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ducks

ducks ducks and drakes a game of throwing flat stones so that they skim along the surface of water; in figurative use, play ducks and drakes with trifle with; treat frivolously or wastefully.
get one's ducks in a row get one's facts straight or have everything organized; the reference is to lining up one's targets.

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ducks

ducks See ANATIDAE.

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Ducks

Ducks

Dabbling ducks

Bay and sea ducks

Tree or whistling ducks

Stiff-tailed ducks

Mergansers

Economic importance of ducks

Factors affecting the abundance of ducks

Agencies and actions

Resources

Ducks are waterfowl in the order Anseriformes, in the family Anatidae, which also includes geese and swans. Ducks occur on all continents except Antarctica and are widespread in many types of aquatic habitats. Almost all ducks breed in freshwater habitats, especially shallow lakes, marshes, and swamps. Most species of ducks also winter in these habitats, sometimes additionally using grain fields and other areas developed by humans. Some species of sea ducks breed on marine coasts, wintering in near-shore habitats. Most species of ducks undertake substantial migrations between their breeding and wintering grounds, in some cases flying thousands of miles, twice each year.

Ducks are well adapted to aquatic environments and are excellent swimmers with waterproof feathers, short legs, and webbed feet. The feathers are waterproofed by oil transferred from an oil gland at the base of the tail by the bill. Ducks eat a wide range of aquatic plants and animals, with the various species of ducks having long necks, wide bills and other attributes that are specialized for their particular diets. Most ducks obtain their food by either dabbling or diving. Dabbling ducks feed on the surface of the water, or they tip down to submerge their head and feed on reachable items in shallow water. Diving ducks swim underwater to reach deeper foods. Ducks have great economic importance as the targets of hunters and several species have been domesticated for agriculture. In general, duck populations have greatly declined worldwide, as a combined result of overhunting, habitat loss, and pollution.

Dabbling ducks

Dabbling ducks (subfamily Anatinae) are surface-feeding birds that eat vegetation and invertebrates found in shallow water they can reach without diving. Their plant foods include colonial algae, small vascular plants such as duckweed (e.g., Lemna minor ), roots and tubers of aquatic plants, and the seeds of pond-weed (Potamogeton spp.), smartweed (Polygonum spp.), wild rice (Zizania aquatica ), sedges (Carex spp.), and bulrushes (Scirpus spp.). Dabbling ducks also eat aquatic invertebrates, and in fact these are the most important foods of rapidly growing ducklings.

Two widespread species of dabbling duck are mallards (Anas platyrhynchos ) and pintails (A. acuta ). These ducks range throughout the Northern Hemisphere, occurring in both North America and Eurasia. Other North American species include black ducks (A. rubripes ), American widgeons (Mareca americana ), shovelers (Spatula clypeata ), blue-winged teals (A. discors ), and wood ducks (Aix sponsa ).

Bay and sea ducks

Bay and sea ducks (subfamily Aythyinae) are diving ducks that swim beneath the surface of the water in search of aquatic animals. Some species also eat plants, but this is generally less important than in the herbivorous dabbling ducks. Some bay and sea ducks, for example, the common goldeneye (Bucephala clan-gula ), ring-necked duck (Aythya collaris ), and hooded merganser (Lophodytes cucullatus ), eat mostly arthropods occurring in the water column. Other species, including oldsquaws (Clangula hyemalis ), lesser scaups (Aythya affinis ), surf scoters (Melanitta perspicillata ), and common eiders (Somateria mollissima ), specialize on bottom living invertebrates. Some of these species are remarkable divers, descending as deep as 246 ft (75 m) in the case of oldsquaw ducks.

Tree or whistling ducks

Tree ducks (subfamily Dendrocygninae) are long-legged birds, and are much less common than most dabbling or diving ducks. Tree ducks tend to be surface feeders in aquatic habitats, but they also forage

for nuts and seeds on land. Tree ducks have a generally southern distribution in North America. The most common North American species is the fulvous tree duck (Dendrocygna bicolor ).

Stiff-tailed ducks

Stiff-tailed ducks (subfamily Oxyurinae) are small diving ducks with distinctive, stiffly-erect tails. This group is represented in North America by the ruddy duck (Oxyura jamaicensis ).

Mergansers

Mergansers (subfamily Merginae) are sleek, diving ducks specialized for feeding on small fish. They have serrated bills that apply a firm grip on their slippery prey. The most abundant species are the common merganser (Mergus merganser ) and the red-breasted merganser (M. serrator ).

Economic importance of ducks

Wild ducks have long been hunted for food, and more recently for sport. In recent decades, hunters kill about 10-20 million ducks each year in North America, shooting about 20% in Canada, and the rest in the United States. Duck hunting has a very significant economic impact, because of the money hunters spend on travel, license fees, private hunting fees, and on firearms, ammunition, and other paraphernalia.

