 In 2004, a study of mitochondrial DNA sequences suggested a close relationship between Rapa shearwater ("Puffinus myrtae") and Newell's shearwater and the authors proposed that Rapa shearwater be treated as a subspecies of "P. newelli" pending further study.The Rapa shearwater is now treated as a full species.It breeds in at least 20 colonies on mountain slopes in the Hawaiian Islands.