During the day the bird did produce on two occasions what sounded like a very Chiffchaff like "Chiff-chaff" song. This worried me, although the bird only did this 2 times in the 5 of so hours I spent with it I felt it warranted further investigation.
Please watch the whole video below, but please take special note from 31 seconds to 41, the bird appears to think its some sort of DJ and is singing both Iberian and Chiffchaff notes.
This concerned me at first, then I found recordings of Iberian Chiffchaffs from elsewhere which also do this, when speaking to Mr Garner about the bird on the phone it was suggested that perhaps what I was hearing was a conflict song. In essence what happens is that if the bird feels or thinks there is another Ibe in the area it will let out this conflict song. Listen to this song below from the Netherlands:
Here is exactly the same bird as above singing, though some may argue not quite as well as the Durham bird:
So my mind is put at ease. FEW!
Until next time, Foghorn out!