Berlin: Sarah Darwin, the great-great granddaughter of British biologist Charles Darwin, was sleepless in Berlin when, to her “enormous surprise”, she heard a nightingale warbling merrily outside her window.

“It’s very, very rare in the UK, so to be living in the middle of a capital city in Europe and hearing a nightingale singing outside your bedroom window is quite an extraordinary experience,” the Berlin-based British botanist told AFP.

The trills got Darwin thinking, and led to the launch of a citizens’ project examining why the non-descript-looking brown bird, with its distinctive song, has been flocking to the German capital. The project by Berlin’s Natural History Museum, where Darwin works, asks city dwellers to go out and record nightingales’ song with their smartphone and upload it onto an app.

Through the sound clips collected, scientists are also seeking to map out whether the birds take on “different dialects” in different parts of Berlin. “What’s really exciting in Berlin is that, unlike for instance in England, where the population of nightingales has plunged by 90 percent in the last 60 years, in Berlin there’s in fact a positive trend,” said Silke Voigt-Heucke.