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Smithsonian Field Guide to the Birds of North America
Chapter One
Waterfowl
Whistling-Ducks, Geese & Swans, and Ducks
Order Anseriformes
Waterfowl—the familiar ducks, geese, and swans—are widespread and well represented in North America. All species are affiliated with aquatic habitats during some or all of their life cycle, and most are legally hunted across large swaths of the continent. Waterfowl classification is in a state of flux, with three subfamilies currently recognized as occurring in North America: the goose-like whistling-ducks (Dendrocygninae) of the southern states; the large-bodied geese and swans (Anserinae) of chiefly northern climes; and the widespread and remarkably diverse ducks (Anatinae).
Favored habitats for waterfowl are sprawling wetland complexes both in coastal districts and inland. Every high-quality marsh in the northern Midwest, it seems, harbors a dozen or more species of breeding ducks. Twenty or more species of waterfowl are easily found in a day afield in fall or winter along the Pacific and Atlantic coasts. But it would not be accurate to say that waterfowl are habitat generalists, indiscriminately accepting any aquatic habitat. On the contrary, knowledge of microhabitat preferences plays an important role in identifying waterfowl.
The breeding biology of waterfowl is more easily observed than in most other birds. Courting is conspicuous, and the precocial young are frequently seen paddling furiously behind dutiful parents—hens only, in most species. Nesting always takes place in the general vicinity of water, but actual nest placement is often insurprisingly non-aquatic microhabitats: Gadwalls out in sagebrush flats, Canada Geese atop tall office buildings, Common Mergansers in caves on sheer cliffs. Most waterfowl species are intermediate-distance migrants, and a few can legitimately be classed as long-distance migrants. Migration is typically by day, and passages along the coast can be spectacular. Daily movements of species wintering along the coast are likewise impressive.
Waterfowl population health has been well studied for two reasons: first, wildlife agencies carefully monitor populations that are legally hunted; second, waterfowl are high-fidelity indicators of wetland quality, and their numbers provide an important baseline for conservation action. Some species—particularly in the subfamily Anserinae (geese and swans)—are enjoying sustained population growth, but many duck species are worrisomely declining, notably the American Black Duck and King Eider. The overarching threat to waterfowl populations is habitat loss. Bioaccumulation of toxins such as selenium is a local threat, and climate change may eventually prove to be a serious challenge for species with substantial arctic-breeding populations.
Smithsonian Field Guide to the Birds of North America. Copyright © by Ted Floyd. Reprinted by permission of HarperCollins Publishers, Inc. All rights reserved. Available now wherever books are sold.