Thursday, February 2nd, 2023
Thursday, February 2nd, 2023

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Agencies investigate cormorant die-off

St. Paul – Officials from several state and federal agencies are
investigating the cause of a die-off of nearly 700 double-crested
cormorants, as well as about 40 pelicans, some ring-billed gulls,
and a great blue heron, at two locations in southern Minnesota.

The die-offs were discovered last week by DNR staff and
researchers banding pelicans at Minnesota Lake in Faribault County
(near the town of Minnesota Lake) and at Pigeon Lake in Meeker
County (near the town of Dassel). Several samples (whole birds, in
some cases) were sent for testing to facilities in Ames, Iowa, and
Madison, Wis., according to Dr. Michelle Carstensen, DNR wildlife
health program coordinator.

As of earlier this week, there had been no confirmed cause of
the die-offs, though Carstensen said some suspects include
botulism, Newcastle’s disease, avian cholera, and West Nile virus.
Initial tests for avian influenza were negative. Tests were being
conducted by the U.S. Geological Survey’s National Wildlife Health
Center in Wisconsin, and the USDA’s Veterinary Services Laboratory
in Iowa.

“Those are the things we look for at this time of year,” she
said, adding that the symptoms are consistent with a few different
diseases. Further, she said, the die-offs at the two sites might
not be from the same cause.

However, Jeff DiMatteo, a pelican researcher, said staff saw the
same thing happen at both lakes.

“We saw dead and dying adult cormorants, with the live ones
unable to hold their heads up” at Pigeon Lake, he said in a press

Carstensen said many of the birds appeared emaciated and
exhibited labored breathing. The birds at Minnesota Lake included
sick and dying birds. Whatever was killing them appeared to be in
the earlier stages than at Pigeon Lake, where biologists found “old
carcasses, which would suggest that it has been going on at least a
couple of weeks,” DiMatteo said.

DNR Wildlife Chief Dennis Simon called the two die-off sites
“classic cormorant colonial nesting sites.” Officials are checking
at other locations in the state where the species nests, including
the Lac qui Parle area.

Meanwhile, officials are cleaning up at the current die-off
locations. In some cases, bird carcasses have been incinerated; in
others, the carcasses are double-bagged and buried at

Besides working with federal officials, the DNR also is
coordinating with the state Board of Animal Health, which has
warned domestic poultry producers to monitor their livestock.

“…state animal health officials remind farmers to practice sound
biosecurity, including monitoring their poultry flocks for signs of
illness and taking steps to prevent wild birds from having contact
with their domestic birds.”

Cleanup of dead birds and proper disposal is the state’s best
chance to reduce the threat of disease, officials say.

According to the state DNR, there are about 39 nesting colonies
of double-crested cormorants in Minnesota, 87 percent of which
occur along with other colonial nesting birds. Most nests have been
used since the 1960s and ’70s.

Lori Naumann, DNR nongame wildlife information officer, said
most cormorant colonies include from 300 to 600 nesting pairs. Two
of the larger established cormorant colonies are located at Marsh
Lake (Lac qui Parle) and on Lake of the Woods islands.

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