Wood Warbler
Seeswood Pool 2008
Thursday 27 February 2014
22nd & 23rd February 2014
Headed over to Alrewas Pits,Staffs for another look at the Sibe Chiffchaffs (2 birds present last visit but mostly silent) The 1 Showy bird was still present,however it's call certainly resembled Collybita but only called briefly on the Saturday so decided to head back on the Sunday where the bird constantly called for the 2+ hours I spent on site & was calling as Collybita (So unless anyone with more experience on these difficult subs has a reasonable explanation then surely it's a Collybita?) Just goes to prove though that not all pale birds should be treated as Siberian............
For a detailed analysis please read Alan Deans comment in the comments section (Many thanks to Alan for this detailed response)
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I see that you have said that, as the birds in question are calling like collybita, then they probably are collybita. They are not nominate collybita, which is always shows more olive and yellow. At a push they could be ‘greyer’ examples of abietinus but they look closer to ‘fulvescens’. That they are calling consistently like collybita/abietinus obviously raises questions, as in their area of origin ‘fulvescens’ has the same call as classic tristis. It is being suggested by some that these birds are tristis which have abandoned their innate call and adopted (‘copied’) the call of Common Chiffchaff. There is no evidence for such a phenomenon in oscine passerines. Song is learned (‘copied’) to a large extent but call is much more fundamentally innate. However, if for the moment it were assumed that these are Siberian Chiffchaffs copying the call of Common Chiffchaff, then this would imply that they have been surrounded by calling Common Chiffchaffs during their call development. This would mean that they have originated in the region of sympatry in the Urals. The range of Common Chiffchaffs does not extend further east. At the stage of their call development, Siberian Chiffchaffs originating further east will not have encountered any Common Chiffchaffs to copy. In the region of sympatry in the Urals region, extensive hybridization between tristis and abietinus has been inferred by Marova et al. An even wilder suggestion by some in the UK is that these birds have originally used the innate call but then abandoned it after reaching the wintering grounds and encountering Common Chiffchaffs there. This is equally unlikely. Having developed and employed the innate call, a Chiffchaff is highly unlikely to abandon it completely. An occasional ‘copied’ call interrupting the normal tristis call is conceivable but consistent, persistent and exclusive use of another taxon’s call is quite another matter. Even more tellingly, on the wintering grounds from November onwards (when most tristis reach the UK), they are hardly surrounded by a plethora of calling Common Chiffchaffs. Indeed, at Mike Langman’s study area in Devon, where he video’d and sound-recorded ‘tristis types’ calling like Common Chiffchaff, there were more ‘tristis-types’ than Common Chiffchaffs! Thus, under this scenario, it should be the Common Chiffchaffs adopting the tristis call! While almost anything is possible, there is no substantive basis for suggesting that these anomalous Chiffchaffs are tristis copying Common Chiffchaffs. The fact is that, currently, we simply don’t know the origins of these birds. They raise serious and important questions and glib approaches to their identity should be avoided. As I’ve said repeatedly, while we may all have our opinions (or suspicions), their identity should be left unassigned at present.
Regards, Alan
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