This was a very nice surprise this morning as it is a bird I thought was likely to stay on my 'Billinge possibles' come 'wish list'. The site is looking quite bleak now that most of the trees and bushes have lost their leaves and being on a hill it does not have the sort of micro climate that attracts and holds late autumn and winter warblers. However, it is a great site for migrants and this Siberian Chiffchaff ('tristis') is presumably still on route to a nice warm sewage works or some wetland scrub on lower ground.
I am not going to go through all the plumage criteria as the images speak for themselves and there is plenty of information out there on the web, but it ticks all the boxes with one teeny weeny exception. The one thing it has that 'tristis' is not supposed to have is a hint of yellow in the supercillium immediately above the eye but then the full plumage limits of 'tristis' have yet to be determined so it isn't necessarily a problem. However, if a clincher was needed it came when it conveniently called, once in the hand and several times after release, with the call being a monosyllabic 'peep', a bit like a high pitched Bullfinch, and perfectly fitting the diagnostic call of 'tristis'.
Given that hint of yellow in the supercillium (not that I think it would have been noticed in the field) and as the plumage limits of 'tristis' are not fully understood I retained a couple of small feathers that the bird dropped. Hopefully, they will allow the bird's identity to be confirmed from their DNA so this may not be the last you here about this particular Chiffchaff.
Ringing totals for 17/11/17 were: Goldcrest 1; Siberian Chiffchaff 1; Blackbird 1; Redwing 11; Chaffinch 1.