Waterfowl crossbreed more often than any other family of birds. Scientists have recorded more than 400 hybrid combinations among waterfowl species. Mallards crossbreed with nearly 50 other species, and wood ducks hybridize with a surprising 26 other species. Nearly 20 percent of waterfowl hybrid offspring are capable of reproducing.
In North America, one of the most common wild hybrids results from mallard/pintail breeding. Mallards also commonly crossbreed with black ducks, wigeon, shovelers, cinnamon teal, green-winged teal, and gadwalls. Ducks Unlimited