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By Dan Gunderson

The Minnesota Department of Natural Resources is investigating a number of wild waterfowl deaths in the first half of December, likely caused by avian influenza.

Through Dec. 17 there were 29 reports from 20 counties in the southern half of Minnesota, according to DNR wildlife health supervisor Erik Hildebrand.

The dead waterfowl were Canada geese as well as some tundra swans and trumpeter swans. The number of dead birds ranged from a handful to more than 50, Hildebrand said.

“The fact that we were seeing mortality with the waterfowl species, that’s kind of an eye-opener,” he said. “Because not all avian influenza viruses kill waterfowl, since they are the host reservoir for the virus.”

By comparison, Minnesota had five confirmed wild waterfowl deaths from avian influenza in December 2023, according to a USDA database.

Hildebrand said thin ice made it difficult to collect bird carcasses for testing, but the birds tested were positive for the H5N1 virus — and necropsies by a pathologist showed organ damage consistent with highly pathogenic avian influenza infection. The agency is waiting for confirmatory test results from the National Veterinary Services Laboratories.

Hildebrand said wild waterfowl deaths are also being reported in surrounding states. He called the number of reports unusual.

“This is a little later than we would thought it (the virus) would be active,” he said.

The reports of dead waterfowl have slowed in the past week, but there is concern about scavengers contracting the virus because of the number of waterfowl deaths.

“When you have that many carcasses on the landscape, you’re going to have scavenging at some level,” said Hildebrand. “And the avian influenza virus can affect mammals and other birds such as raptors.”

Anyone spotting more than five dead waterfowl is asked to report the location to the DNR. People should avoid contact with the dead birds.

Earlier this month, health officials in Wisconsin reported that state’s first human case of highly-contagious avian flu.

Highly pathogenic avian influenza has also been detected in six commercial turkey flocks in Minnesota over the past month. Scientists have pointed to wild bird migration as a likely spreader of avian flu.