This is a male. The female has an orange bill and the male has a yellow bill. Females also have broader buff fringes on the body feathers giving them a subtly lighter overall appearance.
The Florida population is now recognized as a separate subspecies (A. f. fulvigula) from the allopatric Texas and Louisiana population (A. f. maculosa). Florida birds have a yellower bill, paler and less distinctly marked plumage. The population breeding in coastal South Carolina was introduced primarily from A. f. maculosa. It is not a natural range extension from Florida.
The Mexican Duck (A. p. diazi) is genetically closer to the Mottled Duck than it is to the Mallard with which it is currently lumped. Current classification is untenable. The main threat to both Mottled and Mexican Ducks is hybridization with feral Mallards.
Nikon P510 Coolpix Point-and-shoot.