Pincoya Storm-Petrel is one of the least known members of the family. It is reported only from at-sea observations, of both adults and juveniles, from a small area in south central Chile, near Chiloe Island. Pincoya Storm-Petrel is suspected to breed in the Chiloe region, but it is possible that its nesting sites are farther inland and at higher elevations. Pincoya Storm-Petrel is very similar to the other species in the genus, Wilson's Storm-Petrel (O. oceanicus chilensis) and Elliot's Storm-Petrel (O. gracilis), and the identification criteria that distinguish these three species still are being refined. On current evidence, Pincoya Storm-Petrel has a white belly patch, like Elliot's, but differs from both Wilson's and Elliot's by having a much bolder, whiter bar across the upper surface of the wing, and with more white on the vanes of the outer rectrices. The total population of Pincoya Storm-Petrel is estimated to be as few as 3000 individuals.