Nightingales can adjust the pitch of their whistle songs to precisely match the songs of other nightingales, just as we humans modulate our tone of voice during a conversation.
The common nightingale (Luscinia megarhynchos), a migratory bird found in Europe, Asia and Africa, has inspired countless writers and musicians with its melodious songs.
Male nightingales have very large repertoires of up to 150 to 200 different song types, one of which is known as a whistle song. During the mating season, male nightingales perform these songs in duels to defend territory and attract mates, sometimes for many consecutive nights.
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at the Max Planck Institute for Biological Intelligence in Germany and his colleagues recorded whistle songs from pairs of male nightingales during their mating season in Brandenburg, Germany. They also conducted playback experiments during the mating season and at the birds’ wintering grounds in The Gambia in West Africa.
They found that nightingales flexibly adjusted the pitch of their whistle songs to match that of their opponent. When the researchers played pitch-controlled artificial whistle sounds from speakers, the nightingales also matched their pitch to these across a wide range of frequencies.
“These findings show how flexible the singing behaviour of these birds is,” says Costalunga.
When they responded within 2 seconds, the birds’ pitch matching was more precise than if they responded after a delay of 6 to 8 seconds, suggesting they only have a very brief memory of the sound they are imitating.
It is unclear exactly why the nightingales replicate the pitch of other males’ whistles, or how the winner of a singing duel is decided. It might be that females choose mates based on their pitch-matching ability, but this is just speculation, says Costalunga.
Parts of nightingales’ brains involved in singing shrink in autumn and regrow in springtime. Their singing waxes and wanes in tandem with these annual cycles, but the researchers found that the birds were still able to perform pitch matching during the winter, when they rarely sing and don’t mate.
“Even though these birds on their wintering grounds have regressed their brains and are no longer producing well-formed, crystallised songs, they’re still doing this pitch matching,” says  at Duke University, North Carolina, who wasn’t involved in the research.
“From a behavioural point of view, it suggests that there’s some kind of information that is being conveyed in these non-breeding interactions,” he says.
Costalunga and his colleagues hope to unravel the neural underpinnings of pitch matching in nightingales by recording the birds’ brain activity to learn how they perceive and reproduce the pitch of whistles.
Current Biology
