While many ducks in North America are adorned with bright blues, greens, or reds, the Gadwall’s coloration is far more subdued. The male is gray overall with a tan head and gray bill, while the female is brownish overall with a dull yellow bill. Besides their medium size (19-23 inches) and nondescript plumage, Gadwalls may be identified in flight by a small white patch on the trailing edge of their wings. Gadwalls are found widely across the Northern Hemisphere. In North America, Gadwalls breed primarily in the northern Great Plains. Smaller breeding areas can be found in the Rocky Mountains, in Alaska, in coastal California, and along the Great Lakes. Many Gadwall populations in the Rockies are non-migratory, but the majority of Gadwalls migrate south for the winter, when they may be found along the Atlantic and Gulf coasts of the southeast, the southern Plains, the Pacific coast from northern California north to Washington, and in southern portions of the Great Lakes. In Eurasia, Gadwalls breed in northern and central Europe, wintering from central Europe south to North Africa. In summer, the Gadwall breeds primarily in wetlands surrounded by grasslands or prairie. In winter, Gadwalls frequent small ponds as well as freshwater and saltwater marshes. Gadwalls feed on aquatic plants, seeds, and invertebrates in the water column. Gadwalls may be seen either on land or in the water, where they may be observed foraging for food. This species may also be observed taking off straight up from the water or undertaking straight, swift flights on migration or between breeding or foraging grounds. Gadwalls are most active during the day.
Description of Anas strepera
Anas strepera is a migratory bird. It winters from southern Mexico and Guatemala to coastal Alaska, the Atlantic, and Gulf coast regions of the United States and many areas in-between. Their summer breeding grounds range from the Atlantic coast of Canada to as far north as the western coastal regions of Alaska. Although, the largest concentration of them are found in the summer breeding grounds of the prairie pot-hole region of southern Canada and northern United States. Gadwalls can also be found in Iceland during the breeding season. They can also be found breeding in the Iceland, British Isles, Europe, and Asia (Tesky 1993, LeSchack et. al. 1997).
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDS: North America: southern Alaska, southern Yukon, southern Mackenzie (north to near Yellowknife; Can. Field-Nat. 106:254-256), northern Saskatchewan, central Manitoba, southern Ontario, southwestern Quebec, Prince Edward Island, Anticosti Island (rarely), and the New Brunswick-Nova Scotia border south locally to southern California, southern Nevada, northern Arizona, southern New Mexico, northern Texas, southern Kansas, Iowa, centralMinnesota, southern Wisconsin, northern Ohio, northern Pennsylvania (formerly), and, on the Atlantic coast, to North Carolina (one isolated breeding area in northern Alabama); also in the Old World (AOU 1983). Highest breeding densities occur in the northern Great Plains and intermountain valleys of the western U.S.; some portions of Alaskan, Pacific, and Atlantic coasts also have important breeding populations (Ringelman 1990). Range may be expanding eastward. WINTERS: North America: southern Alaska, southern British Columbia, Idaho, Colorado, southern South Dakota, Iowa, the southern Great Lakes, and Chesapeake Bay on the Atlantic coast (rarely from New Brunswick and Nova Scotia) south to northern Baja California, Oaxaca, the state of Mexico, Puebla, Veracruz, Tabasco, Yucatan, the Gulf Coast, Florida, the Bahamas, western Cuba, and (formerly) Jamaica; also in Old World (AOU 1983). Major wintering areas include coastal Louisiana and Texas, Gulf Coast of Mexico to Yucatan Peninsula, central and southern Atlantic coast of U.S., Central Valley of California, and much of the west coast of Mexico (Ringelman 1990); also northwestern Utah (Bear River refuge) and southeastern Missouri (Mingo refuge) (Root 1988). Formerly resident (COUESI group) in the northern Line Islands (Washington and New York islands); now extinct (AOU 1983).
Alaska and southern Yukon to the New Brunswick-Nova Scotia border, south
locally to southern California, northern Texas, central Minnesota, and
northern Pennsylvania, and along the Atlantic Coast south to Florida and
the Gulf Coast [6,19]. It also breeds in Iceland, the British Isles,
Europe, and Asia .
