WE walked slowly down the park road, scanning the trees for the rare Altamira oriole. Overhead, great-tailed grackles sailed from tree to tree, sending up a racket that sounded like the soundtrack for a Hollywood jungle movie. Sliced oranges and bright-red oriole feeders, set up to attract the orange and black Altamira, dotted campsites.
Suddenly my wife caught sight of some movement in the roadside underbrush. We grabbed our binoculars, and were rewarded with our first-ever sighting of chachalacas, a pale-gray, pheasant-sized fowl unique to the Rio Grande Valley.
Birding is not everyone's idea of the way to spend a vacation. My father-in-law insists that when he was a child in rural Michigan, there were only two kinds of birds: robins and sparrows. He jokes that he still hunts for the elusive brown-crusted bread-wrapper.
If you're a birder, however, the Rio Grande Valley of south Texas is not to be missed. Many species, especially waterfowl, winter here, but others unique to the area can be found year-round. The bird life of the Lone Star State is so different from the rest of the United States that special bird guides dealing just with our feathered friends in Texas are available.
The ''Valley'' is not really a valley at all, but the former Rio Grande delta. Construction of the Falcon Dam in 1953 greatly reduced the flow of the river downstream and dried up many small ponds and oxbows.
My wife and I traveled to the Valley to visit my parents, who have spent some time there each of the last three winters. But just to visit the area's wildlife refuges and parks would have been worth the trip: We saw an incredible number of bird species for the first time.
If you're new to birding, you'll need a good pair of binoculars, clothing suitable for the day, and a bird guide. The best guides are those by Roger Tory Peterson, the Golden Books Guide, or one published by the Audubon Society. At least one of these can be found in major bookstores; be sure you have a guide that covers the region you intend to visit.
All these guides contain tips on how to identify birds and have maps that show where the birds are most likely to be located during summer and winter. A good way to start birding is to go on a walk with a knowledgeable guide who can spot different species and tell you what to look for. Experienced birders often purchase spotting scopes and tripods to get a better look than ordinary binoculars can give.
Our first outing on this trip was to the Laguna Atascosa National Wildlife Refuge, north and west of South Padre Island on the Gulf coast. Several large fresh- and salt-water lakes provide winter habitat for 80 percent of North America's redhead ducks.
On the way to the refuge, driving past fields of sugar cane and pastures dotted with yucca and prickly pear cactus, we screeched the car to a halt when we saw three Harris's hawks sitting like swallows on a telephone line and a bright yellow and black Kiskadee flycatcher sitting on a fence post.
We drove to another observation point, where we simultaneously watched a great blue heron, a little blue heron, a reddish egret, a Louisiana (or tricolor) heron, a common egret, and a snowy egret.
Visitors should be sure to include the 15-mile drive in the refuge along shallow Laguna Atascosa, which separates South Padre Island from the mainland. This provides spectacular views of rafts of white pelicans, while herons seem to be everywhere.
Chances of seeing one are slim, but the refuge is also home to several wild cats, including the rare jaguarundi, a small feline that's right at home in the refuge's briar thickets.
Within an hour's drive upriver, southeast of McAllen, the Santa Ana National Wildlife Refuge sits on a narrow strip of land between cotton fields and the Rio Grande. The area is agriculturally rich: oranges, grapefruit, sugar cane, onions, beets, and aloe vera are significant crops.
In the peak winter season, roughly from January through March, visitors can take a tram ride along the refuge's scenic drive. During the rest of the year, visitors can drive their own car down the narrow road. Several trails provide access to ponds, lakes, and the river, and observation blinds and platforms allow for leisurely birding.
We spotted the chachalaca farther upriver at Bentsen State Park, west of McAllen. The park also is home for a multitude of native doves. We didn't find an Altamira oriole until one flew across the road and perched in a tree just as we had given up and were driving away.
If you don't want to spend every minute birding, don't despair. The Brownsville Zoo has several exhibits featuring rare and endangered mammals and reptiles. History buffs should travel north to the Palo Alto battlefield memorial, which commemorates the beginning of the Mexican War in 1846 and now stands for Mexican-American friendship.
Drive to Los Ebanos, named after the area's abundant ebony trees, and you can see the only hand-pulled ferry on a US border.
A day trip to Mexico provides another world of sights and smells. We parked the car in Hidalgo, Texas, and walked across the bridge to Reynosa. If you're interested in sampling the local handicrafts and clothing, a pedestrian street and indoor market provide ample opportunities. US citizens should have no difficulty with immigration on either side; other nationals need documentation in both directions and should check with US and Mexican authorities before making the trip.
Finally, if the beach beckons, South Padre Island has sand and sun aplenty. The climate in the Rio Grande Valley is near tropical; however, temperatures occasionally drop to freezing in midwinter and are hot and humid in summer. The Brownsville, Harlingen, and McAllen airports can be reached via Dallas or Houston. Most major hotel chains are represented; reservations are a must.