Yeah, it's a mallard. I sometimes see them around here. I've even seen them in my front yard a couple times. I don't know where they come from. They usually come two by two, one male with his bright green head and one female with her dark brown coat.
I've said it before I'm sure, but you could hold some kind of exhibition with these photos of yours. Maybe make a slideshow or set them to some songs that you feel fit.
Or you could even run a small business selling prints!
If I were you I'd set up some kind of portfolio site and get your name out there. That is, if you want. I'm just saying you've trained your eye well and a lot of people are enjoying your work