1966 年 4 巻 5 号 p. 378-383
In February, 1963, April, 1964 and April, 1965, the "Umitaka Maru" of the Tokyo University of Fisheries, cruised around Kusagaki-jima lying about 65 miles WSW of Sata Misaki, Kagoshima Prefecture.
Flying Brown Boobies were seen as far as approximately 60 miles from the islands, and the number increased as the ship approached the islands. In April, 1965, downy chicks were found by powerful binoculars on the ledges of cliffs, some of them with the adults.
When the ship approached Sumisu-to Island lying about 30 miles SSE of Bayonnaise Rocks on August 3, 1965 on her cruise southwards, some Brown Boobies were sighted near the island. The individuals of this species were also seen on ledges of the ridge of island. Other tropical or subtropical species, such as Sooty Tern Sterna fuscata, probably Common Noddy Anous stolidus, as well as Bonin Gadfly Petrel Pterodoma hypoleuca, were sometimes in sight in the vicinity.
Conclusively, the observations suggest that the Brown Booby ranges as far north as the above islands, forming the northernmost limit of its breeding range in the North-west Pacific Ocean.