Prior to the regulation of the hunting of ducks and other game animals, especially before the 1920s, the killing of ducks was essentially uncontrolled. In areas where ducks were abundant, there were even commercial hunts to supply ducks to urban markets. The excessive hunting during these times caused tremendous decreases in the populations of ducks and other waterfowl, as well as in other species of edible birds and mammals. Consequently, governments in the United States and Canada began to control excessive hunting, to protect breeding habitat, and to provide a network of habitat refuges to provide for the needs of waterfowl during migration and wintering. These actions have allowed subsequent increases in the populations of most species of waterfowl, although the numbers of some species still remain much smaller than they used to be.

A relatively minor but interesting use of ducks concerns the harvesting of the down of wild common eiders.

The female of this species plucks down from her breast for use in lining the nest, and this highly insulating material has long been collected in northern countries, and used to produce eiderdown quilts and clothing.

Several species of ducks have been domesticated, and in some areas they are an important agricultural commodity. The common domestic duck is derived from the mallard, which was domesticated about 2, 000 years ago in China. Farm mallards are usually white, and are sometimes called Peking ducks. The common domestic muscovy duck (Cairina moschata ) was domesticated by aboriginal South Americans prior to the European colonization of the Americas.

Ducks are being increasingly used in a nonconsumptive fashion. For example, bird watchers often go to great efforts to see ducks and other birds, trying to view as many species as possible, especially in natural habitats. Like hunters, birders spend a great deal of money while engaging in their sportto travel, to purchase binoculars and books, and to belong to birding, natural history, and conservation organizations.

Factors affecting the abundance of ducks

The best aquatic habitats for ducks and other waterfowl are those with relatively shallow water, with very productive vegetation and large populations of invertebrates. Those habitats with a large ratio of shoreline to surface area favor the availability of secluded nesting sites. These sorts of habitats occur to some degree in most regions, and are primarily associated with wetlands, especially marshes, swamps, and shallow, open water. In North America and elsewhere during the past century, extensive areas of these types of wetlands have been lost or degraded, mostly because they have been drained or filled in for agricultural, urban, or industrial use. Wetlands have also been degraded by eutrophication caused by excessive nutrient inputs, and by pollution by toxic chemicals and organic materials. These losses of habitat, in combination with overhunting, have caused large decreases in the populations of ducks throughout North America, and in most other places where these birds occur. Consequently, there are now substantial efforts to preserve or restore the wetlands required as habitat by ducks and other wildlife, and to regulate hunting of these animals.

The most important breeding habitats for ducks in North America occur in the fringing marshes and shallow open-water wetlands of small ponds in the prairies, known as potholes. The marshy borders of potholes provide important breeding habitat for various species of dabbling ducks such as mallard, pintail, widgeon, and blue-winged teal, while deeper waters are important to lesser scaup, canvasbacks (Aythya valisneria ), redheads (Aythya americana ), and ruddy ducks. Unfortunately, most of the original prairie potholes have been filled in or drained to provide more land for agriculture. This extensive conversion of prairie wetlands has increased the importance of the remaining potholes as breeding habitat for North Americas declining populations of ducks, and for other wildlife. As a result, further conversions of potholes are resisted by the conservation community, although agricultural interests still encourage the drainage of these important wetlands.

In years when the prairies are subject to severe drought, many of the smaller potholes are too dry to allow ducks to breed successfully, and ponds and wet-lands farther to the north in Canada become relatively important for breeding ducks. Another important source of natural mortality of ducks and other waterfowl are infectious disease, such as avian cholera, which can sweep through dense staging or wintering populations and kill tens of thousands of birds in a short period of time. When an epidemic of avian cholera occurs, wildlife managers attempt to manage the problem by collecting and burning or burying as many carcasses as possible, in order to decrease the exposure of living birds to the pathogen.

Lead shot is an important type of toxic pollution that kills large numbers of ducks and other birds each year. Lead shot from spent shotgun pellets on the surface mud and sediment of wetlands where ducks feed, may be ingested during feeding and retained in the ducks gizzard. There the shot is abraded, dissolved by acidic stomach fluids, absorbed into the blood, and then transported to sensitive organs, causing toxicity. An estimated 23% of the autumn and winter duck population of North America (some 23 million birds) dies each year from lead toxicity. As few as one or two pellets retained in the gizzard can be enough to kill a duck. Fortunately, steel shot is rapidly replacing lead shot, in order to reduce this unintended, toxic hazard to ducks and other wildlife.

Ducks and other aquatic birds may also be at some risk from acidification of surface waters as a result of acid rain. Although it is unlikely that acidification would have direct, toxic effects on aquatic birds, important changes could be caused to their habitat, which might indirectly affect the ducks. For example, fish are very sensitive to acidification, and losses of fish populations would be detrimental to fish-eating ducks, such as mergansers. However, in the absence of the predation pressure exerted by fish in acidic lakes, aquatic invertebrates would become more abundant, possibly benefiting other species of ducks, such as the common goldeneye, ring-necked duck, and black duck. These scenarios are inevitably speculative, for not much is known about the effects of acid rain on ducks.

