McALLEN, Texas — Birds care nothing for international borders, but big bodies of water give them pause. The Gulf of Mexico squeezes two major migratory flyways through southern Texas, where the subtropical climate, attractive habitats and plentiful fresh water invite thousands to stay for at least a brief layover before or after they cross the U.S.-Mexico border. And where there are birds, there are bird-watchers. Human visitors flock to the lower Rio Grande Valley to spot the broad-winged hawks, hook-billed kites and more than 500 other avian species that can be found along the river that separates Texas and Mexico. On the American side, the World Birding Center offers nine prime bird-watching sites spread across 120 miles, from Roma on the west to South Padre Island on the east. The center is a collaboration between federal and state conservation offices and local governments. The nine sites include state parks, a grand estate and a simple platform perched above the Rio Grande in a historic border town. The habitats at the sites are diverse, too, with freshwater marshes, coastal wetlands, dry chaparral, riparian woodlands and many other bird-friendly ecosystems. The center’s headquarters is at Bentsen-Rio Grande Valley State Park, near the town of Mission. Bird-watchers and nature-lovers there will find a large interpretive center and miles of trails. Much of the 795 acres is inaccessible by car, but visitors can rent bicycles or hop aboard trams that give rides to distant corners of the park. The park also offers rental binoculars, which can come in handy: More than 300 species of birds have been sighted there. Near the town of Weslaco, another World Birding Center site, Estero Llano Grande State Park, is dotted with ponds often filled with wading birds and other waterfowl. On my visit, I joined several bird-watchers on the park’s large, canopied observation deck. “Have you seen the cinnamon teal?” someone asked me. “I honestly don’t know,” I confessed. I’m not a very knowledgeable birder and I had left my field guide back in the car. But I was content to relax for a bit on the deck next to Ibis Pond, named after a bird I do know and could identify wading right in front of me. Not that anyone asked. A much different World Birding Center stop is Quinta Mazatlan, a historic adobe hacienda and estate near the McAllen International Airport. Although the site is in an urban setting, it attracts plenty of birds to its gardens and nature trails and was one of my favorite World Birding Center destinations. Now owned by the city of McAllen, Quinta Mazatlan would be a must-see destination even if all the birds in Texas went on strike. The grand, 10,000-square-foot hacienda, built by adventurer and publisher Jason Matthews in 1935, is an architectural delight, decorated with beautiful Mexican tilework inside and out, and is one of the largest adobe structures in Texas. The compound is built around a sun-soaked courtyard containing gardens, palms and a large, bridged pond. Inside the hacienda, the vast “Cedar Hall” is built with beams of Lebanon cedar purportedly given by the king of Lebanon in gratitude for Matthews’ assistance in fighting the Ottoman Empire alongside Lawrence of Arabia. Fortunately, plenty of birds were evident on my visit, including several that, though common in the area, I had never identified before: Green jays, clay-colored thrushes, ladder-backed woodpeckers and, most amusingly, chachalacas. These turkeylike wild birds kept darting across the trail like skittish, inebriated chickens. I might not have known what I was seeing, though, if not for naturalist John Brush, who led a bird walk along the nature trails that wind through the estate’s 20 acres of thorn forest. He offered interesting tidbits about avian habits and habitats, making the short hike interesting for even the most casual of bird-watchers. Another World Birding Center site that is fascinating even beyond the birds is the Hidalgo Pumphouse, a former pumping station that once drew water from the Rio Grande for farm irrigation. The big, picturesque building is now a museum and popular venue for wedding photography. It’s also a productive bird-watching site, with nature trails and observation decks built around the now-quiet pumphouse and a canal that connects to the Rio Grande. My last stop was the westernmost, Roma Bluffs Overlook in the small town of Roma. The overlook is built high above the Rio Grande and offers a tremendous view of Ciudad Miguel Aleman, the Mexican city just across the river. Although many bird species can be spotted from the overlook, I didn’t see them. Perhaps I was distracted by watching the vagaries of my own species: Mexican families splashing in the water along the southern bank of the shallow Rio Grande, careful not to go too far; trucks and cars traversing, turtlelike, the short span of Roma’s big international bridge and a gantlet of sniffer-dogs; a U.S. Border Patrol agent fixing the tire on his bicycle in the dusty and eerily quiet Roma town plaza. I wouldn’t be surprised if the chachalacas also enjoy watching us. — Steve Stephens can be reached at firstname.lastname@example.org or on Twitter @SteveStephens.