The
refuge falls at the juncture of the Great Plains and Gulf Coast bioregions.
In addition, the refuge straddles the divide between the Colorado and
Brazos watersheds. Beneath the land lies a mysterious labyrinth of caves.
Add the unusual limestone geology of the Edwards Plateau and it’s
not surprising to find plants and animals adapted to live here and nowhere
else. At least a third of the state’s threatened and endangered
species live or migrate through the area. Balcones Canyonlands National
Wildlife Refuge offers some of the best bird watching and habitat left
in Texas for two endangered songbirds-the Black-capped Vireo and the
Golden-cheeked Warbler. Try stopping at the Doeskin Ranch for a hike
along the Rimrock trail to see Golden-cheeked Warbler country.
Chuck Sexton, Wildlife Biologist at the refuge has written an article on the Balcones Canyonland birds and a description of the refuge from a Naturalist’s point of view. The articles are below.
Well, let's see. There are a zillion "Black-crested" Titmice at Balcones Canyonlands National Wildlife Refuge--so many in fact than John Kelly has jokingly called for renaming this a National Titmouse Refuge. John certainly knows the birds of Balcones Canyonlands better than any other individual; it is from his efforts and from his detailed annotated species list (available from our office) that much of the following information is derived.
Our key species, the Golden-cheeked Warbler and Black-capped Vireo, are happily abundant in suitable habitat. For the vireo, two extensive oak shinneries on the Eckhardt and Gainer tracts and a handful of smaller habitat patches provide enough room for more than 60 territories at latest count. A few more vireos are on private lands within the refuge. We are beginning to create much more habitat for this species, but we don't expect to have that additional habitat on-line for at least two to four years. A patch of shin oak on the Simons tract, which lacked vireos in the refuge's early years (1992-1994), was colonized by 2 males in 1995; 4 males were on territory for all or part of the 1996 nesting season. This is an encouraging sign that our efforts are paying off.
The rugged canyonlands in the central and southern portion of the refuge host one of the largest populations of Golden-cheeked Warblers in the species' range. From the most recent territorial mapping available (1993-1996), we have counted at least 480 Goldencheek territories. At least 200-300 more probably occur on the private ranchlands within the refuge boundary. That's a lot of Goldencheeks! It's not uncommon to find yourself on the rim of one of the canyons, with an extensive band of Texas oaks unfolding along the slope below you, and to have 3 or 4 male Goldencheeks fighting for turf within earshot.
Among its 80 or so breeding species, the refuge hosts some of the easternmost nesting populations of Vermilion Flycatchers, Bushtits, Black-throated Sparrows, and Canyon Towhees. Each of these species is resident on several refuge tracts. Although the refuge lacks much habitat for waterbirds (Common Snipe is rare, and Least Sandpiper hasn't even been recorded yet), it is situated great for raptors. Redtails and Red-shouldered Hawks nest regularly, and there are one or a few Cooper's Hawk pairs nesting. We are finding that several species such as Peregrine Falcons and Mississippi Kites routinely migrate through corridors right over the refuge both northbound and southbound, and we suspect we will eventually see the massive flights of Broad-winged and Swainson's hawks that come through the Hill Country in the fall.
Winter is fun, with its innumerable flocks of sparrows (18 species). One expansive area of wet prairie on the Eckhardt tract is the most reliable place in the Austin area to find lots of LeConte's Sparrows and even a few Sedge Wrens. We will never run out of berries for the vast flocks of wintering robins and waxwings. Happily, we can report that the following species are locally uncommon to rare on the refuge: House Sparrow, Great-tailed Grackle, Starling, and Rock Dove. The bird life of the refuge area is, of course, very dynamic. As we watch the trends of these urban-adapted species (and the ominous specter of increasing Blue Jay populations), we are happy to see Cave Swallows colonizing culverts in the refuge area and flocks of Chestnut-collared Longspurs settling into native grasslands in the winter.
