PALE-LEGGED AND SAKHALIN LEAF WARBLERS
Perhaps we could begin this discussion with Sibley & Monroe's brief comments:
BELOW: (L) Pale-legged Leaf Warbler, unknown source and (R) Sakhalin Leaf Warbler 22 May 1996 on Hegurajima (Y. Watabe)
May 10, 2000: Yuko Sasaki
In the book Birds of Sakhalin Island by V. A. Nechaef, 1991, I found the name of a strange Phylloscopus that does not exist in A World List of Birds with Japanese Names by Y. Yamashina, 1986. It is not rare to find bird names missing from this list, because of changes in genera for example; however, for this Phylloscopus, I could find no other species name. The mysterious name for me is Phylloscopus borealoides Portenko (Saharin-Mushikui in Japanese). Some breed on Sakhalin.
May 10, 2000: Mark Brazil
The Phylloscopus you refer to is the Sakhalin Leaf Warbler, currently still known in Japan as the Pale-legged Leaf Warbler (Ezo-mushikui), P. tenellipes. Confusion has been maintained here in all recent books, it seems. However, if you listen to recordings of the songs of birds from Sakhalin and of Ezo-mushikui, you will find them to be identical, whereas if you listen to recordings of Pale-legged Warbler from elsewhere in Asia, their songs are totally different from the birds in Japan. The confusion between these two Phylloscopus warblers is rather like the historical confusion between the Dollarbird (Bupposo) and the Oriental Scops Owl (Konohasuku), which calls 'bu-po-so'. We will look back on it in a few decades' time with the same degree of amusement, no doubt.
May 11, 2000: Yuko Sasaki
Thank you very much for the information about Sakhalin Leaf Warbler. From your indication, I partially understand what Nechaef wrote in his book. As we know, the song of Pale-legged Leaf Warbler (Ezomushikui) in Hokkaido is a trilled 'tsyu, tsyu-pi-tsi, tsyu-pi-tsi....', and he wrote that that of the continental bird is 'che, che, che...' with a metallic sound like an insect. Of the bird's song/call recordings you recommended, I have only those for birds in the Soviet Union, and unfortunately the song of the Sakhalin Leaf Warbler is not included. In Japanese Birds 550, Ezomushikui is indicated as Sakhalin Leaf Warbler (P. borealoides), while in Kanouchi's book of Japanese birds it is as Pale-legged Warbler (P. tenellipes). When I read back through Nechaef's book, it looks as though there has been a controversial history for this species, as you mentioned. P. tenellipes was first collected in 1860 and this stuffed specimen is in the British Museum collection, he writes. After measurement of this specimen, he recommends separating this species into two. One, the continental bird, as P. tenellipes; and the other on Sakhalin, Kunashiri, Hokkaido, and northern Honshu as P. borealoides.
May 14, 2000: Nick Lethaby
I know Nial Moores said he had heard birds calling like tenellipes on rare occasions on Ainoshima. I didn't think they were separable on plumage. I note that in Birds of Thailand and Southeast Asia, Craig Robson does not mention borealoides, though he is not a man to shy away from a good split! I have some experience of Pale-legged Leaf Warbler, and I saw two (and heard many) Sakhalin Warblers a couple of years ago on a visit to Hokkaido. I could not see any difference in plumage or behavior (e.g. both tail pump and both are rather shy on the nesting grounds, especially compared to E. Crowned Warbler). Per Alstrom, who is one of the world's leading experts on Phylloscopus warblers told me he could not see any difference when studying skins. To me the call sounds identical in both. Of course, the song is completely different and that is why they were split.
November 28, 2004: Nial Moores
Re Sakhalin (Ezo-mushikui) and Pale-legged Leaf Warblers ('Nishi'-Ezo-mushikui): this species pair might be the toughest ID challenge in our region; but then again, their identification might not be so very difficult after all. Perhaps the ID criteria have become very confused, as they are largely based on migrants or birds in wintering areas. Personally, I have no answers, many questions, and a few observations that I hope might be of interest.
1) Pale-legged Leaf Warbler Records in Japan
Although the record has not been published, I have seen and heard singing Pale-legged Leaf Warbler in Japan, on Ainoshima, Shingu-machi, Fukuoka Ken (four on May 23rd, 1993; and one in 'late April' 1997). I submitted a written description of the 1993 birds to what used to be the rarities committee in 1994. Important ID points separating them from Sakhalin Leaf Warbler seem to be that all appeared brownish and dull on the upperparts and, unlike typical Sakhalin seen on Ainoshima, they fed more actively up in the canopy of low trees, rather than on or near the ground. The song was thin, very like Asian Stubtail, Urosephena squameiceps, 'see-see-see-see-si-si-sit-si', but a bit more silvery and given with an upended rhythm sometimes suggesting a very thin-voiced Yellowhammer, Emberiza citrinella. I believe Hiroto Okabe also heard one or two singing Pale-legged Leaf Warblers the next day in the same area. He also banded a Sakhalin / Pale-legged Leaf Warbler there on May 24th . It was a very dull, brown-looking individual on the upperparts, and I believe he took photos of it in the hand. The chances that the bird Okabe-san banded was a Pale-legged seem high. There were no singing Sakhalins on the island at that time (and most Sakhalins seem to migrate through northern Kyushu in late April anyway). Additionally, May 23rd was a truly exceptional day for mainland Asian species, with very few or no typical Japanese migrants present. The fallout on the 23rd followed a day of rain, clearing skies and then a torrential thunderstorm, a cold front which moved almost due south through the Yellow Sea to reach Kyushu.
