Common around Bonin Is and Volcano Is, but small population and less opportunity to see. Also rarely seen N Izu Is.
Breeding sites are confirmed on Higashijima, Bonin Is; at least more than 100 birds, and Minami-Iwo-jima, Volcano Is; estimate 6,000 pairs. Breeds Apr-Nov.
Fig.1. Off Chichijima, Ogasawara. Aug. 31 2022.
Fig.2. Off Mukojima, Ogasawara. Sep. 3 2022.
Fig.3. Off Minami-iwo-to. Jul. 5 2013. Typical individual. Presumed adult; pale gray around the eyes and upperparts are no blackness. This individual is prominent white saddlebags. White saddlebags variable, many birds absent.
Fig.4. Same bird as Fig.3. Slightly striking whitish tips to upperwing covers.
Fig.5. Off Minami-iwo-jima. Jul. 5 2013. Typical individual. Presumed adult. Lacking whitish tips to upperwing covers by worn plumage.
Fig.6. Off Minami-iwo-to. Sep. 9 2013. Presumed adult. Adult birds molt mid-primary and secondary in Sep. In cloudy conditions, upperparts looks dark. This bird absents white saddlebags.
Fig.7. Off Muko-jima. Sep. 7 2014. Presumed adult. Molt as Fig.6. Low-angle sunlight conditions, upperparts looks darkish brown.
Fig.8. Off Minami-iwo-to. Jul. 5 2013. Presumed adult. Some birds have white notch behind cheeks like Manx Shearwater.
Fig.9. Off Minami-iwo-to. Jul. 5 2013. Presumed adult. This bird has small white notch behind cheeks.
Fig.10. Off Minami-iwo-to. Jul. 5 2013. Presumed adult. This bird kind of looks like Wedge-tailed Shearwater.
Fig.12. Off Muko-jima. Sep. 9 2013. Presumed immature. No molting primary in Sep and blackish upperparts (especially wing and tail). Note some birds have large white area behind eyes as this bird, looks like Bryan’s Shearwater face pattarn at long distance.
Fig.13. Off Muko-jima. Sep. 9 2017. Ages unknown (adult?). White face pattern looks like Bryan’s Shearwater, but has big bill and heavily body.
Fig.14. Presumed immature. Same bird as Fig.15-19. Seen 280km east of Minami-Iwo jima, Volcano Islands. Apr 9 2019. This photo shows ’true color’ this bird; paler hindneck and slightly brownish upperparts. Due to low-angle sunlight condition, other photos show blackish upperparts like Tropical Shearwater and Newell’s Shearwater. Immature has blackish upperparts, especially darker head than adult in Apr-May.
Fig.15. Same bird as Fig.14.
Fig.16. Same bird as Fig.14.
Fig.17. Same bird as Fig.14.
Fig.18. Same bird as Fig.14. Pale behind eyes than forehead.
