These creatures are called Frigate birds. They are swarming around the carcass of a stingray trying to get their fair share. I think this shot is reminiscent of The Birds by Alfred Hitchcock. These birds are very interesting. Despite the fact they feed mostly on fish, they cannot swim or take off from flat surfaces. They catch fish by flying low to the water and scooping them up from the surface. They can actually fly for more than a week at a time.