The Black-bellied Whistling DuckDendrocygna autumnalis, formerly also called Black-bellied Tree Duck, is a whistling duck that breeds from the southernmost United Stated and tropical Central to south-central South America. In the USA, it can be found year-round in parts of southeast Texas (see ComingsBirds.com/Texas).
These were photographed at Cano Negro and Hacienda Solimar.