What does the Raven(bird) symbolism in 18th century art?

It really depends on what area you’re looking at, but for centuries the raven was mostly viewed as a ill omen. During the 18th century (by the way, did you mean the 18th century as in the 1700’s or the 1800’s, lots of people get confused) ravens were attached a great deal of importance by England and the Tower of London. For once Wikipedia has a good article about it, with several links at the bottom.

http://en.wikipedia.org/wiki/Cultural_depictions_of_ravens

http://www.equinoxjournals.com/index.php/pom/article/view/3325

http://www.guardian.co.uk/uk/2004/nov/15/britishidentity.artsandhumanities

The Symbolism of Birds