In addition, I also made a tape recording of the singing 1997 individual, which I sent soon after to Per Alstrom and Krister Mild for expert confirmation: they confirmed the identification. At least one or two birders met elsewhere said they had also heard Sakhalin Leaf Warbler 'singing like an Asian Stubtail' (one of which was in Hokkaido, I believe). It seems that Pale-legged Leaf Warbler might not be so very rare in Japan, after all.
Although the calls of the two might be very subtly different and separable with practice by those hearing both taxa regularly, it is probably very tough to separate Pale-legged from Sakhalin confidently just on call. To me, the two seem extremely similar-- a high-pitched, sharp, squeeky 'zink', like a sharper version of a Red-flanked Bluetail anxiety-type call, with Pale-legged perhaps very slightly sharper still.
3) Pale-legged Leaf Warbler in Korea
The very distinctive Asian Stubtail type song is fairly easy to hear in South Korea, where Pale-legged Leaf is one of the commonest Phylloscopus in spring. Based on calls (i.e. Sakhalin / Pale-legged) and then on the small percentage of singing birds (to rule out Sakhalin), Pale-legged is probably the second most common Phylloscopus in mid-late April (after Eastern Crowned), with personal peak counts of over 100 in a day (e.g. on Eocheong Island, an island about 800 or 900 km west of Hegura, on April 22nd, 2002), and in May outnumbered only by Yellow-browed and then Arctic Warblers. It is common as a migrant until about May 20th on the west coast at least, and again in late August and September.
4) Plumage Differences
In my first sightings of Pale-legged Leaf Warblers in Korea, they appeared significantly darker than my memory of (singing) Sakhalin Leaf Warblers in Kyushu, lacking the obvious green tones to the mantle and the brightish blaze shown by some on the remiges, and with paler, perhaps less powerful legs, similar to the Ainoshima birds. However, my confidence in the dull 'brown-backed Pale-legged Leaf' and brighter 'green-backed Sakhalin' criteria was somewhat weakened by seeing how different many individuals appeared in different light, and by realising that at least some fairly to very greenish birds sing like Pale-legged.
5) How to be sure then?
Records of Pale-legged Leaf Warbler in Japan seem to make it much less straightforward to claim all Sakhalin / Pale-legged in Japan as Sakhalin Leaf Warblers simply on range. It is possible therefore that at least some descriptions of 'Sakhalin Leaf' in Japan are actually of migrant Pale-legged Leaf Warblers. It is very interesting in this respect to look at the 550 Guide for Bird Lovers, and also at Watabe-san's images of Sakhalin Leaf Warblers. All of these images were taken on Hegurajima, and all in May, when Pale-leggeds are still on migration and 'vagrants' to Japan are to be expected only there. How were such migrant individuals actually identified as Sakhalin Leafs for sure? Might they not be Pale-legged Leafs instead?
Perhaps in a similar way, not all 'Pale-leggeds' can be claimed with confidence in Korea. Visiting birders to Korea saw many Sakhalin / Pale-leggeds in the far southwest in April 1993 and 1994, and eventually heard one of them singing the beautiful and distinctive Sakhalin Leaf song! I also heard one Sakhalin Leaf singing here in the far southwest in April 2000. Clearly, considering how few of these birds actually sing here, they are not exceptionally rare. Much farther north, on Happy Island in Hebei Province, a claimed sight record of a non-singing bird a couple of years ago was also apparently followed this spring by a singing Sakhalin Leaf Warbler.
These records show that both Sakhalin and Pale-legged can be found on migration in Japan, Korea, and even coastal China. Any identification criteria built up on expected range and on migrants in these areas (even banded birds) seem to be less than watertight, and yet it is quite likely that it is exactly these migrants, along with non-singing wintering birds in e.g. Hong Kong, which are still being described in much of the literature. How certain can anyone be, for example, that the greenish-looking Pale-Leggeds are not Sakhalin Leaf Warblers after all? It even seems quite possible, based on many people's unfamiliarity with these taxa, that at least some unseen but singing Pale-legged Leaf Warblers in Japan in mid-summer could be overlooked as Stubtails, and when seen simply accepted as Sakhalin Leaf Warblers.
