Department of Biology, University of British Columbia Okanagan, Kelowna, BC, Canada.
Tierra de Aves, Veracruz, Mexico.
Ecotoxicology. 2022 Mar;31(2):234-250. doi: 10.1007/s10646-021-02510-6. Epub 2022 Jan 1.
Mercury (Hg) is an environmental contaminant that can negatively impact human and wildlife health. For songbirds, Hg risk may be elevated near riparian habitats due to the transfer of methylmercury (MeHg) from aquatic to terrestrial food webs. We measured Hg levels in tail feathers sampled across the breeding range of the Yellow-breasted Chat (Icteria virens), a riparian songbird species of conservation concern. We assessed the risk of Hg toxicity based on published benchmarks. Simultaneously, we measured corticosterone, a hormone implicated in the stress response system, released via the hypothalamus-pituitary-adrenal axis. To better understand range-wide trends in Hg and corticosterone, we examined whether age, sex, subspecies, or range position were important predictors. Lastly, we examined whether Hg and corticosterone were correlated. Hg levels in chats were relatively low: 0.30 ± 0.02 µg/g dry weight. 148 out of 150 (98.6%) had Hg levels considered background, and 2 (1.6%) had levels considered low toxicity risk. Hg levels were similar between sexes and subspecies. Younger chats (<1 year) had higher Hg levels than older chats (>1 year). Hg levels were lowest in the northern and central portion of the eastern subspecies' range. Corticosterone concentrations in feathers averaged 3.68 ± 0.23 pg/mm. Corticosterone levels were similar between ages and sexes. Western chats had higher levels of corticosterone than eastern chats. Hg and corticosterone were not correlated, suggesting these low Hg burdens did not affect the activity of the hypothalamus-pituitary-adrenal axis. Altogether, the chat has low Hg toxicity risk across its breeding range, despite living in riparian habitats.
汞 (Hg) 是一种环境污染物，会对人类和野生动物的健康产生负面影响。对于鸣禽来说，由于甲基汞 (MeHg) 从水生食物链向陆地食物链的转移，在河岸栖息地附近，Hg 的风险可能会升高。我们测量了在黄胸鸣鸟（Icteria virens）的繁殖范围内采集的尾羽中的 Hg 水平，黄胸鸣鸟是一种受保护关注的河岸鸣禽物种。我们根据已发表的基准评估了 Hg 毒性的风险。同时，我们测量了皮质酮，这是一种与应激反应系统有关的激素，通过下丘脑-垂体-肾上腺轴释放。为了更好地了解 Hg 和皮质酮在整个范围内的趋势，我们检查了年龄、性别、亚种或范围位置是否是重要的预测因素。最后，我们检查了 Hg 和皮质酮是否相关。鸣鸟中的 Hg 水平相对较低：0.30 ± 0.02 µg/g 干重。150 个中的 148 个（98.6%）的 Hg 水平被认为是背景水平，2 个（1.6%）的 Hg 水平被认为是低毒性风险。性别和亚种之间的 Hg 水平相似。年龄较小的鸣鸟（<1 岁）的 Hg 水平高于年龄较大的鸣鸟（>1 岁）。在东部亚种范围的北部和中部，Hg 水平最低。羽毛中的皮质酮浓度平均为 3.68 ± 0.23 pg/mm。年龄和性别之间的皮质酮水平相似。西部鸣鸟的皮质酮水平高于东部鸣鸟。Hg 和皮质酮没有相关性，这表明这些低 Hg 负担并没有影响下丘脑-垂体-肾上腺轴的活性。总的来说，尽管栖息在河岸栖息地，但鸣鸟在其繁殖范围内的 Hg 毒性风险较低。
