Thanks BB and Loupey.

BB, I have read that the change in color is often caused by staining. The cranes beaks get dirty from digging in the mud for food, and when they prean, the mud from their beaks stains their feathers.

Loupey, I will check on the file sizes when I get home, and report back. The reason I stitched these together was because at 500mm I couldn't get the whole bird in the frame. When I went to a wider focal length, to get the entire crane in the shot, it appeared smaller than I wanted.