Bird populations across the French countryside have fallen by a third over the last decade and a half, researchers have said. Dozens of species have seen their numbers decline, in some cases by two-thirds, the scientists said in a pair of studies - one national in scope and the other covering a large agricultural region in central France. The situation is catastrophic," said Benoit Fontaine, a conservation biologist at France's National Museum of Natural History and co-author of one of the studies. A migratory song bird, the meadow pipit, has declined by nearly 70%. The museum described the pace and extent of the wipe-out as "a level approaching an ecological catastrophe". The primary culprit, researchers speculate, is the intensive use of pesticides on vast tracts of monoculture crops, especially wheat and corn. The problem is not that birds are being poisoned, but that the insects on which they depend for food have disappeared. Recent research ... has uncovered similar trends across Europe. Flying insects have declined by 80%, and bird populations has dropped by more than 400m in 30 years. Despite a government plan to cut pesticide use in half by 2020, sales in France have climbed steadily, reaching more than 75,000 tonnes of active ingredient in 2014, according to European Union figures. "What is really alarming, is that all the birds in an agricultural setting are declining at the same speed, even 'generalist' birds," which also thrive in other settings such as wooded areas, said [ecologist Vincent] Bretagnolle.