The male has fine gray patterning and a distinctive black rear.
The male is finely patterned in gray, while the brown female resembles a female Mallard. During its late-summer molt, the male takes on a duller, female-like plumage.
Gadwalls sometimes eat aquatic plants brought up by another bird. At Kleiner Weikerlsee in Linz, Austria, they gathered around coots and approached as soon as a coot surfaced with plants in its bill. As the coot shook its head to break up long shoots, the ducks collected fragments that fell away. Gadwalls also took plants directly from the coots’ bills.
A report published in 2023 describes approximately 50 Gadwalls, 30 Eurasian Wigeons and 20–30 coots at this lake in each of the winters of 2021/22 and 2022/23. On 19 December 2022, however, a Gadwall pair repeatedly dived for waterweed themselves, using their wings underwater. Ducks that usually obtain food near the surface entered headfirst and splashed as they collected submerged plants.
An extinction-risk assessment has not been added yet.
A 1993 U.S. Forest Service management account reports that mowing and livestock grazing can remove preferred Gadwall nesting cover. Late-spring and summer fires may destroy nests, while ducklings and moulting adults are especially vulnerable. Retaining cover during nesting is a conservation priority in the North American breeding habitats discussed.