He is a mallard male about over a year almost 2. She is an Anacona, adult but not quite a year. I have 7 females and one male. They all get time to run free so not penned up and board. Over the weekend, the male has singled out one female to attack and chase off. Other females are fine with him and when I separate him, the attacked female goes back to the group and is fine. Problem is the male. What the heck?