After studying some recent close-up shots of Sharpies and Coopers (some side by side) it is clear that the Cooper has its eyes located closer to the beak. The eyes on a Sharpie are located almost exactly halfay between the beak and the side of its head where the Cooper is about 1/3 of the way over from the beak. Whether this is a key I.D. in the field is debatable as you would need to be fairly close or have a high powered scope and a stationary bird to see this. Overall size is the better I.D. here.

Bryan
Shorleine, Wa.
jennandbryan at msn.com