Chiffchaff, Phylloscopus collybita.
A small olive-brown warbler which actively flits through trees and shrubs, with a distinctive tail-wagging movement. Less bright than the similar willow warbler and readily distinguished by its song, from where it gets its name. Picks insects from trees and also flies out to snap them up in flight. Seen all year round, but most arrive in late March and depart in August and September. Eats insects.
Photo: © Nottsexminer