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Chesapeake Bay Waterfowl Ecology: Submerged Aquatic Vegetation, Canvasbacks, and Tundra Swans

2 days ago
24 min read

Updated: 4 days ago

Tundra swans flying over water near marshy land

On a still December morning off the mouth of a Chesapeake tributary, the water can look empty until the light comes up. Then the dark shapes resolve: a long, loose raft of canvasbacks riding low over the shallows, white backs catching the sun, heads tucked, a few birds at the edges diving and surfacing with a beard of green in their bills. A few hundred yards toward shore, buffleheads work in small, nervous groups. Farther out, where the bottom drops away, long-tailed ducks call to each other in a sound that carries a surprising distance across flat water. And somewhere inland, over a stubble field behind a line of loblolly pine, a flock of tundra swans drops out of the sky with the high, wavering whistle that gave the species its older name.


Nothing about that scene is accidental. The Chesapeake Bay is a diving-duck estuary, and its waterfowl distribution is written into the bottom of the Bay itself: into which shallows have grass, which have only mud, and how far light can reach on a given winter. That makes it a fundamentally different system from the Gulf Coast dabbling-duck marshes and the bottomland hardwood flats that define so much of Southeastern waterfowl ecology. In the Mississippi Flyway, water levels in the timber and the rice country set the table. On the Chesapeake, water clarity does.


This post follows that thread. It starts with the plants, the submerged aquatic vegetation that scientists shorten to SAV and that most watermen simply call grass, and then moves through the birds that depend on it, the swans that learned to depend on it less, and the regulatory machinery that is trying to bring the grass back. Where the record does not support a popular claim, we say so.


The Largest Estuary in North America, and Why Its Shape Matters

NOAA describes the Chesapeake as the largest estuary in the United States, and on the same fact page as the largest estuary in North America. Its watershed covers about 64,000 square miles, reaching from the Bay itself across parts of six states and the District of Columbia, and that scale is the first thing to understand about its waterfowl. Every acre of farmland, every suburban lawn, every wastewater plant in that drainage contributes something to the water that eventually flows over the Bay's grass beds.


The second thing to understand is the shape. The Chesapeake is a drowned river valley, the flooded lower course of the ancestral Susquehanna. A relatively narrow, deep central channel runs down its length, flanked by broad shallow shoals, tidal creeks, and coves. The channel is of limited use to a feeding duck. The shallows are where the action is, because they are where sunlight can reach the bottom, and where sunlight reaches the bottom, rooted plants can grow.


The third thing is salinity. The Bay grades from tidal fresh water at the head and up the tributaries, through low-salinity (oligohaline) and moderate-salinity (mesohaline) reaches, to the saltier polyhaline lower Bay. The Virginia Institute of Marine Science (VIMS) reports its annual grass survey by those zones, because salinity largely decides which grasses grow where, and the grasses largely decide which ducks winter where.


Underwater Grass: The Foundation of the Diving-Duck Food Web

Submerged aquatic vegetation is a catch-all term for rooted, flowering plants that grow entirely or mostly underwater. They are not seaweeds; they are true plants with roots, stems, leaves, and in many cases flowers and seeds. In the Chesapeake, more than a dozen species occur, but three carry most of the weight in the waterfowl story.


Wild celery (Vallisneria americana) is the plant of the fresh and low-salinity reaches: the upper Bay, the Susquehanna Flats, and the tidal-fresh stretches of the big tributaries. It grows long, ribbon-like leaves from a creeping base and, critically for waterfowl, stores energy in winter buds and tubers in the sediment. Those buried stores are a dense, high-energy winter food, and the canvasback's scientific name, Aythya valisineria, is a direct nod to the plant's genus. The bird was named for the food it was seen to depend on.


Widgeon grass (Ruppia maritima) is the generalist. It tolerates a wide range of salinity and turns up from brackish creeks to the saltier mid-Bay, often colonizing quickly in good years and vanishing just as quickly in bad ones. Its seeds and vegetative parts are eaten by a long list of ducks, and its boom-and-bust tendency is one reason the Bay-wide grass total can swing sharply from one survey to the next.


