A striking and gregarious duck of the Neo-tropics, the Black-bellied Whistling-Duck breeds from the southernmost United States and tropical
Central to south-central South America. Its long neck, long legs, black belly, and white wing patch make it a distinctive-looking
waterfowl. The whistling-ducks were formerly known as tree-ducks, but only a few, such as the Black-bellied
Whistling-Duck, actually perch or nest in trees.

Joanne Kamo has an excellent gallery of these ducks on Pbase:
http://www.pbase.com/jitams/black_bellied_whistling_duck