Warbler in Tajikistan (2 Viewers)

[PhilSteiner]

A friend photographed this bird on Sunday and left it at Iduna/Hippolais/Acrocephalus sp. but would like to get it IDed to species if possible. He wrote:

"Would appreciate input on this one. Foraging on wall and in bushes and small trees, did not observe any particular motion of wings or tail but I was not looking for those things. Pale warbler with grayish upperparts, white underparts, pale supercilium that extended beyond eye, dark legs, square-tipped tail, and entirely pale lower mandible. Square-tipped tail seems to eliminate Blyth’s Reed Warbler; Entirely pale lower mandible and fairly long supercilium seems to rule out Syke’s and Booted Warblers; and Eastern Olivaceous Warbler seems unlikely due to different ground color and lack of a pale wing panel."

Any ideas? I ran it through Merlin for fun and it was all over the place, returning Sykes', Blyth's, and Chiffchaff on different photos.

 

[KenM]

Here’s a Chiffy from the garden a few days ago Phil?

 

[Grahame Walbridge]

Booted Warbler Phil.

A how apt that Ken should have likened it to a Chiffy since, compared to Sykes's, it has a more Phylloscopine appearance with the small bill, rounded head, moderate pp and tail versus Sykes's which has an altogether more Acrocephaline look, particularly about the head and bill. Plumagewise, note the supercilium is rather broad above and beyond the eye where it ends squarely and abrubtly. This individual has a rather poorly defined eyestripe, as are the darker centres to the tertials, likely due to bleaching. Bill pattern is variable in Booted so the absence of a dark tip, though not typical, is within range.

Grahame,

 

[PhilSteiner]

Booted Warbler Phil.

Grahame

Thanks Grahame. My friend had eliminated Booted based on the pale lower mandible (to me, my friend's photos don't show the lower mandible so clearly as to conclude there's not a dark smudge at the tip)... what about this bird makes it Booted anyway? The dark tip of the lower bill isn't prominent in my field guide, but looking through Macaulay Library, it does seem consistently present. Might this be a young bird?

Edit:
Thank you so much for the extended reply above! It's very helpful.

 

[Butty]

it has a more Phylloscopine appearance...

Indeed. So... would be most useful if you could fill in the missing part of the ID process: why isn't it a Phylloscopus?

 

[KenM]

Booted Warbler Phil.

A how apt that Ken should have likened it to a Chiffy since, compared to Sykes's, it has a more Phylloscopine appearance with the small bill, rounded head, moderate pp and tail versus Sykes's which has an altogether more Acrocephaline look, particularly about the head and bill.

Grahame,

Yes, in more ways than one Grahame, the first
Booted that I encountered some 21 years ago
now, (a very pale example) had a Phyllosc.like
“movement” not unlike Chiffy, darting around
in hot pursuit of invertebrates in the
shrubbery at very close quarters.

Cheers

 

[DMW]

The very pale legs and pinkish lower mandible exclude Chiffchaff. When faced with a small, pale milky brown warbler like this, these are the first clues you might be looking at a smaller Iduna warbler (or an Acro Warbler, which differ in structure). Grahame has explained why this is Booted rather than Sykes's. In the field it's always useful to listen for calls, as the hard tacking calls are very different from Chiffchaff.

 

[Grahame Walbridge]

Thanks Grahame. My friend had eliminated Booted based on the pale lower mandible (to me, my friend's photos don't show the lower mandible so clearly as to conclude there's not a dark smudge at the tip)... what about this bird makes it Booted anyway? The dark tip of the lower bill isn't prominent in my field guide, but looking through Macaulay Library, it does seem consistently present. Might this be a young bird?

Edit:
Thank you so much for the extended reply above! It's very helpful.

Phil, bill pattern is highly variable in Booted, most typically exhibiting a dark tip or, at least a variable dark smudge short of the tip (which may be present in the OP) but, I repeat, they can (on occasion) show an unmarked lower mandible. I don't know whether or not there is any link to age, it is plausible ML323480101 Booted Warbler Macaulay Library Sykes's lower mandible is unmarked or, it shows a subtle dark smudge near the tip and so, there is a clear overlap between the two. as is the case with other features including biometrics and wing formula. Some individuals may not be identifiable in the field (or from photos) such is the degree of overlap, a few (rarely) in the hand will require a feather sample for mtDNA analysis to confirm ID. That is not the case here IMO.

To expand on DMW's succinct comments above, the OP also has a white outer margin to R6 + a white tip to (at least) R5.

Paddyfield Warbler is another pitfall (particularly in worn plumage) which, compared to the OP, structurally, it has a more peaked crown and a longer, more graduated tail. The facial pattern is, on average, more marked and in particular, the eyestripe is more distinct. Bill invariably displays a more obvious black tip, the eyes are pale.

Grahame