In North America the gadwall winters from coastal Alaska south to
southern Mexico, the Gulf Coast, and along the Atlantic Coast to
southern New England [6,19].
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
Occurrence in North America
Gadwalls can be very easy to identify in hand, but they can be very difficult to identify in the field. They are a medium-sized dabbling duck with non-distinct plumage and are most commonly misidentified in the field. The male and female gadwalls look very similar and resemble the hen mallard in drab plumage. The adult male has a gray plumage in the breeding season with distinct vermiculation on the scapular and back feathers. The head is brown and the upper and lower tail covers are black. The adult male tertials are long, and acutely pointed colored silver-gray. In basic plumage, the male Gadwall looks almost identical to the female. The adult female tertials are shorter and more bluntly pointed. The females lack the vermiculation but look very similar to the males with plumage more is more brownish on the back and buffy tan on the breast. The most distinguishing marks for both male and females are the white secondaries with black greater secondary coverts. This is very easy to see when in flight. The white speculum is the most identifying mark to recognize both sexes in the field but is only visible when in flight. The males will begin their prebasic molt after breeding with the female sometime during early to mid-summer depending on mating time and nest success. During this time they are not able to fly and are very vulnerable to predation (Bellrose 1980, Tesky 1993, LeSchack et al. 1997).
The Gadwall has to go through its juvenile plumage that may last 10 weeks until they begin their prealternate molt. The juvenile plumage of both the male and females look almost identical to the female plumage of all dabbling ducks. When the male juvenile goes through its prealternate molt, it then begins to take on the distinct male plumage with silver tipped tertials, puffy gray head, vermiculation, and rusty colored speculum (Bellrose 1980, LeSchack et al. 1997).
Range mass: 500 to 1044 g.
Average mass: 860 g.
Range length: 46 to 57 cm.
Average length: 50 cm.
Other Physical Features: endothermic ; bilateral symmetry
Length: 51 cm
Weight: 990 grams
Gadwalls prefer marshes, sloughs, ponds, and small lakes with grasslands in both fresh and brackish water as breading habitats. They tend to be more abundant on small prairie marshes than in temporary water areas, deep marshes, and open water marshes. They generally avoid wetlands that are bordered by woodlands or thick vegetation. In the winter they prefer the brackish water marshes with abundant leafy aquatic vegetation. There are many winter populations that have made yearly migrations back to the same waterfowl refuges, reservoirs, beaver ponds, and sewage treatment plants (Johnsguard 1979, Tesky 1993, LeSchack et al. 1997).
Range elevation: 0 (low) m.
Habitat Regions: temperate ; freshwater
Terrestrial Biomes: tundra ; taiga
Habitat and Ecology
Comments: Lakes, ponds, rivers, marshes. Prefers freshwater but may be found on any open water during migration and winter. Moderate- to large-sized wetland of a permanent or semipermanent nature, expanses of open water with submersed vegetation, and open undisturbed shorelines are important molting habitats (Ringelman 1990).
Nests in thick vegetation near freshwater lakes, ponds, or streams, including open brackish or alkaline waters. Nests usually in dry upland site under clump of shrubs or in herbaceous vegetation, average of 300 m from water. Tends to nest near semipermanent wetlands that are relatively resistant to drought (Ringelman 1990). Commonly uses man-made ponds. May nest on island, upland meadow or grassland. Suitable nesting islands should be 0.1-0.5 ha in size, elongate, and separated from mainland by at least 150 m of water that remains 0.9 m deep in nesting season (Ringelman 1990). Successful breeders usually return to nesting area used the previous year (Szymczak and Rexstad 1991). A diversity of wetland types is required for successful reproduction, so that brood-rearing habitat is near nesting habitat; females will move brood up to 1.9 km to brood habitat (Ringelman 1990).
For escape cover, gadwalls prefer large areas of open water water rather
than with emergents . Tall, dense vegetation provides good nesting
cover for gadwalls. As the vegetative cover increases, the potential
for nest establishment and success increases. Height and density of
vegetation is assumed to be more important than species composition. In
a California study, most gadwall nests were in vegetation 13 to 36
inches (33-91 cm) tall that provided concealment on all sides and above.
