156857 Swift (Apus apus) in Flight. L 16-17cm. Invariably seen in flight: has anchor-shaped outline and mainly dark plumage. Catches insects on the wing. Sexes are similar. Adult has mainly blackish brown plumage with pale throat. Tail is forked but often held closed in active flight. Juvenile is overall darker but throat and forehead are paler. Voice Loud screaming calls uttered in flight. Status Locally common summer visitor. Nests in churches and loft spaces. Feeding birds gather where insects are numerous. Observation tips Easy to see in late spring in villages and towns. Most adults leave Britain in August.