Dabbling duck trends on Bolinas Lagoon
The “dabblers” include waterfowl with various methods of foraging in wetland habitats. Some feed by tipping their back end up, stretching their head and neck into the water to reach submerged aquatic plants. Others truly “dabble” by using their bills (beaks) to strain small invertebrates and plant material from the surface water or mud layers. This guild includes wigeons, pintails, mallards, gadwalls, and shovelers.
For other waterbird trend pages click a link below:
Shorebird trends
Diving Duck trends
Grebe trends
Cormorant trends
Heron & Egret trends
Tern trends
Other waterbird trends
For dabbling duck graphs and profiles click a link below:
Mallard
Northern Pintail
Gadwall
American Wigeon
Eurasian Wigeon
Green-winged Teal
Northern Shoveler
About Graphs
References
Mallard
Anas platyrhynchos
Description
Male Mallards have a green head, white neck ring, chestnut breast, and grayish body. The inner feathers of their wings (speculum) are metallic blue, bordered in front and back with white. Female is mottled brown with a white tail, blue speculum and an orange and brown bill.
Range
Breeds from Alaska across Canada to Nova Scotia and south through California, Texas, and northern Mexico. Winters throughout the United States and south to Central America and the West Indies.
Diet
The Mallard is an omnivorous generalist feeder. They have a varied diet including insects, aquatic invertebrates such as snails and shrimp, aquatic vegetation, and grain from agricultural fields.
Natural History Notes
The Mallard is the predecessor of almost all of the domestic ducks today. In North America, the Mallard is the most abundant duck species. Its success in the wild reflects its adaptability to varied habitats and foods, and its tolerance of human activities.
Male and female Mallards form breeding pairs in the fall. Courtship can be seen throughout winter.
Bolinas Lagoon Population Trends
An average of about 30 birds from the 1970s to 1990s was punctuated by a peak of nearly 90 birds in the mid-1980s. Since 1993 numbers have increased to more than 100 birds currently.
Northern Pintail
Anas acutas
Description
Breeding male Northern Pintails have a “pin tail” made up of long, slender pointed tail feathers, a brown head, white chest, long neck and white stripe at the back of its face. Males have a gray body and brown and green speculum (wing patch), with white behind. Females are mottled pale brown and gray with a long, slender neck and a somewhat pointed tail like the male.
Range
Breeds throughout Alaska and Canada, in the central Great Plains and south to California. Winters from the central United States to northern South America.
Diet
Eats a variety of foods including seeds from aquatic plants and small aquatic animals like insects and crustaceans. It also forages in agricultural fields for grain.
Natural History Notes
A widespread dabbling duck throughout North America. Close to half of the country’s six million Northern Pintails are found in the West. Wintering pintail flocks can contain thousands of individuals.
Bolinas Lagoon Population Trends
Except for a peak of over 2500 birds in the mid-1970s, the population fluctuated between about 1000 to 1500 birds until the late 1990s. Since then it has declined to less than 500 birds in 2004.
Gadwall
Anas strepera
Description
Gadwalls, one of the larger stockier ducks, have simple brownish-gray plumage. In breeding plumage, the male has a distinct black rump, silvery tertials, and coppery upper wing coverts.
Range
Gadwalls breed from north-central United States through south central Canada as well as in southern Alaska. After breeding in North America, Gadwalls migrate to southern United States and Mexico for the winter. Some Gadwall winter along the West coast of the United States.
Diet
Gadwalls feed in groups by skimming their beaks along the water’s surface or by gathering submerged vegetation up to 30 cm below the surface. Their diet consists mainly of aquatic vegetation, seeds, and aquatic invertebrates. Gadwalls prefer deeper water than most other Anas species.
Natural History Notes
The Gadwall is a common winter and very rare summer resident in Point Reyes, arriving in the fall from August throughout December. Although they commonly breed throughout the San Francisco Bay, very few Gadwall have been known to breed in Point Reyes. Gadwalls prefer to live in “freshwater ponds and the innermost reaches of estuaries where the substrate is soft and muddy.” At Bolinas Lagoon, Gadwall are most abundant at the Pine Gulch Creek mouth.
Conservation Status
After major wetland habitat destruction and drought, Gadwall numbers plummeted from the 1960s through 1980s. Fortunately, during the decade 1986-1996, numbers increased 129% after northern wetlands were restored, making the largest comeback of any species during that time. According to C.R. Leschack, the Gadwall “range has changed during this century more than any other duck in North America.” (Leschack, 1997).
Bolinas Lagoon Population Trends
Since 1972, when there were only about 5 Gadwalls on Bolinas Lagoon, the population has increased. The population peaked in 1986 at close to 100 birds, then decreased to about 50 birds, peaked again at 80 birds, and currently has dropped to about 50 birds.
American Wigeon
Anas americana
Description
Breeding male American Wigeons are distinguishable by their white forehead and crown and dark green eye patch. Female wigeons have a brownish grey head with a dark smudge around the eye.
