The Pacific Lowlands sub-region of the Sonoran Joint Venture extends from northeastern Sonora between the Sonoran Desert and the Sierra Madre Occidental to the coast of northern Sinaloa and continues along the coast to the border of Nayarit. On the eastern boundary it parallels the Pacific slope of the Sierra Madre Occidental at approximately 775 m above sea level. This sub-region includes Bird Conservation Regions 43 and 44.
Habitats in this region are primarily thorn scrub, tropical deciduous forest, and pine-oak forests, crossed by ribbons of riparian vegetation. Mangroves, coastal marine wetlands, shoreline, and other marine habitats are found on the coast. Important breeding bird islands and foraging waters are found offshore.
The area hosts important ecosystems that support an impressive and diverse flora and fauna. Tropical deciduous forests are one of the most endangered communities in the western hemisphere. The region is rich in endemic species, some of which have legal conservation status. Important bird species include Bare-throated Tiger Heron, Peregrine Falcon, West Mexican Chachalaca, Yellow-Breasted Crake, Military Macaw, Sinaloa Martin, Elegant Trogon, Pale-billed Woodpecker, Purplish-backed Jay, Black-capped Vireo, Western Sandpiper, and Snowy Plover.