South Padre Island has a good handful of birds that other Texas sites just don't share. Some of them may be best seen by boat, as they don't always linger near the shore. A walk along the less developed areas of the island, though, will often reveal more accessible species, often very rare. Look out for Peregrine Falcons.
The Laguna Madre Nature Trail is particularly good spot to watch shore-bound birds, or, we should say, marsh-bound birds. Six species of rails gather here, among them the Clapper, the Yellow, and the Virginia rail, largely in the winter. Isla Blanca County Park has its share of waterfowl and shorebirds, but is also the place to cast off to search for the true seabirds, the Magnificent Frigatebird, the Northern Gannet, as well as Cory's Shearwater and the Bridled Tern.