||it has long been a practice among ornithologists to study the distribution, variation, and ecological relationships of birds in areas characterized by diverse physiographic features. Such studies are motivated usually by the desire to aid in finding solutions for the many problems concerning the distribution and variation of birds. Following this custom and this objective in mind, the writer has attempted to make a contribution to our knowledge of the birds of western North America in general and those of Utah in particular by selecting the highly diversified southwestern part of the state for an avifaunistic study. The area chosen includes the Pine Valley Mountains, the Beaver Dam Mountains, the Beaver Dam Wash and the valleys of the Santa Clara and Virgin rivers. As such it corresponds essentially with the limits of Washington County, Utah.