Hi Adams- I hope this one is less problematic than the White-tailed Hawk!
According to my Princeton Illustrated Checklist "Birds of Southern South America and Antarctica" by M. de la Peņa and M. Rumboll, this is a Yellow-headed Caracara (Milvago chimachima). There's one other caracara in the Milvago genus- the familiar Chimango Caracara.
I like the image. Too bad there's not a bit more detail in the face.
Good call John....looked through my books and could not place this bird although it looked like a Caracara type bird...checked the Yellow Headed and its spot on. LOL on the White Tailed Hawk...image nice, wish it was a little closer, but you have to take what you get some times...Paul