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Bird of the Month: Tundra Swan

Tundra swans can be spotted during their summer and fall migrations through Minnesota. (Photo by Rebecca Fields)

By Tim Schlagenhaft, Audubon Minnesota Upper Mississippi River Program Manager

In Minnesota, you can see two types of swans: trumpeter swans and tundra swans

Migrating tundra swans can be difficult to distinguish from resident trumpeter swans during their spring and fall migration through Minnesota. Even skilled bird watchers and field ornithologists can be challenged by their identification unless the birds are side by side. Both birds are elegant, large, white, and have mostly black bills and feet, unless they are very young.

The tundra swan is smaller and usually displays a small, yellow spot at the base of the bill. The bill is also smaller and the upper ridge is a bit concave compared to that of the trumpeter. When viewed from the front, the base of the trumpeter’s bill is v-shaped between the eyes compared to a u-shape on the tundra. Despite these challenges, the call of the trumpeter swan is distinct and upon first hearing it, the listener will understand why the bird is called a “Trumpeter.” Its deep, rich honking call is horn-like in resonance, unlike the higher, raspy call of the tundra swan that sounds more similar to a goose. (Audubon Minnesota “Stewardship Birds of Minnesota”)

To see tundra swans, visit the Mississippi River between mid-October and mid-November. The best time to see trumpeter swans in Minnesota is typically in February. Learn more about hotspots for tundra swans, trumpeter swans and host of other amazing birds in Minnesota, visit eBird.org and explore birding hotspots, species maps, and more.

Nutrients for tundra swans

One of the most exciting and challenging projects Audubon Minnesota is working on is to restore natural low water variability to the Mississippi River by lowering water levels during the summer growing season.  These “drawdowns” have been conducted with great success on several Mississippi River pools.

The natural pattern of water levels on the Upper Mississippi River included a spring flood followed by low water levels during summer. For centuries, this pattern created ideal habitat for hundreds of species of migratory and resident birds, including tundra swans, bald eagles and spotted sandpipers.

When locks and dams were constructed during the 1930s, they changed this pattern and eliminated the natural low-water conditions. Temporary, low-water levels are important for plants like arrowhead, or duck potato, to establish. When arrowhead benefits from drawdowns, the plants produce large beds of tubers or sprouts that are a critical food source for migrating tundra swans.  

For many millennia, the Mississippi River flowed freely across its vast floodplain. Floods would change the course of the river, scouring new channels and abandoning old ones. Backwater lakes, sandbars, sloughs, forests and marshes evolved in an ever-changing pattern dictated by when and where water moved across the floodplain. Whether it was for food during migration, tree cavities for nesting, or beds of aquatic plants for shelter, many species of birds, like swans, thrived within a free flowing Mississippi River.

Over time, the alteration of the natural water levels has resulted in declines in many water plants, like arrowhead, and many areas have converted to more turbid, open water conditions with poor habitat for fish and wildlife. Fortunately, we can restore some of the natural low-water conditions by conducting summer, pool-scale drawdowns. Audubon Minnesota and partners are working to accomplish these by changing the way the dams are operated.  

In the 1930s, the river was dramatically changed when a series of 29 locks and dams were built from Minneapolis to St. Louis. Dams were constructed to maintain higher than normal water levels during low-flow periods in order to float commercial barges. This created “pools” above the dams and greatly altered the river’s natural flow.

While the dams don’t control floods, low water levels during the summer growing season were greatly impacted. Large areas that typically dried out now remain permanently flooded. Plant seeds stored in the river sediments are no longer exposed to air and are unable to sprout. As a result, many annual moist-soil and perennial emergent plants have suffered. Aquatic plants are important indicators of the health of the river’s ecosystem. A diverse and abundant native aquatic plant community provides the food and shelter necessary for survival of many species of birds, wildlife and fish. Without aquatic vegetation, the entire ecosystem suffers.

Audubon and other partners including the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, Minnesota Department of Natural Results, Wisconsin DNR and The Nature Conservancy are working to restore aquatic plants by mimicking the river’s natural lo- water variability. The most promising solution is to conduct water level drawdowns that let water through the dam to lower water levels in the impounded areas upstream.   

Since 2000, drawdowns have been completed during summer on three Mississippi River Pools between the Twin Cities and the Iowa border: Pools 8, 5, and 6. These drawdowns lowered water at the dams by up to 1.5 feet and have exposed between 200 and 2,000 acres at a time.

As a result, the growth of water plants like arrowhead has been remarkable. In some areas, more than 70 species of plants were found growing on newly exposed soils including annual plants, like smartweed, which are excellent food for migrating waterfowl. In Pool 8, arrowhead resulting from the drawdown attracted large concentrations of tundra swans that fed heavily on the plants roots.

Unfortunately, drawdowns aren’t as simple to implement as it might seem. Shipping industries rely on a deep channels for commercial navigation, and extra dredging prior to a drawdown is necessary to ensure a safe channel. In addition, marinas, boat docks, water intakes and other infrastructure depend upon minimum water levels maintained by the locks and dams. With impacts to so many different users, a single pool drawdown often requires several years of planning and coordination.

Because drawdowns are proving so valuable for restoring water plants and bird habitat, Audubon Minnesota is working to make them easier and more frequent. More frequent drawdowns would better emulate the river’s natural hydrology and restore plants essential to a healthy Mississippi River.

Pool 3, located near Red Wing and within the Cannon and Vermillion River Important Bird Area is the next pool scheduled for drawdown. With your help we can continue to advocate for food for Tundra Swans and get additional pool drawdowns on the Mississippi River.

To learn more about Audubon Minnesota’s efforts to restore natural water levels, contact audubonminnesota@audubon.org

Tim Schlagenhaf is the  Upper Mississippi River program manager for Audubon Minnesota.  Before coming to Audubon Minnesota, he spent more than 20 years working on the Mississippi River as a fisheries biologist and river planner for the Minnesota DNR. During this time, he grew familiar with the cycles of the river and, working with other state, federal, and local partners, learning how to improve habitat to better protect this magnificent resource. With his active involvement, Audubon is assisting partners in implementing this drawdown to improve hundreds to thousands of acres of floodplain habitat.

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