There may be a good reason why birds are most vocal at first light, according to new research.
By singing early and often, birds perform better during the day, a new study suggests.
“It’s like they’re warming up backstage, before the sun comes up and the curtain rises.”
The morning cacophony is mostly males, whose songs are meant to impress potential mates and rivals.
“It’s like they’re warming up backstage, before the sun comes up and the curtain rises,” says coauthor Stephen Nowicki, a biology professor at Duke University.
Scientists have proposed various hypotheses for why birds do their most vigorous singing in the early morning hours. One idea is that it’s the best time to broadcast, since there’s little wind to distort their sound. Others have suggested that the dim light makes it difficult to do much else, like hunt for insects.
But the new study points to another benefit: the early morning vocal warm-up works wonders for their singing.
To test the “warm-up hypothesis,” Nowicki and biologist Susan Peters recorded 11 male swamp sparrows between 2 AM and noon for two to three mornings each.
The song of the swamp sparrow is a simple trill of up to five notes, repeated around 5 to 10 times a second. It sounds a bit “like a melodious police whistle,” Nowicki says.
Birdsong may look effortless, but it requires balancing competing demands of speed and dexterity, says first author Jason Dinh, a biology PhD student who did the study while still an undergraduate.
Birds switch from one note to the next by opening and closing their beaks. To go from low to high and back down again in rapid-fire succession, a bird must precisely coordinate the movements of their beak and voice box with each breath.
To monitor the birds’ performance, the researchers measured each bird’s trill rate and vocal range over the course of the morning.
“They’re able to perform more difficult songs later in the morning.”
For swamp sparrows, the concert can start as early at 2:30 AM. But they don’t wake up singing like virtuosos, the researchers found.
Statistical analysis of the recordings revealed that they start off taking it easy; singing slower, or with a more limited range.
They only start to nail their songs—picking up the tempo and reaching for higher and lower pitch—just after dawn, after hundreds of takes.
The more they warmed up, the better they got. “They’re able to perform more difficult songs later in the morning,” Dinh says.
While it’s hard to make direct comparisons to the physiological effects in humans, Dinh says, the warm-up up may help get their blood flowing and temperature rising to meet the physical demands of singing.
Previous playback experiments by this research team have shown that a well-sung song, compared to a rusty one, is a bigger turn-on for females and more threatening to eavesdropping males, Peters says.
If male swamp sparrows see improvements in their singing within hours, the researchers say, the next step is to find out if females take note. If so, then males that sing early and often may have an advantage in attracting a mate.
The National Science Foundation funded the research.
The research appears in Animal Behaviour.
Source: Duke University