I guess he was not feeling particularly social. When you can't see the butt color, you can tell male from female by their bills. The females have an orange stripe down the side while the males are solid black.
Gadwalls (Anas strepera)
Anas streperaGadwallDuckwhite rock lakedallas texasspillwaydabbling duckmale gadwallaquatic birdaquaticwater fowlfemale gadwallpreeningswimmingupper spillwaysocialloner