Viral Newcastle disease kills cormorants at LqP

Watson, Minn. – The haze you may have seen rising from the
islands of Marsh Lake in west-central Minnesota this week and last
might have come from fires ignited by the DNR, blazes created by
the burning of birds recently found dead on islands within the
lake.

The DNR says Newcastle disease is the likely culprit in the
death of hundreds of double-crested cormorants nesting on the
islands of March Lake in Big Stone County.

Also confirmed dead at Marsh Lake (part of the Minnesota River)
were several hundred ring-billed gulls, though Newcastle hasn’t
been confirmed in those birds, according to Erika Butler, DNR
wildlife veterinarian. Nor has it been confirmed in dead pelicans,
a species the DNR says experiences various levels of “natural”
die-off each year. If disease does take pelicans, it’s usually West
Nile virus, said John Wollenberg, DNR assistant area wildlife
manager at Lac qui Parle Wildlife Management Area.

The carcasses of the gulls and cormorants not sent in for
testing are being burned on-site. Wollenberg said this week that
212 cormorant carcasses and 293 gull carcasses had been
incinerated. He said that was about “two-thirds of the way
completed with initial clean-up.”

“We’ll get the clean-up done, then it’s a matter of seeing if
anything else is dropping dead out there,” he said.

The presence of Newcastle disease might place the Marsh Lake
islands off-limits to duck hunters this year; Wollenberg said the
situation likely will be monitored until ice-up this fall.

Keeping the islands clear of human activity serves a couple
purposes, Wollenberg said. (Signs had been in place, but recently
were lost to frost heaves or otherwise.) Human interference can
reduce nesting success; by keeping duck hunters off the die-off
islands, possibility of disease spread is reduced.

A DNR press release says the dead birds included 500 cormorants
and 400 gulls; Wollenberg said the cormorant carcass count won’t be
that high, it appears.

He said it’s not uncommon for disease and natural mortality (a
young pelican that dies from exposure to too-cold weather, for
example) to claim pelicans by the thousands, though this year’s
pelican deaths can be counted in the hundreds.

“Last year was better than most years, and this year has been
better still,” Wollenberg said.

According to the Minnesota DNR, Newcastle disease – a viral
disease that most commonly infects cormorants, but has been
documented in gulls and pelicans – isn’t new to the state. In 2008,
in a seven-county area, about 2,400 birds died. And in 1992,
multiple mortality events affected cormorant colonies across the
Great Lakes, Upper Midwest, and Canada. That year, estimates
indicate more than 35,000 birds died.

Butler said research has shown Newcastle cycling through bird
populations every couple years. Places like Marsh Lake are prime
settings for bird die-offs. An estimated 14,000 pelican pairs nest
on the lake’s islands, along with thousands of other birds.

“It’s such a concentration,” Butler said. “There are birds
everywhere.”

Samples from dead cormorants were tested at the National
Wildlife Health Center in Madison, Wis. Butler said it’s unknown if
the birds were killed by the virulent (most deadly and contagious)
strain of Newcastle, so the department’s actions were based on the
assumption that is was the virulent strain.

If birds show signs of illness (droopy head, twisted neck, lack
of coordination, inability to fly or dive, and complete or partial
paralysis), they should call their veterinarian or the Minnesota
Board of Animal Health at (320) 231-5170.

The DNR also reported a die-off of some 50 cormorants on Wells
Lake in Rice County. Samples are being tested, but the specific
cause of the birds’ illness is unknown.

Categories: Hunting News

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