First, notice the lettering, such as "Drawn from Nature by J.J.
Audubon", and "Lithographed, Printed & Colored by J.T.Bowen" toward the
bottom of the print. These will appear in block lettering for plates 1 - 150,
and plates 186 - 189. The lettering will be in italics for plates 151 - 186
and 190 - 500.
For plates 136 - 150 the lithography is attributed to Endicott,
instead of Bowen.