What Are Dawn Choruses All About?
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By Dr. Richard Collins
Although they can't match human speech, birds do 'talk' to each other. We have, as yet, only a hazy idea of what they may be saying, or why their songs are so complex, but, apart from ourselves, birds are the world's most sophisticated vocal communicators. Each species has its own particular song. Some are simple in form and structure. Others are incredibly complex. But why do birds produce these sounds?
One thing is certain. It's hard to see your neighbours in the thick of a forest; colourful feathers and visual displays won't get a message out. Furry mammals use scent marks to solve the problem. Birds have almost no sense of smell and those who live in woods have no option but to sing.
Chiffchaff (photo by David Dillon)
The sound is not produced in the throat, as human speech is, but comes from a special voicebox deep within the bird's chest. As with speech in humans, song is controlled by one side of the bird's brain. Low frequency sounds carry best, but only big birds are able to produce them. As a general rule, the smaller a bird is, the shriller its song will be.
Women talk more than men. Among the birds, it is the males who do the blathering. But what are they blathering about and why start talking so early in the morning?
At daybreak, it's too dark to forage for breakfast, but conditions are ideal for sending messages; the wind tends to drop around dawn and sound travels best in cool air. Songs are 'trespassers will be prosecuted' warnings; the singer is telling his neighbours to keep out of his patch.
Local radio stations broadcast death notices and, at one level, the birds are doing something similar. The lives of birds are precarious and short. Death is ever present and, each morning, a bird needs to know if his neighbours have made it through the night. So, at the start of each day, there is a sort of rollcall. Each territory-holder informs his neighbours that he is alive and well. After a burst of song, there is a pause as the singer listens for replies to his message. Silence may indicate that a neighbour has passed away and that a territory is up for grabs, presenting an opportunity to extend one's borders. As unkind colleagues of the deceased whisper at funerals; 'who'll get his job now?'
Robin (photo by Michael Finn)
Bird songs are more like broadcasts than conversations, but what information is being transmitted? The singer's first task is to identify himself. A Robin must produce traditional Robin song, if he is to be recognised by other Robins. Having established what sort of bird he is, he wants to become personally known to his neighbours. There is a tension here because, to do this, he must depart somewhat from the standard song. While he can't stretch the species template too much, he must give his song a unique slant.
To a male rival, the song is a warning but, to an unattached female, it is an invitation. A singer usually tries to enrich his song; the more elaborate his performance, the more successful a singer is likely to be in attracting a mate. Some birds go to ridiculous extremes. The song of the Sedge Warbler is the vocal equivalent of the Peacock's tail, with thousands of notes poured forth in an elaborate cadence. No two of a Sedge Warbler's songs are the same, but he always begins his performance by quoting the last few phrases of his previous recital.
The refinements of bird song may be Greek to human ears, but the dawn chorus in woodland, on a fine May morning, is one of the great experiences of Irish nature.
Richard Collins has studied the morals and mores of Mute Swans for two decades. He writes for the Irish Examiner and gives courses on ornithology with the Adult Education Department, UCD, where he is known for his quirky and colourful lecturing style.