Ducks can also be affected by eutrophication in aquatic habitats, a condition characterized by large increases in productivity caused by large nutrient loads from sewage dumping or from the runoff of agricultural fertilizers. Moderate eutrophication often improves duck habitat by stimulating plant growth and their invertebrate grazers. However, intense eutrophication kills fish and severely degrades the quality of aquatic habitats for ducks and other wildlife.

Some species of ducks nest in cavities in trees, a niche that has become increasingly uncommon because of forestry and losses of woodlands to agriculture and urbanization. Together with overhunting, the loss of natural cavities was an important cause of the decline of the wood duck and hooded merganser (Lophodytes cucullatus ) in North America. Fortunately, these species will nest in artificial cavities provided by humans, and these ducks have recovered somewhat, thanks in part to widespread programs of nest box erection in wetland habitats.

Agencies and actions

Because the populations of ducks and other waterfowl have been badly depleted by overhunting and habitat loss, conservation has become a high priority for governments and some private agencies. In North America, the U.S. Fish and Wildlife Service and the Canadian Wildlife Service have responsibilities for waterfowl at the federal level, as do states and provinces at the regional level. Ducks Unlimited is a non-governmental organization whose central concern is the conservation of duck populations. The Ducks Unlimited mandate is mostly pursued by raising and spending money to increase duck productivity through habitat management, with an aim of providing more birds for hunters. Other organizations have a non-consumptive mandate that is partly relevant to ducks, for example, the World Wildlife Fund, The Nature Conservancy, and the Nature Conservancy of Canada. On the international stage, the Convention on Wetlands of International Importance, Especially as Waterfowl Habitat is a treaty among national governments intended to facilitate worldwide cooperation in the conservation of wetlands, thereby benefiting ducks and other wildlife.

All of these agencies are undertaking important activities on behalf of ducks, other animals, and natural ecosystems. However, duck populations are still much smaller than they used to be, and some species are endangered. Much more must be done to provide the ducks of North America and the world with the protection and habitat that they require.