December 3, 2004: Yoshiki Watabe
1) Pale-legged Leaf Warbler Records in Japan
On my website, I wrote that only one record of Pale-legged Leaf Warbler has occured in Japan, on Tsushima Island. This record was published in the Japanese birdwatching magazine, Birder 14 (7), in July 2000. According to this record, the song of the Pale-legged Leaf Warbler was heard on 6 May 2000 in Nakahara, Kamiagata-gun, Tsushima Island, Nagasaki prefecture by Tomohisa Masuda, et al. However, other details and photos were not included. To my knowledge, this is the only Pale-legged record for Japan that has been reported in any publication. TheCheck-list of Japanese Birds, 6th Revised Edition(Committee for Check-list of Japanese Birds, 2000) does not include the Pale-legged Leaf Warbler. Although Maki and Oonishi (Nihon no Yacho 590, 2000) include both recorded and unrecorded species, Pale-legged Leaf Warbler is not included even in this list. They state that this species is very likely to be recorded in Japan in the future. I was not aware of Nial's record, so was interested in his observation. If Okabe-san photographed or ringed the bird, I hope that the record will be published in an ornithological journal like Strix, Japanese Journal of Ornithology, Ornithological Science, or the Journal of the Yamashina Institute for Ornithology, as well as in Forktail.
Nial's mention that other birders had heard Sakhalin Leaf Warbler singing like an Asian Stubtail suggests that a few Pale-legged Leaf Warblers may pass through Japan. In the collection at Yamashina Institute for Ornithology, there are possible Pale-legged Leaf Warbler specimens. Both Sakhalin and Pale-legged Leaf Warbler were once treated as P. tenellipes; therefore, specimens of both species may be labeled as P. tenellipes. Specimens taken in Korea, China and other locations, mainly before 1945, also may be in the collection of the Yamashina Institute.
I was surprised to see on Nial's Birds Korea website the first Korean record for Sakhalin Leaf Warbler, and that Pale-legged Leaf Warbler seems to be rather common. So, I think the Pale-legged will be recorded here in future, especially on Tsushima. Pale-legged Leaf Warbler may have been overlooked in Japan. If a record is published with details and photos, the number of subsequent records will likely increase rapidly. For example, Dusky Warbler was once not officially recorded in Japan (with only a few sight records). However, after the publications of a complete record in 1984 with photographs and details of ID, the number of subsequent records increased rapidly, and it is recorded every year now in Japan.
2) How to be sure then?
We usually photograph Sakhalin Leaf Warbler in migration season on the island, because it is difficult to see in its breeding areas. It is seen usually in dense bush near the ground, so it is very difficult to photograph. When I visited Hegurajima in the past, Phylloscopus were easy to see, so I started a study of the ID points for Sakhalin Leaf Warbler (it was almost undescribed in Japanese fieldguides). First, I listened for its song, because I had heard Sakhalin's song in several breeding areas in Japan and knew it well. Second, I studied its call, which is based on its song. Finally, I observed and took the photos based on songs and calls. Thus I learned the Sakhalin's characteristics. Now, I sometimes identify it without song or call. For the individuals on my website, I may not have heard calls or songs. Sakhalin Leaf Warbler is rather difficult to see even on Hegurajima; therefore many of my Sakhalin records are based mainly on calls and songs. In my memory, I have never heard the call or song of Pale-legged. If Pale-legged perhaps pass through Hegurajima, the number must be very small. It would more likely be recorded more to the west than Hegurajima. Regarding the ID distinctions between Sakhalin and Pale-legged, more research (and publication) based on information from the breeding areas is needed.
December 4, 2004: Nial Moores
How close is the song of Pale-legged Leaf to Asian Stubtail (a song most Kantorians, especially those living in Japan, are likely very familiar with)? I think it fair to say, VERY similar, especially when hearing the song at a range of 30 m to 50 m or more through woodland. As I suggested before, the song of Pale-legged is a little more silvery (fuller, clearer notes), lacking the Stubtail's piercing, hissy sound, and given with a slightly different rhythm. Pale-legged's song often lilts towards the end of each sequence, while Stubtail seems to deliver the repeated note quite flat, though with an obvious increase in volume as the bird gets into stride (starting a little hesitantly and quietly, increasing in volume insect-like, then stopping fairly abruptly, 'si-si-si-Si-SI-SI-Si-SI-SI-SI-SI-s'). Stubtails can also maintain this incessant song sequence for longer than is typical of Pale-legged Leaf Warbler. These differences are, however, only really obvious at close range when there is not a lot of background noise. I think too that, in common with many Phylloscopus, there might also be some variation in the song of Pale-legged Leaf. This might be individual variation, or it might be that birds sing differently on migration when a long distance from their breeding areas, compared to how they sing, perhaps in response to other singing birds, nearer their breeding areas. This difference in songs has apparently been suggested for several other Phylloscopus taxa. In regard to this, the tape-recorded Ainoshima singing bird in late April was said by Per Alstrom to be slower than typical in the breeding areas, and I have heard this slower song on several occasions in Korea, from memory also especially in April (one observer from Germany suggested that this slower song was to his ears midway between Asian Stubtail and Western Bonellis Warbler, Phylloscopus bonelli). A few others I have heard inland in Korea in June in song (they nest here, probably reasonably commonly) sounded at medium distance very like Asian Stubtail, and I would have simply overlooked them as that, had I not known the song from Ainoshima and from island migrants. It is because of this difficulty that it was easy to imagine how the species might easily be overlooked in Japan.
