Dark brown, fork-tailed seabird of the northwestern and central Pacific, where it breeds on Japanese and Hawaiian islands. Generally forages far offshore and does not associate with boats. Dark chocolate-brown overall with prominent pale carpal bars. In optimal light, rump is slightly paler than the plumage of the back and tail, unlike in Markham’s and Leach’s Storm-Petrels; in fresh plumage, note gray sheen to head and back. Lacks the distinctively pale primary shafts of Matsudaira's and Swinhoe’s Storm-Petrels.