English Name : Arctic Warbler
Scientific Name : Phylloscopus borealis
Two races are said to have been recorded in Japan: ssp. xanthodryas that breeds in Honshu, Shikoku and Kyushu; and the nominate ssp. borealis that is thought to occur mainly as a migrant (OSJ 2000), but may well be present as a breeding bird in Eastern Hokkaido.
Two types of songs are observed in Japan. One is a repeated quadruple 'chori-chori,
chori-chori', which can be heard in high elevation coniferous forests of
Honshu, Shikoku, and Kyushu. This song belongs to the migrant breeding
ssp. xanthodryas. The other type is a repeated triple 'ji-ji-ro, ji-ji-ro', which is heard
during migration season (especially in late May and early June). This song
was earlier attributed to the nominate subspecies.
Three ssp: xanthodryas, examinandus and borealis was already recorded in Japan before the Second World War (Hachisuka et al. 1932, Yamashina 1941). Xanthodryas's song ('chori-chori' type) was also well-known in Japan.
Takio Nagara, in Ishikawa Prefecture, however, had noticed another type
(i.e. 'ji-ji-ro') of song which ware heard in early June. As he didn't
know it belongs to which ssp.., so he asked Jicyou Ishizawa by letter.
Furthermore he sent the specimens collected in oct. 1961 and May 1963 to
Jicyou Ishizawa.
Jicyou Ishizawa had known that ssp. examinandus was passed along the coast of the Japan Sea, while ssp. borealis had not collected in the area in spring. Therefore, he actually expect
that the 'ji-ji-ro' type song belongs to ssp. examinandus, before he saw the specimens.
Jicyou Ishizawa investigated specimens collected by Takio Nagara, and surprisingly, he identified it as ssp. borealis. He tought only the results of identification to Takio Nagara, without
the details. After Ishizawa's suggestion, Nagara sent parsonal papers which
was written about Ishizawa's identification, to some ornithologists and
birders. Therefore, authors of subsequent ornithology books ascribed this
type of song to ssp. borealis. It is still obsure why Ishizawa identified 'ji-ji-ro'type specimens collected
by Nagara as ssp. borealis. And the specimens have disappeared.
This, however, might be wrong. When listening to recordings of the nominate subspecies from Europe, we notice that the song is rather a 'ziririri......' like thrill, unlike the song that had been attributed to the nominate ssp. in Japan.
Current research suggests that the 'ji-ji-ro' song is attributable to ssp.
examinandus, distributed mainly in Kamchatka, Russia. But this race is now thought
to be synonymous with ssp. xanthodryas. Furthermore, other populations of unknown ssp. seem to use the same type of song.
The anatomical and molecular (DNA) characteristics, vocalizations and distribution
patterns of various Arctic Warbler populations are currently investigated
by young Japanese ornithologists - Takema Saito, Isao Nishiumi, Haruo Kuroda
et al.. - to clarify the picture. Ssp. xanthodryas and ssp. examinandus are very similar to each other in the coloriations and the morphs. Molecular
data , however, suggests that both ssp. are very different with each other
as the separated species.
The subspecific complexity of this species is detailed in the Japanese version of this page. I'll intend to include the English translation in the future.
The lower photos are probably that of birds of the 'ji-ji-ro' type of song (I heard some of them). Their exact subspecific status is obscure. These birds probably belong to one of the "island forms' (populations breeding on the islands of Japan as well as on Sakhalin and Kamchatka) and are definitely not one of the 'continental forms' (ssp. borealis, ssp. kennicotti).
 |
1. 3rd Jun 2002 Wajima-shi, Ishikawa Prefecture Note the lack of contrast of colours between the top of the head and the mantle. The green colour of the mantle is duller than on Eastern Crowned warbler, but is more intense than that of the Sakhalin warbler. The primary projection is as long as the tertials. The primary projection seems to be longer than in ssp. borealis and, kennicotti. The one or two wing bars are rather thin, and are indistinct in worn plumage. Arctic Warbler is the largest Japanese Warbler with strong bill and legs. |
 |
2. 5th Jun 2003 Wajima-shi, Ishikawa Prefecture Note the dark tip on the lower mandible. Call is "Dzi" or "Dzri", but in one population it might sound like "vi". |
 |
3. 4th Jun 2003 Wajima-shi, Ishikawa Prefecture A dead bird on the ground. The dark lower mandible has a yellowish edge. The bill of the 'Japanese' Arctic Warbler is longer and thicker than that of the continental races. |
 |
4. 4th Jun 2003 Wajima-shi, Ishikawa Prefecture The same bird as on picture No.3. Males seem to have blackish lower mandibles, while females seem to have brownish lower mandibles. |
 |
5. 4th Jun 2003 Wajima-shi, Ishikawa Prefecture The same bird as on picture No.3. The bird's first primary is as long as the longest primary coverts. Based on Yamashina's data (1941), this bird either belongs to the nominate race or ssp. examinandus, but not to the race xanthodryas. The length of the first primary of ssp. xanthodryas is supposed to be 2 or 3 mm longer than the longest primary coverts. But based on the recent survey, this description seems to be wrong. |
 |
6. 4th Jun 2003 Wajima-shi, Ishikawa Prefecture The same bird as on picture No.3. The bird has strong brownish legs. |
 |
7. 26th May 1998 Wajima-shi, Ishikawa Prefecture The same bird as on picture No.3. The bird with opened wings. The first primary is shorter than that of the dusky warbler or Radde's warbler (hard to see on this photo). |
 |
8. 4th Jun 2003 Wajima-shi, Ishikawa Prefecture The supercilium of this bird is long, but does not reach the nostrils, and is cut sharply. This seems to be an important diagnostic feature. In spring, the supercilium is usually rather thin. |
 |
9. 18th Oct. 1994 Wajima-shi, Ishikawa Prefecture In autumn, the supercilium often looks thick. In some individuals, it is especially thick behind the eyes. Therefore, be careful, when separating Arctic and Greenish Warblers. I think that the sharply cut supercilium is the best feature for identification. |
 |
10. 18th Oct. 1994 Wajima-shi, Ishikawa Prefecture The same bird as on picture No.9. |