Prairie Falcon (Falco mexicanus) 16" long, WS 40"
This rather large bird of prey resembles the Peregrine Falcon but is lighter in color. Typically found in fairly dry, open country--grasslands and desert. It often perches on rocks, fence posts or utility poles when it scans for prey; it feeds mainly on small birds and mammals and tends to focus on abundant and easily caught prey species. It also eats large insects.
Alderfer, Jonathan (ed.). National Geographic Field Guide to Birds: Arizona/New Mexico . Washington, D.C.: National Geographic, 2006. This handy, really pocket-size (4x6) guide includes most of the birds you're likely to see in Arizona. In addition to a photo, it includes information about behavior, habitat and specific local sites where you are likely to find the bird.