Lesser Scaup Highlight Ecological Changes Caused by Dams
TNC and partners aim to restore critical habitat on the Mississippi River
Driving along Illinois State Highway 96 following the banks of the Mississippi River, the water appears sprinkled with salt and pepper. Closer examination reveals thousands of ducks—mostly lesser scaup—resting on the surface in the morning light.
“Just seeing all the birds in this one place really makes me want to do the right thing to make sure these birds can continue coming here,” said Randy Smith, Illinois River project director at The Nature Conservancy (TNC). “And it’s not just waterfowl that depend on this portion of the river. This is a critical link in the chain for a variety of fish and people as well.”
It is mid-March, and migratory waterfowl are making their annual trek north to the prairie potholes of the northern U.S. and the boreal forests in northern Canada, where they will nest and raise their ducklings through the summer. This section of the river—known as Pool 19—is a mid-migration stopover. The ducks will spend several weeks here resting and feeding, building up strength for the next stretch of this seasonal journey and the breeding season that follows. The Mississippi River serves as a migratory pathway to 325 different bird species, including 50% of North American waterfowl.
The lesser scaup travel here from the southern coast because the conditions cater to their needs. A diving duck variety, the scaup eat submerged plants, such as wild celery, and mollusks, including fingernail clams. Those food sources remain in sufficient abundance here to make Pool 19 a viable stopover, but the features in this stretch of the river are changing and those favorable conditions are slowly disappearing.
“We are seeing the lesser scaup population declining, which is cause for concern,” Smith said. “And whenever we see a decline in population, the first place we look is habitat.”
Studies reveal changes over time
Scientists have been studying the lesser scaup population for decades with the help of a banding study currently led by the University of Illinois-Illinois National History Survey. Staff at the Forbes Biological Station, supported by hundreds of professional and enthusiast volunteers, capture lesser scaup in Pool 19 and clip numbered bands to their legs so researchers can track their movements and understand changes in migratory patterns. The researchers might also implant a tracking chip, weigh the birds and take blood samples to assess the health of the population.
Stephen Winter, a wildlife biologist at the Upper Mississippi River National Wildlife and Fish Refuge, has volunteered with the study for several years.
“The banding project has proved itself to be a critically important tool to understand scaup population dynamics at a continental scale,” Winter said. “We might not notice changes unless we have long-term rigorous research available.”
Volunteers clip a numbered band to one leg of a lesser scaup.
Researchers and hunters report band numbers of captured birds to the U.S. Geological Survey Bird Banding Laboratory, where scientists accumulate data points that begin to tell a story of a species’ migratory patterns, population dynamics and disease trends. This data helps conservation scientists make decisions about wildlife management and habitat restoration. Long-term studies like this one help experts notice changes that might otherwise be missed.
Restoration needed to protect habitat
Pool 19 was created by a dam built in Keokuk, Iowa, more than 100 years ago. Installed by a utility company for hydroelectric services, this dam is 38 feet tall, significantly larger than the navigational dams found elsewhere on the river. When it was first installed, the pool created to the north of the structure stretching to Burlington was a boon for wildlife. Over time, changes to the flow of water caused by the structure gradually deteriorated those features.
This is not unusual. There is a cycle of change associated with dam installations. What makes Pool 19 unique is that the dam was not constructed by the U.S. Army Corps of Engineers (Corps) to aid navigation. Since the Corps began implementing nature-based engineering methods in 1986, many other pools created by dams on the river have benefited from restoration work to preserve a more natural state and protect valuable wildlife habitats.
“If you look at where all the restoration projects are on the Mississippi River, you see a gap. That gap is Pool 19,” said Bryan Hopkins, Midwest strategy director of great rivers and floodplains at TNC.
Because Dam 19 wasn’t built by the Corps, it has been excluded from comprehensive restoration projects led by the Corps and numerous federal, state and private partners. But rivers are linear systems, and you can’t ignore a 46-mile stretch of the system and expect the river to function effectively.
Quote: Bryan Hopkins
We know what these large river systems need...we need to simply follow the road map that has been so effective on the upper Mississippi River.
Migrating ducks on the Mississippi River near Hamilton, Illinois.
TNC and its partners hope to bring attention to the restoration needs in this stretch of the river. Large river restoration has made significant gains over the past 40 years, and experts today have the experience needed to catch up this part of the river to the rest of the Upper Mississippi.
“We know what these large river systems need, and to return the ecological and recreational function to this section of the river, we need to simply follow the road map that has been so effective on the upper Mississippi River,” Hopkins said.
We Can't Save Nature Without You
Sign up to receive updates from The Nature Conservancy
You might also like
Upper Mississippi River Foodscape
A collaborative approach to a more resilient and profitable food system.
Atchafalaya River Basin
At almost a million acres, Louisiana's Atchafalaya River Basin is North America's largest floodplain swamp.
Protecting and Restoring Missouri's Rivers
TNC has been working to protect Missouri’s rivers and streams since 1956. With our partners, we’re dedicated to ensuring these irreplaceable resources are available for generations to come.