Status of Seabirds on Daikoku Island, Hokkaido

The status of seabirds breeding on Daikoku Island, eastern Hokkaido, Japan, was updated. The number of nest burrows of Leach's Storm Petrel Oceanodroma leucorhoa was estimated using nest densities and areas of each habitat in 2014, and was 415,674; about half of the annual population estimates for 1972‒1994. The number of nest burrows of the Rhinoceros Auklet Cerorhinca monocerata was estimated similarly, and was 77,734; about 10 times the estimate for 1986. These population changes were due to changes of both nest density and area of habitats. The number of nests of the Slaty-backed Gull Larus schistisagus was directly counted, and was 5‒30 in 2014‒2018; less than 5% of that recorded annually from 1982‒1994 (3,500‒8,200 pairs). The number of nests of the Japanese Cormorant Phalacrocorax capillatus was counted directly and was 120‒245 in 2014‒2018, except 2016; similar to that seen in 1980‒2015 (172‒321 nests). Disturbance by White-tailed Eagles Haliaeetus albicilla was observed in the colonies of Slaty-backed Gulls and Japanese Cormorants.