Sangan Island Streaked Shearwater and Matsudaira's Storm Petrel Breeding Ground

The streaked shearwater is a long-winged seabird that spends most of its life at sea, coming ashore on islands only to nest in burrows. It returns to its colony at night, making distinctive calls. Breeding colonies on islands from Hokkaido to Okinawa, including Iwate, Niigata, Kyoto, Shimane and Okinawa sites, are mostly designated Natural Monuments.

Swinhoe's Storm Petrel is a small storm petrel, dark brown nearly all over. It feeds at sea on small plankton and fish and comes ashore only to incubate eggs in burrows. Sankanjima in Iwate is known as a site where it breeds together with Streaked Shearwaters, and the colony is designated a Natural Monument.