No nests were found in herbaceous cover less than 6 inches (15 cm) tall.
Fifty-one percent of nests in North Dakota nesting fields were in
herbaceous cover from 12 to 24 inches (30-60 cm) tall, while 47 percent
were in cover less than 6 inches (15 cm) tall .
nesting . They prefer prairie marshes, sloughs, ponds, or small
lakes in grasslands of both freshwater and brackish habitats. They
generally avoid wetlands bordered by woodlands or thick brush,
preferring those bordered by dense, low herbaceous vegetation, or with
grassy islands [6,17,19]. Shallow semipermanent prairie marshes are
preferred over deeper marshes, lakes or temporary water areas [6,16].
Sixy one percent of 1,073 gadwall broods observed over a 20-year period
in North and South Dakota were in semipermanent wetlands .
Winter habitat - Gadwalls prefer to winter in freshwater, marshy
habitats and slightly brackish estuarine bays [6,19].
Nesting - Gadwalls nest on well-drained sites on islands in lakes,
upland meadows or pastures, alfalfa fields, or on prairies usually
within 150 feet (45 m) of water. They prefer to nest in uplands rather
than over water  and generally select the tallest, densest,
herbaceous or shrubby vegetation available to nest in .
Associated Plant Communities
During the breeding season, gadwalls often inhabit islands in wetland
communities with patches of dense western snowberry (Symphoricarpos
occidentalis), slim nettle (Urtica gracilis), Canada thistle (Cirsium
arvense), rose (Rosa spp.), and brome (Bromus spp.). Additionally,
gadwalls commonly use areas dominated by cattail (Typha spp.), bulrush
(Scirpus spp.), sedge (Carex spp.), and common rivergrass (Scolochloa
festucacea) . Gadwalls will also use upland cover types of cropland,
pasture and hayland, grassland, and mixed prairie and weed [8,9,16].
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K047 Fescue - oatgrass
K048 California steppe
K049 Tule marshes
K050 Fescue - wheatgrass
K051 Wheatgrass - bluegrass
K053 Grama - galleta steppe
K054 Grama - tobosa prairie
K056 Wheatgrass - needlegrass shrubsteppe
K057 Galleta - three-awn shrubsteppe
K058 Grama - tobosa shrubsteppe
K063 Foothills prairie
K064 Grama - needlegrass - wheatgrass
K065 Grama - buffalograss
K066 Wheatgrass - needlegrass
K067 Wheatgrass - bluestem - needlegrass
K068 Wheatgrass - grama - buffalograss
K069 Bluestem - grama prairie
K072 Sea oats prairie
K073 Northern cordgrass prairie
K074 Bluestem prairie
K075 Nebraska Sandhills prairie
K076 Blackland prairie
K077 Bluestem - sacahuista prairie
K078 Southern cordgrass prairie
K079 Palmetto prairie
K094 Conifer bog
K098 Northern floodplain forest
K100 Oak - hickory forest
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES38 Plains grasslands
FRES41 Wet grasslands
FRES42 Annual grasslands
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
17 Pin cherry
18 Paper birch
88 Willow oak - water oak - diamondleaf oak
89 Live oak
95 Black willow
203 Balsam poplar
235 Cottonwood - willow
252 Paper birch
Depth range (m): 0 - 0
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Partially migratory. Migratory populations move northward in spring, departing wintering areas by March or early April, usually arriving at northernmost breeding grounds late April-early May; move southward September-October (sometimes later) (Ringelman 1990, Terres 1980). Primary migration corridor originates in the prairies and extends through the low plains region of the central and south-central U.S. and into Mexico; secondary migration routes link the prairies with the Pacific Northwest, northern and central California, and northern Utah; Utah breeders winter in central and southern California and Mexico; migrates also along diagonal routes from Great Plains to central and southern Atlantic coast (Ringelman 1990). Gadwalls banded in breeding areas in north-central Colorado were recovered primarily near the banding areas and in central and coastal Texas, northern Utah, along the east and west coast of Mexico, and in the Interior Highlands of Mexico (Szymczak and Rexstad 1991).
