WATERFOWL BIOLOGY

Edward C. Cleary Fig. 1. Cliff swallow (Hirundo pyrrhonota) with nests on a building.
Assistant State Director
USDA-APHIS-Wildlife Services
Sandusky, Ohio 44870

Fig. 1.  Geese, ducks, and other waterfowl may damage crops by feeding in fields.

Identification

The term waterfowl is properly applied only to ducks, geese, and swans (Fig. 1). Space does not permit full species descriptions here. A bird identification guide should be consulted for exact species descriptions.

Many of the control techniques are equally applicable to damage situations involving coots, rails, and cranes, which are not discussed in this publication.

Range

In North America, most waterfowl are migratory, flying long distances in the spring and fall between the summer breeding grounds and wintering areas. Some species or geographic populations of some species, however, never leave the breeding areas. The Florida and mottled ducks, southern populations of wood ducks and hooded mergansers, and some populations of Canada geese are nonmigratory.

Ducks and geese breed throughout North America. The primary goose production areas for Central, Mississippi, and Atlantic Flyway geese are Banks Island, Baffin Island, and the greater Hudson Bay area. Most of these birds winter in the southern Great Plains, Texas, Louisiana, and Mississippi coastal marshes, or the Chesapeake Bay and mid-Atlantic states’ coastal marshes and barrier islands.

The primary breeding grounds for geese using the Pacific Flyway are the Yukon, Kuskokwin, and Copper River deltas and the north and west coasts of Alaska. These birds typically winter in Washington, Oregon, and California (especially Baja California, the Baja California Sur coastal marshes, and the central valley of California).

The primary North American breeding grounds for ducks are the prairie pothole region of Alberta, Saskatchewan, Manitoba, Montana, North and South Dakota, and Minnesota. Historically, this area probably produced more ducks than the rest of the continent combined. Other important breeding areas include coastal and interior Alaska, and the Mackenzie River Delta. Primary duck wintering grounds include the central valley of California, the southern Great Plains, Gulf Coast marshes, Caribbean Islands, and Central and South America.

Many of the historical North American waterfowl breeding, migrating, and wintering areas are changing because of agricultural and land-clearing practices, northern prairie pothole drainage, and development of the US Fish and Wildlife Service’s National Wildlife Refuge system. Worldwide, waterfowl occur on every major land mass except Antarctica.

Habitat

Waterfowl, as their name implies, are most often found near water. They can, however, fly long distances to and from favorite feeding grounds, which may include agricultural or upland sites. Some species, such as the mallard and certain subspecies of Canada geese, are extremely adaptable. They are equally at home in rural and urban environments, on a pond in a city park, or on a marsh in Alaska.

Food Habits

The food of individual waterfowl species ranges from fish to insects to plants in various combinations, depending on availability. Waterfowl bills have evolved to allow the exploitation of a wide variety of food sources and associated habitats. Even though many species are adapted to feeding in the water, most will readily come on land to take advantage of available food. Since space does not permit a species-by-species description of food habits, a few general comments will suffice.

During the prefledging period, young waterfowl feed primarily on aquatic insects and other invertebrates. As adults, waterfowl have an omnivorous diet. Dabbling ducks, whistling ducks, and shovelers are primarily filter feeders and will consume almost anything edible. Torrent ducks, blue ducks, and scaups feed heavily on aquatic insect larvae, snails, and other invertebrates found on and under rocks in streams and ponds. Large eiders, scoters, and steamer ducks feed heavily on mollusks and shellfish. Steller’s eider feeds more on soft-shelled invertebrates. Fish are the main food of mergansers. Swans are aquatic grazers and geese are terrestrial grazers.

General Biology, Reproduction, and Behavior

Waterfowl are normally monogamous and solitary nesters. The size of the nesting territory is determined by the aggressiveness of the particular pair of birds. Pair formation in geese and swans tends to be permanent until one of the pair dies; the remaining bird will often remate. Ducks seek a new mate each year.

Ducks and the Ross’s goose generally lay one egg each day until the clutch is complete. Most other geese and probably all swans lay an egg every other day until the clutch is complete. Incubation is not started until the last or next-to-the-last egg is laid, thus all the eggs hatch at about the same time. There is a slight correlation between the length of incubation and the size of the adult bird. Incubation periods range from about 23 days for cackling Canada geese, 28 days for giant Canada geese and mallards, to 38 days for trumpeter swans. Young waterfowl are precocial and begin foraging shortly after hatching. The nest site is abandoned 1 to 2 days after hatching.

Studies indicate many species have a first-year mortality rate of 60% to 70% and a 35% to 40% mortality rate in subsequent years. Life spans of 10 to 20 years for captive ducks and 20 to 30 for captive geese and swans are not uncommon.

Editors

Scott E. Hygnstrom; Robert M. Timm; Gary E. Larson

Prevention and Control of Wildlife Damage Logo 1994

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska -Lincoln

United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control

Great Plains Agricultural Council Wildlife Committee

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