“They came back,” says biologist Donald Webster. “This year.” His voice has a wistful note, wondering if the king of ducks, as the beautiful, crimson-headed canvasback is known, will return to rule Chesapeake Bay winter after winter. The Chesapeake is the largest estuary in the U.S. and the third largest in the world. It’s one of the globe’s most productive waterbodies.

Bundled in parka, gloves and hat, Webster, who recently retired as a waterfowl habitat biologist for the Maryland Department of Natural Resources (DNR), raises his binoculars near a seawall at the confluence of Chesapeake Bay and the Choptank River. The Choptank is one of the bay’s 19 major tributaries. The overlook is a mecca for wintering canvasbacks and other ducks.

“Canvasbacks, the ducks everyone comes to see, are usually here in force by Christmas,” Webster says. “They stay until just before St. Patrick’s Day, then they’re gone, heading north to nesting grounds.”

Skeins of Waterfowl

On this January morning with northwest winds and temperatures that hover just above freezing, the canvasbacks’ red heads stand out in winter-dark waters. The ducks glide near the seawall, where photographers jostle for the quintessential shot of an iconic Chesapeake species. “This place is known as the ‘wall of shame,'” laughs Webster, “because it’s almost too easy to get great canvasback pictures here.”

Chesapeake skies fill with migrating seaducks – canvasbacks, buffleheads, greater and lesser scaup, and many others – from December through March. The bay is the Atlantic Coast’s most important waterfowl migration and wintering area. The Chesapeake offers refuge to 24 species of ducks as well as Canada geese, greater snow geese and tundra swans.

“Long-term worsening of the bay’s water quality, however, and loss of habitat, especially the seagrasses so many of these birds depend on, have contributed to declines in wintering waterfowl populations,” says Webster.

Seesawing Seagrass Estimates

An estimated 82,778 acres of submerged aquatic vegetation (SAV) remained in the bay and its tributaries in 2024, the most recent year with available data, down from historic levels that may have reached more than 600,000 acres. Globally, seagrasses have declined almost 30% since the late 1800s; a football field worth of seagrass now disappears every second.

There’s good and bad news in the 2024 Chesapeake Bay SAV estimate. It’s a significant increase over the 38,958 acres observed in the first survey in 1984. But it’s a large decrease from 2018, with its 108,078 acres of underwater grasses. Although the exact reasons for the decline aren’t known, one culprit may be high river flows that reduce water clarity and block sunlight from reaching the grasses.

“This is a dynamic ecosystem with natural variation in SAV from year to year,” says Chris Patrick of the Virginia Institute of Marine Science. “In the context of the decades of data we’ve collected, we remain on a positive trajectory.”

In 2011, the Chesapeake’s SAV declined to 48,195 acres, a result of Hurricane Irene and Tropical Storm Lee. The storms sent a flood of sediment cascading into the bay. After 2011, conditions became relatively dry, reducing the flow of grass-smothering sand and mud. More sunlight reached submerged grasses, allowing them to rebound. In return, the SAV filtered runoff, helping keep Chesapeake waters clear.

Forty years ago, SAV reached a low point in parts of the bay. Another major storm, Tropical Storm Agnes in 1972, nearly wiped out the SAV at Susquehanna Flats, an expansive bed of grasses where the Susquehanna River widens and becomes Chesapeake Bay. The rush of floodwater from the roiling Susquehanna uprooted grasses at the Flats’ edges and deposited sediment there, blocking sunlight and photosynthesis. Then the storms of 2011 exacerbated the damage to the relatively shallow “Flats.”

The grasses, however, fought back. Their blades impede the river’s flow enough to prevent erosion of the beds’ inner cores. The plants create clear water in the middle of the beds, which promotes their growth and improves overall water clarity. When clean water sluices out of an SAV bed’s center into the surrounding bay, more light is available for the grasses to grow, allowing them to shoot up faster.

Duck Feast to Famine

Over Chesapeake Bay’s history, SAV has foundered and flourished. Canvasbacks and other waterfowl species have done the same. As recently as 1950, half the continent’s population of canvasbacks – more than a quarter million – wintered in the Chesapeake, relying on aquatic grasses as favored food sources.

During Colonial times, as many as 1 million of the ducks may have spent wintertime on the bay. In the 19th century, their abundance and, to many, good taste made them a favored selection in many East Coast restaurants, says Matt Kneisley, a regional director at Delta Waterfowl, a waterfowl conservation and hunting organization.

Canvasbacks congregate in large flocks on open waters, leading to easy – too-easy – harvesting. By the end of the 19th century, commercial hunters with batteries of weapons went after rafts of the ducks, often killing dozens with one shot. The “cans,” as hunters call them, were shipped by boxcar to markets from Baltimore to Boston. Such market hunting was outlawed with the passage of the U.S. Migratory Bird Treaty Act of 1918.

