Joe, et al, The books I use to supplement the "Geo Guide" are specific to groups of birds. Sparrows, I use James Risings guide, and I dont know the exact title, but something about a "Guide to the Sparrows of North America." Gulls I use PJ Grant's "Gulls." Hawks, I like three. The Peterson series guide by Clark and Wheeler. The "Photographic Guide to North American Raptors" (title is something close to that) by Wheeler and Clark. Then "Hawks in FlighT" by Dunne, Sibley, and Sutton. Hope this is some help. Todd Day Jeffersonton, VA BlkVulture@aol.com