It is very difficult to distinguish Vanuatu Petrel from White-necked Petrel except in the vicinity of Vanuatu where breeding ground due to both species features overlap. However, birds with dark bases of under primaries, and looks slightly smaller size recorded several times around Izu Is and Bonin Is, so I post here birds of Vanuatu-type for reference.
Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 2. Same bird as Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 3. Same bird as Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 4. Same bird as Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 5. Same bird as Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 6. Same bird as Fig. 1. Off Chichijima, Bonin Islands, Tokyo. Sep 22 2020.
Fig. 7. Off Kitanoshima, Bonin Islands, Tokyo. Sep. 15 2018.
Fig. 8. Same bird as Fig. 7. Off Kitanoshima, Bonin Islands, Tokyo. Sep. 15 2018.
Fig. 9. Same bird as Fig. 7. Off Kitanoshima, Bonin Islands, Tokyo. Sep. 15 2018.
