The reason birds have such beautiful songs is straightforward – to find mates and declare territories. It’s much like human communication on a night out: people tend to talk either to chat each other up, or to tell one another what’s going on with them. But why do birds choose to do it so dang early in the morning? What’s so special about the hours just after dawn that make it the perfect time for birds to share their gossip?
I pondered the very same question while researching songbirds at Grand Teton National Park, Wyoming, one summer. It was a truly beautiful place to work and I was researching the Brewer’s sparrow – a nondescript little bird that sings incredibly complex songs (listen here). But there was one slight inconvenience – the songbirds liked to get up and sing at dawn (4 a.m.). And I had to be there in order to find them.
An experiment performed by two Canadian zoologists gives us answers. The bird researchers played swamp sparrow and white-throated sparrow songs in grassland and forest at both dawn and midday. Re-recording the songs at varying distances up to 100 m, they found that while the sound travelled just as far at both times of day, it was more consistently clear in the morning. They say that this consistency of sound is vital for individuals to recognize each other.
When the sun comes up each morning it heats the ground which, in turn, heats the air. And as any balloonist will tell you, hot air rises. As the day progresses, all this warm air starts moving around – what we call atmospheric turbulence. And turbulence is not only the bane of aircraft cabin crew but it also interferes with the transmission of birdsong.
Each bird wants to make sure that their message is transmitted loud and clear. Therefore, it makes sense to sing when disturbance from atmospheric turbulence is at a minimum – i.e. before the sun has had long to warm up the air.
It would have made my life easier to wake up at 7:00 a.m. instead of 4:00 a.m., but the birds obviously had more important things on their mind (like finding a mate). Awash in a sea of beautiful birdsong, each individual wants to make themselves heard and to hear each other clearly. Picking this time means that the ladies ‘had their number’ so to speak, and the other males knew who was in which territory.
So the next time you get woken by the dawn chorus don’t get too annoyed – the birds are just trying to chat to their friends before the turbulence drowns them out.
Answer by Autumn Sartain and Nick Waszkowycz
A video of a Brewer’s sparrow singing the short version of its song:
To hear the long song: http://birdnote.org/show/brewers-sparrow-sageland-singer
Brown, T. J. and Handford, P. (2003). Why birds sing at dawn: the role of consistent song transmission. Ibis 145: 120-129. doi: 10.1046/j.1474-919X.2003.00130.x.
Picture credit: TCDavis on Flickr