Gadwalls main food sources are aquatic vegetation, aquatic invertebrates, and seeds. They are surface feeders feeding mostly on plant material growing close to the surface. They can also be found in fields feeding on grain or even in woodlands feeding on acorns. Their main diet of plant material includes leaves and stems of aquatic plants. Gadwalls will also supplement their plant diet with insects, crustaceans, amphibians, mollusks, and fish. Females will eat a protein and fat rich diet prior to mating. This provide them with extra resources for the egg laying and incubation periods. During this time, males eat more plant material than females (LeSchack et al. 1997).
Some of the plant material Gadwalls eat: pondweed (Potamogeton spp.), niad (Najas spp.), water milfoil (Myriophyllum spp.), algae (Cladophoraceae), smartweed (Polygonum spp.), bulrush (Scirpus spp.), spikerush (Eleocharis spp.), saltgrass (Distichlis spp.) and muskgrass (Chara spp.).
Animal Foods: amphibians; fish; insects; terrestrial non-insect arthropods; mollusks
Plant Foods: leaves; seeds, grains, and nuts; algae
Primary Diet: omnivore
Comments: Feeds on leaves, stems, and tubers of aquatic plants. Also eats algae and seeds of sedges and grasses. Occasionally grazes in pastures and grain fields; may feed on acorns. Eats some small fishes and aquatic invertebrates (e.g., insects, crustaceans). Aquatic invertebrates comprise about half the diet in spring and summer; eats green portions of aquatic plants in non-nesting season; feeds generally in water 15-66 cm deep (Ringelman 1990). Juveniles intitally eat equal amount of animal and plant food; plant food begins to dominate after 2 weeks (Ringelman 1990).
rather shallow marshes having abundant aquatic plant life growing close
to the surface . They sometimes feed in stubble fields for grain or
in woods for acorns . They mainly consume leaves and stems of
aquatic plants but also eat insects, mollusks, crustaceans, amphibians,
and fishes [9,16,19]. Aquatic plants commonly eaten by gadwalls include
pondweed (Potamogeton spp.), widgeongrass (Ruppia maritima), saltgrass
(Distichlis spp.), muskgrass (Chara spp.), eelgrass (Zostera marina),
spikerush (Eleocharis spp.), spiked watermilfoil (Myriophyllum spicatum)
and filamentous algae [9,16,19]. The two most prominent plants in the
diet of gadwall in South Carolina are fragrant flatsedge (Cyperus
odoratus) and Carolina redroot (Lachnanthes caroliniana). Major animal
foods include crustaceans, especially those belonging to the order
Anostraca, and insects, especially adult and larval chironomids
Recently hatched gadwalls in Alberta initially fed on invertebrates but
were essentially herbiverous by 3 weeks of age. Major animal foods of
ducklings included adult and larval chironamids, water boatman
(Cerixidae), beetles (Coleoptera), and cladocerans (Cladocera).
Important plants in the duckling's diets were pondweed, green algae
(Cladophoracea), duckweed (Lemna minor), and seeds of American
sloughgrass (Beckmannia syzigachne) .
The Gadwall has many predators, including: humans from hunting and urban accidents, fox (Vulpes spp.), raccoons (Procyon lotor), coyotes (Canis latrans), badgers (Taxidea taxus), weasels (Mustela spp.), hawks (Accipitridae), crows (Corvus spp.), and minks (Neovison vison). (Tesky 1993).
Gadwalls are most vulnerable when females are nesting and when the males are molting from alternate to basic back to alternate plumage. Their main source of defense is to be on the water. Like all ducks, they also become very vulnerable when feeding to close to the shore in dense vegetation. This makes them subject to the quick strike of fox and coyotes (Tesky 1993, LeSchack et al. 1997).
- humans (Homo sapiens)
- foxes (Vulpes)
- raccoons (Procyon lotor)
- coyotes (Canis latrans)
- American badgers (Taxidea taxus)
- weasels (Mustela)
- hawks (Accipitridae)
- crows (Corvus)
- American minks (Neovison vison)
(Procyon lotor), striped skunks (Mephitis mephitis), coyotes (Canis
latrans), badgers (Taxidea taxus), weasels (Mustela spp.), minks
(Mustela vison), crows (Corvus spp.), and magpies (Pica spp.)
