I was at Klamath Basin NWR at the end of last week. Two Canvasback Ducks were about 50 feet apart. One started swimming at a high rate of speed towards the other and they began fighting and biting each other. They were also fighting totally under water at times. Since they were both males I thought it might be a mating or feeding territory fight. Click on link below for photos. Happy Birding, Jim Leonard https://picasaweb.google.com/108302360004365615395/CanvasbackDucksFightingKlamath?authuser=0&authkey=Gv1sRgCOGxs7uhmcS4Ag&feat=directlink