Gadwall

Anas strepera

by Justin Milligan

The Gadwall, Anas strepera, is a medium-sized dabbling duck that very often inhabits this region during the late fall and winter during its migration south. The duck is very easy to identify in hand, but in the field they prove to be very difficult to identify even by experts.The male and female Gadwall look very similar with the male having a gray plumage and the female being a little more brownish on the back and tan on the breast. The most distinguishing mark for both male and female Gadwalls is a white patch on their wings, which is only visible in flight.

Gadwalls inhabit a wide variety of habitats including marshes, sloughs, ponds, and small lakes. They tend to be more abundant on small prairie marshes than in temporary water areas, deep marshes, and open water marshes. In the winter they prefer the brackish water marshes with abundant leafy aquatic vegetation. Gadwall’s main food sources are aquatic vegetation, aquatic invertebrates, and seeds. They are surface feeders feeding mostly on plant material growing close to the surface. Some of the plant material Gadwalls eat: pondweed, water milfoil, algae, smartweed, bulrush, spikerush, saltgrass, muskgrass.

Gadwalls are monogamous in their breeding behavior. Pairs of adult birds will bond in the mid to late fall. Pair bonds are renewed each year. They leave their breeding grounds in the north from September to late October after some cold weather event occurs, which triggers the migration south. The birds will fly in flocks of 100 individuals or less, but as many as 10, 000 at a time will migrate in separate groups to the same destination all arriving within hours of each other.Although they usually are diurnal in their daily behavior, during migrations flights usually take place at night. This is believed to help them avoid predation and conserve energy by flying in cooler temperatures. Gadwalls have several predators, with  the fox and coyote being their main threats.Their main source of defense is to be on the water. Like all ducks, they become very vulnerable when feeding too close to the shore in dense vegetation, which makes them subject to the quick strike of a number of predators.Although there is no data on longevity or mean life expectancy, there was a Gadwall banded in Alaska and recovered in Louisiana that had reached 19 years of age

Gadwalls are linked with the culture of humans throughout history through hunting. Because of the demand by hunters to continue to harvest these birds, the U.S. fish and wildlife service monitors the populations and sets regulations on hunting of waterfowl. This system can be seen to have a positive impact on humans because of the rewards of the food source from hunting. Also money generated from the sale of hunting permits and licenses help to maintain and create new waterfowl refuges as well as supplies revenue to monitor populations for the next year’s hunting regulations.

 Written spring 2004, as a service learning project for Dr. Gary Coté's Biology 102 class at Radford University.  Copyright Pathways for Radford.