Range
This large dabbling duck is common and widespread throughout North America. The American Wigeon breeds from the Bering Sea to the Hudson Bay, making this one of the most northerly breeding dabbling ducks. The breeding range extends throughout the Alaskan tundra to the northern prairie states in the United States.
Diet
It has a short bill which enables it to nibble or dig up vegetation from land or shallow water. In addition to aquatic vegetation, American Wigeons eat aquatic invertebrates. They are known for stealing food from American Coots and diving ducks as they surface.
Natural History Notes
The American Wigeon is a very rare summer visitor and an abundant winter resident in Point Reyes. The majority of the American Wigeons start arriving around the end of August. These birds prefer shallow water where they can access aquatic vegetation. They can be seen in fresh water ponds and near areas of freshwater inflow in estuaries.
Bolinas Lagoon Population Trends
PRBO data show the American Wigeon population on the Bolinas Lagoon increased, with several population peaks since 1970. In the early 1970s only about 100 wigeons were found on the lagoon, but the population rose to a high of 2200 birds in 1998. In 2004, the population was about 1000 individuals.
Eurasian Wigeon
Anas penelope
Description
The male Eurasian Wigeon can be differentiated from the American Wigeon by its mostly gray body and reddish brown head with buffy crown. The Eurasian Wigeon, much less common than the American Wigeon, can be found with careful observation within flocks of American Wigeons.
Range
The Eurasian Wigeon breeds over North Asia and Europe, including Iceland and Kamchaka. During the winter they can be found through much of Europe, south Asia to central Africa, and the Philippines. Small numbers also winter along the Pacific coast of the United States.
Diet
Like the American Wigeon, the Eurasian Wigeon eats mostly vegetation and supplements its diet with food snatched from diving ducks.
Natural History Notes
This very rare winter resident is most frequently seen at Pine Gulch Creek mouth on Bolinas Lagoon, Walker Creek mouth on Tomales Bay, Muddy Hollow pond at Limantour, and the ponds at Abbott’s Lagoon.
Bolinas Lagoon Population Trends
Although the number of Eurasian Wigeons on Bolinas Lagoon is still low, they have increased from no birds at all in 1972 to 1974, when the population began to increase. Since 1974, the population peaked at 10 birds in 1999 and has dropped to 8 birds in 2004.
Green-winged Teal
Anas crecca
Description
Green-winged Teal are small dabbling ducks, with narrower and shorter bills than other North American dabblers. Both males and females have iridescent green patches in their wings, with a golden stripe in front and a white stripe behind. Breeding males have a white shoulder stripe and a cinnamon head with an iridescent green crescent extending from the eye to the back of the head. Males have a pinkish breast with small black spots.
Range
Breeds in northern Alaska and across Canada south to California, Colorado, Nebraska, and New York. Winters on coasts and southern parts of the United States to Mexico.
Diet
Green-winged Teals have a broad diet, comprised of seeds from sedges, grass, and aquatic vegetation, as well as aquatic insects, mollusks, and crustaceans. They are opportunistic foragers, feeding on foods in high abundance.
Natural History Notes
A migrant along all the major flyways, this is the second most abundant duck taken by hunters in North America. Because its breeding areas are far from human activity, however, its numbers have remained high and are even increasing.
Bolinas Lagoon Population Trends
At Bolinas Lagoon the population has fluctuated from under 100 to over 400 birds. It was about 160 birds in 2004.
Northern Shoveler
Anas clypeata
Description
The Northern Shoveler, a medium sized duck, has a long "shovel" shaped bill. In the breeding season, the male has a brilliant green head, white chest, and rusty sides. Female has subtle gray, brown, and black patterning all over.
Range
The Northern Shovelers' breeding range, extends from the midwestern United States throughout most of Canada to Alaska. Found in a variety of shallow, open wetland habitats.
Diet
The Northern Shoveler’s favorite foods are small swimming crustaceans and aquatic vegetation. This duck feeds by straining the small plants and animals through fine comb-like projections called lamellae located along the edge of the bill. The bill is about 6.5 centimeters long and has about 110 lamallae.
Natural History Notes
In Point Reyes, the Northern Shoveler is a common winter resident. It arrives in the area from September through December. Shovelers can be found mostly on Limantour Estero and Bolinas Lagoon, with numbers decreasing in January and February. On Bolinas Lagoon, shovelers congregate at the muddy Pine Gulch Creek Delta, an area of freshwater inflow. Look for shovelers in the spring and summer, as a few rare spring and summer sightings suggest that Northern Shovelers may be nesting in Point Reyes.
Bolinas Lagoon Population Trends
The number of Nothern Shoverlers on Bolinas Lagoon increased steadily from under 25 birds in 1972 to a peak of 320 birds in 1997. Since 1997, the population has decreased to about 100 birds in 2004.
