By and large I take my guidance on tristis from the works of Ticehurst and Svensson, and, of course, Lars Svensson is the co-author of the paper Siberian Chiffchaff revisited (Dean & Svensson 2005)

Also, as stated in Dean & Svensson 2005 (and I have repeatedly emphasised since) Lars and I do not assert the plumage limits of tristis - we do not know for sure what these are and nor does anyone else. We merely point out what is currently established and what is not, and we simply recommend that (a) people await the results of on-going research and (b) birds which do not conform with the established criteria for certain tristis are best not diagnosed (as any taxon) until that research is completed.

The proposal to set up the panel was initiated by a current member of BBRC and I was merely asked by the Chairman of BBRC if I would be a member of the panel. I agreed to this. I would add that this panel will evaluate reports of tristis submitted against the established criteria for classic tristis, in order to assess the status in Britain of individuals fully matching the stated criteria. The panel does not (and will not) assert that any Chiffchaff not matching the full suite of characters for classic tristis is per se not tristis.

The criteria for certain tristis in Dean & Svensson (2005) are taken from the Identification Guide to European Passerines (Svensson 1992 and in prep) and are nothing radical - they are primarily a refinement of the legacy extending from type description of Blyth through to the Witherby Handbook through to various editions of the IGEP guides.

I have seen photos of one of the Berkshire birds which were taken by Marek Walford I believe.

I must emphasise that below I speak for myself and not for the panel setup by BBRC.

I am very wary of judging photos, as they are all too often misleading (it is perhaps insufficiently appreciated that, although modern digital photos are often splendidly sharp and detailed, their colour rendition is quite often inaccurate, owing to inherent features of the camera, such as its white-balance, and also the prevailing light conditions). However, assuming that the photos are a good colour-likeness, then they are a good example of what I have emphasised above - that some people continue to apply (and misinterpret) the phrase grey-and-white without due reference to its express application in the paper Siberian Chiffchaff revisited (and without examining the photos which I have subsequently published). The photos of the Sandhurst chiffchaff all indicate an evident brown component in the upperparts and a buff suffusion on the supercilium and underparts. The legs and the upper surface to the feet appear quite black. On the basis of the photos this is a brown-and-buff Chiffchaff and is manifestly it is NOT a grey-and-white Chiffchaff sensu Dean & Svensson (2005). It is not at all like the truly grey and white Chiffchaffs exemplified by the Warwickshire Chiffchaff featured in plates 243 & 245 in Siberian Chiffchaff revisited, and its underparts are nowhere near white. In that paper, the phrase grey-and-white was used expressly as a shorthand for chiffchaffs with a level of greyness and whiteness drawing comparisons with a Bonelli's Warbler (particularly Eastern Bonelli's). Surely (if the photos are accurate) no-one would suggest that this Sandhurst bird has the overall greyness and whiteness suggestive of an Eastern Bonelli's Warbler? Its hues are much closer to a paler example of Mountain Chiffchaff or even a Booted Warbler.

It is a little paler than a truly classic tristis but, on the basis of the photos, it is (in my view) within the plumage limits of tristis/fulvescens (note that distinguishing in the field between tristis and some fulvescens is rarely possible).

Regards, Alan Dean