Oceanites gracilis occupies tropical waters of the eastern Pacific Ocean, where it is numerous (Spear and Ainley 2007). The only breeding sites known are for the subspecies gracilis. Prior to 2003, only one nest had ever been found, on Isla Chungungo, Chile (where rats and fire may have caused a decline). During surveys of the island in 2002, three crevices containing perhaps 11 nests were located in the north-east part of the island (Hertel and Torres-Mura 2003). Suitable sites are limited on the island, and alternative sites may be too disturbed by nesting Humboldt Penguins Spheniscus humboldti (Hertel and Torres-Mura 2003). No evidence of rodents or marsupials was found, although the presence of the Short-tailed Snake Tachymenis chilensis may be cause for concern (Hertel and Torres-Mura 2003). Other sites inland in the Atacama Desert (Chile) include a mummified chick found in a crevice at one location (recent DNA analysis has confirmed it to be O. gracilis) and further signs of former activity in many cavities. No live birds have been found despite searches at different times of the year (Schmitt et al. 2015). It is highly likely that O. g. gracilis also breeds in Peru, where it is commonly seen at sea, for example around the islands off Callao, but no breeding site has been found there.          

A breeding population (subspecies galapagoensis) is suspected for the Galápagos, Ecuador. Although commonly seen throughout the archipelago and seemingly numerous, re-sightings of banded birds suggest localized populations with indication of limited overlap in spatial use during breeding season. While common, it is possibly not as populous as it might appear from regular observations of flocks at cruise boat anchorages, of birds following vessels, or of birds in open sea between islands where they are observed feeding over dead marine mammals, dumped organic waste, or around fishing vessels (C. Gaskin in litt. 2016). The population on Galápagos appears to be mostly resident; populations from Peru and Chile appear to move further offshore during post-breeding (Spear and Ainley 2007).