Gadwalls: The Wonder Duck

If the recent trend continues, the sky may be the limit for gadwall populations.

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Photo © Stuart Smith

By Matt Young

An icy northwest wind rocked the surrounding cattails while two college buddies and I placed the last of our decoys on a secluded pond in the heart of a large western Montana marsh. As dawn broke over the mountains to the east, the marsh's many wild inhabitants came to life.

Canada geese honked, mallards quacked, and wigeon whistled, but rising above all the waterfowl clamor was the distinctive, monotone kack, kack-kack of countless gadwalls.

The marsh was seething with the birds, which had just arrived in the area the night before. Moments later, shots rang out throughout the area as milling gadwalls filled the air, their white speculums flashing in the pale light as they circled in disorganized formations.

During the next hour, several gadwall flocks battled the stiff wind to reach the shelter of our hidden pond, and we quickly filled our limits.

At the hunter check station, we joined other pleased waterfowlers who had also collected limits of gadwalls. Apparently, the birds were part of a large migration from a staging area on the Alberta prairies that had chosen the marsh as a stopping place to feed and rest. The area biologist was baffled because the birds were typically rare in the region.

Our hunt took place in 1989, when the gadwall breeding population was only 1.4 million birds. In 1999, the U.S. Fish and Wildlife Service estimated 3.2 million breeding gadwalls across the continent, and the birds are now quite common on the Montana marsh that I hunted as a student more than a decade ago.

The meteoric rise of the gadwall to become one of the continent's most abundant and widely distributed ducks is among the most remarkable waterfowl stories of our time.

Historically a much less abundant species, gadwall populations have grown exponentially over the past several decades, surpassing pintails, green-winged teal, and wigeon to become the fourth most numerous duck, exceeded only by mallards, lesser scaup, and blue-winged teal. As their numbers have soared, gadwalls have become increasingly familiar to waterfowl enthusiasts in many areas of the continent.

Gadwall harvests have kept pace with the birds' booming population and liberalized hunting regulations, making them increasingly important to waterfowlers in many regions as a large part of the daily bag.

In 1998, U.S. and Canadian waterfowlers bagged an estimated 1.8 million gadwalls, up 15 percent from the year before. Gadwalls now rank third in total harvest behind only mallards and green-winged teal, respectively.

The primary breeding grounds of the gadwall are the mixed-grass prairies of the north-central U.S. and Canada.

Much of the population nests in rugged coteau regions of South Dakota, North Dakota, and Montana, where large tracts of native grassland remain intact and several million acres of former croplands have been retired to permanent cover under the U.S Department of Agriculture's Conservation Reserve Program.

Research has revealed that waterfowl nest success is strongly influenced by the abundance of undisturbed upland nesting cover on the landscape.

By nesting in large numbers on grassland-dominated landscapes, gadwalls have had excellent production during the past several years of unusually wet weather on the prairies. Gadwalls have also been expanding their breeding range in recent decades, and nesting birds are now found from Texas to Alaska to New Brunswick.

Hen gadwalls are among the last waterfowl to establish nests, typically in early to mid-June, long after mallards and pintails have laid their first clutches. Before the prairies were settled, early-nesting ducks were far more prolific than late nesters because they had greater nesting opportunities each year.

Today, on intensively farmed areas of the prairies, early nesters are highly vulnerable to predators when they establish their first nests shortly after the spring thaw. Upland cover is sparse at this time, and few other prey are available to feed hungry skunks, foxes, and raccoons.

In contrast, when gadwalls begin to nest in late spring and early summer, there is an abundance of lush, new vegetation surrounding wetlands, and buffer prey species, including amphibians, reptiles, rodents, and insects, are more plentiful on the landscape.

Another adaptive strategy that has helped gadwalls to thrive on modern prairie landscapes is their preference for deeper, semipermanent marshes and ponds that are not as severely impacted by drought and agriculture as shallower, temporary wetlands favored by many other breeding dabblers. Hens build their nests amid dense vegetation or woody shrubs near water.

They have a particular penchant for nesting on islands, giving them almost complete protection from land-based predators.

In addition, gadwall pairs occupy smaller territories than most dabbling ducks, enabling large numbers of pairs to exploit highly productive breeding habitats, such as islands. Waterfowl biologists have documented breeding gadwall densities as high as 150 nests per acre on islands in North Dakota.