This is quite a stunning piece of portable rock art and looks to be an authentic Native American Indian piece, and a good size too, being over 8 inches. They were copied during the 60's and 70's and perhaps as far back as the 1880's some people claim there is no such thing, but patinas cannot be faked, the patina looks authentic here and I am obviously unwilling to chip the item to be certain. Often called Thunder bird effigies this artifact is also known as a ceremonial eagle effigy. It looks to be made from Burlington Chert which is not unusual for native American Indian art and artifacts. More Modern examples can be see here: 

 Portable Rock Art and Figure Stones vs Native American Indians