Corpus Christi's bays are often crowded with shorebirds and waterfowl, but landbirds and raptors can occur in surprising numbers. Particularly, Hazel Bazemore County Park is famous for its massive hawk migration in September and October. The sky darkens with more hawks than could be counted in a lifetime, species including Broad-winged Hawks and Mississippi Kites. And as such mass migration is usually associated with more social birds, like geese, it's especially astounding to watch. Peregrine Falcons also make a mass-migration in the fall, if they're more likely to number in the hundreds than in the thousands. You can watch them from the Padre Island National Seashore.
Some of the area rarities to watch for are the Sooty Tern, Gray Kingbird, Sulphur-bellied Flycatcher, and the Black-whiskered Vireo (the three latter have been found in Packery Channel Park). Not necessarily rare, but best found in Corpus Christi are the Hooded Merganser and the Common Goldeneye. Other interesting birds include the Black Skimmer, the Groove-billed Ani, the Olive Sparrow, the Couch's Kingbird, the Horned Lark, and the Roseate Spoonbill.