18 December 2009

Devon Recorder Mike Langman recently circulated a series of photos he took of a grey (rather than brown) Chiffchaff at Clennon Valley on 9 December, posing the question as to whether the bird is an Eastern Chiffchaff, Phylloscopus collybita tristis.

Mike made the following notes of his observations of the bird. All 10 photos are included below.

1.  Responded to tape of tristis Chiffchaff song and not Chiffchaff by approaching with wing quivering.
2.  No song returned or normal call, just a chup…chup call similar to the call Chiffs make quietly between song.
3.  Lacked the normal browny, warm brown tones of a tristis – much greyer.
4.  No olive tones to scapulars, mantle or nape – as tristis.
5.  Legs not black like most tristis, more browny black.
6.  Supercilium lacked yellow of Chiffchaff, but also buffy tones of tristis.
7.  Underside very clean and white, lacking buffy flanks and chest of tristis.
8.  Bill had pinkish base – best tristis are almost all black-billed.
9.  Undertail coverts buffy – many tristis white; Chiffchaff normally yellowy.
10.  Only yellow in plumage on underwing – perfect for tristis.
11.  Slightly buffier around throat in certain (brighter) light conditions – good for tristis.

Eastern/tristis Chiffchaff? – Clennon Valley – © Mike Langman – 9 December 2009

Mike offers the following conclusion: "Without a normal tristis call or song, I think this type of bird is left unidentified. Perhaps an intergrade with abietinus or just a pale abietinus that responds to tristis song?" 

As Mike points out, it's not always easy to sort these birds out!

Warbler expert Alan Dean, responding to Mike's circulation of his notes and photos, replied:

"Thanks for the photos. Your comments raise the problematic issue of ‘colour nomenclature’, which I’ve written about in British Birds. While this is a paler individual than some tristis, it is certainly a ‘brown and buff’ Chiffchaff and is not a ‘grey and white’ individual in the sense of Dean & Svensson 2005.

Your sharpest images all show an obvious brown component in the upperparts, consistent with tristis, and there is also evident buff in the supercilium and cheeks. The rest of the underparts (apart from the undertail coverts) are indeed rather paler than a classic bird but not outside the plumage limits of tristis. In fact, in plumage your bird meets the criteria listed by the ‘tristis panel’ in its original BB announcement.

It’s always worth recalling the analogy of Eastern Bonelli’s Warbler when dealing with the true ‘grey and white’ Chiffchaffs. The analogy refers to the level of grey and white (and not just the olive fringes to the remiges!), as they really do have a comparable level of grey and white aspects to the plumage. Some people describe these grey and white Chiffchaffs as ‘silvery’ – a bit of an exaggeration but it makes the point. Clearly your bird is not a ‘silvery’ Chiffchaff, and is not similar in these respects to a Bonelli’s.

A truly complete identification of tristis really requires a combination of plumage and vocalisations of course. So, if this bird stays around and you get any clearer calls, do please let me know.

The findings of the ‘tristis panel’ have been written up and will appear in BB, hopefully sometime in the first half of 2010 (but there’s quite a queue of papers at BB at the moment, so publication may be delayed). The write-up includes a lot of relevant background data and also some intriguing findings emerging from the latest research in Russia.