In Florida's Everglades, few species are more closely tied to the habitat's health than an endangered bird, the snail kite. Over the past century, as much of their habitat was drained and water stopped flowing through parts of the Everglades, the snail kite population plummeted. It was one of the first birds put on the endangered species list in the 1960s. Droughts contributed to the snail kite's decline and by 2007, there were fewer than 800 remaining. But the kite has bounced back recently thanks to an exotic snail. It's a rare case of an invasive species having a positive impact.
Photos by Sydney Walsh for NPR