Duck, Duck, Goose? The Black-bellied Whistling Duck

The black-bellied whistling duck is an odd duck. Sure, you may say that about a crazy old uncle too, but a duck with the gestalt of a goose and a genus name that means “tree swan,” the species is truly an odd duck.

The unique appearance and behavior of black-bellieds is enough to pique interest in birders, biologists, and hunters. They’re catching more attention now with their expanding range. The black-bellied whistling duck has always been a southern species, and a very uncommon visitor to Illinois, but it’s no longer impossible to see a black-bellied whistling duck in the Prairie State.

You’ll know a black-bellied whistling duck when you see one, but you’ll often hear it first. Their constant vocalization is a dead give-away. Gregarious birds, they can make quite a racket when gathered in large groups. They whistle while hanging out large groups in fields, on the water, and perched in trees. When taking flight, they shout, or “yip.” Give a listen: https://www.allaboutbirds.org/guide/Black-bellied_Whistling-Duck/sounds

The eye-catching pink bill combined with the chestnut head and nape are key identification clues. The bird has a broad white wing band, which is visible both on the ground and in flight. And of course, there’s the signature black belly. With long legs, a long neck, and erect posture, the black-bellied takes on a goose-like air.

Black-bellied whistling ducks congregate in large, talkative groups day and night, although are more likely to be seen in pairs or small groups in Illinois. They forage in grassy areas and in agricultural fields after harvest. They wade at the edge of ponds to glean vegetation. Black-bellieds are not big on swimming, but they do cruise on shallow waters, feeding on submerged plants, “butts up” like dabblers. They are tolerant of human disturbance and seem equally at home in marshes, forested wetlands or around water in developed areas such as parks, business complexes, subdivisions and backyard ponds.

Most species of ducks exhibit sexual dimorphism, in which males and females look distinctly different. Male and female black-bellied whistling ducks, however, look the same. Their nesting behavior is remarkably un-duck-like, too. They will nest on the ground, but they often nest in low-hanging snags with cavities. They are similar to wood ducks in this respect, and whistlers, as they are sometimes called, often use nest boxes intended for woodies. There are even reports of black-bellieds nesting in chimneys and barns.

One key habitat requirement is proximity to dense woody cover, whether in an urban landscape, an agricultural setting, or a natural area. In these thickets, black-bellied whistling ducks may nest in colonies, somewhat like cormorants and herons. The social black-bellieds tend to perch on branches and just “hang out” during nesting.

With scant attention to detail, females lay eggs directly on the substrate of a tree cavity or wood duck box. If nesting on the ground, the female may put a little effort into weaving some grasses together. A female may lay 12 to 16 eggs, but from here it can get a little crazy. In a practice called egg-dumping, female black-bellieds lay eggs in other females’ nests. This may occur if a female wasn’t able to find a good nest site, if the nest was destroyed in a storm, or “just because.” Egg dumping is an effort to pass on genes to another generation and is used by many species of waterfowl. After dumping, one nest may hold 50 to 60 eggs, but chances are slim that all eggs will survive, and many dump-nests are abandoned by the original host female.

The population of the black-bellied whistling duck has increased since the 1950s. Now, as the species extends its range northward, the population continues to grow. They have been spotted in Illinois and Wisconsin for the past 25 years. Over the past few years successful nests have been confirmed in southern Illinois and in 2020, a successful brood was confirmed in La Crosse, Wisconsin!

Wildlife biologists are puzzled by the northward trend. Numerous species are shifting their ranges as the climate changes, but the black-bellied’s expansion appears to be driven more by something other than climate. In an interview for WSIL, John O’Connell from Southern Illinois University said, “It might be metabolism, it might be dietary requirements, there’s all kind of nuances there that might affect [range expansion].”

Tara Beveroth, ornithologist with the Illinois Natural History Survey, added, “One of the likely reasons for the success of this species is its ability to adapt and its gregarious nature. It can adapt to different habitats in both rural and urban environments.” The increase in wood duck nest boxes in the north has been a draw for black-bellieds.

Randy Smith, Wetland Wildlife Program Manager at the Illinois Department of Natural Resources, notes “Black-bellied whistling ducks are a relatively lightly harvested species throughout their range, so hunting regulations are liberal; hunters can take six per day. However, they’re a very early migrant so hunters in Illinois are unlikely to encounter them during open seasons, but as their range expands, those odds may increase.”

In Illinois, we expect to see more black-bellied whistling ducks in the coming years. It will be a lifer for some birders and hunters. Keep your eyes and ears open for these loquacious goose-like swan ducks!

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Valerie Blaine has worked as a naturalist for more than 40 years, from the prairies and woodlands of Illinois to the shores of the San Francisco Bay. She earned a master’s degree in forestry and a bachelor’s degree in botany from the University of Illinois. Blaine retired as the Nature Programs Manager for the Forest Preserve District of Kane County.