This is the northern terminus of the Sierra Madre Occidental. In the United States it is made up of isolated mountain ranges in southeast Arizona and southwest New Mexico as well as the more northerly forested Mogollon Rim. Of the many landbirds more typical of Mexico that extend into the United States in this region, highest priorities include the Red-faced Warbler, Strickland's Woodpecker, and Montezuma Quail. Riparian areas in lowlands support many in-transit migrants as well as breeding Thick-billed Kingbirds, Western Yellow-billed Cuckoos, and Southwestern Willow Flycatcher. Most uplands are publicly owned, but lower elevation grasslands and riparian habitat are subject to development and conversion.

ABC-designated Globally Important Bird Areas in this BCR

Anza-Borrego Desert State Park

Bill Williams River National Wildlife Refuge (Lower Colorado River)

Buenos Aires National Wildlife Refuge

Butterbredt Spring Wildlife Sanctuary

Cabeza Prieta National Wildlife Refuge and Organ Pipe National Monument

Cibola National Wildlife Refuge (Lower Colorado River)

Havasu National Wildlife Refuge (Lower Colorado River)

Imperial National Wildlife Refuge (Lower Colorado River)

Joshua Tree National Park

Madera Canyon

Mojave National Preserve

Otay Sweetwater and Vernal Pools Unit (San Diego National Wildlife Refuge Complex)

Salton Sea

San Bernadino National Forest

Upper Newport Bay Regional Park and Ecological Reserve

Vandenberg Air Force Base