December 6, 2004: Yoshiki Watabe
In my previous comments, I wrote that I have never heard the call or song of Pale-legged Warbler . Re-reading Nial's comments, however, I cannot say that I have never heard the call of Pale-legged Warbler; I have possibly not distinguished Pale-legged's call from Sakhalin's. And as I have often identifed Sakhalin Leaf Warblers by calls alone, I have possibly overlooked many Pale-legged Leaf Warblers. In regard to song, however, I have never observed a Sakhalin Leaf Warbler 'singing like an Asian Stubtail'.
I observed mystery Phylloscopus on 9 September 1999 and on 6 or 7 September 2000. They were most similar to Sakhalin Leaf Warbler, but their call was 'knee, knee' or 'kwee, kwee', slightly similar to Varied Tit. The individual in 1999 was observed with other Sakhalin Leaf Warblers, and seemed to have rather plain upperparts; the bird in 2000 had a contrast of colors between the top of the head and the mantle. Furthermore, in the photograph which was taken then, the undertail coverts looked slightly yellowish, unlike normal Sakhalin Leaf Warblers. I did not record other details; I am unsure now whether they might have been Pale-legged Leaf Warblers.
P. tenellipes borealoides was described first in 1950 by Portenko. Therefore, earlier Japanese literature, e.g. A Natural History of Japanese Birds (Yamashina, 1941) confused the taxa tenellipes / borealoides. Even in the Check-list of Japanese Birds 5th edition (The Ornithological Society of Japan, 1974), P. borealoides was treated as synonymous with P. tenellipes. Many Japanese birders have become aware of the continental form of Pale-legged Leaf Warbler only within the last ten years. Therefore, past records in Japan of Pale-legged / Sakhalin Leaf Warbler are all but useless, at least in regard to migrants. Even now, many Japanese birders (including myself ) are unfamiliar with the characteristics of Pale-legged Leaf Warbler. If they observe the Sakhalin Leaf Warbler singing like an Asian Stubtail, they will record them in their fieldnotes as an 'unknown warbler' if anything.
Ishikawa (Yacho no Kai, 1979), during a survey from 31 May 1975 to 23 November 1978, recorded Sakhalin Warblers in spring (from mid-April to late June) and autumn ( from mid-September to mid-October). Maximum numbers were recorded on 23 May 1976 and 5 May 1978 (about 5 individuals) in spring, and on 25 September 1977 and 2 October 1977 (2 individuals). In my experience, there are more individuals recorded in spring than autumn. Also in my experience, they possibly mainly pass through Hegurajima in early September; but in autumn, the numbers are less than in spring. Pale-legged Leaf Warblers possibly also pass through in the same seasons. According to Williams (1986), neither Pale-legged nor Sakhalin Warbler were recorded in spring (from 15 March to 1 June 1985) at Beidaihe, China. At least in spring, the migration route of both species could occur more to the east.
Yamashina Institute for Ornithology has collected very many specimens. There must be many specimens labeled as P. tenellipes, and they may include both Pale-legged and Sakhalin Leaf Warblers.
Looking at the photos of Pale-legged Leaf Warblers at the Oriental Bird Club website, I note the lack of contrast of colours between the top of the head and the mantle, and the supercilium seems rather broader than normal in Sakhalin Warblers. What do you think about these images? Do Pale-legged Leaf Warbler actually have no contrast of colours between the top of the head and the mantle?
Ishikawa, Yacho no Kai 1979: Birds of Hegura-jima (in Japanese)
Williams, M. D. (ed) 1986. Report on the Cambridge Ornithological Expedition to China 1985
December 6, 2004: Nial Moores
As suggested before, Pale-legged Leaf and Sakhalin Leaf Warblers really seem to produce more questions than answers. It seems that the two taxa might be relatively easy to separate on plumage in the field, but also that these criteria might have become confused by misidentification of non-singing birds, and by the lack of clear and easily accessible information on known individuals in breeding areas. It seems too that even with birds collected or photographed in 'breeding areas' some caution is needed: can we be certain that Pale-legged does not breed in parts of Japan? That Sakhalin does not breed in areas mapped too simply for Pale-legged Leaf? It has been said that the Sakhalin Leaf nests in Japan and Sakhalin, and Pale-legged on the Asian mainland. On what information is this mapping based, and what might the ecological preferences be, if any, to create this distribution? Surely both would come into very close contact on the mainland adjacent to Sakhalin, presumably in areas with very similar climate and habitat.
As I wrote before, my impression of the singing Pale-legged Leaf Warblers that I saw on Ainoshima, Fukuoka Prefecture, was that they were very much duller and rather darker than the singing Sakhalin Leaf that I had also seen there, as well as duller and darker, browner on the upperparts than the majority of (non-singing) presumed Sakhalin. They also seemed, perhaps, to have slightly less-powerful looking legs and feet (an impression no doubt suggested because I often saw Sakhalin hopping around on the ground, and these Pale-leggeds were moving through bushes, more like Eastern Crowned Warblers). Allowing for what appears to be significant individual variation and differences dependent on light conditions, many birds I suspect of being Pale-legged look reasonably similar to the first of the two OBC images that Watabe-san links us to.
