For weeks, biologists in New Mexico have observed strange and alarming behavior in migratory birds: Warblers, sparrows, and western wood pewees have been clustering together in large groups, only to die en masse from unknown causes.
“It is terribly frightening,” Martha Desmond, a professor at New Mexico State University’s Department of Fish, Wildlife and Conservation Ecology, told the Las Cruces Sun News. “We’ve never seen anything like this. We’re losing probably hundreds of thousands, if not millions, of migratory birds.”
Last month, flocks of avian carcasses — from swallows, blackbirds, and flycatchers as well — were found at the White Sands Missile Range and the White Sands National Monument in Southern New Mexico. At first, officials didn’t think the incidents were related, but now, according to Desmond, the death toll has reached “an unprecedented and a very large number.” Trish Butler, a wildlife biologist at the missile range, told KOB 4 that she and her colleagues typically find fewer than half a dozen dead birds in a week, but in the last seven days, “we’ve had a couple hundred, so that really got our attention.” Meanwhile, bodies have also been found in Doña Ana County, Jemez Pueblo, Roswell, and Socorro.
Wildlife experts at NMSU, the Bureau of Land Management, and the missile range are working together to pinpoint a single most likely explanation, but so far, they’re somewhat baffled. Desmond told the Sun News that some witnesses have reported birds looking “sleepy … just really lethargic” before they expire; many of them have also molted, as if ready for winter travel.
“You have to be healthy to do that,” she said. “But somewhere after that, as they initiated their migratory route, they got in trouble.”
The die-offs have primarily affected insect eaters, but not resident species. Desmond speculated that droughts and the massive wildfires currently ravaging the West Coast might play a role. The smoke could have damaged the birds’ lungs, she told the Sun News, and prevented them from fully preparing their bodies for the journey south.
“They may have been pushed out before they were ready to migrate,” Desmond said. “They have to put on a certain amount of fat for them to be able to survive the migration. These birds migrate at night and they get up in the jet stream, and they might migrate for three nights in succession, they’ll come down and they’ll feed like crazy, put on more fat, and go again.”
The dead birds will be shipped to U.S. Fish and Wildlife Service Forensics Laboratory in Ashland, Oregon, for analysis, and officials are asking observers to report any group fatalities they might spot to an iNaturalist online database. And while it could still be weeks before researchers get concrete answers as to New Mexico’s bird scourge, we know the climate crisis is already having an adverse impact on animals — orcas, polar bears, koalas, birds, and beyond — that only stands to get worse if humans fail to drastically curb atmospheric warming.
“Climate change is affecting the abundance of insects, it’s affecting the volatility of the fires,” Desmond said. “And the scary thing is this may be an indication of the future.”