Songbirds sing loudest at dawn "to warm up their voices," ready for a busy day of performances, the study claims
- Scientists have long known that songbirds sing loudest at dawn
- But the reason and why birds do this has remained a mystery
- The study now shows that the animals can use the first rays of the sun to warm up their vocal cords
Songbirds sing loudest at dawn and in the budding light of a new day, but the reason for this has never been fully understood.
A new study may have finally provided an answer to the puzzle, suggesting that the animals use the early morning to warm up their voices before a day of singing.
For some birds, the concert can start as early as 2.30am and their songs get better and more complicated as the day goes on as they warm up.
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A new study suggests that songbirds use the early morning to warm up their vocal cords for the day's performance. The researchers examined swamp sparrows (picture) and found that they start slowly before warming up during the day
Study co-author, Professor Stephen Nowicki of Duke University in North Carolina, said, “It's like they're warming up backstage before the sun comes up and the curtain goes up.
"The morning cacophony consists mostly of men whose songs are meant to impress potential friends and rivals."
Scientists have proposed several hypotheses as to why birds sing most vigorously in the early hours of the morning.
One idea is that it is the best time to broadcast as there is little wind to distort their sound.
Others have suggested that the dim light makes it difficult to do many other things, like hunting insects.
Depicted is a swamp sparrow that has a simple reputation of just five notes. Researchers say it sounds like a "melodious police whistle" and the gap between notes gets longer as the day goes on
Three billion fewer birds in the US and Canada than 50 years ago
Experts studying historical birdwatches and a decade of radar data on migratory birds report a "widespread ecological crisis."
A study last year reports that there are now three billion fewer birds in the United States and Canada than there were 50 years ago.
They found that North American bird populations have declined 29 percent since 1970.
The analysis found "tremendous losses" in various groups of birds and habitats – from iconic songbirds like the meadow lark to long-distance migrants like swallows and even such common garden birds like sparrows.
Although the study did not examine the causes of the decline in each species, the team suggests that habitat loss from agriculture and urbanization is likely a major cause.
To test the warm-up hypothesis, Professor Nowicki and Duke biologist Susan Peters recorded 11 male swamp sparrows between 2 a.m. and 12 noon.
"The Swamp Sparrow Song is a simple trill with up to five notes that is repeated about five to ten times per second," says Professor Nowicki.
"It sounds a bit like a melodious police whistle."
Birds switch from one note to the next by opening and closing their beaks.
In order to go from low to high and back down again in quick succession, a bird must precisely coordinate the movements of its beak and voice box with each breath.
Lead study author Jason Dinh, a PhD student in biology who completed the study as a Duke undergraduate, said, "Birdsong may look effortless, but it requires a balance between competing demands for speed and skill."
To monitor the performance of each bird, the researchers measured their trill frequency and vocal range over the course of the morning.
Analysis of the recordings revealed that the birds start slowly before opening tubes later in the day.
Mr. Dinh said, “The more they warmed up, the better they got. You can play more difficult songs later in the morning.
"While it is difficult to make direct comparisons with the physiological effects in humans, warming up can help the blood flow and the temperature rise to meet the physical demands of singing."
The results were published in the journal Animal Behavior.
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