The Sakhalin Leaf Warbler I saw (and heard singing) in Korea (on April 28th, 2000) I noted at the time as being 'typical Sakhalin' (i.e. the same as birds I had watched singing or saw regularly in Japan), showing 'very great contrast between mantle and crown, bright remiges, sickly pale legs and very little white to the bill tip'. Some Pale-legged Leaf (singing) appear to show more obvious white tips to the bill and rather pink-toned legs than my memories of Sakhalin. However, I accept that such impressions are clearly not enough. I think we will really only be able to develop solid field ID criteria through reference to absolutely known individuals and their plumage and biometrics.
Additionally, I was very interested in the information that Watabe-san gathered on migrants. In the case of Hebei, I was surprised to see the lack of records for Pale-legged / Sakhalin suggested by Martin William's 1986 report. I suspect that this might have been due to the lack of good information on these taxa at that time, especially regarding the calls, or-- less likely-- a recent change in status. I saw Pale-legged / Sakhalin Leaf Warbler several times at Beidaihe in spring 1992 (my only visit), and have been sent some unpublished data by the very experienced and knowledgable Swedish birder, Bjorn Johansson. In spring visits in four years to Happy Island (also in Hebei, at the top end of the Yellow and Bohai Seas) on dates approximately from May 10th to May 25th, Bjorn noted the following numbers of Pale-legged / Sakhalin: 2 individuals over 11 days (1994); 21 birds over 15 days (2000); 48 birds over 17 days (2001); and 150 birds over 15 days (2002) with a peak of 75 individuals on May 22nd. It must be remembered that exceptional counts during migration are often caused by inclement weather (rain and fog); the variance in numbers recorded by Bjorn might be due much more to weather conditions than to a sudden change in status.
In South Korea, it is evident that the peak of spring migration (almost all species) occurs later as you go northward. Most Pale-legged / Sakhalin Leaf Warbler migration appears to be over by early May in the far southwest and west of the country (with e.g. only 5 on May 22nd, 2002, compared to a peak of 100+ in one day in late April that year); while this year I still recorded at least 50 on May 20th in the far northwest (Socheong Island). Although all the evidence is circumstantial, there is a very obvious tendency in South Korea for migrants presumed bound for Japan to peak earlier than birds bound for the Russian Maritimes, and than birds presumed bound for more northern and western areas (please see Birds Korea). The data, taken overall, suggest that Pale-legged is a numerous species having a rather broad breeding range and does migrate through Hebei in spring. In northern Kyushu, Sakhalin Leaf arrived most years (1991-1998) in mid-April, peaking by the end of the month, with considerably fewer singing birds heard in May.
Autumn migration in general in Korea (as elsewhere) is more protracted, and rain does not often produce the large fallouts of migrants experienced in spring, partly because those Korean islands so far studied are not far from the mainland (unlike Hegura). Pale-legged Leaf Warblers are regular on offshore islands at least from mid-August to late September, with personal latest this year on October 7th on Socheong (in the far northwest), and a day peak of only 10 or so. Reference to an unpublished report by Jochen Dierschke and Felix Heintzenberg (Happy Island and Beidiahe Bird Report: 28/08/1994-28/9/1994) shows that Pale-legged / Sakhalin was 'recorded in the period 20.8 - 23.9 with up to 30 birds on Happy Island on 2.9'. This period closely matches the main migration period noted here in South Korea.
December 7, 2004: Nick Lethaby
Pale-legged Leaf Warblers are regular migrants through the Beidaihe area. I remember seeing quite a few on Happy Island. They are reasonably common, but less so than Yellow-browed Warbler, for example. I also heard one singing up on Lao Ling, but it may have been just a migrant. I agree that the song is very different, but the call seems identical. I have seen and heard Sakhalin Warbler in Hokkaido. Both species pump their tails and both are very shy and difficult to see on the breeding grounds. For example, I saw only one Pale-legged in Ussurriland on the breeding grounds in four days of looking, even though they were one of the commonest birds! In Hokkaido, Sakhalin Warbler was just as difficult. My impression is that the Hokkaido birds looked to be more contrasting rusty on the rump compared to the ones at Beidaihe, but it is dangerous to draw conclusions from a couple of birds. I remember seeing birds typically feed low down in Beidahe but cannot recall if they often went onto the ground as well.
December 08, 2004: Bjorn Johansson, Sweden
I've put up some of my photos [link broken—Ed] of Pale-legged Leaf Warblers, Phylloscopus tenellipes, from Happy Island. Any apparent differences in colour of upperparts among the photos are photographic effects of light conditions.
Once you get the hang of it, they are easy to distinguish from Arctic Warbler (P. borealis) on behaviour. They flick their tail quickly up and down, which Arctic never does. Also, the contrast between dark crown and green back is diagnostic, and they show a green wingpanel. As in Arctic, they have one or two wingbars, the upper one often narrow or missing. The call is a high frequency, short 'zitt' that is often repeated, very different from the dipper-like 'dzrrt' of Arctic Warbler. Nial's description of the song is correct. I have yet to see my first Sakhalin Warbler, and apart from what Nial has written, I don't know how to tell them from Pale-legged.
