Blyth’s/Claudia’s/Davison’s: PART 1

Birding in northern Thailand offers you a great opportunity to test your identification skill and increase your personal list of Phylloscopus warblers. The Blyth’s & White-tailed Leaf Warblers Complex is one of the phylloscopus groups that you’d most likely encounter when birding in montane evergreen forests like at Doi Inthanon, Doi Angkhang or Doi Lang. However, identifying them can be problematic at times, especially when you’re not familiar with any of them. This post will be the first part of the Blyth’s/Claudia’s/Davison’s Leaf Warbler Identification trilogy that I’m planning to accomplish. Let’s first explore here the general description of the plumage of each species.

To our current knowledge, 2 species from the Blyth’s Complex and 1 species from the White-tailed Complex can be found in northern Thailand; i.e. Blyth’s Leaf Warbler (P. reguloides assamensis) and Claudia’s Leaf Warbler (P. claudiae) from the Blyth’s Complex and Davison’s Leaf Warbler (P. davisoni) from the White-tailed Complex. Another species from the White-tailed Complex, Kloss’s Leaf Warbler (P. ogilviegranti intensior) is also found in Thailand but only restricted to the south-eastern part of the country.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Generally speaking, Blyth’s and Claudia’s cannot be separated solely by the plumage. The above photo is a Blyth’s Leaf Warbler (P. r. assamensis) from Doi Inthanon summit, the only place where I’ve seen this species in Thailand.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Characteristics of both Blyth’s and Claudia’s plumage are pale greyish median crown stripe contrasting to darkish lateral crown stripes, dark eye stripe, pale yellowish supercilium, no tertial fringes, no rump patch and darkish legs.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Typical appearance of P. r. assamensis, quite prominent greyish median crown stripe. Some yellow but not too much on the supercilium and face.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Median crown stripe is paler towards the back while lateral crown stripes get darker. Also note no tertial fringes nor pale rump patch unlike the Lemon-rumped Complex.

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Claudia’s Leaf Warbler (Phylloscopus claudiae)

Claudia’s Leaf Warbler share pretty much the same tone of head pattern, body plumage and bare parts.

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Davison’s Leaf Warbler (Phylloscopus davisoni)

Davison’s Leaf Warbler, on the other hand, has more yellow tone to the plumage, especially at the supercilium, face and median crown stripe.

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Davison’s Leaf Warbler (Phylloscopus davisoni)

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Davison’s Leaf Warbler (Phylloscopus davisoni)

This photo clearly shows the yellowish tinge on the median crown stripe and the much yellower supercilium of Davison’s compared to Blyth’s and Claudia’s.

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Davison’s Leaf Warbler (Phylloscopus davisoni)

Structurally, Davison’s is also smaller, more delicate-built with probably weaker bill.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Blyth’s and Claudia’s often exhibit a strikingly large-billed appearance when seen in profile. This one is a Blyth’s Leaf Warbler from Doi Inthanon summit as well.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

But of course, the impression of the bill strongly depends on the angle! This one is also a Blyth’s LW from Doi Inthanon summit.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)
© Thanee Wongniwatkajorn

The best feature to tell Blyth’s and Claudia’s from Davison’s is the undertail pattern. This is the typical undertail pattern for Blyth’s Leaf Warbler taken by Thanee Wongniwatkajorn at Doi Inthanon.

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Davison’s Leaf Warbler (Phylloscopus davisoni)

And here’s the typical undertail pattern of Davison’s Leaf Warbler taken at Doi Lang. Notice how the outermost pair of the tail feathers are almost completely white. While in Blyth’s and Claudia’s, they are mostly grey with thin white line on the outer web.

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Blyth’s Leaf Warbler (left) and Claudia’s Leaf Warbler (right)
Left © Thanee Wongniwatkajorn

Actually, the amount of white on the outer web of outer tail feathers also differ between Blyth’s and Claudia’s (Blyth’s having slightly more white than Claudia’s) as you can see from the picture above (Blyth’s on the left and Claudia’s on the right), but the difference is too subtle to be used in the field. Other features like feeding behaviour, which will be for the next post, is much more useful for the identification of the two.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

Now it may already sound easy to identify Blyth’s/Claudia’s from Davison’s, but look at this photo, the outer tail feathers seem to be completely white… so Davison’s?

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

The answer is NO. It’s actually a Blyth’s Leaf Warbler!

Because the outer tail feathers of these birds are so thin that they are translucent, sometimes they can appear totally white when spread against the light like in the photo above. So the best way is not to be so quick at identification and try to take as many photos as possible, especially when the undertail pattern is shown!

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Davison’s Leaf Warbler (Phylloscopus davisoni)

Even though the bill looks pretty large in this photo, the amount of yellowness and particularly the undertail pattern confirm that this is a Davison’s Leaf Warbler. Photo taken at Doi Lang.

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Davison’s Leaf Warbler (Phylloscopus davisoni)

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Davison’s Leaf Warbler (Phylloscopus davisoni)

But some Davison’s can be less strikingly yellow than the others. This individual was photographed at Doi Angkhang.

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

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Blyth’s Leaf Warbler (Phylloscopus reguloides assamensis)

While some Blyth’s can show pretty striking yellow supercilium too, so never forget to check the undertail!

In the next post, I will write about behaviours of each species and how helpful it is to know the differences because it makes identification much easier than when looking at the plumage alone.

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4 thoughts on “Blyth’s/Claudia’s/Davison’s: PART 1

  1. I’m very glad you are doing this series Ayuwat! It would help I think, if you could provide the species name as a caption for each photo. Also, I’m not seeing the difference in undertail pattern – can you perhaps include a little sketch or two so I know what I am looking for? Thanks!

  2. Pingback: Kaeng Krachan and Lung Sin Hide | Birds of Thailand and Beyond

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