chiffchaff

noun

1. A small, common warbler, Phylloscopus collybita, with yellowish-green plumage that breeds throughout northern and temperate Europe and Asia.

2. Any of several other species of the same genus.

3. (Britain, onomatopoeic, uncountable) the song of the chiffchaff.

- I thought I heard something singing chiffchaff, chiffchaff. So I had a look and there was a chiffchaff.