Wildfire smoke affects detection of birds in Washington State

Abstract

Wildfire smoke is likely to have direct health effects on birds as well as influence movement, vocalization, and other avian behaviors. These behavioral changes may affect if and how birds are observed in the wild, although research on the effects of wildfire smoke on bird behavior is limited. To evaluate how wildfire smoke affects detection of birds, we combined data from eBird, an online community science program, with data from an extensive network of air quality monitors in the state of Washington over a 4-year period. We assessed how PM2.5, a marker of smoke pollution, affected the probability of observing 71 bird species during the wildfire seasons of 2015-2018 using bird observations from 62,908 eBird checklists. After accounting for habitat, weather conditions, seasonality, and survey effort, we found that PM2.5 affected the probability of observing 37% of study species. The ambient concentration of PM2.5 was negatively associated with the probability of observing 16 species and positively associated with the probability of observing 10 species, indicating that birds exhibit species-specific behavioral changes during wildfire smoke events that influence how they are observed. Our results suggest that wildfire smoke impacts the presence, availability, and/or perceptibility of birds. Impacts of smoke pollution on human observers, such as impaired visibility, may also influence detection of birds. These results provide a foundation for developing mechanistic hypotheses to explain how birds, and our studies of them, are impacted by wildfire smoke. Given the projected increase in large-scale wildfire smoke events under future climate change scenarios, understanding how birds are affected by wildfire smoke - and how air pollution may influence our ability to detect them - are important next steps to inform wildlife research and avian conservation. LAY SUMMARY: Wildfire smoke events threaten public health and are likely to impact the health and behavior of birds, influencing their perceptibility. In this study, we characterized how wildfire smoke affects detection of birds. We assessed how PM2.5, a marker of wildfire smoke, affected the probability of observing 71 bird species in Washington State. We found that outdoor concentrations of PM2.5 affected the probability of observing 37% of study species. PM2.5 was negatively related to the detection of 16 species and positively related to the detection of 10 species. Our results suggest that wildfire smoke impacts the presence, availability, and/or perceptibility of birds. Given the projected increase in the frequency of large-scale wildfire smoke events, understanding how birds are affected by smoke - and how air pollution may influence our ability to detect birds - are critical next steps in avian conservation.