Just like an opera singer or pop star would never enter the stage or recording studio without stretching their vocal cords, songbirds appear to practice their singing early in the morning before they put on a full performance a little later on, a new study finds.
The research was published in the journal Animal Behaviour.
Scientists have always been curious as to why birds sing so vigorously and so loudly so early in the morning.
“A bunch of reasons have been proposed as to why birds sing most intensely during the dawn chorus,” first author Jason Dinh, a biology PhD student who did the study while an undergraduate at Duke University, told Treehugger. “For example, the temperature might be best for sound transmission, the efficacy of foraging might be low at dawn so birds might invest in other activities like singing, or the rate of territory intrusion is highest at dawn so birds need to sing more to defend their territory.”
But researchers at Duke were interested in a “warm-up hypothesis” that the intense pre-dawn trilling puts them in best form for singing later in the morning.
“I think warming up might be one explanation to the dawn chorus, but it is certainly not the only explanation! There are probably several benefits driving birds to sing so intensely at dawn,” Dinh said.
To test the warming-up theory, researchers recorded 11 male swamp sparrows for several mornings each between 2 a.m. and noon. The swamp sparrow’s song is a simple trill of just five notes or fewer. It repeats five to 10 times a second and sounds a bit “like a melodious police whistle,” co-author Stephen Nowicki, a biology professor at Duke, said in a statement.
(Listen to a recording of a dawn chorus of swamp sparrows singing in Pymatuning marsh in northwest Pennsylvania.)
Practice Makes Perfect
The researchers measured each bird’s trill rate and vocal range throughout the mornings. Although swamp sparrows can start singing as early as 2:30 a.m., they aren’t in their best voice as soon as they open their beaks, researchers found.
Recording analysis showed that the birds start off singing slower or with limited range. They practice hundreds of times, gradually picking up tempo and reaching higher and lower pitch until they perfect their songs right after dawn. The more they practice, the better they sound.
“They’re able to perform more difficult songs later in the morning,” Dinh said.
It’s difficult to directly compare birds to humans, said Dinh, but warming up may help birds get their blood flowing and help their temperature increase so their bodies are prepared for the physiological demands of singing.
“It is physically challenging to sing high performance songs,” Dinh explained. But the payoff may come in romantic and defensive ways.
“In swamp sparrows, we know that females are more attracted to high performance songs. Furthermore, high performance songs are more threatening to rival males.”