  • Mallard (Anas platyrhynchos ). Often poisoned by lead shot. Has been poisoned in the West by foraging in temporarily damp lake beds. One of the most abundant ducks in the world today. The population on the Great Plains seems to have been permanently diminished from historical levels. The status of wild mallards is unclear due to the large feral populations.
  • Mottled duck (Anas fulvigula ). Has suffered more from encroaching human habitation (draining and destruction of marshland) and agriculture than from hunting. Interbreeding with feral mallards threatens the genetic purity of the species.
  • American black duck (Anas rubripes ). The population has decreased in response to aerial spraying for spruce budworm, destruction of habitat, acid rain, overhunting, clearing of forests, and competition with the mallard (with which it hybridizes).
  • Gadwall (Anas strepera ). Settlement of the northern Great Plains took a relatively large toll on this species. Current populations vary each year, but the population does not seem to be diminishing.
  • Green-winged teal (Anas crecca ). Audubon wrote in 1840 that hunters in the West shot six dozen of these birds per day upon their first migratory arrival. Today the population appears stable.
  • American wigeon (Anas americana ). Population apparently stable. Since the 1930s, the breeding range has expanded into eastern Canada and the northeastern United States.
  • Northern pintail (Anas acuta ). This birds nests in fields are often plowed up. It has also suffered lead shot poisoning. There is some indication of a decline in population since the 1960s, but the species is widespread and abundant today. Droughts on the northern plains may drastically reduce nesting success there.
  • Northern shoveler (Anas clypeata ). Population apparently stable.
  • Blue-winged teal (Anas discors ). Population apparently stable. Because this bird usually winters in Latin America, international cooperation is required to protect it.
  • Cinnamon teal (Anas cyanoptera ). Although the population has suffered by encroaching human habitation and agriculture (draining of wetlands and diverting water for irrigation), the current numbers appear stable.
  • Ruddy duck (Oxyura jamaicensis ). Current population is much less than historical levels, due mainly to shoot-inginthe early1900s and loss of breeding habitat.
  • Masked duck (Oxyura dominica ). Uncommon everywhere, but wide ranging in the tropics. Its secretive and nomadic behavior makes it hard to estimate this ducks population, or to protect it.
  • Fulvous whistling duck (Dendrocygna bicolor ). Population has declined in the Southwest in recent decades, but increased in the Southeast. There is some controversy over its effect on rice cultivation; some say it damages crops, others that it eats the weeds in the fields.
  • Black-bellied whistling duck (Dendrocygna autumnalis ). This bird is hunted mainly in Mexico. It will use nesting boxes. The population in the United States has increased greatly since the 1950s. Rare in Arizona before 1949, this bird in now a common nesting bird in that state.
  • Wood duck (Aix sponsa ). This duck has been hunted for its plumage, as a food source, and for its eggs. Development and forestry practices contributed to its decline. By the early 1900s, this bird was on the verge of extinction, but has since made a comeback. The wood duck readily uses nesting boxes.
  • Canvasback (Aythya valisineria ). Numbers have declined, probably as a result of the reduction of breeding grounds due to draining and cultivating of prairie potholes and freshwater marshes.
  • Redhead (Aythya americana ). Current population is well below historical levels, probably due to loss of nesting areas.
  • Ring-necked duck (Aythya collaris ). This ducks breeding range expanded eastward in the mid-1900s. The population suffered from lead shot poisoning. Since the 1930s, this bird has become a widespread breeder in eastern Canada and northern New England.
  • Greater scaup (Aythya marila ). Abundant. The fact that this bird congregates in large numbers in coastal bays in winter has caused concern that the species may be vulnerable to oil spills and other water pollution.
  • Lesser scaup (Aythya affinis ). Abundant, with relatively small fluctuations from year to year.
  • Common eider (Somateria mollissima ). Down from this duck, collected during incubation, is commercially valued. The taking of down, however, usually does not result in desertion of the nest. The populations have been increasing and stabilizing since 1930. Today this species is abundant, with a population estimated at several million. Local populations may be threatened by oil spills and other water pollution.
  • King eider (Somateria spectabilis ). Commercially valued as a source of down. Abundant in the Far North, with a population estimated to be several million.
  • Spectacled eider (Somateria fischeri ). The population in the Yukon-Kuskokwim delta of western Alaska declined by 96% from 1970 to 1993, but no similar decline was observed in Russia and a large population was found in the Bering Sea in the late 1990s. In 2002, the global population was estimated at 330, 000-390, 000 and it does not appear to be declining.
  • Stellers eider (Polysticta stelleri ). Population in Alaska has declined significantly in recent decades, but these declines may represent population shifts rather than true declines. Listed as vulnerable by the IUCN.
  • Labrador duck (Camptorhynchus labradorius ). Extinct. The last known specimen was shot in 1875 on Long Island. Never abundant, this duck had a limited breeding range. Its extinction probably resulted from loss of habitat and hunting.
  • Black scoter (Melanitta nigra ). Population apparently stable. Birds at sea vulnerable to oil and other forms of pollution.
  • White-winged scoter (Melanitta fusca ). Population has declined in parklands and boreal forest of Canada, possibly due to advancing the hunting season to 2-3 weeks before some of the young can fly. Population today is apparently stable.
  • Surf scoter (Melanitta perspicillata ). Population apparently declined greatly in the early 1900s, but is now stable. Wintering populations are vulnerable to oil and other forms of pollution.
  • Harlequin duck (Histrionicus histrionicus ). The population appears stable in the Northwest. In the eastern part of North America, there has been a substantial decline over the past century.
  • Oldsquaw (Clangula hyemalis ). Abundant, with a population estimated to be in the millions. The tendency to congregate in large numbers makes it vulnerable to oil spills in northern seas. Large numbers of these birds are sometimes caught and killed in fishing nets.
  • Barrows goldeneye (Bucephala islandica ). Population apparently stable. Will use nesting boxes.
  • Common goldeneye (Bucephala clangula ). Population apparently stable. Readily uses nesting boxes.
  • Bufflehead (Bucephala albeola ). Fairly common and widespread. Today less numerous than historically, due to unrestricted shooting in the early 1900s, and loss of habitat. Uses nesting boxes when cavities in trees are scarce.
  • Common merganser (Mergus merganser ). Population apparently stable in North America, possibly increasing in Europe.
  • Red-breasted merganser (Mergus serrator ). Population apparently stable.
  • Hooded merganser (Lophodytes cucullatus ). Population has declined due to loss of nesting habitat (large trees near water). Will use nesting boxes and cavities set up for wood ducks. Today the population appears to be increasing.
  • Mandarin duck (Aix galericulata ). Exotic. A native of Asia, this duck occasionally escapes, ending up in the wild.
  • Spot-billed duck (Anas poecilorhyncha ). An Alaskan stray. Native of Asia.
  • Tufted duck (Aythya fuligula ). A Western stray. The Eurasian counterpart of the North American ring-necked duck. This bird occasionally reaches Alaska and the Pacific Coast from Asia, or the Northeast from Europe and Iceland.

See also Eutrophication.

Resources

BOOKS

Bellrose, F.C. Ducks, Geese, and Swans of North America. Rev. ed. Harrisburg, PA: Stackpole Books, 1980.

del Hoyo, J., A. Elliott, and J. Sargatal. Handbook of the Birds of the World. Vol. 1, Ostriches to Ducks. Barcelona: Lynx Edicions, 1992.

Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.

Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1995.

