Fall bird migration in western North America during a period of heightened wildfire activity

Authors: Kyle D. Kittelberger , Megan K. Miller, and Çağan H. Şekercioğlu

Year: 2022

Publication: Avian Conservation & Ecology

Publication Link: https://ace-eco.org/vol17/iss2/art43/

Keywords: avian abundance; bird banding; body condition; climate change; emaciation; lag effect; movement ecology; mortality; ornithology

Abstract: Billions of birds annually migrate between breeding and nonbreeding grounds in North America. During fall 2020, there
was a series of alarming mass-mortality events of migratory birds across the western United States, with estimates of 100,000 to 1
million birds having perished. One potential culprit behind these die-offs is wildfires, though there has been little research documenting
the indirect effects of wildfires on actively migrating birds. We undertook a multi-year assessment of potential impacts that wildfires
may have had on fall bird migration over the past decade, with a particular focus on fall 2020, using systematic bird banding data from
southeastern Utah. We used a correlative approach to evaluate the relationship between estimates of acres burned by wildfires in western
North America on several variables representing bird abundance and body condition. Notably, in our best fit models of birds banded
at our research site during fall 2020, we found both a positive relationship for the number of bird captures and a negative relationship
for body mass index with more daily burned acres. We provide an examination of incorporating lag effects of wildfires on different
metrics of bird migration to account for potential impacts of fires on birds before migration and banding. Additionally, we assess the
usefulness of different proxies of body condition in highly stressed land birds and introduce a scale for scoring emaciation of birds in
the hand while banding. Our insights into avian migration ecology are one of the few studies that explore the role wildfires may have
had in affecting migratory bird movements and health.

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