chiffchaff, I think

I went for a wander round the park at Cusworth, and managed to nearly get blips of a little grebe (kept diving), a poppy and daddy longlegs (poppy out of focus), and mallard ducklings (slightly blurred as they will keep darting about). As I was on my way back I heard a chiffchaff and saw this bird on the top of a tree. So I blipped, without taking the time to find my glasses, in the hope that I'd get a reasonable picture - I've frequently heard these birds but never managed to see one. I got several shots before it flew off, this is the clearest.