The wings and deeply forked tail are long, and it has dark grey upperparts and white underparts.

This bird is migratory and dispersive, wintering more widely through the tropical oceans.

The Atlantic subspecies melanopterus breeds in Mexico, the Caribbean and west Africa; other races occur around the Arabian Peninsula and in Southeast Asia and Australasia, but the exact number of valid subspecies is disputed.

These are the four subspecies listed by the IOC: This species breeds in colonies on rocky islands.

The offering of fish by the male to the female is part of the courtship display.