关联，且对野生生物具有毒害作用。既往研究表明，此类金属对鸟类的体况、免疫功能与繁殖成功率兼具负面（如铅（lead）、镉（cadmium））与正面（如锌（zinc））效应。鉴于痕量金属可影响鸟类体况，其或可调控体况依赖型羽色的生成——此类羽色常被用于配偶选择。本研究以野鸽（Columba livia）为研究对象，分别针对铅与锌的实验暴露（即在标准化条件下开展金属补充）与自然暴露（即检测野生城市鸽羽毛中的金属浓度）两种场景，探究了其虹彩羽色的响应；同时针对实验性铅、锌暴露，研究了其黑素型羽色的变化。两项研究（即实验性研究与相关性研究）均一致显示，无论羽色形态（colour morph）如何，铅暴露均会降低虹彩颈羽的亮度。此外，单独施用铅时，会降低中波长段内的黑素型羽毛反射率；而补充锌则可提升紫光波长段内的黑素型羽毛反射率。综上，本研究结果表明，虹彩羽与黑素型羽毛的着色水平取决于污染物暴露程度。目前仍未明确的是，痕量金属暴露是否会影响鸟类生成黑色素的能力、生长出实现最优色彩展示所需的羽毛微结构组分，或是应对降解羽毛微结构的细菌的能力。未来研究可进一步探究这类由金属诱导的羽色变化，是否会影响性选择相关的行为。