Found in the woods in the spring and summer, the willow warbler is similar to the chiffchaff, but has a very different song, a sweet lilting, descending whistle. For me, it's the descending of notes that make this bird easy to recognise.
They are quite elusive birds, hiding in the foliage. I didn't see any in 2017, but this one was seen in April 2018, singing loudly in the trees along the entrance path to the church.