December 12, 2004: Yoshiki Watabe
1) Distinguishing between Pale-legged and Sakhalin Leaf Warblers
The distinction between Pale-legged and Sakhalin Warblers seems to be difficult except for the songs. Bjorn's photos on the internet are very useful and interesting for me. The 1st and 6th photos (in hand) on the website possibly show a slightly shorter primary compared to Sakhalin Leaf Warbler photos taken in Japan (including my own). However, this may be hard to confirm in the field. Based on Nechaev's data (1991), Sakhalin's p6 is 4-5 mm (average 4.4 mm) longer than p5, while Pale-legged's p6 is 2.2-3.8 mm (average 2.8 mm) longer than p5 (primary number is counted from inside to outside). The longest primaries are p6, p7 and p8 in both species. Therefore, the position of the tip of p5 may be easy to confirm even in photographs.
In most of Bjorn's photos, the contrast between the top of the head and the mantle seems to be less than in Sakhalin Leaf Warbler. However, his 5th photo shows obvious contrast between the head and mantle. This may be individual variation. This bird also has a very broad supercilium. I have never seen Sakhalin (possibly including Pale-legged) Warblers which had such a broad supercilium. The 2nd photo looks very greenish to me; is it individual variation? The legs of Pale-legged are possibly thinner than Sakahlin's, but I am not sure whether this is a useful character; neither do I think that the white bill tip is very useful to distinguish between species.
2) In Beidaihe, southern Korea and Hegurajima, individual numbers in autumn migration seem to be less than in spring. Why? I expect that the birds leaving their breeding area fly a long distance initially, so that the distance between their first landing point and second landing point is greater than the distance between their second and third landing points; therefore, the probability of landing near the breeding area is perhaps less than doing so nearer their wintering area.
December 13, 2004: Nick Lethaby
I think there are several reasons for the absence or lower numbers of Pale-legged / Sakhalin Warblers from Hegura (and Korea?) in fall:
1) I think these species are early fall migrants, so just do not often occur at the time most birders get to Hegura. I have failed to see them also on the mainland of Japan in late September.
2) The geographical position of the western Korean islands and Hegura means that, in spring, birds have to make a long sea crossing prior to reaching them; therefore they are more likely to need to stop on the island than in autumn, when they are departing from the nearby mainland.
3) In Japan, I have seen a lot of migrants up in the mountains in autumn (e.g. in Karuizawa in September-October). I think it is possible that summer migrants take advantage of the rich food source up in the mountains in autumn while migrating; therefore, they would leave Japan from farther south. In the US, warblers similarly use mountain habitats to feed in autumn. These habitats are much less attractive in spring because they are still cold and have less food.
Although I have yet to go to Hegura in spring, it is clear that many species of Japanese summer visitors (Japanese Yellow Bunting, Narcissus Flycatcher, Japanese Robin, etc.) are much much more common than in autumn.
December 15, 2004: Nial Moores
Bjorn wrote, 'What I would like to hear from Watabe-san and Nial, who have both seen borealoides, is whether they also flick their tails up and down, as tenellipes do constantly and which is very typical for the birds in the Hebei area. My friend Bo Petersson had a singing Sakhalin on Happy Island, Hebei, this May, and he never saw it flick its tail. It would be great if there were such a difference.' Bjorn, from memory, Sakhalin Leaf flick the tail exactly like Pale-legged Leaf. However, my recent experience of borealoides is extremely limited, and I think people who have seen proven individuals on the breeding grounds would be much better placed to answer.
Pale-legged and Sakhalin are indeed early migrant species in Korea too; they do occur in lower concentrations, but can both be found from August through to late September. Migration is spread over two months; many birds are easy to overlook, as the vegetation is thicker; they are less vocal; less feeding time is required, as food is more abundant; and also maybe they do not need to migrate in periods of poor weather (unlike in spring), so do not get caught out by poor weather as much as in spring (hence, lower concentrations). Additionally, northeast winds, from a good direction for autumn migration in the Yellow Sea, are dry winds here, while southwest winds (blowing a good direction in spring) are often associated with rain fronts, etc.
Nick wrote: 'The geographical position of the western Korean Islands and Hegura mean that in spring birds have to make a long sea crossing prior to reaching the islands. Therefore they are more likely to need to stop on the island than in autumn, when they are departing from the nearby mainland.' I think this is very significant for the Korean west coast islands: heavy rain and fog produce big fallouts in either season, but only in spring do we get 'clear sky falls', often of very tired birds, and often in the company of obvious overshoot species. There is as yet no good data for the only two islands off the South Korean east coast (the massive Ulleung Island and the extremely remote and disputed Tok Do), but it seems likely that big falls in autumn could be expected, as these islands are reached only after a long sea crossing.
December 16, 2004: Nick Lethaby
Do Sakhalin Leaf Warblers pump their tails like Pale-legged? Yes, in my limited experience with two Sakhalin Leaf Warblers. I specifically checked for this.
December 16, 2004: Yoshiki Watabe
1) Distinguishing between Pale-legged and Sakhalin Leaf Warblers
Based on Bjorn's photos, Pale-legged Leaf Warblers have a contrast between crown and mantle; I guess that this contrast may be more inconspicuous than Sakhalin's. As I mention at my website [link broken—Ed], Nechaev (1991) describes this as follows: 'the top of the Sakhalin's head and nape are dark gray with little greenish tone, contrasting with the greenish mantle and uppertail coverts: but Pale-legged 's upperparts are rather plain colored, and the top of the head is slightly darker than the green-olivaceous mantle and uppertail coverts.'
