I sent the video links to Keith Vinicombe a while ago and today I received the following reply:
Thanks for giving me a link to the video sequence. Lee sent me a couple of cracking shots that Jim Lawrence had taken and he forwarded copies onto Lars Svensson. I’ve posted three poor shots on Surfbirds but one of them, despite being blurred, shows the very long and strongly arched hind claw, which is supposed to be a feature of EYW.
This is the fifth such bird I’ve seen in Britain (three on Scilly and another that wintered at Aust Sewage Farm near the Severn Bridge from 16 December 1993 to 19 January 1994). All I can say is that all these birds looked and sounded the same. The Aust bird also had a long hind claw which easily spanned a 10mm mortar joint on a brick wall. Brian Lancastle visited Tring after the Aust bird disappeared and he found that simillima form NE Siberia was the closest match (but this form is now included within tschutschensis).
As for the call, the first call that I heard from this year’s Scilly bird sound like a normal Yellow Wagtail but other calls sounded more buzzy and rasping: spzzeu was what I wrote down at the time. Also, when it was sat on the roof of a nearby bungalow, it gave a sibilant, trillingspspsp – a very strange call that I’ve never heard from any wagtail before! I didn’t record it – I’m not that technical!
Whether these birds are Eastern Yellow Wags I don’t know, but these late autumn birds are certainly consistent in their appearance and vocalisations and logic would dictate that they have an eastern origin.
The last I heard was that the BOURC were going to analyse the DNA from some specimens of simillima from Fair Isle, obtained in 1908, 1909 and 1912.
I certainly look forward to seeing whether anything comes of these birds.