As a result of DNA work carried out in The Netherlands on a large number of Chiffchaffs trapped and ringed during 2009-2011, it has now been proven that those 'grey and white' chiffchaffs that I have recently been recording as 'abietinus intergrades' are actually SIBERIAN CHIFFCHAFFS and reveals the true variability of this species (see Dutch Birding 34: 386-392).
I had previously stated that UK-acceptable Siberian Chiffchaffs would have to conform to the Dusky Warbler-type paler brown, dark-billed and black-legged birds but this new study has revealed that those 'grey' birds are diagnosable as pure tristis rather than intergrades. This new information suggests that Siberian Chiffchaff is a much commoner passage and winter visitor to Britain than has recently been recognised.
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