This is peak neotropical northbound bird migration season. If stormy weather causes fallout of migrants, this can be epic birdwatching. If it’s smooth sailing for birds heading north, sometimes just a few will stop and rest. Most years it's average, with a variety of migrants but not the diversity you get on epic years. Birds that have overwintered in the Keys head north, including brown and white pelicans, osprey, blue-winged teal, many shorebirds and wading birds.
Sea turtle nesting season starts in April. Greens and loggerheads nest on beaches throughout the Florida Keys.
Peak season for Bartram's Hairstreak Butterflies flying in pine rockland. Sawgrass Skipper Butterflies are active in wetlands.
It is also peak wading bird nesting (reddish egrets, great white herons, Wurdemann’s heron, black-necked stilt). Cuban yellow warblers and prairie warblers are also looking for mates, building nests and raising young along mangrove shorelines and islands. Alligators may be heard bellowing to attract a mate.