Pale-legged Leaf Warbler probably has a shorter primary than Sakhalin; however, it may be hard to confirm this in the field. Based on information which Akiyo-san received from Hiroto Okabe-san: primaries 7-8 show exposed tips beyond the longest tertial in the Sakhalin Leaf Warbler, while primaries 5-6 show exposed tips beyond the longest tertial in the Pale-legged Leaf Warbler. This suggestion was by Mr. Yoshikimitu Shigeta at the Yamashina Institute for Ornithology.
2) Regarding the absence or lower numbers of Pale-legged / Sakhalin from Hegura (and Korea?) in autumn: actually, few Japanese birders have visited Hegurajima from August to mid-September. I have visited Hegurajima during 5-8 September 2000, 4-7 September 2002, and 17-19 August 2003, and I saw or heard few Sakhalin Leaf Warblers: 0-3 individuals daily.
December 16, 2004: Martin Williams
Looking at Watabe-san's page on Sakhalin Leaf Warbler, I have to say that, if shown the first photo and asked to identify it on a quick look, I believe I would have said Arctic Warbler, partly because there is not much contrast between the mantle and the rest of the upperparts, and it seems pretty bright green. I'm glad they behave and call very differently! I am not sure how the 'brown' came into the literature for Pale-legged/Sahkalin. It is mentioned in the Sonobe guide ('no green tinge'), which was a major guide for us when I first went to Beidaihe. The 1988 edition of the Hong Kong guide (which we did not have in Beidaihe) says 'brownish warbler identified by rusty rump (visible in flight); call a loud "tic-tic" '. Even a few years after my first visit to Beidaihe, I remember being at the town one spring, and some birders gave a fine description of Pale-legged for a warbler they couldn't identify. 'Pale-legged,' I said, 'for sure.' 'They're brown, Martin!' one of the birders protested: even though he hadn't seen Pale-legged, he had read about them.
December 18, 2004: Yoshiki Watabe
When I started the study of Phylloscopus ID, many Japanese field guides (including the Sonobe guide) mentioned only the brownish colouration and the voice as the Sakhalin Leaf Warbler's ID points. As I have red-green colour blindness, I cannot distinguish between the Sakhalin Leaf Warblers and Arctic Warblers by colour. Therefore, I have tried to discover other ID points, mainly while on Hegurajima. Since I knew the songs of Sakhalin Leaf and Arctic Warbler, I studied their ID points with the help of their songs (and later, their calls).
I have thought that the most useful difference separating Sakhalin Leaf Warbler from Arctic Warbler is the contrast between crown/nape and mantle in the former. However, a small number of Sakhalin Leaf Warblers also seem to have a rather indistinct contrast between nape and mantle; such birds may be Pale-legged Leaf Warblers. The first photo on my page seems to show rather little contrast between the mantle and crown. However, I think that the contrast between mantle and crown of Arctic Warbler is even less distinct; Arctic Warbler's upperparts have an essentially plain coloration.
Additionally, I think that the shape of the supercilium is differs between Sakhalin Leaf Warbler and Arctic Warbler. Sakhalin's supercilium tends to be rather slimmer in front of the eye than behind and tends to extend to the forehead. Comparatively, Arctic's supercilium tends to cut off vertically in front of the eye; however, this superciliar shape may vary slightly between subspecies (or populations or ages). Nevertheless, I think that the more whitish supercilium and underparts of Sakhalin Warbler are useful differences from Arctic Warbler.
The call of Sakhalin Leaf Warbler is a higher, metallic 'pit', while the call of Arctic Warbler is a lower 'zit'.
As I said, I am red-green color-blind, so I have paid little attention to the colour of the mantles and wings of many warblers. The colouration of Sakhalin Leaf Warbler may be variable and some Sakhalin Leaf Warblers possibly have rather greenish mantles and wings; however, I cannot really offer an opinion on this. I was not aware of the rusty rump of Sakhalin Warbler, but when I re-read A Natural History of Japanese Birds (Yamashina 1941), I noticed his description of the colour of the rump. Yamashina (1941) states that the upperparts from the forehead to the uppertail coverts are olive brown with a little green, and the rump and the uppertail coverts look rather rusty in Sakhalin Leaf Warbler. He also describes the crown as darker than other parts. Although I examined several photographs (including in the fieldguide), I could not perceive the colour of the rump, perhaps because of my color blindness.
December 27, 2004: Nial Moores
I want to pass on some records of Pale-legged Leaf Warbler by Okabe Hiroto in Kyushu between 1988 and 2002, very kindly mailed on to me by Nakamichi Akiyo around two weeks ago. None of these birds was photographed by Okabe-san, nor were they sound-recorded, unfortunately. It would be good to amend this Kantorilode discussion to reflect that although Okabe-san heard Pale-legged on May 24th 1993, he did NOT photograph or band one at that time. However, his five records below, all based on song, suggest that Pale-legged Leaf is not especially rare in Japan on migration. For further context, I would suspect that of the Pale-legged/Sakhalin Leaf Warblers I hear/see in Korea, probably rather fewer than 10 per cent are actually singing; also that all but the Ainoshima bird were found during the Japanese national holiday, Golden Week, likely reflecting observer bias rather than peaks in migrant numbers.