Godfrey, W.E. The Birds of Canada. Rev. ed. Ottawa: Canadian Museum of Nature, 1995.

Johnsgard, P.A. Ducks in the Wild. Conserving Waterfowl and Their Habitats. New York: Macmillan, 1993.

Owen, M., and J.M. Black. Waterfowl Ecology. London: Blackie Pub., 1990.

Peterson, Roger Tory. North American Birds. Houghton Mifflin Interactive (CD-ROM). Somerville, MA: Houghton Mifflin, 1995.

Bill Freedman

Randall Frost

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Ducks

Ducks

Ducks are waterfowl in the order Anseriformes, in the family Anatidae, which also includes geese and swans . Ducks occur on all continents except Antarctica , and are widespread in many types of aquatic habitats. Almost all ducks breed in freshwater habitats, especially shallow lakes, marshes, and swamps. Most species of ducks also winter in these habitats, sometimes additionally using grain fields and other areas developed by humans. Some species of sea ducks breed on marine coasts, wintering in near-shore habitats. Most species of ducks undertake substantial migrations between their breeding and wintering grounds, in some cases flying thousands of miles, twice each year.

Ducks are well adapted to aquatic environments and are excellent swimmers with waterproof feathers, short legs, and webbed feet. The feathers are waterproofed by oil transferred from an oil gland at the base of the tail by the bill. Ducks eat a wide range of aquatic plants and animals, with the various species of ducks having long necks, wide bills and other attributes that are specialized for their particular diets. Most ducks obtain their food by either dabbling or diving. Dabbling ducks feed on the surface of the water , or they tip up to submerge their head and feed on reachable items in shallow water. Diving ducks swim underwater to reach deeper foods. Ducks have great economic importance as the targets of hunters and several species have been domesticated for agriculture. In general, duck populations have greatly declined world-wide, as a combined result of overhunting, habitat loss, and pollution .


Dabbling ducks

Dabbling ducks (subfamily Anatinae) are surface-feeding birds that eat vegetation and invertebrates found in shallow water they can reach without diving. Their plant foods include colonial algae , small vascular plants such as duckweed (e.g., Lemna minor), roots and tubers of aquatic plants, and the seeds of pondweed (Potamogeton spp.), smartweed (Polygonum spp.), wild rice (Zizania aquatica), sedges (Carex spp.), and bulrushes (Scirpus spp.). Dabbling ducks also eat aquatic invertebrates, and in fact these are the most important foods of rapidly growing ducklings.

Two widespread species of dabbling duck are mallards (Anas platyrhynchos) and pintails (A. acuta). These ducks range throughout the Northern Hemisphere, occurring in both North America and Eurasia. Other North American species include black ducks (A. rubripes), American widgeons (Mareca americana), shovelers (Spatula clypeata), blue-winged teals (A. discors), and wood ducks (Aix sponsa).


Bay and sea ducks

Bay and sea ducks (Aythyinae) are diving ducks that swim beneath the surface of the water in search of aquatic animals. Some species also eat plants, but this is generally less important than in the herbivorous dabbling ducks. Some bay and sea ducks, for example, common goldeneye (Bucephala clangula), ring-necked duck (Aythya collaris), and hooded merganser (Lophodytes cucullatus), eat mostly arthropods occurring in the water column. Other species including oldsquaws (Clangula hyemalis), lesser scaups (Aythya affinis), surf scoters (Melanitta perspicillata), and common eiders (Somateria mollissima) specialize on bottom living invertebrates. Some of these species are remarkable divers, descending as deep as 246 ft (75 m) in the case of oldsquaw ducks.

Tree or whistling ducks

Tree ducks (Dendrocygninae) are long-legged birds, and are much less common than most dabbling or diving ducks. Tree ducks tend to be surface feeders in aquatic habitats, but they also forage for nuts and seeds on land. Tree ducks have a generally southern distribution in North America. The most common North American species is the fulvous tree duck (Dendrocygna bicolor).


Stiff-tailed ducks

Stiff-tailed ducks (Oxyurinae) are small diving ducks with distinctive, stiffly-erect tails. This group is represented in North America by the ruddy duck (Oxyura jamaicensis).


Mergansers

Mergansers (Merginae) are sleek, diving ducks specialized for feeding on small fish , and have serrated bills, which apply a firm grip on their slippery prey . The most abundant species are the common merganser (Mergus merganser) and the red-breasted merganser (M. serrator).


Economic importance of ducks

Wild ducks have long been hunted for food, and more recently for sport. In recent decades, hunters kill about 10-20 million ducks each year in North America, shooting about 20% in Canada, and the rest in the United States. Duck hunting has a very large economic impact, because of the money hunters spend on travel, license fees, private hunting fees, and on firearms, ammunition, and other paraphernalia.

