One of the most widespread duck species in the northern hemisphere, found all across North America, Europe, and Asia, the Gadwall is also one of the least ornate. Even males in full breeding plumage have only subtle patterns. As a result, this duck may not command as much attention as more colorful species. Still, it has been recognized for a long time — its simple name has been in use at least since the 1660s, clearly applied first by everyday people, not by scientists. No one seems to know the origin of the word.
In North America, Gadwalls are most numerous in the West, breeding mainly on the northern Great Plains and in western lowland marshes. Smaller numbers nest north to southern Alaska and east to the Great Lakes and Atlantic Coast. In winter, they’re found across the southern U.S. and northern Mexico. The species can be expected at some seasons practically everywhere on this continent, except the far north.
The male Gadwall in breeding plumage has markings that are subtle but distinctive enough. The black rump, uppertail coverts, and undertail coverts combine to create a contrasting back end to an otherwise gray-brown duck, a pattern that’s diagnostic at any distance. Seen up close, it has beautiful fine vermiculations of black on the body plumage, thin cinnamon edges on the scapulars, and pale gray tertials. The narrow bill is black.
The female Gadwall is one of our most nondescript ducks. Head shape is a good clue, with a relatively steep forehead rising above a narrow bill. The small white square on the trailing edge of the wing is sometimes visible when the bird is swimming. But the best mark is bill color: gray, with a neatly defined orange side panel. Only a few female ducks have orange on the bill, mainly the Mallard complex and Northern Shoveler, and those differ in both the shape and pattern of the bill.
Potentially the most confusing Gadwall plumage is the male in non-breeding plumage, or “eclipse plumage,” in summer. At that stage, most of the black feathers near its tail are replaced by brown, and the sides of its bill are orange, similar to the female’s pattern. It shares enough of the female’s field marks — including head shape — to be identifiable, as long as we remember that this plumage is expected at that season.
Observers are sometimes confused to see male ducks in non-breeding plumage in summer, when females are actively raising young. But ducks have an unusual approach to seasons. Gadwalls begin pairing up during migration — not in spring but in fall, as they head south for the winter. Studies on the wintering grounds have found more than 80 percent of female Gadwalls already paired up by December. So the males are in their brightest breeding plumage by fall to find a mate, even though nesting activities won’t commence until months later.
What to look for
Overall pattern. Fairly plain brown (female) or grayish (male), with strongly contrasting black tail coverts forming black rear end (or “stern”) on male.
Head and tail shape. Relatively steep forehead, more pronounced on male, and thin bill.
Bill color. On male, black for most of year. On female and non-breeding male, orange on sides, neatly separated from gray on top.
Flight pattern. White inner secondaries create a small white square on trailing edge of wing near the body.
With enough practice, most North American ducks can be identified by the shape of the head and bill. These shapes are easier to see than they are to describe, but the Gadwall typically shows a relatively slender bill and steep forehead. Compare this bird with the female Mallard, below. The forehead may look more noticeably steep on the male Gadwall, which often keeps the head feathers more puffed out, as seen on the facing page. For identifying the female Gadwall, bill color is one of the best marks: orange along the sides, neatly separated from the gray upper ridge. The small white square in the wing, barely visible here, is another good clue when it can be seen.
As the most widespread and familiar duck species in North America, the Mallard makes a good basis for comparison to others. The female Mallard is a typical dabbler, with strongly patterned body feathers; females of many diving ducks have smooth brown or gray bodies, without noticeable feather patterns. It has a fairly large head, warm brown but with finer markings than the body. Its bill is thick at the base, mostly orange with irregular blackish markings wrapped over the top. The speculum, the patch of color on the trailing edge of the wing, is blue with white borders. On the swimming bird, however, this is often completely hidden, or it may be partly hidden as in this photo.
One thing about ducks that can be confusing to new birders is the fact that so much of their wing pattern is completely hidden when the bird is at rest. This image shows the striking wing pattern of black and rich chestnut of the male Gadwall; in the portrait at the top of this article, none of that color is visible. When the bird is at rest, the wing is almost completely tucked in among the body plumage, buried under the scapular feathers from above and the breast feathers coming up from below. This photo also gives a good view of the diagnostic black tail coverts, but the appearance of a black chest is mostly an illusion caused by shadow.
Many female ducks are easier to identify in flight, by details of wing pattern, than they are when standing or swimming. This is another reason why it’s worthwhile for birders to train ourselves to look at details on flying birds. In the case of the female Gadwall, it looks almost as unremarkable in the air as it does on the water, but aspects of head shape and bill color are still visible. Its diagnostic wing pattern — with a small white square on the trailing edge of the wing, next to the body — is usually evident. However, the white patch consists of just a few secondary feathers, and this mark can be smaller or absent on a few individuals.
The forgotten Gadwall
Migrating or wandering ducks, winding up on remote oceanic islands, have been known to establish distinctive resident populations. In Hawaii, for example, the Hawaiian Duck is clearly descended from Mallard ancestors. But a thousand miles south of Hawaii, a unique subspecies of Gadwall was once a permanent resident on what is now called Teraina Island in the Northern Line Islands of Kiribati.
We probably wouldn’t even know this duck ever existed if not for the fact that a U.S. Navy surgeon, Thomas Streets, happened to visit Teraina Island (then called Washington Island) in 1874. Streets noted that a resident population of ducks lived on the lake and bogs of the southeastern part of the island, and that these ducks were very similar to Gadwalls but much smaller. In the Bulletin of the Nuttall Ornithological Club in 1876, he described these ducks as a new species and named them in honor of the famed ornithologist Elliott Coues.
Today this duck is listed as an extinct subspecies of Gadwall: Mareca strepera couesi. We know it really existed, because Streets brought back two specimens which are now in the U.S. National Museum. But we don’t know anything more. A person who spent time on the island around 1900 reported that some migratory ducks arrived for the winter but that no resident ducks were present, so it must have gone extinct sometime before then.
This article was first published in the September/October 2020 issue of BirdWatching magazine.