A classical Old English style drop cap letter C surrounded by leaves and curlicues. This great vintage fancy letter C looks more like a rubber stamp than an illustration.
This is one of those wonderful stock publisher images. In this case it was used by Claxton, Remsen & Haffelfinger and William D Baker (Engraver) in Cecil’s Book of Birds from 1869.
This image is copyright free and in the public domain anywhere that extends copyrights 70 years after death or at least 120 years after publication when the original illustrator is unknown.