Monday, January 30th, 2023
Monday, January 30th, 2023

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Scaup studies enter pivotal final phase

Associate Editor

St. Paul A decline in the population of lesser scaup may be
connected to a reduction in food available to the species on its
return route to Canadian breeding grounds, according to research
that continued in 2004.

While researchers had already expected that to be true, their
study expanded this year and included surveys of wetlands in
Minnesota and elsewhere along the northern travel route of the
ducks.

Researcher Michael Anteau, a graduate student at the University
of Louisiana, said there appears to be less of the foods scaup
(also known as bluebills) prefer along their travel corridor.

“Basically, we think there’s been a decline in amphipods (scuds,
freshwater shrimp, or other small crustaceans that bluebills
prefer),” Anteau said.

That was true not only in Minnesota, but in other places the
ducks stage on their trip north.

“Even in North Dakota, where we thought we’d find a lot we still
found fewer than we thought we’d find,” he said. Areas of Iowa also
are included in the study.

Anteau and Al Afton, of the Louisiana State University
Cooperative Wildlife Unit, have been conducting research on the
scaup decline for the past several years. This year will mark the
final phase, as Anteau expects to distribute the final report (his
Ph.D. dissertation) in December.

Produced from the research has been the Spring Condition
Hypothesis, which links a decline in the body condition of scaup as
they migrate north to poor reproduction.

“Our preliminary results suggest that females currently are
arriving on many northern breeding areas in poor body condition or
perhaps arrive late or not at all,” the researchers wrote in their
2004 report. “Females that arrive on breeding areas in poor
condition or arrive late probably have decreased nesting
propensity, delayed nest initiation, and reduced breeding
success.”

In other words, clutch size may be reduced, nesting success may
decline, and duckling survival may be negatively influenced.

It’s well established that scaup like to dine on amphipods
during northern migration, Anteau said. And while there’s little
historical data to demonstrate a decline in the availability of
this forage, there appears to be less in important areas of
Minnesota than there once were.

“We have a lot of accounts from landowners and hunters who say
that some of the wetlands used to be full of scuds, but there just
aren’t any now,” Anteau said.

What affects amphipods? Primarily fish populations and landscape
impacts.

“It looked like there were pretty strong fish effects,” Anteau
said. Regarding landscape impacts, “We haven’t found much that
jumped out,” he said.

However, Anteau added, wetland studies showed good submerged
vegetation in many places, something that protects and aids in the
propagation of amphipods.

While the research has focused on scaup and habitat preferred by
that species, the lack of amphipods in some areas may point more
generally to wetland quality issues, Anteau said.

“What we’re seeing here might be the canary’ syndrome,” he said.
“Whether or not we’ll see a decline in other species, we’d need a
crystal ball. But it could have an effect. Wetland quality is not
that great in the Midwest.”

New in ’04, the researchers included a paint survey, where scaup
were collected at Pool 19 of the Mississippi River, near Keokuk,
Iowa, and were banded and marked with a paint stain. Re-sightings
were to help the researchers establish travel corridors and habitat
use.

Anteau said results of that survey were “mixed” and that this
year a similar project will likely occur, with some adjustments. In
general, the researchers hope to increase the number of scaup
sightings in 2005.

By banding and recapturing birds, researchers hoped to pinpoint
where along the migration route birds aren’t accumulating needed
fat and protein reserves.

At the conclusion of the study, researchers hope determining
when and where scaup are losing body mass will help target
conservation efforts, including:

How large is the geographic area that females are unable to
accumulate the appropriate levels of nutrient reserves;

In which areas are females in the lowest body condition?

“Accordingly, it is important to document when and where females
are accumulating or using lipid (fatty) reserves during migration
through the Upper Midwest,” the report states. “Furthermore, an
understanding of spring migration corridors and rates of movement
is needed for better interpretation of body condition data.

“Finally, a rigorous examination of forage availability and
quality clearly is needed; moreover, understanding mechanisms that
affect amphipods across the Upper Midwest are critical for
effective conservation and management of migration habitats.”

Ray Norrgard, DNR wetland wildlife program leader, said that
knowing there are habitat issues in Minnesota is not a
“revelation.” The biggest challenge is using the information
available and converting it to a management plan, he said.

Alluded to in the report was a 10-year, multi-million-dollar
effort to improve scaup migration habitat in Minnesota, sponsored
by Ducks Unlimited, the DNR, and the U.S. Fish and Wildlife
Service. The winter edition of DU’s Cattails announces
implementation of DU’s “Living Lakes Initiative,” a “conservation
focus on shallow lakes and large wetlands in Minnesota and
Iowa.”

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