Common chiffchaff point, appears to be used to advertise an established territory and contact the female, rather than as a paternity guard strategy. Beyond the core territory, there is a larger feeding range which is variable in size, but typically ten or more times the area of the breeding territory. It is believed that the female has a larger feeding range than the male. After breeding has finished, this species abandons its territory, and may join small flocks including other warblers prior to migration. The male common chiffchaff returns to its breeding territory two or three weeks before the female and immediately
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.