Handsome small seabird of Humboldt Current; not seen from shore, but breeds inland in Atacama Desert where it visits colonies at night to avoid predators. Plumage unlike all other storm-petrels, with black cap and collar, and white underparts contrasting with dark underwings. Upperparts also striking, with black cap, strong upperwing pattern, and gray tail (no contrasting white rump). Larger than most storm-petrels in its range, but size similar to Markham’s and Black Storm-Petrels, with which it readily associates.