Thousands of migratory birds have inexplicably died in the southwestern United States in what ornithologists have described as a national tragedy likely to be related to the climate crisis.
Flycatchers, swallows and warblers are among the species that “fall out of the sky” as part of a mass death over New Mexico, Colorado, Texas, Arizona and further north to Nebraska, with growing concern there may already be hundreds of thousands of dead said Martha Desmond, professor of biology at New Mexico State University (NMSU). Many carcasses have little residual fat reserves or muscle mass, with some appearing to be nose-dipped into the ground in the middle of the flight.
“I collected more than a dozen in just one mile in front of my house,”
Long-distance migrants flying south from tundra landscapes in Alaska and Canada pass over the southwestern part of America to reach wintering grounds in Central and South America. During this migration, it is crucial that they land every few days to refuel before continuing their journey.
Historical forest fires over the western states of the United States could mean they had to redirect their migration away from resource-rich coastal areas and move inland across the Chihuahuan Desert, where food and water are scarce, essentially starving them to death. “They are literally just feathers and bones,” Allison Salas, a graduate student at NMSU who has collected carcasses, wrote in a Twitter thread about the death. “Almost as if they had flown until they just could not fly any more.”
The southwestern states of the United States have experienced extremely dry conditions – believed to be related to the climate crisis – meaning there may be fewer insects, the main food source for migratory birds. A cold dirt locally between 9 and 10 September could also have worsened the bird’s conditions.
Any of these weather events may have caused birds to begin their migration early as they have not built up sufficient fat reserves. Another theory is that smoke from fires may have damaged their lungs. “It could be a combination of things. It may be something that is still completely unknown to us, ”Salas said.
“The fact that we find hundreds of these birds dying just falling out of the sky is extremely alarming … The amount of carcasses we have found has literally given me chills.”
The first deaths were reported on August 20 on the White Sands Missile Range in New Mexico. Initially, it was assumed that incidents were unrelated, but thanks to online forums, ornithologists noted that they happened everywhere in the region. Inhabitant bird species such as basket-picture thrashers, large-tailed grackles and white-winged pigeons do not appear to have been affected.
Reports suggest that some birds have shown unusual behavior before they die – becoming lethargic, inaccessible and gathering in groups. Species that usually rest in trees and shrubs have been seen jumping around the earth looking for insects, Desmond said.
Large bird deaths during migration are rare, and few have been as large as this one. Records – dating back to the 19th century – show that these events are always associated with extreme weather events such as a drop in temperature, blizzard or hailstorm. The largest event recorded in the region was a snowstorm in Minnesota and Iowa in March 1904 that killed 1.5 million birds.
The climate crisis is also changing the tundra landscape, where many of these birds breed, while the destruction of rainforests in Central and South America damages their winter habitats. Since 1970, three billion birds have been lost in the United States and Canada. Mass deaths like this can have an effect on populations of both common and sensitive species. Salas said: “We are coming a little after them from all sides … if we do nothing to protect their habitat, we will lose a large number of the population in several species.”
Carcasses are being sent to the U.S. Fish and Wildlife Service forensics lab in Oregon and the National Wildlife Health Center in Wisconsin for testing, which is expected to take at least two weeks. Researchers are urging people in the area to record sightings of dead birds on the civil science website inaturalist.
Tristanna Bickford, communications director at the New Mexico Department of Game and Fish, said it was a possibility that the climate crisis had affected migration. “Until we get the actual reports back from the National Wildlife Health Center, we can not say what is happening or not happening,” she added.
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