The Short-tailed Hawk has both light and dark morphs. They never morph between the two. The dark morph is more numerous in Florida than the light morph. In Florida the only dark buteo that appears regularly is the dark morph Short-tailed Hawk.
We can ID this bird as a dark morph Short-tailed Hawk by its almost completely blackish brown color, its small size (which we estimated to be 15"+-), and the small white patch where the lore and forehead meet.
The Short-tailed Hawk is a new species to our Life List, which now stands at 257.