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Hearing bird sounds

Whether its finding their mate or sending out warning signals, birds have their own sound variations. P U Antony explains different avian musical tones.

Many animal sounds share characteristics with the music of man. The units from which these sound patterns are constructed are sometimes simple noises of varying sound quality, resembling those produced by our own musical instruments.

And the parallels are more prominent among birds. Birds rely

extensively on sounds as means of social communication.

Non vocal sounds

Some bird communications take place by way of sounds that are not vocal. The most common example is furnished by the woodpeckers which tap on dead trees in a rapid rhythm. The volume of the sound depends on the size of the bird and the resonant characteristics of the tree. The male red-bellied woodpecker taps at a prospective nest site, then the female comes along and joins the tapping apparently to indicate approval of the site and finally that is where they drill the hole.

The bill is used for sounds other than tapping. Some species click beaks together to communicate while certain birds in flight produce audible sounds with their wings. Some young nestlings begin to beg when they hear the wings of the parent bird approaching the nests. Sometimes the sound of wings on take off may constitute a warning signal. Birds like the woodcock flies up and then flies rapidly down with a sort of winnowing feathers which evidently is a part of the technique for arousing the interest of the female.

Call notes

Many birds communicate by means of sounds made by the vocal apparatus which are simpler than the usual song. They usually indicate some emotional state. Such cords are significant to other members of the species and elicit different responses in different situations. If a bird spies an enemy, it notifies the hazard to other birds. The operation of these alarm notes can be seen clearly when they are recorded on a tape and played back to the birds.

Herring gulls fled from the feeding dumps when appropriate alarm note was played. Starlings respond to alarm notes by leaving the roost temporarily. Some bird calls indicate distress. These distress calls can be evoked from a bird held in the hand or in the grip of some enemy or predator. Young birds will frequently give such calls if they are cold. Other birds hearing the distress calls may come to investigate out of curiosity or in order to help the bird.

Bird watchers make a squeak on the back of the hand which resembles a distress call and many birds pop out of the underbrush for a closer look. Another response to a distress call is to fly away from the source in an apparent effort to avoid trouble. Some species have an assembly or rallying call, which some times unite them against a common enemy. Food calls are used by birds to announce the presence of food and special notes are uttered by some birds during nest building. Penguin recognises its mate by the voice when the mate returns after an absence of months.

Bird songs

Probably the most conspicuous manifestation of song takes place when the male is setting up territory prior to nesting. Most of the vigorous outbursts that we hear on spring mornings serve this general purpose, which is usually the initial phase of the nesting cycle. The male selects a place in appropriate habitat for the species and essentially stakes a claim, then announces this fact to the world - especially to any rivals who might want the same territory. Some times this is called an advertising song.

Song is also used to attract a mate. Birds can recognise individual birds of the same species in an area through songs. When the birds are paired together as part of the mating process they sing duets.