No place can more quickly erase a vision of the desert as monotony than Big Bend National Park. From canyon to summit, there's a 6,000-foot range in elevations, and the park's 1,200 square-miles are a labyrinth of arroyos, washes, mesas, cuestas and monoclines.
Less evident, perhaps, is the diversity of living things this landscape supports. But from cacti to butterflies, bats to reptiles, Big Bend's biodiversity shames other national parks.
The most vivid illustration of that biodiversity may be the park's bird life. Big Bend is one of the nation's premier birding destinations. As of summer 2019, 452 species have been documented.
David Larson is the park's chief of science and resource management. And he's a passionate birder.
“If you spend a week here during a certain month in the springtime or even during the summer breeding months – when, you know, it's very hot – in a week you can definitely document 150 species,” Larson said. “You might even be able to get 200-plus.”
Big Bend doesn't lack for dazzling avians. The vermillion flycatcher, radiant red. The painted bunting, in blue, red, yellow and green. The summer tanager. The Scott's oriole. They can be seen elsewhere in the region. But all can be seen of a summer morning along the river, at Rio Grande Village. Larson calls these the “Corvettes of Big Bend.”
But the birder's prize here is – appearance-wise – unremarkable. The Colima warbler is gray-brown, with yellow undertail feathers. Thousand of birders come each year for a sighting.
Many want to record as many species as they can within the United States. Though the warbler is common in Mexico, the Chisos Mountains are the only place here where it nests. Colimas specialize in foraging on oak trees for insects. With 14 oak species, the high Chisos are a pocket of habitat.
The Colima highlights part of what makes Big Bend a birding hotspot.
“Having the Chisos sky island here, it's just that opportunity – you'll get a lot of birds overshooting moving north from Mexico,” Larson said. “The quintessential example of that is the Colima warbler – that's number 1.”
Other birds common to the Mexican Sierras, for which the Chisos are a northern frontier, include the painted redstart, the blue-throated mountaingem – the largest hummingbird in the U.S. – and the Mexican jay. A Mexican jay can live for 20 years in a 300-acre territory in the Chisos.
Near Rio Grande Village, signs direct visitors to a nesting area for common black hawks – another bird at the northern edge of its range.
Diverse landscapes are the key. Colima warblers set up housekeeping above 5,500 feet. Black-capped vireos – listed as endangered until 2018 – thrive between 3,500 and 5,500 feet. The low desert is home to roadrunners and quail. Canoeing the Rio Grande, a birder can sight dozens of species of ducks, herons, grebes, egrets and shorebirds.
Park staff is mindful of this remarkable bird life, and works to support it. There are regular surveys of Colima warbler populations. The park irrigates an area near Rio Grande Village, to provide lush bird habitat.
And broader restoration efforts can benefit birds.
In collaboration with Mexican partners, the park has worked to eradicate giant river cane – the invasive, non-native plant that once lined the river from Mariscal through Boquillas Canyon. It's a boon for paddlers. But if native plants return, it also means bird habitat.
One bird that could benefit is the yellow-billed cuckoo. The western subspecies of the bird – which winters in Central and South America – is listed as threatened.
Yet there are also changes that imperil bird habitat.
In 2011, Texas experienced its worst single-year drought on record. Big Bend forests were decimated – 17 percent of trees in the Chisos died. It's bad news for birds – like the Colima warbler – that are drawn to these woodland outposts. And such intense droughts could be a fixture of a changing climate.
“And if you have 17 percent in one year, and if this happens again the near future – we're going to see some significant changes,” Larson said. “We're probably not going to see Colima warbler blink out anytime soon, but, you can say that there's a potential trend here, that it's going to change the avifauna.”
West Texas is a “wasteland” only to the unitiated. Big Bend's rich bird life is exhibit A. It's a bounty to be savored – and safeguarded.
