What is the differnce between a crow and a raven?

Ravens are larger, call is different, tail differs in shape, the heads differ also. Manner in which they fly is significant. Ravens often soaring somewhat like hawks or eagles. While crows flap frequently, with short glides in between flaps. Some ravens found at higher altitudes than most crows. Ravens being somewhat restricted to colder northern areas of the US, as opposed crows being found in many places.

Ravens versus Crows

Within, are embedded hot links to each species

http://www.allaboutbirds.org/page.aspx?pid=2501