Lewis James has recorded an interesting Chiffchaff singing at Pantmaenog Forest today which sounds very good for Iberian Chiffchaff. The grid reference for the bird is SN084308 (map here: https://goo.gl/maps/FXVcE8fbTGsg5QdL8).
The bird has been giving classic IC song around 70% of the time, but has been 'mixing it up a bit' (my words!), but having read both the Collins Bird Guide & the Handbook of Western Palearctic Birds (Volume 1) variations of the classic chiff chiff chiff chiff chiff te-te-te-te swee swee swee are quite common, especially switching the last two parts or missing either of them altogether.
Clearly worth a look....
