BUFFALO, N.Y. — Despite burning hundreds of miles away, Canadian wildfires have become a familiar source of disruption in New York State.
Air quality advisories. A spike in emergency room visits for asthma.
Now, a University at Buffalo study has identified another consequence: fewer sightings of dozens of bird species across the Empire State.
In a study published earlier this month in Biodiversity and Conservation , a Springer Nature journal, researchers found that 40 different bird species were less likely to be observed in New York as levels of fine particulate matter (PM2.5) in the air increased during recent breeding seasons. The analysis included the 2023 season that overlapped with Canada's worst wildfire season on record.
"Our results show a link between wildfire smoke and the probability of observing particular bird species," says corresponding author Festus Adegbola, a PhD candidate in the Department of Geography, within the UB College of Arts and Sciences. "Wildfire smoke is often underexplored when monitoring biodiversity. Failing to account for air quality may bias models of species distributions and abundance."
The researchers first analyzed PM2.5 levels, a key marker of wildfire smoke, during New York's 2021–2023 breeding seasons. The highest concentrations occurred in 2023, when smoke from Canada's historic wildfires degraded air quality across New York throughout June and July. PM2.5 levels exceeded World Health Organization guidelines on multiple occasions, at times reaching eight times the recommended limit.
The researchers then matched the PM2.5 data with nearly 99,000 birdwatching checklists submitted to Cornell University's eBird database. The citizen science project, run by the Cornell Lab of Ornithology, allows birdwatchers to record the birds they observe, creating one of the world's largest collections of bird observations.
Because the observations come from birdwatchers with varying levels of experience, the UB researchers used rigorous data filtering and statistical methods to ensure reliable results.
In all, they analyzed 84 different bird species across nearly 99,000 eBird checklists collected across all of New York during the three recent breeding seasons.
Nearly half of the species studied were less likely to be observed when PM2.5 rose. These included many migratory forest songbirds, such as warblers, thrushes and vireos.
"It's possible that smoky conditions changed the birds' behavior — singing and moving less, spending more time in dense forest canopy — and therefore made them harder to detect," Adegbola says.
However, 15 species were actually more likely to be observed as PM2.5 levels rose, while another 29 showed no significant change in how likely they were to be observed. These included many aerial insectivores and some wetland-associated birds.
That doesn't necessarily mean wildfire smoke benefited those birds.
"These species often occupy more open environments than forest songbirds, so it's possible their increased sightings had more to do with where birdwatchers chose to observe during smoky conditions than how the birds themselves responded," says co-author Adam Wilson, PhD, associate professor of geography and Adegbola's adviser.
The findings suggest that fewer bird sightings during smoky periods don't necessarily mean there are fewer birds — they may simply be harder to detect. Understanding that distinction is crucial for biodiversity monitoring so that temporary declines in detectability aren't mistaken for true population declines.
"Still, as climate change continues to intensify wildfires, it's crucial we understand how birds will be affected by increased smoke pollution," Wilson says. "This study is hopefully a first step to better understanding how species respond to wildfire smoke exposure."
Other co-authors include Stuart Evans, PhD, assistant professor of geography, and Olivia Sanderfoot, PhD, a research scientist with the Cornell Lab of Ornithology.
