Watch The Life Collection online: Episode 6 Signals and Songs

This installment describes ways of communicating. A colony of fieldfares in Sweden deters a 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. The nature of tropical rainforests means that their occupants tend to make much louder calls than those in other habitats, and several such species are shown. Saddlebacks vary their calls so that even individuals from different areas can be identified. The dawn chorus provides a mystery, as there is still much to learn about why so many different birds sing together at the same time of day. (Proclaiming territory or attracting mates are two likely reasons.) Finally, Attenborough introduces the Superb Lyrebird as one of the most versatile performers: it is a skilled mimic, and this particular one imitates not only other species, but also cameras, a car alarm and a chain saw.

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