This list may not be complete but is based on published studies.
Known prey organisms
This list may not be complete but is based on published studies.
Molting males may form groups of hundreds or thousands in mid-summer. Annual survivorship of adults banded in Colorado was 69-75% (Szymczak and Rexstad 1991).
Habitat-related Fire Effects
Burning can change the growth form and pattern of nesting cover for
gadwalls . Gadwalls prefer nesting in dense cover , which can
be destroyed by fire. A study of the effects of nesting cover removal
on breeding puddle ducks at Lower Souris National Wildlife Refuge, North
Dakota, showed that after spring burning, nest densities of gadwalls
were greater in areas where the vegetation was not burned .
Additionally, gadwall nests were significantly (P less than 0.01) less abundant in
mowed meadows that would be expected by chance. They made up 29 percent
of all nests found, but only 13 percent of the nests were in mowed
meadows. Gadwalls will, however, use areas that have been burned if
cover development is sufficent when they begin nesting . Changes in
vegetation cover induced by fire can also benefit gadwalls by destroying
unwanted vegetation and increasing vegetation preffed by gadwalls .
Timing of Major Life History Events
occurs in May through mid-July, somewhat later in the northern regions
and earlier in the south [2,11].
Clutch/incubation - Gadwalls lay 5 to 13 eggs per nest, and incubation
is 24 to 28 days [1,13].
Fledge - Gadwalls fledge 7 to 8 weeks after hatching .
Maturity - Gadwalls become sexually mature and acquire their breeding
plummage during their first winter .
Migration - Gadwalls are one of the last ducks to arrive on breeding
areas in the spring . Some early dates of arrival for various areas
in North America are as follows :
Southern Iowa - March 10
Minnesota, Heron Lake - March 17
Montana - April 1
Manitoba - April 23
Saskatchewan - April 18
Alberta - May 5
Life History and Behavior
Perception Channels: visual ; tactile ; acoustic ; chemical
Although there is no data on longevity or mean life expectancy, there was a banded Gadwall in Alaska that was recovered in Louisiana that had reached 19 years of age (Tesky 1997).
Status: wild: 234 months.
Lifespan, longevity, and ageing
The courtship displays of Gadwall males can be very elaborate. The displays that the males perform range from the Head-Up-Tail-Up (male throws his head back and jerks with his tail feathers erect) to the Grunt-Whistle (male rears out of the water and slowly sinks back down while making a loud whistle). Both the male and accepting female then continues the courtship by performing other displays separately or in unison. Copulation begins with both sexes bobbing their heads up and down and touching their bills to the water horizontally with their necks extended. As the female extends her neck the male mounts her. After copulation the female bathes while the male faces her and then he bathes. There have been reported occurrences of extra-pair copulations. In the late laying and incubation season paired females unaccompanied by their mates have been chased by one to several paired males which occasionally has ended up in rape.If the nest is predated, then the female will usually make another nest and lay a second clutch. (Bellrose 1980, Tesky 1993, LeSchack et al. 1997).
Mating System: monogamous
Gadwalls are monogamous in their breeding behavior. Pairs of adult birds will bond in the mid to late fall, while inmature birds will pair by mid winter. Pair bonds are renewed each year. Most yearlings will mate the following breding season but studies on domestic flocks have showed that sometimes the late hatchlings were not sexually active untill their second year. The breeding season will vary but usually can occur in May and go through mid-July (Johnsguard 1979).
Breeding season: May-July
Range eggs per season: 7 to 12.
Average eggs per season: 9.
Range time to hatching: 24 to 27 days.
Average time to hatching: 26 days.
Range fledging age: 49 to 70 days.
Average fledging age: 63 days.
Range age at sexual or reproductive maturity (female): 10 to 22 months.
Average age at sexual or reproductive maturity (female): 12 months.
Range age at sexual or reproductive maturity (male): 10 to 22 months.
Average age at sexual or reproductive maturity (male): 12 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average eggs per season: 9.
The male and the female will fly low over meadows and upland habitat in search of a nesting site. The female will usually choose a nest site near her natal nesting grounds. It is believed that this behavior is from the imprinting of familiar and successful nesting areas. As the male stands guard, the female will inspect an area that has suitable materials for nest building. When an area has been chosen, the female constructs a nest bowl by scraping a depression in the soil. She then lines it with leaves, grasses, and twigs from nearby material. She may then line the nest with down feathers plucked from her body.
