Troubling mass bird die-offs in the southwestern U.S.

Published: September 24, 2020

Western Wood-pewee flycatcher Hayley Crews/shutterstock

The massive wildfires devastating large swaths of the western U.S. may be a contributing factor in a series of mass bird die-offs that have been recorded across several southwestern states.

The first incident was reported on August 20 on the grounds of the White Sands Missile Range in New Mexico. Since then, multiple mass deaths have been reported in Arizona, Colorado, Nebraska, and Texas cumulatively totalling hundreds of thousands of individual birds. One researcher said that the birds were “just…falling out of the sky.”

Many of the dead birds are species that breed in Canada, then migrate south for the winter including warblers, flycatchers, and the western wood pewee. “Migratory birds are at a higher risk [than non-migrants]. They have a lot of stresses,” says Dan Kraus, senior conservation biologist for the Nature Conservancy of Canada.

One suspected cause of the die-offs is the wildfires raging in California, Oregon, and Washington State. Haze from those fires had reached southern Ontario by mid-September. The smoke may have caused migrating birds to divert their course away from the western U.S. coastline—where there’s generally plentiful food to fuel their journey—and through the relatively barren Chihuahan desert that spans across the southwestern U.S. and northern Mexico. The fact that many of the recovered birds were severely emaciated seems to support this theory. Another possibility is that they ingested the smoke and it damaged their lungs.

Closer to home, there have also been reports of mass bird die-offs in Canada in recent years, though unrelated to forest fires. In 2018, 42 starlings were found dead on the ground near a ferry terminal in Vancouver. The Canadian Wildlife Service later determined that a larger flock had been trying to escape a predator when several of the juveniles failed to pull out of a dive in time and crashed into the ground. In 2013, dozens of grackles fell to the ground dead in Winnipeg. A toxicology report found that they’d consumed a pest control poison.

One way concerned readers can help out is by becoming a “citizen scientist” and documenting any unusual sightings of dead birds on the iNaturalist app.

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