A large, thickset but sprightly warbler; can be sluggish in movements, especially if feeding on berry clusters on honeysuckle or elder. Sometimes aggressive, noisy, with hard, abrupt calls and a brilliant song.

The Blackcap song is a rapid, throaty performance, initially subdued but quickly becoming a faster, louder outburst. Yet while traditionally a summer visitor in Britain, the Blackcap has changed its habits and is now often seen in winter as birds from central Europe move west to replace UK breeders that fly south in autumn.