Brewster County is the largest county in the State of Texas and comprises what has long been known as the "Big Bend" of Texas, where the Rio Grande changes course to head northeast. Located in the northeastern portion of the vast Chihuahuan Desert, elevations in the Big Bend range from 7,835 ft. (Emory Peak in the Chisos Mountains) to about 1,500 ft. where the Rio Grande exits the county at its southeastern corner.
Overall the Chihuahuan Desert ecological region covers approximately 243,000 square miles with about 65% occurring below the United States border in Mexico. The Chihuahuan Desert is considered a grassland type desert, one that is broken by high plateaus and islands of mountains containing vastly different habitats. Perhaps more than any other factor, changes in elevation dictate changes in climate, which results in changes in habitat. It is this diversity of habitats that contributes to one of the most diverse avifaunas of any region of the country. Over 500 species of birds have been observed within the Texas portion of the ecosystem. For those interested in obtaining a comprehensive listing of these species along with detailed occurrence and status information refer to Birds of the Trans-Pecos, a field checklist, published by Texas Parks and Wildlife Department (Bryan 2002).
As stated above the climate of the region varies with topography. Average annual rainfall can be as low as five inches in the lower desert but over fifteen inches in the Chisos Mountains. About 75% of rainfall occurs during the annual monsoon season, which can begin as early as late June but typically is over by the first part of September. A variety of habitats cloaks the landscape in a mosaic pattern dictated by elevation as stated above and in part by geology. Within Brewster County these habitats range from, but are not limited to, desert-scrub, arid canyons, oak-juniper woodlands, pine-oak woodlands, lush riparian woodlands (cottonwood-willow), altered riparian woodlands (salt cedar), desert and plateau grasslands, and cienegas (desert springs).
Note that the Rio Grande riparian habitat is one of the most disturbed habitats along the trail. Where exotic salt cedar thickets now occur, native cane thickets historically lined the floodplain, in some places covering hundreds of yards of streamside bank. Most of the large stands of cottonwoods, once a part of that riparian zone, are now gone as well, only scattered mature trees remaining except in a few locations such as Rio Grande Village and Cottonwood Campground.
The geology of the region is dominated by that resulting from volcanic activity which ended approximately thirty million years ago.
The Chisos Mountains are a prime example as they were formed by volcanic activities and are extinct volcanoes. Most of the rocks, soils and sediments you will see are igneous in nature. Examples of limestone geology (sedimentary deposits) do exist along the trail, in the foothills of the Chisos Mountains, in the riverside escarpment at Santa Elena Canyon, and in the hills and mountains surrounding Black Gap Wildlife Management Area. Also the Glass Mountains of northern Brewster County are entirely sedimentary having been formed from the same coral reef that eventually formed the Guadalupe Mountains near Texas’ border with New Mexico.
For persons desiring to visit the region some precautions are advised. These would include:
- Plan ahead and make sure you have plenty of provisions; food, supplies, water, gas and other commodities are only found at the major communities.
- Watch the weather; a sunny day can turn into a raging flood by afternoon; the heat of summer can be deadly; always were appropriate clothing that includes a hat.
- Don’t expect cell phone coverage except around the major communities such as at Alpine and Marathon.
- Beware things that sting, bite, stick, and prick; such is the nature of desert inhabitants.
- Respect private property; when in doubt about ownership—DO NOT ENTER.
- Always obtain permits for entry where required.
The Big Bend Birding Trail offers unique opportunities for a quality birding experience in the Trans-Pecos Region of Texas and the Chihuahuan Desert. Since the majority of this trail passes through Big Bend National Park, more public lands are available along this trail to pursue birds than for most other suggested trail offerings.
Enjoy the broad, scenic views and be sure to take a camera and seize the multiple opportunities to photograph these spectacular landscapes along the trail. If you encounter rare or accidental species along the trail, please attempt to document them with photographs and/or tape recordings and share you observations with other birders.
The Texas Bird Records Committee of the Texas Ornithological Society is interested in reviewing and obtaining copies of any existing documentation concerning these observations; for details refer to www.texasbirds.org.
List of Suggested Birding Sites
Big Bend National Park
a. Old Maverick Road
b. Santa Elena Canyon
c. Cottonwood Campground
d. Ross Maxwell Drive
e. The Chisos Mountains
f. Pine Canyon
g. Rio Grande Village
2. Black Gap Wildlife Management Area
3. Post Peña Colorado Park
4. The Marathon Plateau
The Big Bend Birding Itinerary was researched and written by the Rio Grande Institute, and is used with the Institute's permission by the Texas Mountain Trail.