A large, heavy-bodied seabird (and largest of all terns), with a large head; thick, straight, pointed bill; and shallowly forked tail. The long, pointed wings are broad for a tern. White overall, with pale gray upperwings. From below, the outer primaries in the wing are dark gray. Breeding adults have a black crown; winter adults and juveniles have a partially black crown with grayish speckling. The bill is coral red with a dusky tip. Feet and legs are blackish. https://www.allaboutbirds.org/guide/Caspian_Tern/id