Common chiffchaff and generally pale legs. Bonelli's warbler ("P. bonelli)" might be confused with the common chiffchaff subspecies "tristis", but it has a plain face and green in the wings. The common chiffchaff also has rounded wings in flight, and a diagnostic tail movement consisting of a dip, then sidewards wag, that distinguishes it from other "Phylloscopus" warblers and gives rise to the name "tailwagger" in India. Perhaps the greatest challenge is distinguishing non-singing birds of the nominate subspecies from Iberian chiffchaff in the field. In Great Britain and the Netherlands, all accepted records of vagrant Iberian chiffchaffs relate to singing males.
The Life of Birds raven from raiding a nest by collectively raising an audible alarm. However, in an English wood, all species co-operate to warn each other surreptitiously of approaching danger. By contrast, a sunbittern is shown expanding its plumage to discourage a group of marauding hawks. The members of the finch family exemplify how colour aids recognition. Birds have excellent colour vision, and the feathers of many species react to ultraviolet light. Flocking birds, such as sparrows, also have a 'ranking system' that determines seniority. In Patagonia, Attenborough demonstrates the effectiveness of sound: he summons a Magellanic woodpecker by knocking on a tree.