Garden Birds: The Dawn Chorus

The dawn chorus begins by lapping at your toes, and ends up as total immersion. What starts as a lone voice in the darkness builds up, bit by bit, into a multitude of voices, all competing for attention, like the din from dealers on the floor of the Stock Exchange. A wave of sound forms in the twilight, gets stronger and stronger, crashes over, then subsides as the brighter light of the new day takes hold and banishes the shouts to whispers, and the babble to individual homily. In April it is over by half past five, and by then much business has been done.

The first strains of the new day are heard from a wakeful blackbird or robin, both of which have large eyes and can see well in half-light. They are joined by other species in a particular order, always much the same in a certain location, but varying from place to place. Song thrushes are always in the first round, stating each of their phrases several times, with slow, clear enunciation, and with a wild-sounding air. Sooner or later a wren will intervene, blurting out its long, over-fast and indignantly loud sentence again and again, like a cornered politician. The woodpigeon soothes matters with its rhythmic, five-note coo, throaty and deep, the alto to a company of sopranos. The dunnock warbles unremarkably, the great tit chimes cheerfully and, always a little later, the chaffinch utters an accelerating rattle with a flourish for a finish. If we heard such a racket from our human neighbours we would complain about the noise, and yet most of suburbia sleeps through this dawn din, unaware of the miracle on its doorstep.

But if the buzz outside should awaken us from our slumber, perhaps we might- not necessarily politely or appreciatively- pause to wonder at the purpose behind it? Even if we do understand the general reason for singing, we might still question why this outpouring of noise should be happening now, in the chilly half-light, when we would rather be asleep? What makes birds shout so loudly when the day hasn't yet started?

The answer, as it seems, is as concealed as the vocalists themselves behind their darkened cloak of spring leaves. There are plenty of theories, but a definitive one has so far proven elusive. Currently, the different ideas compete among themselves for attention. But perhaps they all hold a degree of truth, each explaining a small piece of a wider puzzle? Nothing in the lives of our garden birds is entirely neat and simple, so why should this be?

We can quickly admit some meteorological evidence. It appears that, of all times of day, dawn is the best moment to be heard. It's a gentle time atmospherically, with reduced wind turbulence and close conditions, when sound echoes off an invisible ceiling of air a few metres above ground, keeping it locked in and easily heard. The dawn is also environmentally apposite. If you were to make a speech at dawn, it would transmit to your neighbourhood twenty times more efficiently than at midday, when the garden reverberates to the sound of cars, planes, children, lawnmowers, radios, workmen and thousands of other pollutants. It is an ideal time to make an impression.

At the same time, it's by no means an ideal time for feeding. Much as birds' stomach must rumble, after a long period without any food, searching for anything may well prove unsuccessful. Birds usually hunt by sight, so the low lighting conditions make foraging difficult. At the same time, the relative cold renders invertebrates, the mainspring food of our garden birds, as inactive as early-morning students after a night at a club. Being cold-blooded, the insects require warmth before they can emerge on to leaves and branches. What better time for birds to put all their efforts into singing, a task that requires no light or warmth from the sun.

Birds can be food items too, of course, and yet another theory of dawn singing is that it's a way of making a lot of noise without putting yourself at unacceptable risk from predators. Most things that eat birds require good light by which to hunt and those that don't, such as owls, could perhaps be expected to have full stomachs by dawn after a night of feeding. Singing, making a commotion from a prominent perch, is a potentially dangerous occupation whose threats may be contained by performing under the cover of the semi-darkness.

But what of the birds' relationship to each other? We know that singing birds are in competition, so perhaps this holds another key to the dawn dilemma? One possibility seems especially likely. The nights, even in April can be cold, and some birds, tragically overstretched or inopportunely diseased, expire overnight. Like a bunch of school kids answering the register, maybe birds sing at dawn to confirm their presence, to put their hands and say 'I'm here?' If so, vacancies would quickly become apparent, and new occupants would then be rapidly and unceremoniously installed. So much for the discredited notion that birds sing when they are happy.

But the most intriguing explanation for the dawn chorus is also by far the sauciest. Drawn from studies of great tits, it contends that birds may sing during the earliest part of the day to keep their females out of mischief. In the great tit at least, and probably in the blackbird too, the peak of the dawn chorus coincides with the females' fertile periods, the time when a male's paternity is potentially most at risk. Females lay their daily egg at dawn, and from this moment on are rabidly fertile. It is in a male's urgent interest that, as soon as the female comes off the nest, he is ready outside for her, singing loudly, and speaking the language of copulation. Once he succeeds in mating with her, his song output drops- one is tempted to suggest, in sheer relief. If he is absent from his post, she will be vulnerable to the charms and attentions of neighbouring males, and his paternity is compromised. In the great tit, then, the dawn chorus appears to be a form of mate-guarding.

Whatever theory you choose, the dawn-chorus carries on. That's sometimes the beauty of the familiar. We all know it happens, and many good minds have been stretched to explain it, but it's still a mystery welling up from the apparently commonplace. When it wakes you next, though, spare a thought for the stressed-out-mate-guarding great tit, and go back to sleep with your irritation soothed by a degree of suitable sympathy.