Despite the increased frequency with which wildfire smoke now blankets
portions of world, the effects of smoke on wildlife, and birds in
particular, are largely unknown. We used two decades of banding data from
the San Francisco Bay Bird Observatory to investigate how fine particulate
matter (PM2.5) – a major component and indicator of wildfire smoke –
influenced capture rates and body condition of 21 passerine or
near-passerine bird species. Across all study species, we found a negative
effect of acute PM2.5 exposure and a positive effect of chronic PM2.5
exposure on avian capture rates. Together, these findings are indicative
of decreased bird activity or local site removal during acute periods of
wildfire smoke, but increased activity or site colonization under chronic
smoke conditions. Importantly, we also observed a negative relationship
between chronic PM2.5 exposure and body mass change in individuals with
multiple captures per season. Our results indicate that wildfire smoke
likely influences the health and behavior of birds, ultimately
contributing to a shift in activity and body condition, with differential
short-term versus long-term impacts. Although more research is needed on
the mechanisms driving these observed changes in bird health and behavior,
as well as validation of these relationships in more areas, our results
suggest that wildfire smoke is a potentially frequent large-scale
environmental stressor to birds that deserves increasing attention and
recognition.