This rugged terrain has spared old Ashe juniper and oak woodlands from logging and shelters some of the best golden-cheeked warbler habitat. The Brazos tributaries to the north cut only shallow canyons. Here, the refuge foothills ease into savannahs where the open country supports oak shinneries (head-high thickets) vital to the black-capped vireo.
Both endangered songbirds share a common dilemma. They depend on very specialized habitats to make a living, and those places grow fewer by the day in the wake of development and human activity. That's why this refuge has a critical role to play in both preserving and restoring their homes.
Beneath the homes of songbirds lies a mysterious world of caves, rivers and sinkholes called "karst". Over time, naturally acidic water dissolved the limestone and sculpted a labyrinth inhabited by night creatures. Ringtail cats and raccoons retreat into cave entrances for shelter. Cliff chirping frogs and whitethroat slimy salamanders squeeze into moist crevices. Cave crickets and daddy longlegs live within caves, but leave to feed and return. Some spiders, beetles and pseudoscorpions never come out to the light, living all their lives in reclusive darkness. Still deeper lies the Edwards Aquifer, the source of many Central Texas springs and beautiful Hill County rivers. These same rivers eventually flow into the marshes, estuaries and bays along the Texas coast.
But here on the refuge, well above the surface, the deep, clear-water pools are not only important sources of water for wildlife during a drought, they are often the last refuge for the hardy fish that remain. An occasional flash flood will sweep through wiping out much of the vegetation but the standing sycamore, elm, oak and hackberry trees that remain provide important habitat for many wildlife species, including many migratory birds. The refuge harbors 245 bird species for part or all of the year. Almost half are neotropical migratory birds that breed in the U.S. and winter south of the border. Because of its importance to birds, this refuge has been identified as being significant for world bird conservation and officially designated a Globally Important Bird Area. The American Bird Conservancy recognized Balcones Canyonlands NWR as an IBA for its significant role in conserving the golden-cheeked warbler, the black-capped vireo, and their habitats.
Like much of the area, the refuge's roadsides and prairies transform to brilliant wildflower gardens each spring, accenting the emerald, olive and forest green of the Hill Country. The flowers in turn attract a myriad of butterflies. In summer, at least 37 kinds of dragonflies zip across refuge ponds, streams and meadows in hot pursuit of their insect prey.