Texas birdlife is strongly influenced by the incredible diversity of habitats found within its borders. The Rio Grande corridor is a great example of this diversity. From El Paso to Brownsville, this once-majestic river forms the 1,569-mile southern and western borders of Texas. At El Paso, the average rainfall is only nine inches per year compared to the 26-inch annual rainfall ofthe subtropical Lower Rio Grande Valley. In between can be found the magnificent Chihuahuan Desert with its mountain islands, the Stockton and Edwards Plateaus, and the brush-covered plains of South Texas.