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It turns out you can teach an old bird new songs. Adult thrush nightingales have been observed practising new songs in their wintering grounds. The new melodies may help them impress mates when the spring breeding season arrives.

Thrush nightingales breed in northern Europe and undertake a lengthy migration to sub-Saharan Africa, where they spend the winter. In Europe, their songs are used to defend territory and attract mates 鈥� but it was unclear why they continued to sing in the wintering grounds.

鈥淭he birds are practising songs in Africa even in their later years,鈥� says Abel Souriau at Charles University in the Czech Republic.

He and his colleagues recorded natural birdsong from thrush nightingale breeding grounds in Poland and Russia, and compared them with the songs heard in wintering grounds in Tanzania.

Common patterns

They broke down each song into the syllables that make up the melodies, looking for common patterns. These include pairs of notes that typically start a song, repeated notes and complex trills, and the rhythmic castanet-like notes that typically end a song.

These elements were in all the songs recorded in Poland and Russia. But 89 per cent of the songs recorded in Tanzania lacked a typical song structure, were missing the silent pauses between phrases and had high variation in the sub-notes that make up the song. In other words, they weren鈥檛 recognisable as nightingale song. This suggests the birds are listening to their neighbours 鈥� and future rivals 鈥� in the spring and having a kind of jam session over the winter as they remix song elements into new patterns.

A similar finding was made a few years ago in a study that focused particularly on another songbird called the great reed warbler.

鈥淲hat we love in nightingales is that they sing with so much complexity and regularity, like classical music. But this is totally random vocalisation 鈥� there鈥檚 no beginning, no end. It鈥檚 more like improvising,鈥� says Souriau.

Thrush nightingales typically know between 23 and 42 songs, and they usually learn them when they are young. 鈥淭he winter songs recorded in this study are more typical of songs sung during early song development and suggest that thrush nightingales may be singing during the winter to improve the quality of their song,鈥� says Marjorie Sorensen at the University of Guelph in Canada. 鈥淕iven that in subsequent breeding seasons females choose mates based partly on the quality of their song, this may be a smart long-term strategy.鈥�

She says migratory birds like nightingales could sing in winter to defend their feeding territories, but more research is needed to show that.