Prior to the regulation of the hunting of ducks and other game animals, especially before the 1920s, the killing of ducks was essentially uncontrolled. In areas where ducks were abundant, there were even commercial hunts to supply ducks to urban markets. The excessive

hunting during these times caused tremendous decreases in the populations of ducks and other waterfowl, as well as in other species of edible birds and mammals . Consequently, governments in the United States and Canada began to control excessive hunting, to protect breeding habitat, and to provide a network of habitat refuges to provide for the needs of waterfowl during migration and wintering. These actions have allowed subsequent increases in the populations of most species of waterfowl, although the numbers of some species still remain much smaller than they used to be.

A relatively minor but interesting use of ducks concerns the harvesting of the down of wild common eiders. The female of this species plucks down from her breast for use in lining the nest, and this highly insulating material has long been collected in northern countries, and used to produce eiderdown quilts and clothing.

Several species of ducks have been domesticated, and in some areas they are an important agricultural commodity. The common domestic duck is derived from the mallard, which was domesticated about 2,000 years ago in China. Farm mallards are usually white, and are sometimes called Peking duck. The common domestic muscovy duck (Cairina moschata) was domesticated by aboriginal South Americans prior to the European colonization of the Americas.

Ducks are being increasingly used in a nonconsumptive fashion. For example, bird watchers often go to great efforts to see ducks and other birds, trying to view as many species as possible, especially in natural habitats. Like hunters, birders spend a great deal of money while engaging in their sport, to travel, to purchase binoculars and books, and to belong to birding, natural-history, and conservation organizations.


Factors affecting the abundance of ducks

The best aquatic habitat for ducks and other waterfowl are those with relatively shallow water, with very productive vegetation and large populations of invertebrates. Those habitats with a large ratio of shoreline to surface area, favors the availability of secluded nesting sites. These sorts of habitat occur to some degree in most regions, and are primarily associated with wetlands , especially marshes, swamps, and shallow, open water. In North America and elsewhere during the past century, extensive areas of these types of wetlands have been lost or degraded, mostly because they have been drained or filled in for agricultural, urban, or industrial use. Wetlands have also been degraded by eutrophication caused by excessive nutrient inputs, and by pollution by toxic chemicals and organic materials. These losses of habitat, in combination with overhunting, have caused large decreases in the populations of ducks throughout North America, and in most other places where these birds occur. Consequently, there are now substantial efforts to preserve or restore the wetlands required as habitat by ducks and other wildlife , and to regulate hunting of these animals.

The most important breeding habitats for ducks in North America occur in the fringing marshes and shallow open-water wetlands of small ponds in the prairies, known as "potholes." The marshy borders of potholes provide important breeding habitat for various species of dabbling ducks such as mallard, pintail, widgeon, and blue-winged teal, while deeper waters are important to lesser scaup, canvasbacks (Aythya valisneria), redheads (Aythya americana), and ruddy ducks. Unfortunately, most of the original prairie potholes have been filled in or drained to provide more land for agriculture. This extensive conversion of prairie wetlands has increased the importance of the remaining potholes as breeding habitat for North America's declining populations of ducks, and for other wildlife. As a result, further conversions of potholes are resisted by the conservation community, although agricultural interests still encourage the drainage of these important wetlands.

In years when the prairies are subject to severe drought , many of the smaller potholes are too dry to allow ducks to breed successfully, and ponds and wetlands farther to the north in Canada become relatively important for breeding ducks. Another important source of natural mortality of ducks and other waterfowl are infectious disease , such as avian cholera , which can sweep through dense staging or wintering populations, and kill tens of thousands of birds in a short period of time . When an epidemic of avian cholera occurs, wildlife managers attempt to manage the problem by collecting and burning or burying as many carcasses as possible, in order to decrease the exposure of living birds to the pathogen.

Lead shot is an important type of toxic pollution that kills large numbers of ducks and other birds each year. Lead shot from spent shotgun pellets on the surface mud and sediment of wetlands where ducks feed, may be ingested during feeding and retained in the duck's gizzard. There the shot is abraded, dissolved by acidic stomach fluids, absorbed into the blood , and then transported to sensitive organs, causing toxicity. An estimated 2-3% of the autumn and winter duck population of North America (some 2-3 million birds) dies each year from lead toxicity. As few as one or two pellets retained in the gizzard can be enough to kill a duck. Fortunately, steel shot is rapidly replacing lead shot, in order to reduce this unintended, toxic hazard to ducks and other wildlife.

Ducks and other aquatic birds may also be at some risk from acidification of surface waters as a result of acid rain . Although it is unlikely that acidification would have direct, toxic effects on aquatic birds, important changes could be caused to their habitat, which might indirectly affect the ducks. For example, fish are very sensitive to acidification, and losses of fish populations would be detrimental to fish-eating ducks such as mergansers. However, in the absence of the predation pressure exerted by fish in acidic lakes, aquatic invertebrates would become more abundant, possibly benefitting other species of ducks such as common goldeneye, ring-necked duck, and black duck. These scenarios are inevitably speculative, for not much is known about the effects of acid rain on ducks.

