A new study in the journal Nature connects neonicotinoids (and imidacloprid in particular) to a serious decline in insectivorous bird numbers in The Netherlands.
Runoff from neonic treated crops ends up in nearby waterways, reducing non-target invertebrate populations. This results in reduced food, such as mayflies and beetles, for insectivorous bird species, especially during the breeding and fledgling seasons. Higher readings of neonic levels in the water corresponded with a 3.4% annual decline in 15 species of insectivorous birds, after controlling for the possible deleterious effects of land use changes.
That’s a decline of over 30% for several bird species in a 10 year period. The most affected bird species were starlings, tree sparrows and swallows.
Additional analyses showed that the population declines only began in the 1990s, corresponding with the introduction of neonicotinoids to agriculture in The Netherlands.
The authors state:
“Our results suggest that the impact of neonicotinoids on the natural environment is even more substantial than has recently been reported and is reminiscent of the effects of persistent insecticides in the past.”
Although the study does not prove a direct causal link between neonicotinoid use and this very large decline in farmland bird populations, the study authors were careful to examine and eliminate many other possible causes.
Bayer, the main manufacturer of imidacloprid says it rejects the findings, saying the study hasn’t proved a “causal link” joining the use of the pesticide and a decline in bird populations.
“Neonicotinoids have gone through an extensive risk assessment which has shown that they are safe to the environment when used responsibly according to the label instructions,” a Bayer spokesman said.
One of the study authors, Hans de Kroon says:
“there is an incredible amount of imidacloprid in the water, and it is not likely these effects will be restricted to birds.”