Right. Chiffchaffs never stop to amaze me. But I now feel we're really getting somewhere.
Only very recently Peter de Knijff and I wrote something about Siberian Chiffchaff look-alikes on this site. The upper bird in that little web article looked like a tristis, but IMHO it was not an exact copy. Something looked off. So I ringed it as a Common Chiffchaff, without specifying the ssp.
More significant is that it called dozens of times, just before I released it. And it called like a Common Chiffchaff collybita/ abietinus.
The spectogram also shows a perfect match for Common, with an upward inflected call:
I did ask Peter to look carefully at the feather material I collected. Now Peter's mtDNA analyses came in: tristis. Yes, this bird with a hueet call shows tristis mtDNA!
Fairly recently they had a similar case in the UK, see here (scroll a few pics down) and here.
In 2018 Peter and his students will run a second test on all tristis we've trapped at five sites over the past five years. In this second test we'll try to figure out if any introgression with abietinus can be found. This will hopefully give new insights into stray Siberian Chiffchaffs in NW Europe. And in this individual - hopefully!
To be continued!
(I will add this web post as a post scriptum to the afore mentioned web article about look-alikes).