Our list of rarities thus far is short but exciting. Our Travis Audubon neighbors Jean and Seay Nance enticed the super-rare Green Violet-ear to their porch last year, and we take the liberty of claiming it on our bird list! Appearances by such vagrant visitors as Zone-tailed Hawk, Sage Thrasher, and "Gray-headed" Juncos should entice birders to try the refuge area, especially when we are open for public visitation on a regular basis. And if you'd like to get a really good look at "Black-crested" Titmice . . . you know where to come.
If
you can break away from the birdlife at the refuge briefly, you'll find
yourself distracted by an array of natural attractions that typify the
Balcones Canyonlands ecoregion. From the ground up, there is something
of interest for everyone. Start with geology. With an expanse of 750-foot-thick
Cretaceous limestones, you can follow ancient environments as you drive
from near Lake Travis up to the highest point near the north end of the
refuge. Giant Oxitropidocerus ammonite fossils, which are evidence of
the abundance of life in ancient shallow seas, litter the ground over
massive limestones, which today support habitat for the Black-capped Vireo.
On several refuge tracts, those massive limestones are pockmarked with
small sinkholes and caves that provide an environment for very specialized
cave critters. None of the federally listed ones from the Austin area
are known from the refuge, but that in itself is intriguing, given that
we probably have our own set of rare endemic species for the Post Oak
Ridge "faunal area." Collections made in several caves await
examination by species experts.
The plant list for the refuge now includes some 525 species and is being added to all the time. As is typical of the eastern edge of the Edwards Plateau, this flora shows a mixture of eastern, western, and southern influences along with a host of endemic species. You might find yourself in a shaded canyon woodland of Texas oak with Carolina basswood and Arizona walnut. As you step out onto the hot limestone slope, you smell the aroma of damianita under foot and see the blossoms of showy menodora, both of which remind you of your last hike in the Chisos Mountains of Big Bend. Back in the shade of the wooded canyon, eastern columbines drape from the moist limestone boulders.
Discovery
is a big part of the intrigue of the refuge, even in a well-studied area
like Travis County with a long and distinguished history of natural history
investigation. As I searched for warblers and vireos back in 1989 on an
isolated ranch on Post Oak Ridge, I came across an unfamiliar shrub. The
same shrub had caught the eye of biologists Rex Wahl and Carol Beardmore
up at Fort Hood just weeks earlier. It turned out to be new to science.
It was hard to imagine how botanists had missed this large and conspicuous
shrub, except by the isolation of the canyons in which it occurs. "Texabama
croton" is now known to be an abundant understory shrub in rugged
canyons in the center of the refuge. It has high horticultural potential.
Although we have compiled the beginnings of checklists of the butterflies, fish, amphibians, reptiles, and mammals at the refuge, these groups remain woefully understudied. We know, for instance, that monarchs can be incredibly abundant over the ridges and at flowering plants in early October, but we don't yet know if the diversity of butterflies year-round can match that found in well-studied areas such as Barton Creek. Rattlesnakes are a regular resident (and hazard) in the vireos' oak shinnery habitat, but we have only slowly added other less conspicuous reptiles and amphibians to the refuge lists as staff and researchers encounter them. How much of an impact are the abundant fire ants having on our "herpetofauna"? We have no idea at present. We have yet to find a Texas horned lizard or a box turtle on the refuge, species that may be particularly susceptible to fire ants.
We presume we have a diversity of small mammals on the refuge, but the threat of hantavirus infection has deterred us from doing intensive mammal surveys without special safety precautions. And what about bats? Bat Conservation International, are you listening? We'd like to know much more about what we have. From ringtails to white-tailed deer, porcupines to predators, we are gradually accumulating data on the medium-sized and large mammals. We've heard rumors for years of the possible occurrence of mountain lions in the region; with that species apparently increasing in many parts of Texas, we would not be surprised to see an increasing number of reports.
Providing a balanced and healthy ecosystem for a full array of Hill Country wildlife is a fundamental mission of the national wildlife refuge system. For the most part, Balcones Canyonlands National Wildlife Refuge has just that, and we hope that it will only improve with time.