Ducks can also be affected by eutrophication in aquatic habitats, a condition characterized by large increases in productivity caused by large nutrient loads from sewage dumping or from the runoff of agricultural fertilizers . Moderate eutrophication often improves duck habitat by stimulating plant growth and their invertebrate grazers. However, intense eutrophication kills fish and severely degrades the quality of aquatic habitats for ducks and other wildlife.

Some species of ducks nest in cavities in trees, a niche that has become increasingly uncommon because of forestry and losses of woodlands to agriculture and urbanization. Together with overhunting, the loss of natural cavities was an important cause of the decline of the wood duck and hooded merganser (Lophodytes cucullatus) in North America. Fortunately, these species will nest in artificial cavities provided by humans, and these ducks have recovered somewhat, thanks in part to widespread programs of nest box erection in wetland habitats.


Agencies and actions

Because the populations of ducks and other waterfowl have been badly depleted by overhunting and habitat loss, conservation has become a high priority for governments and some private agencies. In North America, the U.S. Fish and Wildlife Service and the Canadian Wildlife Service have responsibilities for waterfowl at the federal level, as do states and provinces at the regional level. Ducks Unlimited is a non-governmental organization whose central concern is the conservation of duck populations. The Ducks Unlimited mandate is mostly pursued by raising and spending money to increase duck productivity through habitat management, with an aim of providing more birds for hunters. Other organizations have a non-consumptive mandate that is partly relevant to ducks, for example, the World Wildlife Fund, The Nature Conservancy, and the Nature Conservancy of Canada. On the international stage, the Convention on Wetlands of International Importance, Especially as Waterfowl Habitat is a treaty among national governments intended to facilitate worldwide cooperation in the conservation of wetlands, thereby benefiting ducks and other wildlife.

All of these agencies are undertaking important activities on behalf of ducks, other animals, and natural ecosystems. However, duck populations are still much smaller than they used to be, and some species are endangered. Much more must be done to provide the ducks of North America and the world with the protection and habitat that they require.


