A lodgepole pine forest smolders following a fire in Yellowstone National Park. Photo: Raymond Gehman/National Geographic Creative

Science

How Wildfires Affect Birds

Big burns are natural, but climate change could make especially destructive fire seasons the new normal.

Devastating and deadly wildfires in California’s wine country this week made it clear that this summer’s brutal fire season in the West isn’t over yet. Nationwide, 38 fires are still burning, 17 of them large and uncontained, according to a daily report from the National Interagency Fire Center. Fires have scorched more than 8.5 million acres in 2017 so far, compared to a 10-year average of about 6 million acres. Multiple firefighters and citizens have died in blazes this season, and thousands of homes and businesses have been destroyed. Smoke has made the air dangerous to breathe in many parts of the West.

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. With that in mind, it's worth exploring how wildfires affect birds. It's hard to definitively say how avian communities will be affected in the long term, but generally speaking—for now, anyway—wildfires don't pose a major threat for most 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. But 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. “Direct mortality is not a big concern,” Saab says.

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.

Black-backed Woodpeckers move in soon after forest fires to feed on bark beetle larvae. Photo: Robert Royse/Minden Pictures

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 on this year’s ferocious fires, which may be just a glimpse of things to come. In northern California, for example, heavy winter rains 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; Columbia University scientists last year 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.”

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