Booted/Sykes' Warbler in Hong Kong (1 Viewer)

I would be interested in feedback on this warbler, photographed in Hong Kong yesterday (14th October): http://www.hkbws.org.hk/BBS/viewthread.php?tid=27668 (note that these are not my photos, but posted by a photographer who was on site).

I saw the bird in the field and identified it at the time as a Booted Warbler, largely because it seemed rather round-headed, small-billed and short-tailed - the impression I had was similar to a small Phylloscopus (my thought on initial brief views was that it was a Chiffchaff). I also thought that the head pattern fit better for Booted, with supercilium extending behind the eye and dark sides to the crown.

However, it has been suggested that photos of the bird may favour Sykes'. The third photo on the linked thread does make the bird quite large-billed, and the tertials and tail are not very dark-centred. It is also very pale and especially whitish below (this was also obvious in the field).

Both species are very rare in Hong Kong (three records of Booted, two of Sykes'). I have very little experience of either, so any feedback from those with more experience would be very welcome.

John I have limited experience of this group, albeit I have seen caligata at close quarters and my bird had an obvious warm buff tint to the shoulder and flanks which your bird appears to lack. Also the bill if anything might appear slightly longer than one might expect from caligata, adding that there does appear to be a slightly darker tip to the lower mandible?

Excellent shots by the way.

Cheers

Hi John,
In my opinion, this is a safe Booted Warbler, and the pics are amazing! The bill doesn't look overly long, plus, as you say, there's a dark smudge towards the tip of the lower mandible. The supercilium extends well behind the eye, the primary projection seems a little long for a Sykes's, the tail doesn't look particularly long and the general impression is somewhat Phylloscopus-like, as associated with Booted. That said, apparent structure can depend on posture, and I've certainly seen an otherwise typical Booted momentarily look a little bit more like an Acro.
Arguably, the habitat choice, with one pic showing the bird on the ground, also favours Booted.
Regards,
Harry.

I would agree with Harry that it looks more like Booted, except that the bill looks a little long in the 3rd image, and that I don't think the primary projection looks that long. The best way to clinch this would be to record the call.

Thanks everyone for your inputs. I'm still leaning towards Booted, perhaps a slightly long-billed individual. Interestingly, one of the previous records was a trapped bird that was longer-billed than expected on Booted.

The bird didn't call, and wasn't relocated yesterday, so ID will rely on photos taken on Sunday (there may be more than the ones on this thread, but I don't have them at the moment).

I agree that these pictures are excellent - we have some very good bird photographers in HK and fortunately there were some on site, because I could never have got anything of this quality (and didn't have a camera with me anyway!)

The behaviour was interesting. The bird spent its time in low vegetation (less than knee-high) and was feeding on the ground. I've seen literature suggesting that this is more typical of Booted, but it's not going to be a 100% reliable difference for a migrant.

I agree with Booted. Not too disimilar bill and jizz wise for comparison to this bird on Shetland at the moment - https://twitter.com/HughHarrop/status/1051741355750363136