These are large to very large seabirds, with long, tapered bodies, long, angular, pointed wings, pointed tails and dagger-like, pointed bills.
They feed by diving into the sea for fish. Only one species is regularly seen in the UK but a few other kinds are found, mostly in tropical seas, around the world.
Most are largely white, with black on the wings, but one species is mostly dark brown. They breed in colonies on cliffs and islands, some tropical species nesting in trees.