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The Surprising Reason Thousands Of Birds Dropped Dead Across The Southwest

rows of dead birds
Photo courtesy of Jenna McCullough

From Texas Standard:

Earlier this month, something unusual happened. Birds — thousands of them – seemingly dropped dead overnight in New Mexico. Jenna McCullough, a PhD student in ornithology at the University of New Mexico, went to investigate.

“I was notified by a colleague that there were birds in the Sandias that were acting abnormally and dead. I and my fellow PhD student Nick Vinciguerra went out and collected 305 birds,” McCullough said.

McCullough got her first call about the bird deaths on Sept. 10. For days afterwards, concerned citizens reached out to her with more sightings. When she and her research partner went out to investigate, all they found were feathers.

“And so what that kind of points to is that ... there might have been a mass die-off, but that birds aren’t continuously dying,” McCullough said.

That’s the good news, sort of. When reports first surfaced of birds dying en masse in New Mexico, Colorado and even potentially in parts of West Texas, there was concern that the deaths were ongoing. Early reports speculated on the causes – wildfires on the West Coast, poisoning or widespread drought.

And while those things could be causes, McCullough said the more likely explanation is a cold snap. Right before she started fielding calls, a historic cold front blew through the Southwest, blanketing areas with early snow.

“And that makes sense because it was hot. It was actually abnormally warm, and then it crashed like 55 to 60 degrees overnight after a huge windstorm,” McCullough said.

Most of the birds that died were migratory. They had been flying long distances, which puts their bodies under a lot of stress, even in good conditions. And when the snow came, those insects they normally feed on to fuel their journeys just disappeared. That lack of food likely caused many of the birds to starve or die of hypothermia.

Cliff Shackelford is the state ornithologist for non-game birds with the Texas Parks and Wildlife Department.

“So these birds were caught up in a system that they were stuck in for days,” Shackelford said. “That’s like you and me driving from, say, South Dakota to Texas, and you can’t find any gas stations.”

He said migratory birds in Texas were mostly spared from this particular die-off, but it’s happened here before.

“Early in my career, in October of 2000, we had the exact same thing happen. That’s 20 years ago, so it’s not common,” Shackelford said.

A cold front like the one that happened a few weeks ago pushed through from the Dakotas down to Texas as birds were flying south.

“And I was living in Austin at the time – there were piles of swallows in various places,” Shackelford said. “I remember people talking about how they had to sweep their porch, because the birds made it and simultaneously they just died.”

Die-offs like this can be alarming. But Shackelford said they’re quite rare. He said the biggest ongoing threats to birds are man-made.

“Clearing land, building houses, putting in subdivisions,” Shackelford said. “Putting in big box stores, we don’t ever think about that ... because we don’t see piles of birds. Habitat loss is a daily, hourly issue for birds.”

McCullough and her New Mexico team are still waiting for autopsy results for the birds they found. It will take a while. They had to send the birds to an Oregon lab, where fires are causing a slowdown. But as for the early wildfire theory that spread in the news and on social media, well, like wildfire, she says, it’s too soon to tell.

“We don’t really know how birds respond to smoke hundred miles away from the actual fires,” McCullough. ”I do think that there needs to be research, and I am very interested in the autopsies that are going to be done.”

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