The following is a short list of the reference books we use to identify birds in the wild and learn about their habits.
National Geographic "Field Guide to the Birds or North America", fifth edition
National Geographic "Complete Birds of North America"
"A photographic Guide to North American Raptors" by Brian K. Wheeler & William S. Clark
"Birds of Prey in the American West" by Richard L. Glinski
"Hawks from Every Angle How to Identify Raptors in Flight" by Jerry Liguori
"Raptors of North America National History and Conservation" by Noel and Helen Snyder
"Raptors of Western North America" by Brian K. Wheeler