In 2020, the fire season affecting the western United States reached unprecedented levels. The 116 fires active in September consumed nearly 20,822 km2 (https://inciweb.nwcg.gov/accessible-view/ Accessed 2020-09-29) with 80% of this footprint (16,567 km2) from 68 fires occurring within California, Oregon, and Washington. Although the 2020 fire season was the most extreme on record, it exemplified patterns of increased wildfire size, number, timing, return frequency, and extent, which are linked to climate-driven changes in precipitation and temperature affecting fire ignition and severity (Westerling 2016, Goss et al. 2020, Weber and Yadav 2020). In addition, wildfire smoke and particulate pollution have expanded greatly in recent decades throughout western North America, posing a threat to both human and ecological health (Burke et al. 2021). Wildfires have increasingly coincided with the start of fall migration (Westerling 2016, Goss et al. 2020) and may present a growing risk to migrating birds in the Pacific Flyway. Migrating birds across several western states were observed dead and dying in 2020. Within the Central Flyway, starvation of insectivorous birds that were recovered in Arizona, Colorado, and New Mexico was linked to a record cold-weather storm in the Rocky Mountains (Fox 2020). But causes of the nearly simultaneous bird mortalities of larger granivorous species (Fig. 1) further west in the Pacific Flyway, where fires were occurring, remain unclear.
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