A new study has found the first piece of hard evidence proving neonicotinoid pesticides used to kill bees has caused the population of insect-eating birds in the Netherlands to decline.
Casper Hallmann, lead author of the study from Radboud University in the Netherlands, and his colleagues looked at the population data of insect-eating birds such as barn swallows, starlings, mistle thrushes, and tree sparrows, among others. The team saw that their numbers dropped the most in areas where neonicotinoid-type pesticides were heavily used.
Nine of 15 bird species studied only ate insects, and all 15 species fed insects to their young. The pesticides affected the birds because it killed the bees and other insects that they eat.
"We cannot say this is proof (that the pesticide causes the decline in bird numbers) but we cannot explain the ... decline of birds by any other factors," Hallman told Reuters.
The European Union (EU) imposed a moratorium on three neonicotinoid-type pesticides for two years to help the bee population recover. But the pesticides are still widely used in other nations and are still legally distributed on barley and wheat crops within the EU.
Agrochemical companies Bayer and Syngenta contested the "unjustified" and "disproportionate" pesticide ban last year. In a court filing, their representatives argued that there were other factors that might have contributed to the bee population decline, such as parasitic mites. This is despite several studies that their products were behind the deaths of millions of bees.
"This study is the first to provide direct evidence that the widespread depletion of insect populations by neonicotinoids has knock-on effects, wrote Dave Goulson of Sussex University, in a commentary.
Pollination expert Professor Charles Godfray from Oxford University told Reuters that while the authors failed to establish a strong cause-and-effect relationship, it showed the need to perform the study in agricultural landscapes to gather more substantial data.
The results of the study were published in the July 9 issue of Nature.
