With the first glow of light in the morning sky, as the sun stirs behind the Eastern Shore, the merry chortle of the yellow-throated honeyeater starts up.
Although I’m a light sleeper, I’m not troubled by the sound ringing through the treetops. And in half-sleep I listen for the emerging songs of the other birds in a soundscape that will soon become a cacophony. The guttural call of the yellow and brush wattlebirds next, and then the beautiful cadence of the butcherbird, its rich notes with the quality of an oboe.
Without looking at the clock, I can work out how time is progressing by the line-up of birds joining the dawn chorus. Forest ravens next, then silvereyes, black-headed and crescent honeyeaters, fantails and the occasional yellow-tailed black cockatoo. The new holland honeyeaters always come last. They must be late-sleepers.
From discovering the dawn chorus during my childhood in the English Home Counties, I have accepted established wisdom that birds sing at first light, as soon as they emerge from their roosts, to proclaim territory. It’s a more efficient time to call or sing because there is less wind to distort the sound. Birds may also choose to sing at this time because it is too dark to begin foraging.
Researchers in the United States, however, have established that there may be much more to the dawn chorus than we realise. Like so much to do with birds, the old notions are being challenged and we are learning that the bird world is far more complex than the early naturalists could ever have imaged.
The new study by ornithologists at Duke University in North Carolina suggests the chorus may be an early morning vocal exercise, birds “limbering up” their singing ability for the rest of the day.
Birdsong requires a delicate balance between speed and dexterity. Because birds switch quickly between successive notes of their songs by rapidly opening and closing their beaks, they must be able to constantly co-ordinate the movements of their beak and their syrinx, or voice box, with great precision. This, like any skill, requires practice to hone.
The researchers used an American songster, the swamp sparrow, to test their theories. They measured each bird’s trill rate and vocal range as the morning progressed.
Statistical analysis revealed the birds did not sing like virtuosos straight away, but sang more slowly, with limited range, first thing in the morning. They only began to increase their tempo and reach higher pitches after dawn – having practised their songs hundreds of times since then and were only able to perform more complex songs later in the morning.
I always view the birds in my garden as players in a great unfolding drama. Now it’s become a musical – they are warming up backstage before the sun comes up and the curtain rises.