Which Warbler, Jiangsu, China (1 Viewer)

[deanman]

Please help the Warbler photoed 2023-10-12. East of China.Tks.

 

[Grahame Walbridge]

Clearly a wing-barred Phylloscopus, combination of bill structure/pattern, head pattern and wing structure confirm it belongs to the 'Arctic' warbler complex. The rather strong green and yellow hues might lead one to suggest Japanese Leaf (perfectly plausible in this location at this time) but a word of caution, this might be a product of the background which is always an issue. To my eyes, the bird does not look particularly heavy-billed and P1 seems (not equivocally) to fall short of the PC's, both of which negate against identification as JLW. On current knowledge, a soundfile is required in support of a firm specific identification in the field given the degree of overlap between the 3 members of the complex.

Assuming there is no supportive soundfile any identification would be purely subjective and so best left as an Arctic Warbler sp. IMO.

Grahame

 

[deanman]

Clearly a wing-barred Phylloscopus, combination of bill structure/pattern, head pattern and wing structure confirm it belongs to the 'Arctic' warbler complex. The rather strong green and yellow hues might lead one to suggest Japanese Leaf (perfectly plausible in this location at this time) but a word of caution, this might be a product of the background which is always an issue. To my eyes, the bird does not look particularly heavy-billed and P1 seems (not equivocally) to fall short of the PC's, both of which negate against identification as JLW. On current knowledge, a soundfile is required in support of a firm specific identification in the field given the degree of overlap between the 3 members of the complex.

Assuming there is no supportive soundfile any identification would be purely subjective and so best left as an Arctic Warbler sp. IMO.

Grahame

Thanks Grahame

 

[MacNara]

Clearly a wing-barred Phylloscopus, combination of bill structure/pattern, head pattern and wing structure confirm it belongs to the 'Arctic' warbler complex. The rather strong green and yellow hues might lead one to suggest Japanese Leaf (perfectly plausible in this location at this time) but a word of caution, this might be a product of the background which is always an issue. To my eyes, the bird does not look particularly heavy-billed and P1 seems (not equivocally) to fall short of the PC's, both of which negate against identification as JLW. On current knowledge, a soundfile is required in support of a firm specific identification in the field given the degree of overlap between the 3 members of the complex.

Assuming there is no supportive soundfile any identification would be purely subjective and so best left as an Arctic Warbler sp. IMO.

Hello Grahame: For my own education, I have a couple of questions.

Given that you agree with most that voice is required for a postive ID among the three species of 'Arctic Warbler' after the split (in many locations, at least) could you say why you think that JLW is 'perfectly plausible in this location (Jiangsu, China) at this time'?

I'm surprised that JLW would be in Jiangsu at all - at least in any numbers - and even more surprised that they would be there this late.

I was in the mountains in Nagano where JLW breed last weekend and roads were already closed for snow and ice (the weather here in Japan has changed from an incredibly hot summer to a cold autumn in a couple of days,thought it's now warming up again a little), and JLW was long gone.

On the other hand, this season is precisely when Kamchatka Leaf are coming through on their migration in my local spot in Nara at a lower elevation (they are a month or so later in each direction than JLW to my best knowledge), and I would have thought that KLW was a much more likely candidate for Deanman's bird.

Also, the photos have an obvious strong yellow cast, and the colours can't be relied on at all for ID between these three species.

Attached below:
Original
Colour cast removed (cast point manual, then automatic via Photoshop)
Yellow toned down and green toned up (manual choice via Photoshop)

 

[Grahame Walbridge]

Hello Grahame: For my own education, I have a couple of questions.

Given that you agree with most that voice is required for a postive ID among the three species of 'Arctic Warbler' after the split (in many locations, at least) could you say why you think that JLW is 'perfectly plausible in this location (Jiangsu, China) at this time'?

I'm surprised that JLW would be in Jiangsu at all - at least in any numbers - and even more surprised that they would be there this late.

I

Mac , there are several confirmed (vocalisation) records from eastern China from Zheziang to Jiangsu in both migration seasons Apr-May and Sep-Oct + it's regular, but very scarce, in Korea. It is regular migrant through Taiwan en route to/from wintering grounds in the Philippines so it is no surprise at all it should occur in this part of China. It has been recorded in Borneo (Sabah) and Hong Kong and is quite regular (but v.scarce) in spring (mid-Apr) in the Gulf of Thailand + there is a single Apr record from Vietnam.

Grahame

 

[MacNara]

Mac , there are several confirmed (vocalisation) records from eastern China from Zheziang to Jiangsu in both migration seasons Apr-May and Sep-Oct + it's regular, but very scarce, in Korea. It is regular migrant through Taiwan en route to/from wintering grounds in the Philippines so it is no surprise at all it should occur in this part of China. It has been recorded in Borneo (Sabah) and Hong Kong and is quite regular (but v.scarce) in spring (mid-Apr) in the Gulf of Thailand + there is a single Apr record from Vietnam.

Thanks for the reply, Grahame.

I wasn't really asking about very scarce sightings, but about your words 'perfectly plausible' for JLW in Jiangsu in October.

I don't think that JLW is 'perfectly plausible' which to me would mean 'common enough to be no surprise', as you say in your reply, either in that region at any season, or in Japan itself, Korea, or coastal east China, at this season (mid-October).

I don't have a problem with JLW occurring as a scarce vagrant in Zheziang and Jiangsu (confirmed by vocalisation), blown off course, perhaps, as is presumably the case for the Gulf of Thailand birds you mention, and the same in other places you mention. But, for example, if JLW were 'no surprise' in that region of China, why would it be 'very scarce' in South Korea, given that South Korea is between the Chinese coastal regions and the JLW's breeding grounds in the highlands of Japan?

Obviously, I agree with you that a voice recording would be necessary if, for some reason, you absolutely had to pin down one or other of the three new species out of season or location. But I submit that Kamchatka Leaf is overwhelmingly more likely both on location and on season for Deanman's bird.

Unless you are suggesting that JLW breeds on the continent (Mongolia?), and therefore might be flying directly to its wintering grounds over Jiangsu, I think it would be much more accurate to reply to Deanman with 'It's almost certainly KLW because of the season and location, but there is a tiny possibility that it's JLW'.

And indeed wouldn't Arctic sensu strictu, P. borealis, (of which I have no knowledge, but based on maps on bird sites online) be more likely than JLW?