Department of Economics and Geosciences, United States Air Force Academy, Colorado Springs, Colorado, USA.
Department of Biology, University of Nevada Reno, Reno, Nevada, USA.
Ecol Appl. 2022 Dec;32(8):e2688. doi: 10.1002/eap.2688. Epub 2022 Jul 27.
Urbanization is increasing at a rapid pace globally. Understanding the links among environmental characteristics, phenotypes, and fitness enables researchers to predict the impact of changing landscapes on individuals and populations. Although avian reproductive output is typically lower in urban compared with natural areas, the underlying reasons for this discrepancy may lie at the intersection of abiotic and biotic environmental and individual differences. Recent advances in urban ecology highlight the effect of heavy metal contamination on stress physiology. As high levels of glucocorticoid hormones decrease parental investment, these hormones might be the link to decreased reproductive success in areas of high environmental pollution. In this study, we aimed to identify which abiotic stressors are linked to avian reproductive output in urban areas and whether this link is mediated by individual hormone levels. We used fine-scaled estimates (2 m spatial resolution) of nighttime light, noise, and urban density to assess their impacts on the physiological condition of adult house sparrows (Passer domesticus). We measured circulating levels of lead and glucocorticoid concentrations in 40 breeding pairs of free-living house sparrows and related these physiological traits to reproductive success. Using structural equation modeling, we found that increased urban density levels linked directly to increased plasma corticosterone and lead concentrations that subsequently led to decreased fledgling mass. Sparrows with increased lead concentrations in plasma also had higher corticosterone levels. Although urban areas may be attractive due to decreased natural predators and available nesting sites, they may act as ecological traps that increase physiological damage and decrease fitness. To illustrate, avian development is strongly explained by parental corticosterone levels, which vary significantly in response to urban density and lead pollution. With fine-scale ecological mapping for a species with small home ranges, we demonstrated the presence and impacts of urban stressors in a small city with high human densities.
城市化正在全球范围内迅速加速。了解环境特征、表型和适应能力之间的联系，使研究人员能够预测不断变化的景观对个体和种群的影响。尽管与自然区域相比，鸟类的繁殖产量通常较低，但造成这种差异的根本原因可能在于非生物和生物环境以及个体差异的交叉点。城市生态学的最新进展强调了重金属污染对压力生理的影响。由于高水平的糖皮质激素会降低亲代投资，这些激素可能是导致高环境污染地区繁殖成功率下降的原因。在这项研究中，我们旨在确定哪些非生物胁迫因子与城市地区的鸟类繁殖产量有关，以及这种联系是否通过个体激素水平来介导。我们使用夜间灯光、噪音和城市密度的精细尺度估计值（2 米空间分辨率）来评估它们对成年麻雀（Passer domesticus）生理状况的影响。我们测量了 40 对自由生活的麻雀繁殖对的循环血铅和糖皮质激素浓度，并将这些生理特征与繁殖成功率相关联。使用结构方程模型，我们发现，城市密度的增加与血浆皮质酮和铅浓度的增加直接相关，而这些浓度的增加随后导致幼鸟体重减轻。血浆中铅浓度增加的麻雀皮质酮水平也较高。尽管由于减少了自然捕食者和可用的筑巢地点，城市地区可能更具吸引力，但它们可能成为生态陷阱，增加生理损伤并降低适应能力。例如，鸟类的发育受到亲代皮质酮水平的强烈解释，而亲代皮质酮水平会因城市密度和铅污染而发生显著变化。通过对具有小巢区的物种进行精细的生态制图，我们展示了一个人口密度高的小城市中存在城市应激源及其影响。