Eelgrass (Zostera marina) is the plant of the salty lower Bay and the coastal lagoons. The Chesapeake Bay Program's field guide lists brant, redheads, wigeon, black ducks, and Canada geese among the waterfowl that feed on it. The field guide does not list canvasbacks among eelgrass feeders, and the canvasback's ecological association in the Bay has historically been with the fresher grass beds up-estuary.


Around those three sit a supporting cast, including redhead grass (Potamogeton perfoliatus) in the moderate-salinity middle Bay and a variety of freshwater species in the tidal rivers. Together they do more than feed ducks. Grass beds baffle waves, trap sediment, take up nutrients, shelter juvenile blue crabs and fish, and support the snails, amphipods, and small clams that invertebrate-eating ducks need. A healthy grass bed is a whole food web, and the ducks sit near the top of it.


Light, Nutrients, and the Clarity Problem

The Bay's grass beds live or die on light. Rooted plants need a certain amount of sunlight to reach the bottom during the growing season, and anything that clouds the water column cuts into that supply. Two things cloud Chesapeake water above all: suspended sediment and phytoplankton.


Sediment is the obvious one. Soil washed off fields, construction sites, and eroding shorelines stays suspended in the water and blocks light directly. Phytoplankton is the subtler problem. Nitrogen and phosphorus running off the watershed fertilize the Bay's microscopic algae the same way they fertilize a cornfield, and in nutrient-rich water those algae bloom thick enough to shade out the grass below. Excess nutrients also feed the epiphytes, the films of algae and small organisms that grow directly on grass blades and shade them from the surface down.


That chain, from land use to nutrients to algae to light to grass, is the core mechanism in this whole post. It is why waterfowl managers care about agricultural runoff hundreds of miles upstream, and why the grass survey is used as one of the Bay's main indicators of water quality. When the water clears, the grass expands; when the grass expands, the shallows hold more food; when the shallows hold more food, they can support more diving ducks through the winter.


Peer-reviewed work has tested that chain at the scale of the whole Bay. Lefcheck and colleagues, writing in the Proceedings of the National Academy of Sciences in 2018, combined three decades of watershed modeling, water-quality data, and aerial grass surveys and concluded that nutrient reductions were linked to the recovery of roughly 17,000 hectares of underwater grass, the highest cover in almost half a century at the time. They also found that higher grass diversity was associated with greater cover. The study drew some debate about how strongly a modeling analysis can assign cause, but it remains the most comprehensive test of the idea that cleaning up the watershed brings the grass back.


The Collapse: What the Record Actually Shows

The Chesapeake's grass collapse is one of the best-documented habitat losses in North American estuarine science, and it is also one of the most often exaggerated in casual retelling, so it is worth walking through carefully.


In 1983, Robert Orth and Kenneth Moore of VIMS published a short paper in Science describing an unprecedented decline in the Bay's submerged aquatic vegetation, a loss that cut across species and regions and accelerated through the 1970s. Tropical Storm Agnes in June 1972 was a defining moment in that story. The storm's enormous freshwater and sediment pulse hit grass beds that were already under pressure, and on the Susquehanna Flats, a large bed at the head of the Bay virtually disappeared after Agnes and showed little regrowth for decades. Later work by the same researchers pointed to deteriorating water quality, rather than any single contaminant, as the underlying driver.


How much grass was there before? VIMS says historical evidence suggests the Bay once held about 200,000 to 600,000 acres of underwater grass before the modern survey began. That is a wide range because it rests on historical records and reconstruction rather than consistent aerial mapping, and it is not pinned to any one decade. You will often see a crisp "200,000 acres in the 1960s" in popular accounts; the agency language does not support that precision.


What is precise is the starting point of the modern survey. When VIMS began Bay-wide aerial monitoring in 1984, the Chesapeake Bay Program estimates the Bay held 38,958 acres. That figure is one survey year, the baseline from which every later trend is measured. It is not an average for the whole decade, and it represents a small fraction of even the low end of the historical range.


