Those who have had the opportunity to venture to the Gulf Coast to hunt, bird watch or just grab some R&R may have encountered some long, slender ducks locally known as squealers. Black-bellied and fulvous whistling ducks are most common in Mexico and Latin America where they are known as pichichi or pato maizal and pijia or pato silvon.
There are eight species of whistling ducks in the world, but only two-the black-bellied and fulvous whistling ducks-occur in the United States. Scientists consider whistling ducks more closely related to geese and swans than to the "true ducks." With their long legs, long necks, bone structure and erect stance, they certainly look more like geese than like ducks. As with geese and swans, the plumage of both sexes of whistling ducks are very similar. They only have one molt (in contrast to two molts in the "true ducks"); both parents share in the brooding of the young; and pairs mate for life.
They also are distinguished by their appearance and behaviors in the field. Black-bellied whistling ducks fly slowly in shapeless formations. In flight, they show long necks, trailing legs, and broad wings, but the most distinguishing feature is the contrasting black and white between the upper and lower wings. When standing or perching, the most striking features are the bird's namesake stark black belly and sides, along with the red bill and pink feet. Biologists recognize two subpopulations of black-bellies.
The northern population breeds from central Texas through coastal Mexico and Central America. The southern population breeds from Panama south into Argentina. Like most of their tropical counterparts, black-bellies do not show strong migratory patterns; instead, they move relatively short distances in response to habitat availability within their breeding range.
Black-bellies breed during their first year of life, establishing lifelong pair bonds during their first winter. Nest initiation occurs from April through August, a period approximately one month longer than prairie nesting ducks. Black-bellies nest in tree cavities and, similar to wood ducks, also have adapted to nesting in boxes. Where tree cavities are lacking, black-bellies will nest on the ground, often in grasses at the base of small trees or shrubs. Females lay an average of 13 eggs and both sexes incubate the eggs. Experiments have revealed that removal of either the female or the male during incubation results in abandonment of the nest. Apparently, participation of both the male and female is necessary for the nesting attempt to be successful. Black-bellies enjoy relatively high nest success rates (an average of 45 percent) compared to prairie nesting ducks. Most nest failures are caused by raccoons, rat snakes and golden-fronted woodpeckers.
During the nonbreeding season, black-bellies primarily use mangrove swamps and coastal lagoons to meet their food and cover requirements. However, similar to their goose cousins, black-bellies have adapted to feeding in agricultural environments, frequenting pastures and cattle feedlots as well as harvested rice, corn and sorghum fields when the opportunity presents itself. Fulvous whistling ducks, with their long necks and legs, short tail and broad wings, also look much more like a goose than a duck.
They are very agile on land, standing erect and walking without the waddle so characteristic of other ducks. A tawny brown head, chest, breast and belly distinguish fulvous whistling ducks. Ivory-edged side and flank feathers form a striking border between the sides and back. In North America, the species is most common in Mexico, but also breeds in California, Florida, Louisiana and Texas. Most fulvous whistling ducks depart their breeding range in the United States during September and October to winter in Mexico, returning north again in March and April.
Like black-bellies, fulvous whistling ducks breed during their first year of life. Nest initiation occurs from May through August. Fulvous whistling ducks nest in rice fields and in wetlands, usually over water among water-tolerant grasses and sedges. Females lay 12 eggs on average, and both sexes incubate the eggs. Unlike most species of waterfowl, fulvous and black-bellied whistling ducks do not add down to their nest bowls. Scientists have also observed that fulvous whistling ducks do not cover their eggs when they depart the nest to feed, possibly because of the high temperatures occurring on their southern breeding grounds.
In late August and early September, fulvous whistling ducks concentrate in flooded rice fields and large ponds. This species is noted for its nocturnal feeding in rice fields, where one observer vividly described a scene in Louisiana in 1943: "When we reached the fields and levees just before dusk, not a duck was seen or heard. Within a few minutes, on they came in no particular formation as with ordinary ducks - singly, in pairs, in companies of a dozen or more, and in irregular groups, and in twenty minutes they were flying and squealing everywhere, hundreds of them." In October, flocks move to coastal marshes where they feed predominantly on the seeds of aquatic vegetation. In November, a general exodus occurs to the east and west coasts of Mexico, where the birds spend the winter on coastal lagoons and rice fields.
Comprehensive population surveys of whistling ducks are lacking. Most of our information comes from mid-winter surveys conducted by the U.S. Fish and Wildlife Service and occasional breeding season surveys associated with short-term research projects. Limited data suggest a relatively stable breeding population of around 20,000 fulvous whistling ducks in Louisiana and Texas. Significant breeding populations also exist in Mexico, but surveys are insufficient to document population status and trends. Many breeding populations in both the United States and Mexico have historically been associated with rice culture. Since the 1980s, rice acreage has declined dramatically in Mexico, Louisiana and Texas. Much of this land is now being used for dryland crops and pasture, which provides little habitat for breeding fulvous whistling ducks.
Available information for black-bellied whistling ducks suggests a stable population in Mexico and growing population in Texas. About 80,000 birds are generally counted along the east and west coasts of Mexico each winter, and researchers estimate a breeding population of several thousand in southern Texas.