The unsound approach

a tristis-type Chiffchaff

Mousehole St, Norwich, 7th Dec 2008

First series of pics was taken in bright light:

In direct sunlight, the green tones in the wing and tail fringes weren't obvious - the whole bird appeared buffish brown with a grey cast to the crown and nape. Note the bright chestnutty tones to the ear coverts, and lack of yellow anywhere.

The underparts seemed very white in some lights, but the breast and flanks were buff, unlike those on grey-and-white abietinus types. 

And here are some pics taken in dull light:

Above pic shows a good representation of the buffy underpart tones.

The green fringes to the wing and tail were much more obvious in dull light. The pale greater covert bar was particularly obvious on this bird (as it is on many  abietinus). You can understand why people used to string these as Greenish back in the day...

The primary projection seemed fairly average for a Chiffchaff. Most of the really striking grey/green/white abietinus birds I've seen have had very long primary projections, making them look more like Bonelli's. Not sure whether this has any relevance to tristis identification. Do fulvescens types tend to have long primary projections?

The following shots show the underwing, where a limited ammount of yellow was apparent (although it did not extend as far as the leading edge, and was never visible when the wing was closed): 

The calls were spot on for tristis-type - the classic high pitched monosyllabic "heeep", given most frequently when the bird landed after making short flights. Unfortunatly I didn't manage a recording due to flat batteries. Will try again next time it visits...