A Chukar, native to Iran/Pakistan region and introduced to the Rocky Mountains of the U.S. This one was in my backyard, Long Island, NY. I can't discount the possibility it is a local domestic bird, but I have never seen any others. No leg band.
Chukars are introduced birds, just like pheasants. They are not what I would consider rare or uncommon. They have adapted quite well and are, I believe, valuable game birds for hunters.