General: White face, neck, breast, and belly. Black legs. Large, thick orange bill. Gonydeal angle is about halfway down the bill from the base. Long, deeply forked tail. Sexes similar.

Adult Alternate: Black cap with spiky crest at rear of head. Pale gray back and upperwings. White rump and tail, often with dark edgings.

Adult Basic: White forehead and crown. Black mask that extends from rear of eye to spiky crest at rear of head. White eye ring in mask. Dark gray outer primaries and tail feathers.

Juvenile: White forehead and crown. Mask similar to adult basic, except color is dark brown instead of black. Pale gray back. Pale legs. Dark brown carpal bar, uppersurface to secondaries, and outer primaries. Gray tail with dark edges. First-year birds usually have dark secondaries and outer primaries; slightly more extensive black mask. Second-year birds are very similar to adults in alternate plumage but often have darker primaries and secondaries; white tips to feathers in black cap. 18-21 inches in length.

Sandy beaches.

Nesting

1-2 buff or whitish colored eggs with brown blotches. The eggs have a 30-31 day incubation period. Fledging occurs in 28-35 days. The nest is an unlined shallow depression in the sand. They nest in large colonies on sandy islands and beaches.