By Michael G. Anderson, Ph.D.
Bracing wind, slate-gray sky, and angry water. If you have a passion for diving ducks, it probably stems from days like this. Canvasbacks streaking over decoys, gone in an instant save for the unforgettable sound of cold air tearing through straining wings. Squadrons of 'bills boring in on the deck like old torpedo planes—rising, falling, and then if everything seems right, dropping their landing gear. Sights and sounds seared in memory.
Scaup, canvasbacks, redheads, and ring-necked ducks—the freshwater diving ducks, or pochards—have stirred every waterfowler who has hunted them. Pochard (pronounced "poachard") is an unfamiliar word to North American ears but common in other places. Its origin seems lost to antiquity, but according to the Oxford English Dictionary the word was first printed in 1552, in reference to the common pochard of Europe—a bird that looks like a cross between our canvasback and redhead.
The label "diver" is often used instead of "pochard," but these ducks share many traits beyond the ability to dive. The plumages of North American pochards and their cousins around the world are similar: browns and grays for the hens, blocks of dark and light colors on the males. Their wings are shades of brown and gray and may be lightly vermiculated or include patches of white in areas where dabbling ducks show bright iridescent colors. Male pochards have striking red, orange, yellow, or white eyes. Their voices show only minor variations among species, and all males have a unique voice box with a thin transparent "windowpane" (fenestrated bullae, if you prefer the technical term) located at the top end of the trachea. Biologists can offer a longer list of less conspicuous pochard traits, but the point is that these birds clearly share a common ancestor.
Among North American pochards, canvasbacks are known for their big feet, long muscular neck, wedge-shaped bill, and unique muscle arrangements that provide special strength for opening the bill after jamming it into the mud—all assets for excavating underground tubers. Canvasbacks eat mainly aquatic plants, concentrating on tubers or rhizomes of sago pondweed, wild celery, duck potato, and other plants (although many cans have switched to eating small clams in places where submersed aquatic plants have declined, such as Chesapeake Bay and the Mississippi River). Redheads graze on aquatic plants, including musk grass or sago pondweed in the north and shoal grass in southern coastal lagoons. Like cans, they also eat tubers, rhizomes, and some invertebrates. Their bodies are similar to those of canvasbacks, but are less specialized for digging. Ring-necked ducks eat lots of seeds, largely from wild rice and various pad plants. They also eat aquatic insects. Scaup are more carnivorous, eating mainly amphipods (scuds) and small mollusks such as fingernail clams. Accordingly, scaup bills and necks are better suited for capturing small mobile prey than for digging tubers.
Pochards all dive for food, using only their feet to move underwater (sea ducks also use their wings). These ducks have compact fusiform bodies (shaped like an unbaked loaf of bread) with legs set well back on their torso, big feet and strong legs for propulsion, and the ability to slow their metabolic rate during dives. A canvasback rooting up tubers dives straight down and comes up in the same place, while a scaup cruising through the water gleaning amphipods may surface 50 feet from where it dove.
Adaptations for diving come with a cost, however. The rearward placement of the feet, while great for paddling underwater, makes these ducks awkward on land. And to help them move efficiently underwater, divers also have compact wings that lay tightly against their bodies. Smaller wings with less surface area means that more speed and power are needed to get airborne. So flushing pochards run across the water rather than jumping into the air like mallards, and they land with a long feet-first skid. Once airborne, they fly with rapid wing beats and are among the fastest ducks on the wing.
Most canvasbacks breed in the Prairie Pothole Region, but some will nest as far north as Alaska. Redheads rely on the prairies too, but many thousands nest in the Great Basin. Although lesser scaup also breed through the prairies and northwestern states, most nest in the Western Boreal Forest of Canada and Alaska, north to the tree line. Greater scaup nest even farther north in Canada and coastal Alaska. The two species overlap from around Yellowknife to Inuvik, but because they can't be differentiated reliably by aerial survey crews, both species are simply counted as "scaup." Ring-necked ducks have a wide breeding range across forested regions of Canada and are the most common breeding pochard in the east.
Of North American pochards, only scaup are truly abundant, with populations in the range of common dabbling ducks. They most likely are numerous because they inhabit such a large breeding range—more than 1.2 billion acres in Canada alone—and because in the nonbreeding season they eat foods that are widely available in large bodies of water including the lower Great Lakes, the Mississippi River, and estuaries along the Atlantic and Gulf coasts. The other pochards have smaller breeding ranges and more selective diets and nesting habits. I suspect they have never been as abundant as scaup or more adaptable species like mallards.
Although the numbers of canvasbacks have fluctuated over the 60 years that the U.S. Fish and Wildlife Service and Canadian Wildlife Service have been surveying breeding ducks, the overall canvasback population trend looks fairly stable at around 600,000 birds. Redheads appear to have been increasing slowly since the 1990s and for the past 10 years have hovered between 1 million and 1.2 million birds. Beginning in the early 1980s, scaup declined steadily for more than 20 years, but recently may have stabilized at 4 million to 4.5 million birds—still well below the scaup population objective of 6.3 million birds. Ring-necked duck numbers have increased by more than 200 percent over the past 30 years in the traditional survey area and presently number well over 1 million birds.
The pochards have been important to North American wildfowling traditions for more than three centuries. The excitement they stir on the wing, and the rewards they offer on the table, have captured our imagination and respect. By supporting Ducks Unlimited, you are helping to ensure that these magnificent birds and their habitats are conserved for current and future generations to enjoy.
Dr. Mike Anderson is emeritus scientist with Ducks Unlimited Canada and a freelance writer based in Winnipeg, Manitoba.
Life Underwater To appreciate the way diving ducks live you must watch them up close, underwater, which I've been privileged to do in experimental diving tanks. Each dive begins with birds subtly compressing their body feathers. This squeezes out air, making the birds less buoyant. Next, they arch their bodies and dive, bill down, with a single thrust of their powerful legs. They descend using their "paddles" like expert oarsmen, stroking with both feet together, steering largely with their head and tail. Near the bottom, head angled down, they use their feet to tread and maintain their position while probing the substrate with their bills, moving their heads from side to side and up and down. Their submerged bodies glisten with air bubbles, and when ready to surface, they simply quit paddling and bob to the surface like feathered corks.