Abstract
(1) In order to investigate the subspecies of Bean Geese Anser fabalis wintering in Japan, the points of field identification for A. f. serrirostris and A. f. middendorfi were discussed.
(2) When nearby these two subspecies can be distinguished easily by the shape of the bill. At a distance of 1 km or more (and using a telescope × 25); it is still possible to identify the subspecies by the combination of the following criteria:
a) Length of culmen/length of head _??_1 A. f. middendorfi <1 A. f. serrirostris
b) Length of culmen/bill depth at base _??_2 A. f. middendorfi <2 A. f. serrirostris
c) Difference of voice (and to some extent difference in feeding habitat)
(3) The above method was used in our goose counts at Fukushima-gata, Niigata Pref. and Kasugawa, Miyagi Pref. Sample specimens were also captured in these areas and the results were compared. Both the field identification and the sample specimens indicate that most individuals of the population wintering in Niigata Pref, are A. f. middendorfi and those in Miyagi Pref. are A. f. serrirostris. The close agreement of the results obtained shows that it is possible to identify the subspecies of Bean Geese reliably in the field.
