American Black Duck (Anas rubripes): An Elusive Yet Treasured Duck Species

Life history and habitat information about black ducks and the strong culture surrounding them.

Life occurs in two seasons on the Eastern Shore of Maryland. The first begins in April when the water temperature rises above 50 degrees. That’s when blue crab season begins, and it lasts until the water temperature plummets. By fall, watermen have traded out their pots for their decoy bags. The second season of life on the Eastern Shore will begin when the black ducks arrive. 

The Havre De Grace Decoy Museum, the Ward Museum of Wildfowl Art (now permanently closed), and the Chesapeake Bay Maritime Museum all stand as monuments to this second season. At their core, they celebrate Eastern Shore hunting culture, and the fabric of that culture is woven with black ducks. In fact, all throughout the mid-Atlantic and Northeast, where most of America’s black ducks reside, hunters seem throttled by their existence. 

Black ducks pose a challenge like no other duck. Being outwitted by one engraves a gaping sentiment of respect and desire into the duck hunter’s psyche. One man who knew a thing or two about this addiction was Harry M. Walsh, an Eastern Shore native, co-founder of the famous Waterfowl Festival in Easton, Maryland, and author of the 1971 book, The Outlaw Gunner.

“The black duck is the wise king of all ducks,” Walsh wrote in his book’s opening pages. “Anyone killing them consistently and in large numbers is probably cheating.” 

American Black Duck Physical Description

To call a black duck a melanistic mallard wouldn’t be too far from the truth. Somewhere around half a million years ago, “black ducks diverged from a group of mallards that became stranded in the boreal forests of Quebec and Labrador,” said Dr. Phil Lavretsky of Ducks Unlimited. Slowly, the landscape whittled them into what we see today. They evolved plumage as dark and dull as a Canadian river bank. They grew violet blue speculums, cheeks streaked with brown, and an unprecedented survival instinct that lands them among America’s all-time favorite birds.

Males and females are virtually indistinguishable if not for the color of their bill. Males carry a bright yellow bill like a mallard drake. Females have a dark olive green bill like a mallard hen. All black ducks, however, can easily be identified on the wing. As they fly, these birds pulse flashes of white. The porcelain-colored feathers on the underside of their wings shine in stark contrast to their dark bodies, and the flashes they create in flight can be seen from hundreds of yards away. 

Black Duck Habitat

Part of the reason that hunters like Harry M. Walsh become so hooked on black ducks is the habitat in which they live. In the mid-Atlantic, they prefer tidal meadows. Although they may seem cold and desolate in the winter, they are full of life. These marshes are embedded with the aroma of brine and legacy of black ducks. 

The Delaware Bay estuary winters more black ducks than anywhere in the world. The Chesapeake Bay emerges as a close second. In New York, where almost 20,000 of them were harvested in 2023 according to USFWS, black ducks prefer the salt marshes surrounding New York City and the mouth of the Hudson, along with the scrub-shrub wetlands pocked throughout the Adirondacks and the beaver swamps nestled in the lowlands. 

Black ducks breed and nest in bogs and forested wetlands, ponds and lakesides, and creek banks along brackish water tidal marshes. The Great Lakes and St. Lawrence River regions of Canada provide essential breeding habitat in the northern tier of their range, however, their nests can be found as far south as the Adirondacks and mid-Atlantic.

Preferred Food

Macroinvertebrates and fish such as mummichogs, grass shrimp, snails, insect nymphs, worms, fiddler crabs, and other shelled creatures comprise a greater majority of a black duck’s diet than most hunters realize. In Maine, macroinvertebrates constituted 75 percent of egg-laying female diets. Other studies have demonstrated that fish like mummichogs provide an invaluable resource for their survival. 

When marshes ice over in the depths of winter, researchers postulate, black ducks congregate on tiny, free flowing tidal creeks for the purpose of feeding on mummichogs. The mummichogs are easy to forage on and provide bioenergetic resources that surpass most other foods on the marsh. While black ducks do feed on aquatic vegetation and seeds like most dabbling ducks, their animal-based preferences distinguish their diet from their close cousin and ecological competitor, the mallard.

Conservation

Black ducks thrive best in undisturbed landscapes with little alteration by humans. A 2023 study conducted by Katheryn Barnhart, then-graduate student at University of Maryland, found that Eastern Shore black ducks disproportionately favored habitats with clearer water quality and lower nitrate levels. Conversely, black ducks were less likely to be found in areas impacted by agricultural run-off, where leaching fertilizer ramped up nitrate levels, or areas closer to human development.

Barnhart’s study can be viewed as just one of the latest pages in a growing research novel meant to understand the population dynamics of black ducks. If you were to read that novel from the beginning, the first couple of chapters would be mayhem. 

