日本産鳥類の分類•分布的研究

1. オオアカハラについて

抄録

Check-list of Japanese Birds (1974) follows VAURIE (1955, 1959) in synonymizing Turdus chrysolaus orii YAMASHINA with nominate chrysolaus. Re-examination of materials, including the type and other specimens from the Kurile Islands, has shown that the breeding males of orii, the northern Kurile population (Paramushir, Araido, Matsuwa), can be separated readily from those of nominate chrysolaus from Sakhalin, Hokkaido and Honshu, on account of the very dark coloration of their head. In this subspecies (breeding males) the head and crown is blackish sooty brown in contrast to the olive-brown nape and back, giving an appearance of being black-capped, whereas in nominate chrysolaus the upper parts are more or less uniform olive brown. The wing length and the bill height (but not bill length) of orii are also larger, although the ranges of variation overlap to some extent between the two forms (Figs. 1-2). It therefore seems to me best to retain orii as a distinct subspecies. In females, juveniles and first winter males orii is rather similar to the nominate form, but in males the characteristics of orii may become recognizable in February or March as the wear of the plumage progresses.