The Susquehanna Flats offer a useful epilogue. Gurbisz and Kemp, writing in Limnology and Oceanography in 2014, analyzed the Flats bed's long absence and its rapid resurgence in the early 2000s. Their time series showed spring nitrogen loading rising for decades and then declining after the late 1980s. The bed's return was not instant once loading began to fall, which is a lesson the whole Bay has repeated: recovery comes in pulses, often after a run of favorable weather, and the system does not respond to cleaner water on a neat schedule.


The Recovery Trajectory: Where the Grass Stands in 2025

The 2025 grass survey, released in late summer 2026, is the most current measure of the habitat base that diving ducks will find on the Bay this winter. Here is the short version, followed by the details that matter.


A four-point card for the Bay's underwater grass:


  • 1984, survey start: 38,958 acres, the Bay Program's estimate when VIMS monitoring began.

  • 2018, survey-era high: 108,078 acres, the last year above 100,000.

  • 2024: 82,778 acres in the Bay Program total, down 1 percent from 83,419 acres in 2023.

  • 2025: 89,385 acres in the Bay Program total, up 7 percent from 2024. The VIMS preliminary report maps 82,989 acres for the same year. These are the same survey, with the Bay Program total accounting for areas that could not be flown.


Two popular claims do not survive that card. The Bay is not currently "over 100,000 acres"; it has not been reported above that line since 2018. And the 2025 total, though encouraging, is not a full recovery: it sits at 45 percent of the partnership's long-term goal.


The 2025 numbers in context. The Chesapeake Bay Program reports that the 2025 total of 89,385 acres is 615 acres short of a 2030 interim goal of 90,000 acres and well above the survey-era long-term average of 70,978 acres. In 2025, the partnership raised its long-term goal to 196,600 acres. Earlier Bay Program releases, including the one covering 2024, still used a long-term target of 185,000 acres, so readers comparing older articles should expect the target to have moved.


Why two 2025 numbers? The VIMS preliminary executive summary reports 33,576 hectares, or 82,989 acres, actually mapped in 2025. It explains that imagery was missing for parts of the Virginia Eastern Shore, the Chickahominy, Mattaponi, and Pamunkey rivers, and some upper-Bay military and tributary waters, because of weather, access restrictions, equipment failure, and the federal shutdown. Those unmapped areas held about 6,417 acres in 2024. The Bay Program's 89,385 figure is the total that accounts for those gaps. Neither number is wrong; they answer different questions.


Where the gains came from. VIMS reports that the 2025 increase was concentrated in the saltier half of the Bay. The polyhaline zone grew from 25,266 acres in 2024 to 28,142 acres in 2025, a record for that zone, and the mesohaline zone grew from 33,033 acres to 37,879. The low-salinity and tidal-fresh zones declined. That pattern matters for waterfowl. The 2024 survey had shown a 14 percent drop in the mesohaline zone, including the Choptank, Little Choptank, and Tangier Sound, so the 2025 mesohaline rebound recovered ground in some of the Bay's most important middle reaches. But the fresher zones, where wild celery grows and where the canvasback's historical relationship with the Bay was strongest, did not share in the gain.


Maryland's piece. Maryland DNR reports that underwater grass in Maryland's portion of the Bay rose from 36,799 acres in 2024 to 41,419 acres in 2025. That is a state figure, not the Bay-wide total, but it covers much of the upper and middle Bay where canvasbacks and swans concentrate.


The broader lesson is the one the Lefcheck team drew: the grass has responded to nutrient reductions, unevenly and with setbacks, and a habitat base that has more than doubled since 1984 is a different winter landscape for a diving duck.


Diving Ducks: Built for Grass Beds and Open Water

Diving ducks and dabbling ducks solve the same problem, finding food in water, in different ways. Dabblers such as mallards, black ducks, and wigeon feed at or just below the surface, tipping up in shallow marsh. Divers, which in the Chesapeake include the pochards (the canvasback, redhead, and scaup) plus sea ducks such as the bufflehead and long-tailed duck, dive completely under and swim to the bottom. Their legs are set far back on the body, which makes them powerful underwater and awkward on land, and most need a running start across the water to take off.


