Jean Cook, photographer of the bald eagle published Nov. 18, the the black-bellied whistling duck, published Nov. 19, offers this background information our the whistling duck:
It's from The Sibley Guide to Birds by the National Audubon Society (copyright 2000, pg 80):
"These oddly gooselike ducks are found in flocks, grazing in open fields or tipping up in shallow ponds. They call constantly in flight, when their broad, rounded wings and long legs are apparent."