ChiffChaffs wintering at Horsebridge STW

• Possible Tristis - Photo slideshow

Have spent a few recently grilling a Chiffchaff at the local Sewage works (Just South of Horsebridge). This venue has always been the pick of the local Sewage works for birds with a good turn out of Thrushes, Pipits and Wagtails on any calm, sunny winter morning. Highlight so far was a Water Pipit seen just once in the winter of 2010/11.

(Other nearby sewage works include Romsey which is a larger complex but always seems to have zero birdlife for some reason, and Nether Wallop which is better for Pipits and Wagtails, but I have never found anything unusual there. There is a fourth works just North of Stockbridge where viewing is dificult, and further afield the works at Downton look excellent)

The works at Horsebridge have 4 Chiff Chaffs present this winter. Two are bog standard olive coloured Collybita, the regular species seen pretty much everywhere in England and regularly overwintering. A third bird is a very pale grey and white oddity with orange legs. I won't even attempt to drill down to subspecies level with this one!
The final bird, for me, is the most interesting, and after reading up no every piece of literature I can find online, I'm of the opinion it is pure Tristis, (or something very close).

So far I have photographed it on two occasions, and you'd be forgiven for thinking it was two different birds! from warm brown bird on February 11th to a cold grey and white bird on February 19th. However, the plumage has eventually fallen into place as ticking all the required features for Tristis (In my opinion at least, plus a few brave souls on Birdforum who have stuck their necks out). Photos below in the slideshow plus the 3rd bird (the "oddity" for 3 pictures in the sewage beds). See what you think!...