That body plan ties them to open water: bays, river mouths, and big impoundments rather than flooded timber or rice fields. And because they feed from the bottom, the quality of the bottom, grass or bare mud, sets the value of any stretch of water.


The Chesapeake's diving-duck community splits roughly into two feeding guilds. The plant-leaning birds, canvasbacks and redheads, have historically been tied to grass beds. The invertebrate-leaning birds, scaup, buffleheads, and long-tailed ducks, take clams, snails, amphipods, and other small animals, some from inside grass beds and some from open bottom. The line between those guilds is not sharp, and on the Chesapeake it has shifted over time, as the canvasback's story shows.


The Canvasback: The Bay's Signature Duck, and What Changed

No bird is more closely identified with the Chesapeake than the canvasback (Aythya valisineria). With its sloping wedge of a head, dark chestnut on the drake, and pale gray-white back, it was the prized market duck of the nineteenth-century Bay, and it remains the bird people picture when they think of Chesapeake waterfowling.


How important was the Bay to the species? The best-supported historical figures come from older survey work summarized in a Virginia Tech thesis: more than half of the Atlantic Flyway's canvasbacks wintered on the upper Chesapeake from 1956 to 1971, and Bay numbers fell from roughly 230,000 in the early 1950s to about 38,500 by the 1980s. The same thesis reports that Maryland held 35,651 canvasbacks in winter 1988-89, about 38 percent of the Atlantic Flyway population at the time. Those numbers describe a bird whose Chesapeake wintering population collapsed alongside the grass.


You will often read that 75 percent or more of the Atlantic population still winters on the Chesapeake. We could not find a current agency or peer-reviewed source that prints that share, and the historical figures above point lower. We do not repeat it here.


What the current data do show is a healthy continental population and a meaningful Bay presence. The U.S. Fish and Wildlife Service's Waterfowl Population Status report for 2025 estimates about 0.7 million breeding canvasbacks in the traditional survey area, similar to 2024 and to the long-term average. That is a breeding-ground count from the prairies and boreal forest, not a winter count on the Bay. On the wintering grounds, Maryland's January 2025 midwinter survey, flown with USFWS, counted 28,500 canvasbacks across Maryland's Chesapeake Bay, tidal Potomac, and Atlantic coast waters, up from 18,800 in the 2024 survey. Midwinter counts swing with weather and survey conditions, so a single year's jump is a signal, not a trend.


The more interesting ecological story is what the canvasback ate while the grass was gone. Matthew Perry and A. S. Deller's 1996 review in Estuaries, which drew on Chesapeake food-habit studies reaching back to 1885, documented a decline of submerged vegetation in the diet of some species, including the canvasback, and an increase in invertebrates. In plain terms, the Bay's canvasbacks adapted. As wild celery and other grasses disappeared from much of the upper Bay, the birds that stayed leaned more heavily on animal foods such as small clams. That flexibility likely helped some canvasbacks keep using the Bay through its worst decades, but it also changed where and how they fed.


Whether the canvasback's diet has swung back toward grass as the beds partially recovered is an open question; we found no recent diet study that answers it. What can be said is that the fresher-water zones where that relationship was strongest declined in the 2025 survey, which is worth watching.


Redheads, Scaup, Buffleheads, and Long-tailed Ducks

The canvasback gets the attention, but the Bay's diving-duck community is broader, and each species uses the system differently.


The redhead (Aythya americana) is the canvasback's close relative and frequent companion, with a rounder head, a shorter bill, and a grayer back. It is a strongly plant-oriented diver, and the Bay Program's field guide lists redheads among the waterfowl that feed on eelgrass, which makes the saltier lower Bay and its coastal lagoons part of the redhead's Chesapeake range in a way that is less true of the canvasback. The 2025 record gain in the polyhaline zone is, on paper, good news for redhead foraging habitat.


