Del Rio, pressed up next to Lake Amistad, the Rio Grande, and the Mexican border, has borderland and riverland birds a-plenty. Although some birds are common to Texas as a whole, Del Rio has a number of Mexican birds, such as the Tropical Parula and Rufous-capped Warbler, from time to time. The rare Black-capped Vireo thrives here.
Oddly, Del Rio plays host to a number of eastern species as well, such as Chuck-will's-widow, Carolina Wren, and the Indigo Bunting. Other exciting (if not eastern) finds are the Zone-tailed Hawk and the Burrowing Owl, and the cane bed in Rio Bravo Nature Center allows for the Black Phoebe, the Audubon's Oriole, and the White-collared Seedeater. And the birds that any birder can expect to run across are the Spotted and Canyon Towhee, the Great Kiskadee, the Verdin, the Rock Wren, and the Yellow-rumped Warbler.
One would expect Lake Amistad to have mostly waterfowl for the birder, but this is desert country. You'll find desert sparrows like the Cassin's, Field, Vesper, and the Black-Throated Sparrows, and the Pyrrhuloxia and Say's Pheobe also occupy the land near the desert shores. The real "attraction," though, is the Interior Least Tern (an endangered subspecies), which rests here from April into the late summer. Colima Warblers, Golden-cheeked Warblers, and Black-capped Vireos are also findable, if you're lucky. On the lake itself, the Blue-winged Teal winters, as do other waterfowl.