“Canvasbacks were a favored quarry because their meat was considered the tastiest of all the ducks due to their consumption of wild celery,” writes Guy Baldassarre in Ducks, Geese and Swans of North America.

Large beds of wild celery once attracted thousands of the ducks to Susquehanna Flats and elsewhere on the upper bay, according to Kneisley. Then a decline in the Chesapeake’s water quality greatly reduced the amount of wild celery. Tropical Storm Agnes was the final blow. “After the storm, wild celery was virtually impossible for canvasbacks to find,” says Kneisley.

The waterfowl switched their foraging efforts to small clams on the Chesapeake’s shallow bottom. A less nutritious diet of such shellfish as Baltic clams, scientists believe, may affect the ducks’ winter survival rates.

A Common Future

Annual bird counts, Webster says, “give us a very good picture of how much declines in SAV have affected wintering waterfowl.”

Half a century ago, 4 to 5 million ducks, geese and swans spent time on Chesapeake Bay during the winter. Now, that number is less than 1 million, according to results from an annual midwinter waterfowl survey. The nationwide count has taken place every year since the 1950s.

On the Chesapeake, survey teams of biologists from the Maryland DNR and the U.S. Fish and Wildlife Service fly transects to make visual estimates of waterfowl in the bay and along the nearby Atlantic coast. In 2026, the teams counted 926,900 ducks, geese and swans, higher than the 563,800 birds observed five years earlier in 2022. The best recent year was 2018, at 1,023,300.

Estimates of canvasbacks in 2026 were 25,300, and in 2022, 7,700. In 2023, the total for canvasbacks was 57,800. “Waterfowl are continuously responding to environmental cues, including weather, food availability and habitat quality,” says Karina Stonesifer, director of the Maryland DNR’s Wildlife and Heritage Service. Seven decades ago, in 1955, 225,450 canvasbacks were sighted. Nonetheless, says Webster, the Chesapeake “is still one of the best places on Earth to see waterfowl in winter.”

From Midwest Bird Nursery to the Chesapeake

Many of the bay’s wintering ducks began life in the prairie pothole region, which extends from the U.S. Midwest’s northern tier states into Canada. There, about half North America’s ducklings hatch.

As the ice sheets of the last glacial period retreated northward, tens of thousands of landlocked icebergs were left in their wakes, writes Michael Furtman in On the Wings of a North Wind: The Waterfowl and Wetlands of North America’s Inland Flyways.

These small icebergs melted into the soil. As they faded, Furtman states, “they became the foundation of the prairie potholes. An estimated 10 million glacially carved depressions once pockmarked the landscape of the prairie-pothole region of the United States and Canada.” As climate warmed, the potholes evolved into a habitat so enticing that more than 130 bird species have used a single pothole in a year.

With millions of potholes from which to choose, waterfowl had plenty of room to find nesting sites. “The diversity of potholes, ranging from small spring ponds to large permanent wetlands, provided ducks with the habitats necessary for each stage in their breeding and brood-rearing cycles,” Furtman states.

As wetlands in the region made way for agriculture, however, the number of potholes has decreased, especially over the last 40 years. In North Dakota’s pothole region, where as many as 100 of the basins per square mile once existed, “60 percent of the original 5 million acres of wetlands have been lost,” Furtman reports. “Ninety-five percent of that loss is attributable to agriculture.”

Is Past Prologue?

If increasing agriculture isn’t challenge enough for waterfowl, rising temperatures may result in more frequent and severe droughts in the prairie pothole region, with a significant effect on breeding ducks.

“Decades ago,” Webster says, “the Chesapeake was full of wintering canvasbacks. But no more. I’d like to see the days again when their dark red heads line up as far as you can see.”

Canvasbacks and the many other ducks that winter on the bay have come a long way to get there, Webster says. “The least we can do is show them some hospitality by making sure the environment – on their wintering and their breeding grounds – is healthy.”

Otherwise, he says, the Chesapeake’s winter waterfowl spectacle may vanish, the seawall along the Choptank indeed becoming a wall of shame as the last canvasback’s wingbeats fade into silence.

This story is an update of an article that ran in Oceanography magazine.

Written by Cheryl Lyn Dybas

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About the Author

Award-winning science journalist and ecologist Cheryl Lyn Dybas, a Fellow of the International League of Conservation Writers, brings a passion for wildlife and conservation to Ocean Geographic, BioScience, Natural History, Canadian Geographic, National Wildlife, Northern Wilds and many other publications, and is a Field Editor at Ocean Geographic.

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