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Naturalists are not as quick as they were only a few years ago to print inverness dismiss the idea that birds may sing from sheer high spirits. But it is print inverness difficult to reconcile too sentimental an interpretation of bird-song with the basic utilitarianism of a bird’s way of life. When a bird sings, it is using up time and energy which could equally be well spent in finding food. At the same time print inverness, it is advertising its presence to predators. Birds would have ceased singing long ago if the survival value of conspicuousness did not outweigh its dangers.
Song is only one element in the vocabulary of birds. Each bird has a number of calls, too – more than a dozen different sounds for many species, each with its own meaning.
The chaffinch has 13 different calls in addition to its song, and even its young have two different times of begging call, one before they fledge and one after. The collared dove has five calls – an alarm call, an aggressive call, two different notes used in courtship, and a call for showing a nest-site to its mate.
One important factor limiting how much a bird communicates vocally is the degree to which it can ‘say’ the same things visually – a display of plumage may be as effective as any call.
It is often difficult to draw a precise line between a song and a call. But song is concerned primarily with defending a territory or attracting a mate, whereas the function of calls is to pass on other kids of information, such as the fact that a predator is approaching. Songs tend to be complex arrangements of notes, uttered rhythmically and in most cases by the male; calls are generally short groups of up to four or five notes – aesthetically less pleasing, to human ears at least.
A bird can commu8nicate many things by the sounds it makes. It can state is species, its sex, its individual identity, even its condition. It can trigger off sexual excitement, curiosity, alarm or fear in another bird. It can attract a mate or drive off a rival. It can pass on news – where food is to be found or where there is a possible nest site. It can alert others to the presence of predators. But when it sings, the usual message is to broadcast its ownership of the territory.
At the beginning of the breeding season, two instincts shape the lives of a great number of birds – the instinct to lay claim to a territory and the instinct to find a mate. Song, functioning as a language in the sense that it conveys information from one bird to another, makes both things possible.
Most species which sing can be distinguished from another by their songs, and this, in fact, is a vital function of song – to state the bird’s species. Just as distinctive plumage patterns and elaborate displays minimise the likelihood of cross-breeding between different species of ducks, so distinctive songs prevent cross-breeding between different species of ducks, so distinctive songs prevent cross-breeding between similar looking songbirds such as the chiffchaff and the willow warbler.
At the same time, a bird’s song is a statement of its sex – in most cases male; in only a few species, such as the robin, in which both male and female hold territories in the winter, does the female sing. The song is interpreted differently according to the sex of the hearer. The same sound attracts unmated females and repels intruding males. Subtle variations in bitch, rhythm or repertoire can also state the bird’s individual identity.