Black-Bellied Whistling Duck: An Unducklike Duck

The black-bellied whistling duck (Dendrocygna autumnalis, family Anatidae, order Anseriformes) has physical features and behavior patterns more characteristic of geese and swans than of ducks.

Etymology
Black-bellied comes from the color of the duck's underside, while whistling refers to its call.

The genus name, Dendrocygna, is based on New Latin dendro- ("of a tree") and -cygna ("swan"); the duck is so labeled because of its association with trees. The family name, Anatidae, is based on New Latin anat-, a combining form of anas ("duck"). The order name, Anseriformes, is based on New Latin anser ("goose") and -iformes ("ones having such a form").

Physical Description
The black-bellied whistling duck ranges from 18 to 21 inches in length, from 34 to 36 inches in wingspan, and from 23 to 36 ounces in weight.

With its long neck and erect posture (the most erect of all ducks), it looks somewhat like a goose. It has a chestnut-colored cap, lower neck, chest, and back; a gray face and upper neck; a white ring around each eye; a bright orange, spatulate bill; white and black patches on its rounded wings; a black, rounded tail; and long pink legs. Its most distinctive physical feature is its black belly.

Behavior
Black-bellied whistling ducks inhabit mostly Central and South America, but they also reach through Mexico into some southernmost areas of the United States, especially Texas and Florida. Most of the ducks do not migrate, though they are strong fliers.

Their common habitats are lakes, swamps, and marshes. They feed mostly by dabbling.

Favorite foods are aquatic plants, grass, grain, insects, and mollusks.

Courtship among black-bellied whistling ducks is fairly simple and resembles that practiced by swans, including the dipping and stretching of their long necks. The male and female bond very tightly, as exemplified in their preening each other, and they remain faithful to each other for many years.

Mates often engage in a "triumph ceremony" that parallels similar behavior by geese and swans. This behavior cements the bond between the male and female and typically involves excited calling and head waving as if in celebration, as after they have reunited from a separation or after the male has driven off an intruder.

Black-bellied whistling ducks usually build a simple nest in the fork of a tree or lay their eggs in a tree hollow. Sometimes they make a nest on the ground by scraping out a small area or by forming a shallow cup of grasses. A ground nest usually has some kind of protective vegetation overhead, such as cactus or reeds. Unlike other ducks, black-bellied whistling ducks do not line their nests.

The female lays from 9 to 18 white eggs. Incubation takes 25-30 days. Unlike most other male ducks but like male swans, the male black-bellied whistling duck shares in the incubating of the eggs.

Hatchlings, which are covered with down, leave the nest soon after hatching. The male helps the female in brood rearing by guarding the chicks till they can fly, at about 56 days.

Fascinating Facts
Black-bellied whistling ducks have an unusual call. It is a soft, high-pitched whistling call consisting of four to six distinct sounds. The bird accents every second or third sound. The call sounds something like pe-che-che-ne.

Whistling ducks, including the black-bellied whistling duck and the fulvous whistling duck, used to be called tree ducks. However, only a few of them actually perch or nest in trees. The black-bellied whistling duck is one of them. It not only nests in trees but also often perches. In fact, it is still sometimes called a black-bellied tree duck.

Black-bellied whistling ducks look much like geese, and their triumph ceremony, their courtship behavior, their long-term pair bonds, and their male participation in incubation are characteristics that resemble not other ducks but geese and swans. They are probably the most unducklike ducks.
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The Cornell Lab of Ornithology. http://www.allaboutbirds.org/guide/Black-bellied_Whistling-Duck/lifehistory (accessed Sept. 24, 2009).

Encyclopaedia Britannica Ready Reference 2004 (CD-ROM).

The Oxford English Dictionary. 2nd ed. Oxford, England: Clarendon Press, 1989.