Extensive, severe wildfires, and wildfire‐induced smoke occurred across the western and central United States since August 2020. Wildfires resulting in the loss of habitats and emission of particulate matter and volatile organic compounds pose serious threatens to wildlife and human populations, especially for avian species, the respiratory system of which are sensitive to air pollutions. At the same time, the extreme weather (e.g., snowstorms) in late summer may also impact bird migration by cutting off their food supply and promoting their migration before they were physiologically ready. In this study, we investigated the environmental drivers of massive bird die‐offs by combining socioecological earth observations data sets with citizen science observations. We employed the geographically weighted regression models to quantitatively evaluate the effects of different environmental and climatic drivers, including wildfire, air quality, extreme weather, drought, and land cover types, on the spatial pattern of migratory bird mortality across the western and central US during August‐September 2020. We found that these drivers affected the death of migratory birds in different ways, among which air quality and distance to wildfire were two major drivers. Additionally, there were more bird mortality events found in urban areas and close to wildfire in early August. However, fewer bird deaths were detected closer to wildfires in California in late August and September. Our findings highlight the important impact of extreme weather and natural disasters on bird biology, survival, and migration, which can provide significant insights into bird biodiversity, conservation, and ecosystem sustainability.

中文翻译：

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前所未有的候鸟死亡：基于公民的美国西部大规模死亡率事件的时空格局分析

自2020年8月以来，美国西部和中部发生了广泛的，严重的野火和由野火引起的烟雾。野火导致栖息地的丧失以及微粒物质和挥发性有机化合物的排放，对野生动植物和人类尤其是禽类造成了严重威胁种类，其呼吸系统对空气污染敏感。同时，夏末的极端天气（例如暴风雪）也可能通过切断鸟类的食物供应并在其生理上准备好之前促进其迁移而影响鸟类的迁移。在这项研究中，我们通过将社会生态地球观测数据集与公民科学观测数据相结合，研究了大规模鸟类死亡的环境驱动因素。我们采用了地理加权回归模型来定量评估不同环境和气候驱动因素（包括野火，空气质量，极端天气，干旱和土地覆盖类型）对美国西部和中部迁徙鸟类死亡期间空间分布的影响。 2020年8月至9月。我们发现这些驱动因素以不同方式影响候鸟的死亡，其中空气质量和距野火的距离是两个主要驱动因素。另外，8月初在市区和接近野火的地方发现了更多的鸟类死亡事件。然而，在8月下旬和9月下旬，在加州山火附近，发现的鸟类死亡人数较少。我们的研究结果突显了极端天气和自然灾害对鸟类生物学，生存和迁徙的重要影响，