Early Evidence of How Wildfire Smoke Transforms Bird Migration


This story is original appeared in National High News and part of Climate Table collaboration.

Four radio-collared Tule geese left their summer breeding grounds near Alaska’s Cook Inlet in the fall of 2020 to head south for the winter. Migration typically takes about four days: The birds fly over the Gulf of Alaska, stay about 100 miles off the coast from Canada, and land on Vancouver Island. They stopped for a while to float and rest in the Pacific Ocean a few times and then congregate on Summer Lake in central Oregon before making the final push into California’s Sacramento Valley. Last summer, however, migrating birds encountered thick smoke from coastal fires in British Columbia and over Washington — and so their behavior became unusual.

A bird retreated north nearly 80 miles. The two spent nearly four days floating in the ocean before trying to land again; they led to a direct flight of the Beachie Creek Fire in Oregon and then climbed nearly four times higher than usual to overcome the huge puff of smoke. A fourth bird turned and headed farther east than usual, all the way to Idaho. Tule geese usually prefer to spend the night in wetlands, but these four stop at strange locations, even once landing on the side of Mount Hood.

According to a study released by the US Geological Survey (USGS) in early October, the 2020 migration of birds was twice as long as the 2019 migration — nine days versus four — and they flew an additional 470 miles, all to avoid the smoke of the fire. The newspaper says “megafires and thick smoke represent major problems for migratory birds” as wildfires coincide with the onset of migratory migration. There were 68 active fires in California, Oregon, and Washington when the geese passed. Longer migrations require more energy and more time to recover. That can make it difficult for birds to reproduce, and even put them at risk of dying.

Cory Overton, a wildlife biologist at the USGS Western Ecological Research Center and the paper’s lead author, observes the isolated flight of birds in real time, via GPS tracking. “I was stuck on my computer for days, trying to figure out what these birds were doing because it was so obvious, so obvious, so abnormal,” Overton said. All four birds, however, finally reached their desired stop in Oregon.

Overton and his colleagues believe this marks the first time scientists have been able to fully document how fire smoke changes the migration of birds. Birds begin to change their behavior when they encounter fine particulate matter of 161 micrograms per cubic meter, which is just above the surface. The Environmental Protection Agency measure for “bad” air for people. Migrating birds in many Western states were found dead and dying in both summer and early autumn, etc. The research found a correlation between deaths and toxic air.

The tule geese, a subspecies of the larger white front goose, is a “species of special concern” in California because of their low population size; there are less than 10,000 of them. They are especially vulnerable to flight obstacles because they follow the same route and stop at the same places every year. Overton and his colleagues also tracked 12 more waterfowl species, all of which migrate after the fall than Tule geese. The smoke almost disappeared from the Pacific Northwest by the time others traveled the region. But as fire seasons in the West lengthen, scientists worry that smoke could hinder many migrations along the Pacific Flyway. Many beach birds and songbirds cannot store the extra energy needed to change route around fires.



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