The squeal of the wood duck (Aixsponsa) is a sound of the swamp. Duck hunters call them "squealers." A male wood duck is one of the more exquisitely colored birds in Louisiana. He is bedecked in iridescent green feathers bordered in white and accented with black trim. A helmet of green feathers adorns his head along with red eyes and a red patch on his upper mandible. This regal head perches on a white-feathered neck fronted with rufous breast feathers. The more sedately colored female has a distinctive tear-shaped white eye patch. Both vocalize with high pitched, rhythmic shrieks when flying. Unlike other kinds of ducks they perch in trees and nest in cavities. Since many large, old-growth trees with cavities have disappeared from southern swamps, wood duck boxes provide good sites for successful reproduction. Black rat snakes (Elapheobsoletaobsoleta) take a toll on wood ducks, because they are expert tree climbers. I have seen a black rat snake systematically searching tree branches and cavities for nests in the swamp. Watch and listen for wood ducks on swamp walks. Also watch for the nonvenomous black rat snakes, for both are part of nature's web in Louisiana swamps.