Peterson, R. T., National Audubon Society., National Wildlife Federation., & Roger Tory Peterson Institute. (1990). A field guide to western birds: A completely new guide to field marks of all species found in North America west of the 100th meridian and north of Mexico (3rd ed., completely rev. and enl.). Boston: Houghton Mifflin.MLA Citation
Peterson, Roger Tory, National Audubon Society, National Wildlife Federation, and Roger Tory Peterson Institute. A Field Guide to Western Birds: A Completely New Guide to Field Marks of All Species Found in North America West of the 100th Meridian and North of Mexico. 3rd ed., completely rev. and enl. Boston: Houghton Mifflin, 1990.