Rita,
The black-bellied whistling duck (once called the black-bellied tree duck due it its habit of perching on trees/telephone poles) is apparently expanding its range. There are now nesting numbers in both the Upper Texas Coast and the Dallas area. I searched google.com for some additional info, and found
this county map of the Dallas area where black-bellieds have been successfully nesting. I also ran across information from Arkansas' Ouachita National Forest indicating there has been some successful natural nesting there, as well. This
nationwide map, in fact, indicates anywhere in Texas you may have a chance to see these elegant creatures.
Here in San Antonio's northwest side, we see and hear black-bellieds occasionally in the early morning or at dusk -- especially near water, or areas the ducks pass over en route to water.
Thanks for sharing your find! If you want to see black-bellieds up close, a great place to do it is the
San Antonio Zoo. Apparently, word is out among the black-bellied (and other wild bird) populations that the Zoo is
a cool place to be if you're a wild critter looking for attention, free food and some R&R.

In addition to the superb exhibits out there, any given tree in the Zoo usually has some wild egrets, great blue herons, black-crowned night herons or black-bellied whistling ducks roosting in it, as well.