The lesser scaup (Aythya affinis) is the Bay's most flexible diver, an invertebrate-leaning bird that rafts over both grass beds and open bottom and takes small clams, snails, and other animals as readily as plant material. Greater scaup (Aythya marila) also winter on the Bay, generally favoring more open, saltier water. Scaup are managed conservatively across the continent, which is why both Virginia and Maryland split the scaup bag through the winter, as the regulations section below describes.


The bufflehead (Bucephala albeola) is the smallest of the Bay's regular divers, a compact black-and-white bird that feeds in shallow coves, creek mouths, and along shorelines. It takes mostly small invertebrates and works in tight, active groups rather than large rafts, diving in near-unison and popping back up together.


The long-tailed duck (Clangula hyemalis) is the Bay's open-water specialist, a sea duck that feeds on mollusks, crustaceans, and other bottom animals in deeper water than most of its relatives and is famous for its musical, yodeling calls. It connects the Chesapeake's diving-duck system to the broader sea-duck community of the Atlantic coast, including scoters and, in small numbers, eiders.


We have not found reliable, current species-by-species depth figures for the Chesapeake, so we do not put numbers on them. The pattern holds without them: plant-eaters cluster over grass, invertebrate-eaters spread across grass and open bottom, and sea ducks use deeper water the others leave alone.


Rafts and Communal Foraging on Open Water

One of the most recognizable things about diving ducks on the Chesapeake is how they gather. Canvasbacks, redheads, and scaup form rafts, loose flotillas that can stretch across a large expanse of open water, often resting through the middle of the day and feeding in pulses.


Rafting is an answer to several problems at once. Open water offers few places to hide, so many eyes help detect eagles and other threats. Rafts can hold position over productive bottom and shift together as food or weather changes. And because grass beds and clam beds are patchy, a raft settled over a good patch is itself a signal to other birds that food is present, which is part of why rafts can grow quickly once they form.


Feeding in a raft also creates opportunities for other species. American wigeon, dabblers that cannot dive to the bottom, have long been observed loitering near diving ducks and coots and stealing bits of vegetation brought up to the surface. That kind of food theft, called kleptoparasitism, is one more way the grass beds' production moves through the community: the plants support the divers, and the divers in turn feed some of the dabblers.


The Eastern Tundra Swan: Arctic Breeder, Mid-Atlantic Winterer

The tundra swan (Cygnus columbianus) is the other half of this post's title, and it is a very different bird with a very different relationship to the Bay.


Tundra swans breed on the Arctic tundra of Alaska and northern Canada and migrate long distances to temperate wintering grounds. Biologists manage them as two populations. The western population winters mostly on the Pacific side. The eastern population, the birds that arrive on the Chesapeake each fall, makes one of the longest migrations of any North American waterfowl, crossing the continent to winter on the mid-Atlantic coast. The U.S. Fish and Wildlife Service describes the eastern population as wintering on coastal areas from Delaware to North Carolina, and puts continental tundra swan numbers above 200,000.


They are big, all-white birds with black bills, usually with a small yellow spot in front of the eye, and they announce themselves with a high, wavering, whistling call. Older field guides called them whistling swans, and anyone who has heard a flock overhead on a cold evening understands why.


Where Eastern Tundra Swans Actually Winter

A common claim holds that eastern tundra swans winter almost exclusively on the Chesapeake. The record says otherwise, and has for decades.


Jerome Serie and James Bartonek, reporting in Wildfowl in 1991, gave the average wintering distribution of the eastern population for 1987 through 1989: about 59 percent in North Carolina, 29 percent in Maryland, 6 percent in Virginia, 4 percent in New Jersey, and 2 percent elsewhere. They also noted that Maryland's Chesapeake-area count had been declining while North Carolina's rose. Those percentages are from the late 1980s and should not be read as a current split, but they establish that the Chesapeake has not been the majority wintering ground for a long time. North Carolina's coastal sounds and refuges, including Lake Mattamuskeet and Pocosin Lakes, hold the larger share, a story told in our Mattamuskeet field report linked below.