She will lay a clutch from 7 to 13 eggs at the rate of one egg per day. The average incubation period will last 26 days with the female spending 85% of her time on the eggs. Many males will abandon the female after the clutch is laid and to a safe area where they will molt to their basic plumage.
The precocial young will hatch and be led by their mother from the vulnerable nest area to brood-rearing habitat. Since the ducklings are precocial, they obtain their own food. The female will raise the brood for no more than 10 weeks and will then abandon her young (Baldsarre et al. 1994, LeSchack et al. 1997).
Parental Investment: precocial
Breeding usually begins in mid-April in the south to early June in the north. Clutch size: usually about 9-11. Incubation: about 4 weeks, by female. Young are tended by female, can fly at 49-63 days. Relatively high percentage of yearlings do not breed. Up to at least a few hundred nests/ha on islands lacking mammalian predators.
Molecular Biology and Genetics
Barcode data: Anas strepera
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
-- end --
Download FASTA File
Statistics of barcoding coverage: Anas strepera
Public Records: 10
Specimens with Barcodes: 13
Species With Barcodes: 1
There are no conservation plans for the Gadwall at this time. Their populations have been increasing since 1955. With the Conservation Reserve Program (CRP) under the Food Security Act of 1985, the retirement of 14 million acres of cropland in the Prairie Pothole region by 1996 has been attributed to a steady increase of many waterfowl populations including Gadwalls (Tesky 1993, LeSchack et al. 1997).
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N5B,N4N : N5B: Secure - Breeding, N4N: Apparently Secure - Nonbreeding
Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Status in Egypt
Regular passage visitor and winter visitor.
Management Requirements: Wetland management to benefit gadwalls should be directed at maintaining large wetlands with stable water levels suitable for the growth of submersed aquatic vegetation (Ringelman 1990). See Barker et al. (1990) for information on the effects of different livestock grazing systems on nesting success in North Dakota. See Marcy (1986) for specifications for the construction and placement of wire nest baskets.
Use of Fire in Population Management
Wetlands can be burned to reverse plant succession to a subclimax plant
community which is attractive to waterfowl . Fire can be used to
remove the accumulation of dead vegetation built up on marshes over the
years and restore wetlands that are dominated with plants such as common
reed (Phragmites communis). Desirable gadwall foods such as pondweed can
be restored by burning. Burning should be postponed until after the
nesting season to avoid destroying nests .
Grazing and mowing often destroy preferred nesting cover for gadwalls.
Although annual mowing or grazing is not recommended, mowing may be
useful for maintaining vegetative cover in earlier, more productive
successsional stages .
Relevance to Humans and Ecosystems
Humans benefit from Gadwalls not as much economically as they do socially and traditionally. Hunting has been a tradition in the North America since the beginning of recorded history. The Native Americans have told of hunting waterfowl in their traditional stories. The hunting of Gadwalls as well as other waterfowl is deeply rooted in traditions of North Americans. 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 premits and liscenses helps to maintain and create new waterfowl refuges as well as supplies revenue to monitor populations for the next years hunting regulations (LeSchack et al. 1997).
Positive Impacts: food
Comments: Lightly harvested; comprises 4.2% of continental duck breeding population, but only 2.5% of harvest (Ringelman 1990).
The gadwall was first described by Linnaeus in 1758 in his Systema naturae, under its current scientific name. DNA studies have shown that it is a sister species with the falcated duck, and that these two are closely related to the wigeons. There two subspecies:
- A. s. strepera, described by Linnaeus, is the nominate subspecies.
- A. s. couesi, Coues' gadwall, extinct circa 1874, was formerly found on Teraina, a coral atoll in the Pacific Ocean.
The gadwall is 46–56 cm (18–22 in) long with a 78–90 cm (31–35 in) wingspan. The male is slightly larger than the female, weighing on average 990 g (35 oz) against her 850 g (30 oz). The breeding male is patterned grey, with a black rear end, light chestnut wings, and a brilliant white speculum, obvious in flight or at rest. In non-breeding (eclipse) plumage, the drake looks more like the female, but retains the male wing pattern, and is usually greyer above and has less orange on the bill.