Heading Towards Extinction

In the early 1980s, wildlife managers scrambled to get a grip on a black duck population that was rapidly slipping toward extinction. Between 1950 and 1980, their population was chopped in half. Dr. David Anderson, then-researcher out Colorado State University, published a paper in the 1987 edition of the Wildlife Society Bulletin titled “The Need for Experiments to Understand Population Dynamics of American Black Ducks.” “The size of the American black duck population, as indicated by winter surveys, has generally decreased over the past three decades,” the study states. “Controversy has existed for many years as to the cause of the declines.”

Theories ranged from overhunting to habitat loss. Some speculated lead poisoning and others blamed genetic introgression from mallards. Regardless of the cause, which is largely still up to debate, black duck populations plummeted in that thirty year timeframe, leading to a restrictive one black duck harvest limit that was not liberalized until 2017. 

Population Recovery

Adaptive management strategies, better techniques for censusing the population, and an influx of panic-spurred research data revealed that the black duck population began to stabilize in the 1990s and remains stable through today. For example, the “2024 Waterfowl Breeding Population and Habitat Survey” estimates the total number of black ducks in eastern America at around 900,000 birds. Hunters now enjoy a two bird limit. 

Researchers continue to keep close watch on the black duck population and its many fluctuations. Two of the early hypothesized reasons for the black ducks demise in the 1950s still remain major subjects of study today: habitat loss and hybridization with mallards. 

Hybridization Of Black Ducks And Mallards

Hybridization between black ducks and mallards is so pervasive, waterfowl biologists tasked with banding these birds designate individuals on a spectrum. For example, a banded bird could be a black duck, a black duck dominant hybrid, a true 50:50 hybrid, a mallard dominant hybrid, or a pure mallard. Historically, biologists used plumage characteristics to determine just how much of a hybrid each bird is, although, in recent years, research has demonstrated that plumage characteristics alone fail to accurately discern purebred black ducks and mallards from hybrids.

DuckDNA

Managers rely on large-scale data banks, such as the DuckDNA project managed by Dr. Phil Lavretsky and his lab at the University of Texas at El Paso, to understand the diversity and mixing of black duck and mallard genetics in the wild. The DuckDNA project relies on community science. The goal of the project is to untangle the mess of mallard genetics on the North American continent, which has largely been contaminated by gamefarm mallards. However, since mallards also readily hybridize with black ducks, the DuckDNA project provides data references on the black duck genome as well. 

Hunters from across all four of America’s flyways submit harvested samples to Lavretsky’s lab. With the aid of complex genetic sequencing machinery, Lavretsky can figure out exactly what a purebred black duck is and isn’t. 

Atlantic Coast Joint Venture

Managers concerned with habitat loss work collaboratively through state and federal efforts to create, maintain, and manage critical black duck habitat. One of the most important efforts concerning black duck conservation is the Atlantic Coast Joint Venture (ACJV) program. 

The Atlantic Coast Joint Venture comprises 16 states on the Eastern Seaboard and Puerto Rico. The program aims to identify concerns, establish management plans, and set tangible targets for the conservation of many species of concern, including black ducks. The Atlantic Coast Joint Venture ranks the loss of habitat due to sea-level rise as number one threat to black ducks. Second to sea-level rise is loss of habitat due to development. Lastly, the ACJV raises concerns about inland human development, where land-use practices prevent the adaptive capability of the landscape. 

As sea-levels rise, researchers expect salt marsh habitats to migrate inland. However, if human development impedes that migration, localized salt marsh habitats could be lost completely. 

The Culture Surrounding Black Duck Hunting

Usually, hunters depend on the gregarious nature of waterfowl to hunt them. That’s why tools like decoys and duck calls are indispensable. However, Atlantic-based waterfowlers know that black ducks don’t play by the rules. Their reclusive nature sets them apart from all other waterfowl. 

“The black duck is usually a loner and only tolerates others,” Harry M. Walsh wrote in The Outlaw Gunner. “Large flocks are rare and seldom decoy… After rounding out downwind, they approach very cautiously and slowly, scouting the area.”

Black duck hunters find the best success by tailoring their tactics specifically toward this bird’s behavior. This includes using fewer decoys, calling less, and keying in on microhabitats. Moreover, black duck hunters need to hunt in regions that support large populations of black ducks. 

A classic wildlife ecology principle states that population densities will be greatest at the center of the species’ range. For the black duck, the center of their migration falls squarely on the Delaware Bay and Chesapeake Bay estuaries. In the marshes sandwiched between Virginia and New Jersey, such as Harry M. Walsh’s home marsh on the Eastern Shore of Maryland, black ducks represent most of every bird in the wintertime sky.