That said, the Chesapeake still matters a great deal to the species. Maryland's January 2025 midwinter survey counted 12,900 tundra swans across the state's Bay, tidal Potomac, and Atlantic coast waters. The Eastern Shore of Maryland, with its mix of tidal rivers, marsh, and wide farm fields, remains one of the most reliable places in the mid-Atlantic to see and hear wintering swans.


From Grass Beds to Grain Fields: How Swans Adapted

Historically, tundra swans on the Chesapeake were water birds in the fullest sense, feeding on submerged vegetation in the shallows. As the grass collapsed, that food base shrank, and swans, like Canada geese before them, turned increasingly to the land.


The USFWS species account notes that fall and winter flocks feed and loaf in agricultural fields. Perry and Deller's 1996 review made the ecological consequence explicit: field feeding by geese and swans lessened the importance of shallow water for those birds. In other words, the swan did not simply decline with the grass. It changed its winter economy, shifting much of its feeding from submerged plants to waste grain and green growth on the farm fields that surround the Bay, especially on the flat, agricultural Eastern Shore.


That shift has several implications. It probably cushioned the population against the worst of the grass loss, much as the canvasback's turn toward invertebrates did. It ties swan distribution to farming patterns, crop choices, and harvest timing, not only to the condition of the water. And it puts large, highly visible birds onto working private land for much of the winter, which makes landowner relationships part of how swans fit into the landscape. Agencies we reviewed do not publish a current assessment of crop effects from Chesapeake swans, so we leave that question at the level of a relationship to watch rather than a documented conflict.


The Chesapeake Bay TMDL: The Main Lever for Clearer Water

If water clarity sets the Bay's waterfowl carrying capacity, the most important waterfowl habitat program on the Chesapeake is not a refuge or a duck-stamp project. It is a water-quality regulation.


On December 29, 2010, the U.S. Environmental Protection Agency established the Chesapeake Bay Total Maximum Daily Load. A TMDL sets the maximum amount of a pollutant a water body can receive and still meet water-quality standards; EPA describes it as a pollution diet. EPA calls the Chesapeake Bay TMDL the largest and most complex TMDL thus far, covering the roughly 64,000-square-mile watershed. It set annual limits of 185.9 million pounds of nitrogen, 12.5 million pounds of phosphorus, and 6.45 billion pounds of sediment, and divided those loads among the watershed jurisdictions, which carry them out through their own implementation plans.


Those three pollutants map directly onto the clarity problem described earlier. Nitrogen and phosphorus feed the algae that shade grass beds. Sediment clouds the water directly. Every pound that stays on the land rather than washing into a tributary is, in effect, a contribution to light on the Bay bottom.


The TMDL did not start the cleanup; nutrient reductions were already under way, which is why the Lefcheck team could trace grass recovery back into the 1980s and 1990s. But it gave the effort enforceable numbers and accountability. For waterfowl, it is the single most important policy lever on the habitat that makes the Chesapeake a diving-duck estuary in the first place.


The TMDL also works alongside a broader partnership. The Chesapeake Bay Program brings together federal agencies, the watershed states, the District of Columbia, and other partners under Chesapeake Bay agreements stretching back to 1983, with goals for living resources as well as water quality. Underwater grass sits where those two meet: it responds to clarity, so it measures progress on nutrients and sediment, and it provides habitat, so it measures progress for crabs, fish, and waterfowl. That is why the partnership's 2025 decision to raise its long-term grass goal to 196,600 acres matters for ducks. The more of that target the Bay meets, the larger the food base its divers find each winter.


Refuges on the Flyway: Blackwater, Eastern Neck, and Bombay Hook

Water quality is the master lever, but protected land still matters, especially for birds that rest, roost, and in the swans' case feed on the margins of the Bay. Three national wildlife refuges are often named in the Chesapeake waterfowl conversation, and it helps to be precise about where they are.