The female is light brown, with plumage much like a female mallard. It can be distinguished from that species by the dark orange-edged bill, smaller size, the white speculum, and white belly. Both sexes go through two moults annually, following a juvenile moult.
The gadwall is a quieter duck, except during its courtship display. Females give a call similar to the quack of a female mallard but higher-pitched, transcribed as gag-ag-ag-ag. Males give a grunt, transcribed as nheck, and a whistle.
The gadwall breeds in the northern areas of Europe and Asia, and central North America. In North America, its breeding range lies along the Saint Lawrence River, through the Great Lakes, Alberta, Saskatchewan, the Dakotas, south to Kansas, west to California, and along coastal Pacific Canada and southern coastal Alaska. The range of this bird appears to be expanding into eastern North America. This dabbling duck is strongly migratory, and winters farther south than its breeding range, from coastal Alaska, south into Central America, and east into Idaho, Kansas, Ohio, Virginia, and then south all the way into Central America. Its conservation status is Least Concern.
In Great Britain, the gadwall is a scarce-breeding bird and winter visitor, though its population has increased in recent years. It is likely that its expansion was partly through introduction, mainly to England, and partly through colonization to Great Britain, with continental birds staying to breed in Scotland. It has been reported in the River Avon in Hampshire and Wiltshire. In Ireland a small breeding population has recently become established, centred on Wexford in the south and Lough Neagh in the north.
The gadwall is a bird of open wetlands, such as prairie or steppe lakes, wet grassland or marshes with dense fringing vegetation, and usually feeds by dabbling for plant food with head submerged. It nests on the ground, often some distance from water. It is not as gregarious as some dabbling ducks outside the breeding season and tends to form only small flocks. This is a fairly quiet species; the male has a hoarse whistling call, and the female has a Mallard-like quack. The young birds are fed insects at first; adults also eat some molluscs and insects during the nesting season. The gadwall is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.
- BirdLife International (2012). "Anas strepera". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
- Linnaeus, C. (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. (in Latin). Holmiae [Stockholm]: Laurentii Salvii. p. 125. Retrieved 10 August 2014.
A. macula alarum rufa nigra alba.
- Johnson, Kevin P.; Sorenson, Michael D. (1999). "Phylogeny and biogeography of dabbling ducks (genus: Anas): A comparison of molecular and morphological evidence" (PDF). The Auk 116 (3): 792–805. doi:10.2307/4089339.
- "ITIS Report: Anas strepera". Integrated Taxonomic Information System. Retrieved 10 August 2014.
- Hume, Julian P.; Walters, Michael (2012). Extinct Birds. London, UK: T. & A. D. Poyser. p. 48. ISBN 978-1-4081-5725-1. Retrieved 10 August 2014.
- "gadwall". Merriam-Webster. Retrieved 24 August 2011.
- Floyd 2008[page needed]
- Madge, Steve; Burn, Hilary (1988). Wildfowl: An Identification Guide to the Ducks, Geese and Swans of the World. Christopher Helm. pp. 200–202. ISBN 0-7470-2201-1.
- Dunn & Alderfer 2006[page needed]
- Irish Birds 9: 68. 2010.
- Bishop, K. David (1999). "Preliminary notes on some birds in Bhutan". Forktail 15: 87.
- Clements, James (2007). The Clements Checklist of the Birds of the World. Ithaca: Cornell University Press.
- Dunn, J.; Alderfer, J. (2006). National Geographic Field Guide to the Birds of North America (5th ed.).
- Floyd, T. (2008). Smithsonian Field Guide to the Birds of North America. New York: HarperCollins.
Names and Taxonomy
Comments: Considered by some authors as two separate species, A. STREPERA (common gadwall) and A. COUESI (Coues' gadwall), the latter now extinct (AOU 1983). See Livezey (1991) for a phylogenetic analysis and classification (supergenera, subgenera, infragenera, etc.) of dabbling ducks based on comparative morphology, in which STREPERA is placed in the genus MARECA.
gray (grey) duck
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