Black-bellied whistling duck

Appearance

The black-bellied whistling duck is a mid-sized waterfowl species. Length ranges from 47 to 56 cm, body mass from 652 to 1,020 g and wingspan ranges from 76 to 94 cm.

It has a long red bill, long head and longish legs, pale grey head and mostly grey-brown plumage. The belly and tail are black, and the body plumage, back of the neck and cap are a rich chestnut brown. The face and upper neck are grey, and they sport a thin but distinct white eye-ring. The extensive white in the wings is obvious in flight, less so on the ground; it is formed by the secondary remiges while the primaries are black; the wing-coverts are brown. Males and females look alike; juveniles are similar but have a grey bill and less contrasting belly.

The wing bar is unique among living whistling ducks. When on the ground, it may be hard to discern the light flanks present in many of these waterfowl. The fulvous whistling duck is the only sympatric whistling duck that shows such a whitish flank stripe, and it differs from the black-bellied by having dark wings and a lighter belly rather than the other way around. Juvenile "D. autumnalis" are quite similar to young of the white-faced whistling duck, which have a darker bill and no white wing patch; even when sitting they never seem to show white along the sides, as their thin white vertical barring on the black flanks is very indistinct.

As the name implies, these are noisy birds with a clear whistling "waa-chooo" call.

Naming

There are two subspecies, which intergrade in Panama:
⤷  Northern black-bellied whistling duck, "D. a. autumnalis" – Southern USA to Panama
⟶ Larger, with a brown breast and upper back
⤷  Southern black-bellied whistling duck, "D. a. discolor" – Panama to Paraguay and adjacent regions
⟶ Smaller, with grey breast and upper back

Status

This species is not considered to be of conservation concern by the IUCN and the National Audubon Society; its global population is estimated at 1,100,000-2,000,000 birds.

Habitat

The black-bellied whistling duck is a common species that is "quite tame, even in the wild". It is highly gregarious, forming large flocks when not breeding, and is largely resident apart from local movements. It usually nests in hollow trees. The habitat is quiet shallow freshwater ponds, lakes, and marshes, cultivated land or reservoirs with plentiful vegetation, where this duck feeds mainly at night on seeds and other plant food. Tree-lined bodies of water are of particular value and as the old common name suggests, they are quite fond of perching in trees. This species can also be seen "loafing" in flocks on golf courses and other grassy areas near suitable waterways.

Reproduction

The black-bellied whistling duck is quite unique among ducks in their strong monogamous pair-bond. Its pairs often stay together for many years, a trait more often associated with geese and swans. Both parents share all tasks associated with the raising of young, from incubation to the rearing of ducklings. The ducks, primarily cavity nesters, prefer the confines of a hollow tree, but will nest on the ground when necessary. They also make use of chimneys, abandoned buildings, or nest boxes, the latter having been increasingly provided to them over recent decades, especially in southeast Texas and Mexico. Ducklings leap from nest cavities within two days of hatching, can feed themselves immediately, and stay with the parents for up to eight weeks.

Food

Feeding often occurs nocturnally, but they can be encountered eating at any hour of the day. Black-bellied whistling ducks ingest a wide variety of plant material, but also consume arthropods and aquatic invertebrates when available. They often feed on submerged vegetation by wading through shallow water. As its Latin name implies, it is commonly seen gleaning recently harvested fields for leftover seeds and invertebrates brought up by the harvesters disturbing the soil.