Metal mining causes serious ecological disturbance, due partly to heavy metal (HM) pollution that can accumulate at mining sites themselves and be dispersed downstream as runoff. Plumage coloration is important in birds’ social and ecological interactions and sensitive to environmental stressors, and several local-scale studies have found decreased carotenoid-based plumage and/or increased melanin-based plumage in wild birds exposed to HM pollution. We investigated regional-scale effects of proximity to mines and their downstream rivers as a proxy of exposure to HM-contaminated mining waste on plumage coloration in Streak-backed Orioles (Icterus pustulatus) in south-central Mexico. We measured the plumage color of museum skins using reflectance spectrometry and digital photography, then used geographic information systems to estimate each specimen’s distance from the nearest mining concession and river and determine whether that river’s watershed contained mines. Proximity to mines and their downstream rivers was related to ventral (but not dorsal) carotenoid-based coloration; birds collected farther from mines had more vivid yellow-orange breast plumage, and belly plumage was more vivid and redder with increasing distance from rivers with upstream mines. Breast background reflectance unexpectedly decreased with mine distance and was higher among birds whose nearest river had mines upstream. The area (but not reflectance) of melanin-based plumage was also related to mines. The area of dark back streaks decreased with mine distance, while the bib patch was smaller among birds presumably more exposed to mining waste. While some of these results are consistent with predicted effects of HM pollution on plumage, most were not straightforward, and effects differed among plumage patches and variables. Further investigation is needed to understand the direct (e.g., toxicity, oxidative stress) and/or indirect (e.g., decreased availability of carotenoid-rich food) mechanisms responsible and their individual-, population-, and community-level implications.

中文翻译：

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金属矿及其径流会影响羽毛颜色吗？墨西哥的条纹金莺表现出意想不到的模式

金属开采会造成严重的生态干扰，部分原因是重金属 (HM) 污染会在矿场本身积聚并作为径流向下游扩散。羽毛着色在鸟类的社会和生态相互作用中很重要，并且对环境压力因素敏感，一些当地规模的研究发现，暴露于 HM 污染的野生鸟类的基于类胡萝卜素的羽毛减少和/或基于黑色素的羽毛增加。我们调查了靠近矿山及其下游河流的区域尺度影响，作为暴露于 HM 污染的采矿废物对墨西哥中南部条纹背金莺 (Icterus pustulatus) 羽毛着色的代表。我们使用反射光谱法和数码摄影测量了博物馆皮肤的羽毛颜色，然后使用地理信息系统估计每个标本与最近的采矿特许权和河流的距离，并确定该河流的分水岭是否包含地雷。靠近矿山及其下游河流与腹侧（但不是背侧）基于类胡萝卜素的着色有关；离矿越远采集的鸟，胸羽呈橙黄色，胸羽越鲜艳，越靠近矿井上游河流越远，腹羽越鲜艳、越红。乳房背景反射率随着地雷距离出乎意料地降低，并且在最近的河流上游有地雷的鸟类中更高。黑色素羽毛的面积（但不是反射率）也与地雷有关。深色背部条纹的面积随着矿山距离的增加而减少，而鸟类的围兜面积较小，可能更容易暴露于采矿废物中。虽然其中一些结果与 HM 污染对羽毛的预测影响一致，但大多数结果并不简单，而且羽毛斑块和变量之间的影响也不同。需要进一步调查以了解直接（例如，毒性、氧化应激）和/或间接（例如，减少富含类胡萝卜素食物的供应）机制及其对个人、人群和社区层面的影响。