Blackwater National Wildlife Refuge in Dorchester County, Maryland, covers about 32,000 acres of tidal marsh, open water, forest, and managed impoundments on the Eastern Shore. It is one of the anchors of the refuge complex that USFWS manages as Chesapeake Marshlands, and its marshes and fields are some of the best-known places on the Bay to watch wintering waterfowl, including swans and geese.


Eastern Neck National Wildlife Refuge is a small island refuge at the mouth of the Chester River in Kent County, Maryland, part of the same Chesapeake Marshlands complex. Surrounded by open Bay water and shallow shoals, it sits right in the kind of setting this post describes, where diving-duck water and swan habitat meet.


Bombay Hook National Wildlife Refuge is often grouped with Chesapeake refuges, but it is not on the Chesapeake. It sits along Delaware Bay in Delaware and covers 16,251 acres of tidal salt marsh, freshwater impoundments, and upland. It belongs to the same Atlantic Flyway corridor and shares many of the same birds, but it is a different estuary with its own dynamics.


Refuge hunting programs are governed by each refuge's own plans and regulations, which change. If you plan to hunt on any refuge, get the current rules directly from that refuge or USFWS.


Seasons and Regulations Touching These Species, 2026-27

The Chesapeake's waterfowl regulations reflect the ecology described above: conservative limits on species of concern, split scaup limits, and very different approaches to swans in the two Bay states. Everything below is from the agencies' published 2026-27 materials as copied in mid-October 2026. Confirm current regulations with Virginia DWR and Maryland DNR before you hunt; dates and limits can change, and the agency's official guide controls.


Virginia, ducks. Virginia DWR lists 2026-27 duck seasons of October 9-12 (black ducks closed in that segment), November 18-29, and December 19, 2026 through January 31, 2027, with youth and veterans days on October 24, 2026 and February 6, 2027. The daily bag is 6 ducks, including no more than 2 canvasbacks, 2 redheads, 3 pintails, 4 mallards (only 2 hens), 3 wood ducks, and 2 black ducks outside the October closure, along with 1 mottled duck and 1 fulvous whistling duck. Scaup are limited to 1 per day through January 11 and 2 per day from January 12 through 31. Sea ducks count within the 6-duck bag, with no more than 4 sea ducks, including no more than 3 scoters, 3 eiders (only 1 hen), or 3 long-tailed ducks. Harlequin ducks are closed. Possession is three times the daily bag. Mergansers carry a separate limit of 5 per day and 15 in possession on the same dates. Confirm current regulations with Virginia DWR.


Virginia, tundra swans. Virginia DWR runs a drawn-permit tundra swan season from November 15 through January 31 for 2026-27, with no more than 475 permits issued and a limit of 1 swan per permittee per season. The hunt area covers counties and portions of counties east of I-95 and south of the Prince William and Stafford county line at Chopawamsic Creek. The application deadline was September 25, 2026. Confirm current regulations with Virginia DWR.


Maryland, ducks. Maryland DNR's 2026-27 pocket guide lists Eastern Duck Zone seasons of October 10-17, November 14-27, and December 15 through January 30. The Eastern Duck Zone includes Dorchester, Talbot, and Queen Anne's counties. Black duck season in that zone runs November 14-27 and December 15 through January 30, so the October segment is closed to black ducks. The daily bag is 6 ducks, including mergansers, with no more than 2 canvasbacks, 2 redheads, 3 pintails, 4 mallards (2 hens), 3 wood ducks, 2 black ducks during the black duck season, 1 fulvous tree duck, and 1 mottled duck. Scaup are limited to 1 per day, rising to 2 per day from January 8 through January 30. Sea ducks are capped at 4, with no more than 3 eiders (1 hen), 3 long-tailed ducks, or 3 scoters. Coots are 15 per day in addition to the duck bag. Harlequin ducks are closed. Confirm current regulations with Maryland DNR.


Maryland, swans. Maryland DNR's 2026-27 pocket guide lists no open season for swans. Confirm current regulations with Maryland DNR.


