I'm new to this site, but I have a dilemma. I have a male and female mallard that are about 2 and a half years old. The female laid eggs last year, but not this year. In the past month or so she has changed dramatically in appearance. She now looks like a young male. Her color has changed, she now has the white ring around her neck and her head is turning green. Other than her appearance, her behavior is completely normal. There is no chance that it is a different duck or anything like that either. What's going on with her? Is this common?