The Common Gallinule and its relative, the Common Moorhen, are the most commonly seen members of the Rail family (Rallidae) around much of the world. Here in the U.S., it's found year-round in the south, including Florida, and spreads throughout the eastern half of the country in the summer breeding season. The red face patch and bill tipped with yellow make it easily identifiable. NOTE: Despite the new name, don't confuse the Common Gallinule with its arguably more gorgeous relative, the Purple Gallinule (Porphyrio martinica).
You might be wondering, who gets to decide what to call a bird, and how do they make that decision? Well, according to its website, the American Ornithologists' Union is "one of the oldest organizations in the world dedicated to the scientific study of birds". As such, it commands a great deal of respect from ornithologists worldwide, and the research it sponsors and produces greatly increases our understanding of the bird world. In a nutshell, if these folks say the American gallinules are a different species than those found in other parts of the world, then there's an awfully good chance they are.
Science is a search for answers, and what we think we know today can be turned on its head tomorrow. So we're willing to be fluid with the names and classifications of plants and animals as new discoveries are made. After all, none of that takes away from the delight of watching these creatures as they pass through My Florida Backyard, and in the end, that's what matters most to us.