That's Discovery Island. It closed in 1999. My AP Environmental Science Class was the last group to tour the island. They had some birds and other small animals there, wildlife education presentations. I don't think the island is used anymore.
We went there when our kids where little . Trails to walk and look at birds, it was a nice break. When we went there was no MGM or AK so we looked for more to do. We have pic's of the kids there! Time goes to fast!