sicklebill
well-known Cretaceous relic
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White's or Scaly Thrush Taiwan (2 Viewers)
- Thread starter sicklebill
- Start date
Jean FRANCOIS
Well-known member
More likely White's Thrush
Jean
Jean
johnallcock
Well-known member
Is there something in the pictures that makes you suggest this, or based on the relative abundance of the two species?
There is not much known about separation of the various taxa n this complex, and it would be very interesting to know more about separation.
The distribution and potential movements of the taxa breeding in the mountains of China are not known and probably confused by the assumption that wintering birds seen away from breeding sites are aurea.
John, did you get a chance to have a look at the Scaly/White's here? https://www.birdforum.net/showthread.php?t=386779&highlight=scaly
Compared to the bird in this thread, that individual had a more extensive black mark, almost a crescent, behind the ear coverts, more prominent double yellow wing-bars and dark-centered greater coverts. However, there could well be racial differences.
Jean FRANCOIS
Well-known member
Hi Sicklebill,
I'm just looking at this thread for education, but I wonder if you have any photos from the trip that show what you think is definitely Scaly, or definitely White's, so that we could get some idea of why you doubted the guide's ID.
I can't see how you could make a definitive ID, especially on a pair of birds you don't really know and which are very similar (and which are not always split), based on these photos.
This obliging White's was taken at Dasyueshan in Feb this year (2560m).
White's types were not uncommon at altitude, we were seeing up to 6 a day, mainly in the half light at dawn and dusk at the roadsides. We couldn't convince ourselves any were likely Scaly, presumably it is easier in the summer when the winter migrant White's have left for the breeding areas.
is it any clearer where the resident Taiwan birds sit taxonomically these days?
White's types were not uncommon at altitude, we were seeing up to 6 a day, mainly in the half light at dawn and dusk at the roadsides. We couldn't convince ourselves any were likely Scaly, presumably it is easier in the summer when the winter migrant White's have left for the breeding areas.
is it any clearer where the resident Taiwan birds sit taxonomically these days?
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Well, where I live in Japan, the species is presumably White's - though my Japanese-language books even from the last year or two refuse to split them at the species level (or Amami Thrush, either), and call all of them Scaly Thrush with subspecies. So, I'm wondering what the visual difference is supposed to be?
And HBW Alive although it splits them, doesn't have Scaly anywhere near Taiwan (although the winter distributions of Scaly and White's over Vietnam are suspiciously similar).
Bonus question: here's a photo of a White's (presumably) near my house in February. How many retrices are there and are any obviously missing or hidden?
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That is, White's, not Scaly, if the distinction is accepted.
The breeding birds on Taiwan are essentially entirely russet-toned above, lacking the bright yellow-golden tones of White's. You have a White's Thrush there IMO.
Steve
Left: the resident breeding form of 'XXX Thrush' (taken in June). Right: wintering White's Thrush (taken in January).
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I would still like to know what the key, definitive, features are that are supposed to distinguish these species and that allow you to tell them apart on sight?
I attach the distribution map from HBW Alive for Scaly Thrush (which I am assuming that you think the slighty reddish bird you posted is). As you can see, they have Scaly nowhere near Taiwan at all. Is this (very) wrong?
(I repeat, I'm just asking these questions for my personal bird education purposes. I've never seen this bird outside Japan. But I can't see such great differences visually, and my Japanese books don't recognise it at the species level. Reddish tones are not mentioned in anything I have, and it's said that the (sub-)specific status of birds in Taiwan is uncertain.)
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I've added a White's Thrush to #11 above. To me, the differences between the two are striking.
AFAIK, 'Scaly Thrush' involves a number of different taxa, all of which differ from one another in some way or other. The birds breeding on Taiwan 'are essentially entirely russet-toned above, lacking the bright yellow-golden tones of White's', which helps separate them from White's. I have no idea how other forms differ from White's or from each other as I have no experience of them, so am sorry that I cannot help you there.
As regards the map you post, the Chinese Wild Bird Federation recognises Z. dauma as a rare resident breeding species here and Z. aurea as a common winter visitor, this on their most recent update (2019). So, yes, it is indeed wrong.
Steve
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It's not my map, it's the map of Handbook of Birds of the World, which I thought was a fairly authorative source of information about birds. And as you can see, this map shows Scaly nowhere near Taiwan - indeed several hundred kilometres away.
