How Wildfires Affect Birds

This year’s fire season in the western United States still has months to go, and already several fires have shattered records. In just three days, 900,000 acres have burned in Oregon. “We have never seen this amount of uncontained fire across the state,” said Governor Kate Brown on Thursday. More than 2 million acres have burned since mid-August in California, where the complex of blazes known as the August fire is the largest in the state's history, so far scorching 788,880 acres acres across Mendocino and Humboldt counties.

Unearthly orange skies and smoky days devoid of birdsong are side effects of this unprecedented season. At least 17 people have died, with more expected as rescue workers search burned homes. In Oregon alone, some 500,000 people—more than 1 in 10 state residents—are under evacuation warning. Wildfire smoke can cause respiratory issues that make people more prone to lung infections such as COVID-19, according to the CDC, and disproportionately affects already vulnerable people including those with chronic illness (e.g. heart or lung disease), children, older adults, low-income communities, and communities of color.

While wildfires are a part of natural cycles in the western United States, climate change makes every wildfire that sparks more likely to rapidly grow and spread. Like melting glaciers and rising seas, larger fires and longer fire seasons are among the predicted effects of climate change that are now coming to pass. Rising temperatures and shifting rainfall patterns already threaten two-thirds of North American bird species with extinction, so it's worth exploring how this symptom of a hotter planet will affect birds.

What do birds do when wildfires break out? No surprise here: They fly away. A fire might kill weak birds or, depending on the time of year, claim nestlings. At least in the Western forests that U.S. Forest Service research biologist Vicki Saab studies, birds evolved alongside fire and flee in the face of conflagrations. "Historically, I think direct mortality was likely minor," she says. But they might not be able to outrun the larger, more destructive fires we're now experiencing due to climate change, she adds. 

How do wildfires physically affect birds? Assuming birds escape a fire, smoke might still affect their health in ways that aren’t very well understood. “We do know that exposure to particulate matter, which of course is of great concern for human health, can affect birds as well,” says Olivia Sanderfoot, a National Science Foundation Graduate Research Fellow at the University of Washington Seattle who studies how air pollution affects birds. For example, veterinarians and poultry scientists who study captive birds have found that smoke can damage lung tissue and leave the animals susceptible to potentially lethal respiratory infections.

How that plays out in the wild is largely unknown, Sanderfoot says. Her current research aims to track changes in bird populations and diversity after exposure to smoke from large wildfires. In some cases, smoke inhalation might make it harder for birds to flee onrushing flames. Thick smoke, for instance, may have contributed to the deaths of 50 adult White Ibises during a 1999 fire in the Everglades, Sanderfoot reported in a recent paper. And some low-flying species might succumb to smoke inhalation or exhaustion before they can escape forest fires, according to the Alberta Institute for Wildlife Conservation.

How do wildfires affect habitat, and do any birds benefit from blazes? A little disturbance is a good thing for many species. In the dry, mixed-conifer forests Saab studies, most wildfires—even intense ones—burn unevenly, leaving behind a mosaic of habitat patches. “Fire definitely benefits a lot of bird species,” Saab says. “It’s not all doom and gloom.”

For a Black-backed Woodpecker, for example, a newly burned forest provides a smorgasbord. Bark- and wood-boring beetles arrive in droves and lay eggs in charred trees; woodpeckers feast when they reach the larval stage. There’s often an influx of other bugs, too, which draws aerial insectivores like Dusky Flycatchers and Mountain Bluebirds that hunt for midair meals in the new forest openings created by fire, Saab says. The patchwork of post-fire habitats also suits White-headed Woodpeckers and other species that nest in open areas but forage in unburned surrounding forests.

Other birds benefit from fires over the longer term. Kirtland’s Warbler, for instance, nests only in the fire-dependent jack pine forests of Michigan, Wisconsin, and Ontario. Jack pine cones are sealed tight with resin until fire opens them up, releasing the seeds and generating new warbler habitat. Red-headed Woodpeckers, which nest in the high limbs of dead trees, can see a local population boom after a fire devastates a patch of forest. 

Blazes aren’t a boon for all avian species. Wildfire forces those that dwell in old-growth forests—including Pileated Woodpeckers, Townsend’s Warblers, and Golden-crowned Kinglets—to go in search of new places to nest and forage. It also poses a serious risk to a bird that faces plenty of other threats: the Greater Sage-Grouse. Fire in the sagebrush ecosystem—upon which this iconic species depends—often gives invasive plants such as cheatgrass and juniper a leg up on slower-growing sage, and they provide fuel for future fires.

Do birds ever start wildfires? When combined with electricity, yes. We’ve all seen birds perched harmlessly on power lines. But if they manage to touch two transmission lines at once, they form a circuit and get zapped. In two recent fires started by birds, hawks were carrying snakes. Chances are, those writhing meals-to-be touched the second power line, electrocuting dinner and diner both, and sparking the blaze below.

There are credible claims that birds intentionally spread fires, too. Audubon and other publications have covered anecdotal reports of northern Australia raptors picking up burning sticks and dropping them elsewhere on the arid landscape to flush out prey like lizards and snakes. Mark Bonta, the Penn State geographer behind those reports, says that he and colleagues have a forthcoming peer-reviewed paper with further evidence that Black Kites, Brown Falcons, and Whistling Kites all spread fires intentionally. The researchers haven’t yet captured video or photographic evidence of the phenomenon, but Bonta says they’ve confirmed it by interviewing local experts and reviewing publications of aboriginal knowledge.

How big of a role does climate change play? Researchers detect a changing climate’s fingerprints in recent fires, which may be just a glimpse of things to come. In northern California, for example, heavy winter rains in 2017 fueled a riot of new plant growth in the spring, but the summer’s record heat parched that vegetation, turning it to tinder. That’s part of a broader trend; in 2016, Columbia University scientists showed that climate change has doubled the area of the western U.S. affected by forest fires over the past three decades. “Climate is really running the show in terms of what burns,” one of that study’s authors said. “We should be getting ready for bigger fire years than those familiar to previous generations.”

What climate-charged fires will mean for birds is hard to say. “More and more, the past is becoming irrelevant as we advance to the no-analog future climate,” one researcher told Audubon in 2015. Saab, from the Forest Service, says she expects future fires to rearrange habitat types and the distribution of bird species. For now, the patchwork of habitat left behind by blazes helps maintain bird diversity in Western forests. “In the future?” she says, “I don’t know.”

Updated introduction September 11, 2020. View original version, published October 11, 2017, at the Wayback Machine.