This is bird note. A flock of gorgeous waterfowl flies above a marsh on the Texas coastline.

Large and slender, they have bright pink bills and legs, chestnut necks and backs, and black underparts.

Their wings flash boldly black and white.

And as they fly, They whistle. They whistle. They're called black-bellied whistling ducks, and they're widespread

in Central and South America. They've been easy to find in the U.S. along the Western Gulf Coast and Florida,

but they're also expanding northward.

They've been spotted nesting as far north as Wisconsin. The Blackbellied is one of eight species of whistling ducks worldwide in the tropics and subtropics. Whistling ducks are anything but typical ducks, to which they're only distantly related.

Black-bellied whistling ducks are monogamous, and the male and female look alike.

At roost during the day, whistling ducks will sometimes stand on tree branches, their long

pink legs catching the sun.

Late in the day, large flocks gather, then whistle their way overhead

at sunset to nighttime feeding areas and fields or along the shore. A lovely and vibrant spectacle with unique sound effects.

For Bird Note, I'm Michael Stein.