The whistling heron (Syrigma sibilatrix) is a medium-sized, often terrestrial heron of South America. There are two subspecies, the southern S. s. sibilatrix and the northern S. s. fostersmithi.
The whistling heron measures 53 to 64 cm in length and weighs 521 to 546 g. The southern subspecies is bigger but has a shorter bill in proportion to the body.
The subspecies fostersmithi inhabits the Llanos and the Orinoco basin of Colombia and Venezuela. There are no breeding records “yet” from Colombia.The subspecies sibilatrix inhabits eastern Bolivia, Paraguay, western and southern Brazil, Uruguay, Chile, and northeastern Argentina. Recent records suggest that it may be expanding its range northward and eastward in Brazil. It makes seasonal movements at least in northeastern Venezuela, where it does not occur from November to January, but remains all year in other areas, such as Buenos Aires Province, Argentina. source