Abstract
Number of Spectacled Guillemot Cepphus carbo around Teuri Island, Hokkaido, Japan were counted by boat and land-based surveys from 1994 to 2014. The numbers showed marked seasonal differences with the maximum occurring in the pre-laying period. Estimated annual maxima, incorporating this seasonal change, decreased 9.6% ± 1.7% per annum from 1985 to 1995, while counted annual maxima increased 9.7% ± 1.6% per annum from 2004 to 2014, though numbers were fewer than in the 1980s. The number of active nests was 118 in 2013 and 169 in 2014, and was 0.31-0.34 of the maximum number.
