More frequent and intense wildfire — and all the associated smoke — changes what birds are seen and heard, according to a new University of Washington study.

While that’s a rather intuitive finding, it could have implications for bird conservation and future studies looking at air pollution and bird health, said lead researcher Olivia Sanderfoot, a doctoral candidate in the University of Washington School of Environmental and Forest Sciences.

In particular, the study collected reports from eBird, an online citizen science tool run by Cornell Lab of Ornithology, and compared those with air quality metrics in Washington state between the wildfire seasons of 2015 to 2018.

Researchers discovered that smoke concentrations of PM 2.5 or higher decreased the detection of 16 species but increased the detection of 10 others .

The species that were harder to see or hear included Canada geese, two gull species and bald eagles.

The species that were observed more frequently included three types of warblers, cedar waxwing, spotted towhee and California quail.

The study did not look at what caused these differences, but Sanderfoot hypothesizes they could be due in part to smoke having negative health impacts on some birds and in part hazy skies obscuring views.

That’s where she hopes the study can help advance our knowledge about birds. There is, she said, little research on how smoke impacts bird health — or more broadly — animal health.

“Generally speaking, there is not a whole lot out there,” she said.

Birds are the most efficient breathers of all terrestrial vertebrae, extracting more oxygen per unit of air than any other species.

That, Sanderfoot said, would seem to make them particularly vulnerable to air pollution.

The study also revealed how dedicated most birders are, braving even smoky and unhealthy conditions all in the name of checking in on regional birds.

“In this dataset, we didn’t find any evidence that birders were changing their behavior,” she said. “Folks who use eBird tend to be very dedicated birders.”

The results were published in June in the journal Ornithological Applications.

Sanderfoot hopes her study influences and guides any future research looking at the impacts of smoke on bird health.

“We have to know what our observation process looks like,” Sanderfoot said. “What is influencing our ability to detect individuals and species, and account for that in our models.

“Our work does show that smoke pollution is an important component of the observation process and ecologists should keep that in mind when designing future studies.”