Learn about the ecosystems and the early residents of Weedon Island Preserve while hiking the coastal uplands and the boardwalks through mangrove forests. Best for ages 6 and older. 9 to 11 a.m. Free; advance registration required. Weedon Island Preserve, 1800 Weedon Drive NE, St. Petersburg. (727) 453-6500; www.weedonislandpreserve.org.