The refuge, a National Natural Landmark, allows visitors to wander along a remnant of the subtropical woodlands that historically lined the banks of the Rio Grande but were lost due to agricultural development. Located along a strategic flyway that funnels birds migrating to and from Central and South America, the refuge offers 2,088 acres of critical habitat to 400 different types of birds, 300 species of butterflies, and countless other wildlife, including the endangered ocelot.