The black-bellied whistling duck, formerly called the black-bellied tree duck, is a whistling duck that breeds from the southernmost United States and tropical Central to south-central South America. In the US, it can be found year-round in peninsular Florida, parts of southeast Texas, coastal Alabama and seasonally in southeast Arizona, and Louisiana's Gulf Coast. It is a rare breeder in such disparate locations as Arkansas, Georgia, Tennessee, and South Carolina, though it is now a common breeder in parts of central Florida. There is a large population of several hundred that winter each year in Audubon Park in uptown New Orleans, Louisiana. Since it is one of only two whistling duck species native to North America, it is occasionally just known as the "whistling duck" or "Mexican squealer" in the southern USA.
Description
The black-bellied whistling duck is a mid-sized waterfowl species. Length ranges from, body mass from and wingspan ranges from. It has a long red bill, long head and longish legs, pale gray head and mostly gray-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 gray, 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 gray bill and less contrasting belly. The wing bar is unique among 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.
Subspecies
There are two subspecies, which intergrade in Panama:
Northern black-bellied whistling duck, D. a. fulgens - Southern USA to Western Panama.
Southern black-bellied whistling duck, D. a.autumnalis - Eastern Panama to Paraguay and adjacent regions.
Prior to 1978, birds from western Panama north to the southern USA were erroneously referred to as D. a. autumnalis and birds from eastern Panama into South America were referred to as D. a. discolor.
Ecology
The black-bellied whistling duck is a common species that is "quite tame, even in the wild". It is highly gregarious, or social, 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.
Diet
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.
Movements
The black-bellied whistling duck is mainly non-migratory. Birds in the extreme northern portions of their range move south in winter. At the heart of their range, there is a tendency to travel in flocks over the winter months, though this behavior is not a true long-range migration but rather local dispersal. Seven adults and eight ducklings were observed on west side of Lake Apopka, Central Florida on 24 July 2015. They have been in this area for more than a year. Since 2009, this species has now become a common breeder in Lake County, Florida, with adult pairs with offspring seen by lakes and in wetlands near Eustis, Tavares, Leesburg, and other municipalities; large wintering flocks of 30+ birds can be seen throughout the county, even up to Lake Norris in the NE central portion of the county. There has been a large flock noted for about two years in the River Plantation area of Parrish in Manatee County, Florida and inland from Port Manatee in the northern part of the county. This flock has returned every year nesting in a marshy area and observed by residences in the rural area. A large flock was observed and photographed by a local resident in Audubon Park, New Orleans, Louisiana in February 2016. Over 100 of the whistling ducks have resided in the Gum Slough of Sumter County, Florida for over two years. Recent spike from Leesburg to the Ocklawaha region with many nightly flights averaging 10 per flight. Since late 2019, after the dredging of Lake Roberta in Tampa, Florida, a flock of more than 100 whistling ducks has taken up residence on the shores of the lake.
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.