But I'd like to repeat the same point that I have made in all my posts in this thread: what are the visual features that make you able to distinguish these two supposed species? Nobody has replied to this; everyone has resorted to quoting authorities, as you do ('Chinese Wild Bird Federation') without stating any criteria that are supported by (supposedly) reliable organisations.
Why, for example, do you think the Chinese Wild Bird Federation is more authoritative than HBW? And if they are the local experts, why doesn't HBW recognise their work as authoritative?
As I said, Japanese books and authorities go the other way, and don't recognise any species-level split between White's, Scaly and Amami.
Point taken.
I did post in #11 to offer an opinion about the bird in the OP is all. Sorry I'm not able to deal with the follow-up questions. Hopefully another contributor can help out with those.
Steve
Grahame Walbridge
Well-known member
Brazil's latest Helm guide affords full species status to all three which is at odds with OSJ.
White's is both larger and paler than Scaly with little overlap in biometrics. It is longer-winged (no overlap) with a greater spacing between primaries leading to a longer primary projection and, the tail is longer with a slightly different pattern of white to r7 and r6; White's has 14 rectrices compared to Scaly's 12.
Songs of White's and Scaly are quite different.
White's https://www.xeno-canto.org/486493
Scaly https://www.xeno-canto.org/489637
'White's' Taiwan https://www.xeno-canto.org/422037
The issue here seems be that resident birds in Taiwan have been assigned to White's on the basis of song but plumage (and structure?) seems closer to Scaly. Suggest someone needs to examine specimens. In Steve post 11, aside from difference in upperpart tone, notice the difference in primary spacing/projection and in the length of P1.
Grahame
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Thank you Grahame, that's helpful.
I think you are mistaken about the retrices, however. I think it's Amami Thrush, the variant endemic to Amami Island, just south of Kyushu, which has 12 retrices, while White's and Scaly both have 14 (at least according to Brazil's Birds of East Asia and Japanese books I have). That's why I posted my photo above (post #8) with a question about how many retrices there are - if you have an answer, I'd be grateful, just for interest.
And I wonder if you have an opinion on the bird in Sicklebill's original post?
johnallcock
Well-known member
Thanks everyone for an interesting discussion. Steve's experience of the Taiwan 'Scaly' population is useful regarding this bird.
It's a species complex that clearly needs a lot of work to sort out. It's not helped by the fact that they are often so difficult to see.
One problem for me is that there are populations that don't match either aurea or dauma, but are forced into one or the other. The Taiwanese population is one of them, and I think there are also confusing birds breeding in central China and in Vietnam.
A look at the HBW maps shows how confused the situation currently is - White's is shown as a widespread northern migrant and also a resident species in Taiwan, South India, Sri Lanka and Indonesia (this is a very weird distribution!). Scaly is shown as a short-distance migrant/resident sandwiched between the populations of White's. As MacNara has pointed out, the wintering distributions in SE Asia are identical, and populations in southern Vietnam aren't shown at all!
Some of the plumage and biometric differences mentioned by Grahame could be, at least in part, related to migratory behaviour, especially the wing structure. Do these still hold for southern resident populations of White's? What about northern migratory populations of Scaly?
It's a species complex that clearly needs a lot of work to sort out. It's not helped by the fact that they are often so difficult to see.
One problem for me is that there are populations that don't match either aurea or dauma, but are forced into one or the other. The Taiwanese population is one of them, and I think there are also confusing birds breeding in central China and in Vietnam.
A look at the HBW maps shows how confused the situation currently is - White's is shown as a widespread northern migrant and also a resident species in Taiwan, South India, Sri Lanka and Indonesia (this is a very weird distribution!). Scaly is shown as a short-distance migrant/resident sandwiched between the populations of White's. As MacNara has pointed out, the wintering distributions in SE Asia are identical, and populations in southern Vietnam aren't shown at all!
Some of the plumage and biometric differences mentioned by Grahame could be, at least in part, related to migratory behaviour, especially the wing structure. Do these still hold for southern resident populations of White's? What about northern migratory populations of Scaly?
Yes, but HBW doesn't include scaly in Taiwan even as a wintering bird. That was my point.
I'm not trying to be clever; I'm just trying to point out some inconsistencies in the published information, and also to learn from others who know more than I do.