Status

  • Mallard (Anas platyrhynchos). Often poisoned by lead bullets. Has been poisoned in the West by foraging in temporarily damp lake beds. One of the most abundant ducks in the world today. The population on the Great Plains seems to have been permanently diminished from historical levels. The status of wild mallards is unclear due to the large feral populations.
  • Mottled duck (Anas fulvigula). Has suffered more from encroaching human habitation (draining and destruction of marshland) and agriculture than from hunting. Interbreeding with feral mallards threatens the genetic purity of the species.
  • American black duck (Anas rubripes). The population has decreased in response to aerial spraying for spruce budworm, destruction of habitat, acid rain, overhunting, clearing of forests , and competition with the mallard (with which it hybridizes).
  • Gadwall (Anas strepera). This bird's range has been eastward. Settlement of the northern Great Plains took a relatively large toll on this species. Current populations vary each year, but the population does not seem to be diminishing.
  • Green-winged teal (Anas crecca). Audubon wrote in 1840 that hunters in the West shot six dozen of these birds upon their first migratory arrival. Today the population appears stable.
  • American wigeon (Anas americana). Population apparently stable. Since the 1930s, the breeding range has expanded into eastern Canada and the northeastern United States.
  • Northern pintail (Anas acuta). This bird's nests in fields are often plowed up. It has also suffered lead shot poisoning. There is some indication of a decline in population since the 1960s, but the species is widespread and abundant today. Droughts on the northern plains may drastically reduce nesting success there.
  • Northern shoveler (Anas clypeata). Population apparently stable.
  • Blue-winged teal (Anas discors). Population apparently stable. Because this bird usually winters in Latin America, international cooperation is required to protect it.
  • Cinnamon teal (Anas cyanoptera). Although the population has suffered by encroaching human habitation and agriculture (draining of wetlands and diverting water for irrigation ), the current numbers appear stable.
  • Ruddy duck (Oxyura jamaicensis). Current population is much less than historical levels, due mainly to shooting in the early 1900s and loss of breeding habitat.
  • Masked duck (Oxyura dominica). Uncommon everywhere, but wide ranging in the tropics. Its secretive and nomadic behavior makes it hard to estimate this duck's population, or to protect it.
  • Fulvous whistling duck (Dendrocygna bicolor). Population has declined in the Southwest in recent decades, but increased in the Southeast. There is some controversy over its effect on rice cultivation; some say it damages crops , others that it eats the weeds in the fields.
  • Black-bellied whistling duck (Dendrocygna autumnalis). This bird is hunted mainly in Mexico. It will use nesting boxes. The population in the United States has increased greatly since the 1950s. Rare in Arizona before 1949, this bird in now a common nesting bird in that state.
  • Wood duck (Aix sponsa). This duck has been hunted for its plumage, as a food source, and for its eggs. Development and forestry practices contributed to its decline. By the early 1900s, this bird was on the verge of extinction , but has since made a comeback. The wood duck readily uses nesting boxes.
  • Canvasback (Aythya valisineria). The fact that breeding grounds have been reduced due to draining and cultivating of prairie potholes and freshwater marshes is probably responsible for the observed decline in numbers.
  • Redhead (Aythya americana). Current population is well below historical levels, probably due to loss of nesting areas.
  • Ring-necked duck (Aythya collaris). This duck's breeding range expanded eastward in the mid-1900s. The population suffered from lead shot poisoning. Since the 1930s, this bird has become a widespread breeder in eastern Canada and northern New England.
  • Greater scaup (Aythya marila). Abundant. The fact that this bird congregates in large numbers in coastal bays in winter has caused concern that the species may be vulnerable to oil spills and other water pollution .
  • Lesser scaup (Aythya affinis). Abundant, with relatively small fluctuations from year to year.
  • Common eider (Somateria mollissima). Down from this duck, collected during incubation, is commercially valued. The taking of down, however, usually does not result in desertion of the nest. The populations have been increasing and stabilizing since 1930. Today this species is abundant, with a population estimated at several million. Local populations may be threatened by oil spills and other water pollution.
  • King eider (Somateria spectabilis). Commercially valued as a source of down. Abundant in the Far North, with a population estimated to be several million.
  • Spectacled eider (Somateria fischeri). Threatened or endangered. The population in the Yukon-Kuskokwim delta of western Alaska declined by 96% from 1970 to 1993. The status of the Siberian population is not well known.
  • Steller's eider (Polysticta stelleri). Population in Alaska has declined significantly in recent decades.
  • Labrador duck (Camptorhynchus labradorius). Extinct. The last known specimen was shot in 1875 on Long Island. Never abundant, this duck had a limited breeding range. Its extinction probably resulted from loss of habitat and hunting.
  • Black scoter (Melanitta nigra). Population apparently stable. Birds at sea vulnerable to oil and other forms of pollution.
  • White-winged scoter (Melanitta fusca). Population has declined in parklands and boreal forest of Canada, possibly due to advancing the hunting season to 2-3 weeks before some of the young can fly. Population today is apparently stable.
  • Surf scoter (Melanitta perspicillata). Population apparently declined greatly in the early 1900s, but is now stable. Wintering populations are vulnerable to oil and other forms of pollution.
  • Harlequin duck (Histrionicus histrionicus). The population appears stable in the Northwest. In the eastern part of North America, there has been a substantial decline over the past century.
  • Oldsquaw (Clangula hyemalis). Abundant, with a population estimated to be in the millions. The tendency to congregate in large numbers makes it vulnerable to oil spills in northern seas. Large numbers of these birds are sometimes caught and killed in fishing nets.
  • Barrow's goldeneye (Bucephala islandica). Population apparently stable. Will use nesting boxes.
  • Common goldeneye (Bucephala clangula). Population apparently stable. Readily uses nesting boxes.
  • Bufflehead (Bucephala albeola). Fairly common and widespread. Today less numerous than historically, due to unrestricted shooting in the early 1900s, and loss of habitat. Uses nesting boxes when cavities in trees are scarce.
  • Common merganser (Mergus merganser). Population apparently stable in North America, possibly increasing in Europe .
  • Red-breasted merganser (Mergus serrator). Population apparently stable.
  • Hooded merganser (Lophodytes cucullatus). Population has declined due to loss of nesting habitat (large trees near water). Will use nesting boxes and cavities set up for wood ducks. Today the population appears to be increasing.
  • Mandarin duck (Aix galericulata). Exotic. A native of Asia , this duck occasionally escapes, ending up in the wild.
  • Spot-billed duck (Anas poecilorhyncha). An Alaskan stray. Native of Asia.
  • Tufted duck (Aythya fuligula). A Western stray. The Eurasian counterpart of the North American Ring-necked duck. This bird occasionally reaches Alaska and the Pacific Coast from Asia, or the Northeast from Europe and Iceland.

See also ,!Eutrophication.


Resources

books

Bellrose, F.C. Ducks, Geese, and Swans of North America. Harrisburg, PA: Stackpole Books, 1976.

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.

Freedman, B. Environmental Ecology. 2nd ed. San Diego: Academic Press, 1995.

Godfrey, W.E. The Birds of Canada. Toronto: University of Toronto Press, 1986.

Johnsgard, P.A. Ducks in the Wild. Conserving Waterfowl andTheir Habitats. Swan Hill Press, 1992.

Owen, M., and J.M. Black. Waterfowl Ecology. London: Blackie Pub., 1990.

Peterson, Roger Tory. North American Birds. Houghton Miflin Interactive (CD-ROM), Somerville, MA: Houghton Miflin, 1995.


Bill Freedman

Randall Frost

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