Marana, and all of Southern Arizona is a birding hotspot. Its location at the intersection of several migratory routes and habitat types give it a high level of biodiversity. Located along the Santa Cruz River in the shadows of the Tucson Mountains, the El Rio Preserve is one of Southern Arizona's top locations to witness a wide variety of bird species.
The El Rio Preserve protects 104 acres of riparian habitat along the Santa Cruz River. The banks of the Santa Cruz were lined by lush, green, riparian ecosystems for thousands of years, and supported a wide diversity of plant and animal life, including human agriculture. Due to large-scale diversions for irrigation, the once-free-flowing river was transformed into an intermittent stream. The riparian habitat has been restored at the El Rio Preserve, as a result of treated effluent being re-routed into the preserve maintaining its lake year-round.