Mass die-off of birds in south-western US 'caused by starvation'

https://www.theguardian.com/environment/2020/dec/26/mass-die-off-of-birds-in-south-western-us-caused-by-starvation-aoe

 

Phoebe Weston
Sat 26 Dec 2020 11.00 GMT
Last modified on Sat 26 Dec 2020 11.02 GMT


The mass die-off of thousands of songbirds in south-western US was caused by long-term starvation, made worse by unseasonably cold weather probably linked to the climate crisis, scientists have said.

Flycatchers, swallows and warblers were among the migratory birds “falling out of the sky” in September, with carcasses found in New Mexico, Colorado, Texas, Arizona and Nebraska. A USGS National Wildlife Health Center necropsy has found 80% of specimens showed typical signs of starvation.

Muscles controlling the birds’ wings were severely shrunken, blood was found in their intestinal tract and they had kidney failure as well as an overall loss of body fat. The remaining 20% were not in good enough condition to carry out proper tests. Nearly 10,000 dead birds were reported to the wildlife mortality database by citizens, and previous estimates suggest hundreds of thousands may have died.

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“We’re not talking about short-term starvation – this is a longer-term starvation,” said Martha Desmond, a professor in the biology department at New Mexico State University (NMSU), who collected carcasses. “They became so emaciated they actually had to turn to wasting their major flight muscles. This means that this isn’t something that happened overnight.”

The birds probably would have started their migration in poor condition, which could be related to the “mega-drought” in the south west of the country. “Here in New Mexico we’ve seen a very dry year, and we’re forecast to have more of those dry years. And in turn I would say it appears that a change in climate is playing a role in this, and that we can expect to see more of this in the future,” said Desmond.

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Allison Salas, a graduate student at NMSU, said the volume of carcasses she had collected had given her chills. She said: “The fact that we’re finding hundreds of these birds dying, just kind of falling out of the sky is extremely alarming.”

Desmond’s team is hoping to get funding to support more research into mass die-offs in birds so they can better monitor what is happening. Sleeman agreedthat large-scale mass mortality wildlife events are happening more frequently. “It’s something we definitely need to keep track of,” he added.