Wildlife

Hundreds of canvasback ducks on Chesapeake Bay in winter.

Historical Sign of Chesapeake Winter, the Canvasback, Still Brightens the Bay

Hundreds of canvasback ducks on Chesapeake Bay in winter.
Hundreds of canvasback ducks flock to open water on a cold winter morning on Chesapeake Bay. (Photograph: Paul Bramble)

“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 again next winter.

In parka, gloves and hat, Webster, waterfowl coordinator for the Maryland Department of Natural Resources (DNR), raises his binoculars near a seawall that runs along the Choptank River near Cambridge, Maryland. The lookout where the Choptank meets the Chesapeake is a mecca for wintering canvasbacks and other ducks.

“Canvasbacks, the waterfowl everyone comes to see, are usually here by Christmas, sometimes by Thanksgiving,” Webster says. “They stay through March, then they’re gone, heading north to nesting grounds.”

Canvasbacks form large groups in winter.
Canvasbacks form large groups in winter, especially in areas near food sources. Here,
on Chesapeake Bay. (Photograph: Paul Bramble)

Skeins of waterfowl

On this early March morning with calm winds and temperatures that hover around freezing, the canvasbacks’ red heads stand out against winter-dark waters. The ducks glide near the seawall, where a dozen photographers jostle for a quintessential shot of an iconic Chesapeake duck. “This spot is known as the ‘wall of shame,’” laughs Webster, “because it’s almost too easy to get great waterfowl pictures here.”

Chesapeake skies fill with ducks – 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 and its 19 major tributaries, including the Patuxent and Potomac rivers, provide winter habitat for 24 species of ducks as well as Canada geese, greater snow geese and tundra swans on their annual stopovers.

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

Canvasbacks in an out-of-the-way spot on the Chesapeake.
Canvasbacks in a spot along the Chesapeake that’s protected from winter winds, and where aquatic grasses are ready-to-eat. (Photograph: Paul Bramble)

Seesawing duck and grass estimates

According to a 2016 estimate, the most recent available, some 97,433 acres of submerged aquatic vegetation (SAV) remain in the bay and its tributaries, down from historic levels that may have reached more than 600,000 acres.

There’s good news, however. The 2016 estimate is an 8 percent increase over 2015, and more than twice the SAV in 2013.

In 2011, Chesapeake SAV fell to 48,195 acres, a result of the effects of Hurricane Irene and Tropical Storm Lee. The storms sent a flood of sediment downstream and into the bay. Conditions since, which have been relatively dry, reduced the flow of grass-smothering sediment and helped the SAV recover. More sunlight has reached submerged grasses, allowing them to flourish. In turn, SAV filters runoff, helping keep Chesapeake waters clear.

Canvasback dives for dinner.
Several birds watch a canvasback diving for dinner. (Photograph: Paul Bramble)

SAV: A canvasback’s best friend

As recently as 1950, half the continent’s population of canvasbacks – more than a quarter million — wintered in Chesapeake Bay, relying on aquatic grasses as a favored food source.

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

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

“Canvasbacks were a favored quarry of market hunters because their meat was considered the tastiest of all the ducks due to their consumption of wild celery,” writes Guy Baldassarre in the 2014 edition of Ducks, Geese and Swans of North America.

Adds Kneisley, “Large beds of wild celery, a canvasback favorite, once attracted thousands of these ducks to an upper bay area known as Susquehanna Flats.” The decline in the Chesapeake’s water quality greatly reduced the amount of wild celery bay-wide, however.

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

How many canvasbacks on the Chesapeake? Winter waterfowl counts offer answers.
Canvasbacks shed water after diving for food. How many of these ducks winter on the Chesapeake? To find out, scientists conduct an annual count. (Photograph: Paul Bramble)

Counting canvasbacks

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

Half a century ago, four to five million ducks, geese and swans spent time on Chesapeake Bay during the winter. Now, that number is less than one million, according to results from the 2018 Midwinter Waterfowl Survey. The nationwide count has taken place annually since the 1950s.

Along the Chesapeake and nearby Atlantic coast, aerial survey teams of pilots and biologists from the Maryland DNR and the U.S. Fish and Wildlife Service make visual estimates of the region’s waterfowl. In 2018, the teams counted some 1,023,300 ducks, geese and swans, higher than the 812,600 birds observed in 2017 and above the 5-year average of 851,980.

“Cold weather and accompanying ice and snow to the north will typically push birds south as they search for food and open water,” says Maryland DNR Wildlife and Heritage Service director Paul Peditto. With December’s frigid temperatures and iced-in lakes in northern states, ducks were on-the-wing to points south.

Estimates of Chesapeake canvasbacks in 2018 were 60,000; in 2017, 75,100; in 2016, 19,800; and in 2015, 64,200. Sixty years earlier, in 1955, 225,450 canvasbacks were sighted. The last time the canvasback count exceeded 100,000 was in 1967: 133,100.

Nonetheless, says Webster, “Chesapeake Bay is one of the best places on Earth to see waterfowl in winter, and as they migrate in and out in late fall and early spring.”

Most waterfowl migrate along corridors, the well-known “flyways.” Four major routes pass through the United States: the Pacific Flyway, which runs north-south along the West Coast; the Mississippi Flyway, which leads from the bays of northern Canada and the Arctic to the Gulf of Mexico; the Central Flyway from northwestern Canada to Central America and the Yucatan Peninsula; and the Atlantic Flyway, which funnels waterfowl from central and eastern Canada along the Atlantic Coast to Florida. Chesapeake Bay is a major duck stop along the Atlantic Flyway.

Canvasback hen among drakes.
A lone canvasback hen in a crowd of potential suitors. (Photograph: Paul Bramble)

Bird nursery

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

When the Wisconsin ice sheet of the last glacial period retreated northward some 15,000 years ago, tens of thousands of landlocked icebergs were left in its wake, 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 one year. Ducks were likely among the first residents. 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.

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

Fisheye view of canvasbacks on the Chesapeake.
Will the Chesapeake always welcome wintering canvasbacks? (Photograph: Paul Bramble)

Hot times?

If increasing agriculture isn’t challenge enough for waterfowl, rising global temperatures may result in more frequent and severe droughts in the prairie pothole region. The effect on breeding ducks would be devastating, says Webster.

“Decades ago,” he remembers, “the Chesapeake was full of canvasbacks. But no more. I’d like to see the days come back when canvasbacks’ red heads bobbed on the water as far as you could see.”

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

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

The last of the "king of ducks"?
The last Chesapeake canvasback? We need to do our part to help the “king of ducks” grace the bay each winter. (Photograph: Paul Bramble)
Science journalist and ecologist Cheryl Lyn Dybas, a Fellow of the International League of Conservation Writers, brings a passion for wildlife and conservation to National Geographic, Natural History, National Wildlife, BBC Wildlife, Scientific American, The Washington Post, and many other publications, and is a featured speaker on science journalism and conservation biology. Eye-to-eye with the wild is her favorite place to be.

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