There is one bird that is nearly unmistakable in flight and that is the Turkey vulture. You can tell from three things almost immediately. The first is the white trailing edge along the whole wing edge. There are very few birds with this configuration of white. The other is the "V" profile when you are looking at the bird from the front. most hawks and eagles have a flat profile with just the wing tips curled. The last is the tippy flight and hardly any flapping while they soar in circles catching the thermals.