Since time immemorial, farmlands have been as alive with bird songs as the sound of the wind. But now, these melodies are falling silent. For the last forty years, bird species that live in and among farmlands have plummeted worldwide, a downward spiral researchers say has flown under the public's radar.

“There's either large, charismatic animals [that] everybody knows are disappearing, or unknown species that vanish without being noticed—but what of the fate of the common species that are also disappearing without warning?” asks Benoît Fontaine, a conservation biologist at France's National Museum of Natural History.

In March, Fontaine and his colleagues announced the results of a survey of France's bird populations. The findings, which grabbed headlines around the world,