The contrast between the two states is ecologically interesting in its own right. Virginia's limited, permit-based swan season is a narrow harvest opportunity on a bird whose population is managed at the flyway level, while Maryland, which historically has held the larger share of the Chesapeake's wintering swans, does not open a season.


What the Grass Survey Means for This Winter

The habitat base is larger than it was a year ago. The 2025 survey, which describes the grass that grew last summer and is the most recent full measure available, shows 89,385 acres Bay-wide, up 7 percent, with record growth in the saltier lower Bay and a solid rebound in the middle Bay. Those gains favor redheads and the eelgrass feeders of the lower Bay and add bottom habitat that supports the invertebrates scaup and buffleheads eat.


The fresher upper reaches are the soft spot. The low-salinity and tidal-fresh zones declined in 2025, and those are the waters where wild celery grows and where the canvasback's classic relationship with the Bay was strongest. A single year's decline does not make a trend, but it is a reminder that the Bay's recovery is not uniform.


The birds will follow weather as much as habitat. Divers concentrate on the Bay when cold pushes them off interior waters, so the size of any winter's rafts depends heavily on how hard winter comes to the north.


And the swans will be where the fields are. Eastern tundra swans will again winter from Delaware to North Carolina, with Maryland's Eastern Shore and North Carolina's coastal refuges holding the main concentrations, and much of their feeding will happen on farmland rather than over grass.


Frequently Asked Questions

How many acres of underwater grass did the Chesapeake have in 2025?

The Chesapeake Bay Program reported 89,385 acres of underwater grasses in the Bay and its tidal tributaries for 2025, a 7 percent increase from 2024. That total sits 615 acres short of the partnership's 90,000-acre interim goal for 2030 and at 45 percent of its 196,600-acre long-term goal.


Why do the Bay Program and the VIMS preliminary report show different 2025 acreages?

They describe the same survey year. The VIMS preliminary executive summary reports 82,989 acres actually mapped in 2025, because weather, access limits, equipment failure, and the federal shutdown left gaps in imagery. The Bay Program's 89,385-acre figure is the total that accounts for those unmapped areas, which held about 6,417 acres in 2024.


Did grass beds fall under 40,000 acres, and have they passed 100,000 again?

When VIMS monitoring began in 1984, the Bay held an estimated 38,958 acres of underwater grass. The survey-era high is 108,078 acres in 2018, and no year since has been reported above 100,000. The 2025 total of 89,385 acres is well above the long-term survey average of 70,978 acres.


Do most Atlantic canvasbacks still winter on the Chesapeake?

No current agency source we found publishes a Chesapeake share of the Atlantic Flyway canvasback population. Older work summarized in a Virginia Tech thesis puts more than half of the flyway's canvasbacks on the upper Bay from 1956 to 1971 and about 38 percent in Maryland in winter 1988-89. Maryland's January 2025 midwinter survey counted 28,500 canvasbacks across its Bay, tidal Potomac, and Atlantic coast waters.


Where do eastern tundra swans actually spend the winter?

The U.S. Fish and Wildlife Service describes the eastern population as wintering on coastal areas from Delaware to North Carolina. In the late 1980s, about 59 percent wintered in North Carolina, 29 percent in Maryland, and 6 percent in Virginia, according to Serie and Bartonek. Maryland's January 2025 midwinter survey counted 12,900 tundra swans.


When is duck season in Virginia for 2026-27, and how many canvasbacks can you shoot?

Virginia DWR lists 2026-27 duck segments of October 9-12, November 18-29, and December 19 through January 31, with a 6-duck daily bag that includes no more than 2 canvasbacks. Black ducks are closed during the October segment, and scaup limits change in January. Confirm current regulations with Virginia DWR before you hunt.


Can you hunt tundra swans in Virginia and Maryland?

Virginia DWR runs a drawn-permit tundra swan season, November 15 through January 31 for 2026-27, with no more than 475 permits and 1 swan per permittee; the application deadline was September 25, 2026. Maryland DNR's 2026-27 pocket guide lists no open season for swans. Confirm current regulations with each agency.


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