Early evidence of how bushfire smoke is altering bird migration

This story is original featured on High Country News which is part of Climate office cooperation.

Four cordless Tule geese left their summer breeding grounds near Cook Inlet, Alaska in the fall of 2020 to head south for the winter. Migration usually takes about four days: the birds fly over the Gulf of Alaska, stay about 100 miles from Canada, and take off from Vancouver Island. They stop briefly to float and rest in the Pacific Ocean a few times and then gather en masse at Summer Lake in central Oregon before making the final push into California’s Sacramento Valley. But last summer, the migratory birds encountered thick smoke from wildfires off the coast of British Columbia and over Washington — that’s when their behavior became strange.

One bird retreated north nearly 80 miles. Two spent nearly four days floating on the ocean before trying to head inland again; They ended up flying straight into Beachie Creek Fire in Oregon and then climbing nearly four times higher than normal to overcome the massive plume of smoke. A fourth bird turned and headed east further than usual, all the way to Idaho. Tule geese usually prefer to spend the night in wetlands, but these four stopped at exotic locations instead, and even once landed on the side of Mount Hood.

according to A study issued by the United States Geological Survey (USGS) In early October, the 2020 bird migration took twice as long as the 2019 bird migration — nine days versus four — and flew an additional 470 miles, all to avoid bushfire smoke. The paper states that “massive fires and thick smoke portend major problems for migratory birds” as wildfires increasingly coincide with the onset of the autumn migration. There were 68 active fires in California, Oregon, and Washington when the geese passed. Long migrations require more energy and take longer to recover from. This can make it difficult for birds to reproduce, and even put them at risk of death.

Cory Overton, a wildlife biologist at the USGS’s Center for Western Environmental Research and lead author of the paper, was monitoring the birds’ flights in real time, via GPS tracking. “I’ve been glued to my computer for days, trying to figure out what these birds were doing because they were so obvious, so obviously unnatural,” Overton said. However, all four birds eventually made it to their favorite stop in Oregon.

Overton and colleagues believe this is the first time that scientists have been able to definitively document how wildfire smoke affects bird migration. The birds began to change their behavior when they encountered fine particles of 161 micrograms per cubic meter, which is just over EPA Threshold For air “too unhealthy” for humans. Migratory birds across many western countries are found dead and dying in the same summer and early fall, among others The research found a relationship between mortality and toxic air.

Toll geese, a subspecies of the large white-fronted goose, are a “species of particular interest” in California due to their low numbers. There are less than 10,000 of them. They are particularly vulnerable to trip obstacles because they follow the same route and stop at the same locations annually. Overton and colleagues were also tracking 12 more species of waterfowl, which all migrate later in the fall than Tule geese. The smoke had almost disappeared from the Pacific Northwest by the time the others traveled through the area. But as fire seasons lengthen in the West, scientists worry that smoke may hinder further migrations along the Pacific flight path. Many shorebirds and songbirds are unable to store the additional energy needed to alter the course of fires.

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