This plain extending into northeastern Mexico is grassland, savanna and thornscrub habitat, much of which has been converted to more shrubby conditions as a result of grazing history. The very distinctive avifauna of this region includes Audubon's Oriole, Buff-bellied Hummingbird, Long-billed Thrasher, and Plain Chachalaca. Botteri's Sparrow, Attwater's Prairie-Chicken, White-tailed Hawk, and wintering Whooping Crane and LeConte's Sparrows are high priority birds of grassland habitats. Wetlands are habitat for most of the Black-bellied Whistling-Ducks that breed in the United States, a great variety of wading and shorebirds, as well as several wintering waterfowl species.

ABC-designated Globally Important Bird Areas in this BCR

Bentsen-Rio Grande Valley State Park

Falcon Dam

King Ranch

Lower Rio Grande Valley National Wildlife Refuge and Santa Ana National Wildlife Refuge

Sabal Palm Grove Sanctuary