Common chiffchaff the male has little involvement in nesting, but defends his territory against rivals, and attacks potential predators. A small insectivorous bird, it is subject to predation by mammals, such as cats and mustelids, and birds, particularly hawks of the genus "Accipiter". Its large range and population mean that its status is secure, although one subspecies is probably extinct. The British naturalist Gilbert White was one of the first people to separate the similar-looking common chiffchaff, willow warbler and wood warbler by their songs, as detailed in 1789 in "The Natural History and Antiquities of Selborne", but the common chiffchaff was
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.