May 5th, 1988, Sago, Tsushima, Nagasaki Prefecture
May 4th, 1992, Sago, Tsushima ,Nagasaki Prefecture
May 24th, 1993, Ainoshima, Shingu-cho, Kasuya-gun, Fukuoka Prefecture (following on from at least 4 on May 23rd: NM)
May 1st, 1996, Kayo, Ohshima-mura, Munakata-gun, Fukuoka Prefecture
May 4th, 2002, Togo-koen, Tsuyazaki-cho, Munakata-gun, Fukuoka Prefecture
May 29, 2005: Nial Moores
It seems happily that with improving knowledge of the song, Pale-legged Leaf Warbler is already being increasingly recorded in Japan. Apart from Watabe-san's records this year, I received an e-mail from Otani Chikara, who observed Pale-legged Leaf Warbler in Japan on May 15th, 2004, and also met with Onishi Toshikazu this month in Korea. He reported that he had also heard Pale-legged Leaf Warbler on Tsushima (If I remember correctly, back in the late 1980s) and perhaps subsequently. This is in addition to several records by Okabe Hiroto between at least 1997 and 2004 (twice on Tsushima, and at three locations on the northwest coast of Fukuoka Prefecture). Does anybody know approximately how many records have been documented/claimed so far in Japan of this species? (It is also of note perhaps that a singing Sakhalin Leaf Warbler was found on an island off Shanghai this spring: both taxa are indeed to be found in China, Korea and Japan!).
Sadly, to respond to Mark Brazil's request in relation to songs and tapes of Pale-legged Leaf, I no longer have the commercial tape that was sent to me many years back, and I still have yet to relocate the tape of one singing that I made on Ainoshima, Shingu-machi, Fukuoka-ken in April 1997. I believe Per Alstrom has a copy both of that tape and of tape recordings from the breeding grounds (which seem to include parts of Korea, incidentally). And surely some birders have sound-recorded migrants in coastal China?
Additionally, it is perhaps necessary not to overstate too much this comparison with Asian Stubtail. I made it because I believe it is a very useful comparison for people who do not have experience of the species, but the song(s) are really distinctive once the ear is tuned in and the song heard well. As written previously (in November 2004), Pale-legged Leaf seems to have two song variants. The first sounds rather fast and thin (especially at range, this is likely to be passed over as Asian Stubtail by those without experience); the second type, especially when heard well, seems rather fuller, slower, subtly beautiful and silvery (a little Bonellis Warbler-like), with a hint of the rhythm of a Yellowhammer (apologies for the European context of this description, perhaps not so useful on Kantori; another way to describe it might be to cross the song of Arctic Warbler with Asian Stubtail, keeping the thinness, some of the repetitive, slightly swinging rhythm, and adding some silvery tones). How do other Kantorians who have heard Pale-legged Leaf describe the song?
As in previous years, I heard the species singing daily on the outer islands (both Eocheong and Socheong) throughout this spring, first from April 16th; but perhaps because it is quite high-pitched and thin, it really does seem a very easy song to overlook. I know for example that Kenji Mochizuki, who was with Mark Brazil on Socheong in early May, did not hear the song. When I met him there in late May, he said that he still had not heard it once -- nor any birds sounding like Asian Stubtail -- even though we had only been a couple of hundred meters apart when I had heard one or more singing. In this way, maybe the comparison with Asian Stubtail was more of a hindrance than a help to him. Better descriptions obviously needed!
June 1, 2005: Nick Lethaby
When I heard many Pale-legged Leaf Warblers in Ussuriland, I actually drew a comparison with a thinner, shorter version of Lanceolated Warbler. It is a pretty distinctive song.
June 1, 2005: Mark Brazil
I am interested in your comment Nick, because I have just heard a brief recording of Pale-legged (thanks, Des) and that was the very comparison that sprang to mind—like a snatch of Lanceolated song. Comparison with Asian Stubtail is more difficult to imagine, but it certainly shares one aspect in common—it is more like white-noise than true song, without the pitch variations of 'songs'.
June 1, 2005: Nial Moores
I agree that the comparison with Lanceolated is a fairly good one too, especially for birds heard distantly or not well. So the song of Pale-legged Leaf for some can suggest Lanceolated, for some Asian Stubtail, for some Bonelli's Warbler. Anyway, as Nick remarks, the song is quite distinctive—and very different from the typical song of Sakhalin Leaf!
Actually, I have also made the same comparison with Lanceolated, just once and that to Kenji Mochizuki a week ago when on Socheong. However, shortly after making that comment (and seeing his very confused look), I heard another one singing, and felt the comparison to be, to my ears, not so very close. It really does sound more 'song-like', and quite beautiful to my ears when heard well, much more so than the song of Lanceolated Warbler, which is also a fairly common song to hear on Socheong in late May.
One step closer....