The first evidence of how fire smoke changes bird migration

This story was originally appeared on High Country News and is part of Climate Table collaboration.

Four radio-collared geese left their summer breeding site near Cook Island inlet in Tule, Alaska in the fall of 2020 to move south in the winter. The migration usually takes about four days: the birds fly over the Gulf of Alaska, stay about 100 miles from Canada, and surround Vancouver Island. They stop short to float and rest in the Pacific Ocean, and then gather en masse on Summer Lake in central Oregon before giving their final push to the Sacramento Valley in California. Last summer, however, migratory birds encountered intense fire off the coast of British Columbia and Washington, and their behavior was rare at the time.

A bird flew back nearly 80 miles to the north. The two spent almost four days floating in the ocean before attempting to re-enter the interior; They flew directly to Beachie Creek Florence in Oregon and then climbed nearly four times higher than usual to overcome the huge land of smoke. He turned to a fourth bird and headed farther east than usual to Idaho. Tule geese usually prefer to spend the night in wetlands, but these four stayed in strange places, even once they landed on the side of Mount Hood.

According to A Research published by the US Geological Survey (USGS) in early October, the birds ’2020 migration was twice as long as the 2019 migration — nine days versus four — and they flew 470 miles more, all to avoid the smoke from the fires. The article says that “mega-fires and thick smoke cause major problems for migratory birds,” and forest fires are increasingly coinciding with the onset of autumn migration. There were 68 active fires when geese passed through California, Oregon and Washington. Longer migrations require more energy and more time to recover. This can make it difficult for birds to breed, and even put them at risk of death.

Cory Overton, a wildlife biologist at the USGS Western Ecological Research Center and lead author of the paper, was watching disconnected bird flights in real time via GPS tracking. “I was stuck on my computer for days, trying to guess what these birds were doing, very clearly, of course, because it wasn’t normal,” Overton said. The four birds, however, arrived at their preferred stop in Oregon.

Overton and his colleagues believe this is the first time scientists have been able to definitively document how fire smoke changes bird migration. The birds began to change their behavior when they encountered a fine particle of 161 micrograms per cubic meter, that is. Threshold of the Environmental Protection Agency air for humans is “very unhealthy”.. Birds migrating through several western states were found dead and dying in the same summer and early fall, and other studies found a correlation between death and toxic air.

Tule geese, a subspecies of the great white goose, are a “species of special concern” in California because of their low population numbers; There are less than 10,000. They are particularly vulnerable to the obstacles of airplanes because they follow the same route and stop in the same places every year. Overton and his colleagues were monitoring 12 additional waterfowl species, all of which migrate later in the fall than Tule geese. The smoke from the Pacific Northwest was almost gone by the time the others traveled through the region. But as Western fire times lengthen, scientists are concerned that smoke could hinder further migration along the Pacific Ocean. Many shorebirds and songbirds are unable to store the extra energy needed to redirect around fires.