Very observant, Nells250, in fact there are 7 States with cardinals. In the literature that came with the sheet Arthur and Alan Singer explain how this posed a problem as they wanted each state to have an individual stamp. They are the first known father and son team to work on stamp designs: the father did the
birds first and then the son added the flowers.
All of the original paintings were 4 x 8 inches, Arthur Singer knows
birds: in the 1960's he apparently published two books: "
Birds of the world" and "Guide to the
birds of North America".
I think the result was excellent. Here is a small portion of the whole sheet:
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:)