Thousands of Migrating Birds Drop Dead Across Southwestern U.S.

Researchers aren’t sure what’s causing the mass die-off impacting birds flying south for the winter

A dead Townsend's Warbler in gravel
NMSU professor Martha Desmond, biologist in the Department of Fish, Wildlife and Conservation Ecology is trying to find out why hundreds of thousands of migratory birds have been found dead across the state. Stephanie May Joyce / New Mexico State University

Thousands of dead migratory birds in the southwestern United States have scientists baffled, reports Algernon D’Ammassa for the Las Cruces Sun-News. “Unprecedented” numbers of dead birds have turned up in and around New Mexico in the last few weeks, and researchers aren’t yet sure why, Martha Desmond, an ecologist at New Mexico State University (NMSU), tells the Sun-News.

The phenomenon first gained notice when hundreds of dead birds were found at the White Sands Missile Range in New Mexico on August 20 but has since spread across at least five U.S. states and four Mexican states, per the Sun-News.

Speaking with Kevin Johnson of Audubon, Desmond estimates that if dead birds continue to pile up the total could reach six figures. “We haven’t counted all the species yet, but there are lots of species involved,” she adds. Per Audubon, there have been reports of dead owls, warblers, hummingbirds, loons, flycatchers, woodpeckers and other species migrating south to escape the winter cold.

Notably, the region’s resident birds, such as roadrunners or quail, are not among the dead, according to the Sun-News.

Researchers are exploring whether the numerous fires burning along the West Coast might have a hand in the mass die-off, perhaps through smoke inhalation or dangerous route changes to avoid the blazes, reports Simon Romero for the New York Times. Other potential explanations identified by the Times include a sudden bout of cold weather that recently gripped portions of the Rockies and High Plains or a drought in the Southwest that has decimated the insects many migratory birds depend on for food.

Many of the dead birds collected by researchers appear emaciated and some even seem to have simply taken a nose-dive mid-flight. “They’re literally just feathers and bones,” Allison Salas, a graduate student at NMSU who has been collecting carcasses, wrote in a tweet quoted by Phoebe Weston of the Guardian. “Almost as if they have been flying until they just couldn’t fly any more.”

Desmond tells the Guardian she found more than a dozen feathered corpses in a two-mile stretch near her home. “To see this and to be picking up these carcasses and realising how widespread this is, is personally devastating,” she tells the Guardian. “To see this many individuals and species dying is a national tragedy.”

Salas tells the Sun-News that members of the public can log any unusual dead birds they find using the iNaturalist website and mobile app, adding that the data could help researchers understand the species and locations being hit especially hard.

Speaking with the Times, Tristanna Bickford, a spokeswoman for the New Mexico Department of Game and Fish, urged those who encounter dead or unhealthy birds to be cautious and to wear gloves if they intend to collect specimens to pass on to authorities.

Birds recovered from the Southwest will be sent to the National Wildlife Health Center in Wisconsin, per the Times, as well as the U.S. Fish and Wildlife Service Forensics Laboratory in Oregon for further analysis, according to the Sun-News. However, Desmond tells the Sun-News, these analyses are unlikely to offer a clear answer for weeks or even months.

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