Two individuals (A and B) of the Blue Goose morph of the Lesser Snow Goose Anser caerulescens caerulescens
were observed for the first time in Japan during the 2006/2007 winter. One individual (A) was found on 19 October 2006 at Shimoike, Tsuruoka, Yamagata Prefecture in a flock of Tundra Swans Cygnus columbianus
of a five-bird family. A was afterward observed in Niigata Prefecture from November 2006 to March 2007, and in central Hokkaido from March to April 2007, also among Tundra Swans. A had the typical features of an adult Blue Goose, i.e., white head and upper neck with the lower neck and all underparts dark grey. The other bird (B) was first found at Sarobetsu, Hokkaido, on 27 September 2006, and was observed until 20 October, among flocks of Middendorf's Bean Goose Anser fabalis middendorffii
and White-fronted Goose Anser albifrons
. B was later observed in southern Hokkaido in October 2006, and in Miyagi Prefecture in November 2006, still among Middendorf's Bean Goose and White-fronted Goose. B's features were intermediate between the two morphs, i.e., its flanks and chest as well as its head and neck were white, still within in the limits of variation for Blue Goose. Past records of blue morph Snow Geese in Japan are discussed in detail and it is concluded that the observations during 2006/2007 winter were indeed the first authentic record of the blue morph Lesser Snow Goose in Japan.