Explanation of the recent mass mortality of Western birds

In mid-September, New Mexico and other western states experienced mass deaths of migratory birds when wildfires raged in the west. One expert said hundreds of thousands of birds may have died.

Many observers speculated that smoke from the fires might have contributed to her death, but an article published on the American Birding Association’s website suggested a lack of food and hypothermia as the likely cause.

Writer Jenna McCullough, a University of New Mexico PhD student studying avian evolution and systematics, noted that a severe storm in early September brought temperatures down to 40 ° F from the mid-1990s and brought several inches of wet snow .

When the dying brought news, she and a fellow student collected hundreds of carcasses and found that “none of them had stored fat on their bodies. In addition, many birds showed signs of pectoral muscle atrophy, which is indicative of hunger and dehydration. “

Of 305 birds they collected, 85 percent were purple-green swallows that feed by catching insects on the wing. The storm likely caused a sudden drop in the availability of prey for the birds. McCullough wrote that the mass of the birds found was about two-thirds the weight of normal swallows, another sign that “these birds had starved and succumbed to hypothermia.”

Problems for aerial insectivores

The tragedy is also noteworthy because aerial insectivore populations – birds that catch insects on their wings – have been declining for decades. Research shows that aerial insectivores in North America have decreased by an estimated 32 percent.

“This is the most severe decline in any bird group and results in the loss of more than 160 million people in Canada and the United States,” say the authors of an editorial published in Avian Conservation & Ecology in June. “Nine of the 31 types of flycatchers, night owls, swallows and swifts are currently listed in Canada under the Federal Species at Risk Act.”

Written by ornithologists from universities and agencies across Canada, the editorial provides an “urgent” roadmap for aerial insectivore conservation. The authors identify five general steps and numerous elements of action that will help. These include strategies to educate the public about the importance of insects, reduce pesticide use, strengthen wetland protection, and many others.

A version of this article will be published in the November / December 2020 issue of BirdWatching. Subscribe to.

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