This glimpse is all that I could film of our mystery bird. The sound was recorded longer. Due to the fact that the bird already was at a distance when I arrived and the wind was blowing through the trees, also the sound is of poor quality, but one can still get a good idea of the song. A characteristic piece comes with this page.

Some others saw it for an extended period. They are convinced that it looked just like an ordinary Chiffchaff (Phylloscopus collybita). Because of its odd song we wonder if it might belong to a subspecie.