This park is one of the best places in the United States to observe subtropical birds and wildlife that are more commonly found

south in Mexico. Birds from both the eastern and western United States are also found in the area; and during spring migration, the park is especially interesting to birders. Unusual birds include: paraque, groove-billed ani, green kingfisher, blue bunting, black-bellied whistling duck, clay-colored robin, rose-throated becard, tropical parula and masked tityra. The park is also one of the last natural refuges in Texas for cats such as the ocelot and jaguarundi.