Pesticides More problematic for Birds than Previously thought
Farmland species of bird have declined dramatically in both Europe and North America. It has long been suspected that the use of pesticides played a role in this decline. But until recently there was no concrete proof. A Dutch study had shown that bird populations had fallen more sharply in the highest areas of pesticide use, but there had been no research during which the birds were actually tested.
Now, a study conducted by the University of Saskatchewan in Canada has shown that neonicotinoid pesticides harm songbirds and disrupt their migration. Neonicotinoids were known to impact vital pollinators but the new research indicates that the chemicals directly affect birds.
Neonicotinoids Toxic to Birds
The study looked at how the neonicotinoid imidacloprid impacts white-crowned sparrows which migrate from the southern US and Mexico to northern Canada in summer. Imidacloprid is the World’s most widely used insecticide and the study demonstrated that it causes birds to lose their sense of direction and suffer drastic weight loss.
Three neonicotinoid pesticides were banned from use on flowering crops in the European Union in 2013. They were deemed to present an unacceptable risk to bees and other pollinators. A total outdoor ban is now being considered. Canada is likely to follow suit. Neonicotinoids now seriously pollute the environment across the globe but pressure is growing to reduce pesticide use.
Research has indicated that a reduction in the use of Neonicotinoids would not impact food production.
The Canadian study analysed the effect of imidacloprid on the white-crowned sparrow and the researchers were shocked by what they found. They had not anticipated the acute toxicity of the pesticide. Birds were given doses equivalent to less than a single corn seed and within hours became weak, developed stomach issues and stopped eating.
The birds quickly lost up to 25% of their body weight and became unable to identify which direction was north. The birds had essentially become lost. A control group of birds which were not fed the pesticide remained unchanged. The birds were tested again after 14 days and had recovered their weight and sense of direction but any delay to their migration could seriously damage their chances of breeding. Disruption to breeding will reduce population levels.
Neonicotinoids and Mammals
Neonicotinoids are usually applied to the seeds of crops, so they can permeate the entire plant. Another new study has shown that birds and other animals do eat spilled seeds. Birds and a variety of mammals eat the seeds and research is ongoing to investigate how the insecticide impacts the different species.
Bayer, the manufacturers of imidacloprid claim that the insecticide has minimal environmental impact and that songbirds typically remove the seed hull to which the insecticide is applied. They also claim that birds will ignore the treated seed if other foods are available. Which, of course, they often aren’t in areas of intensive agriculture!
The scientists conducting the Canadian study are now measuring levels of the insecticide in the birds’ blood, to assess the actual level of contamination. They are also looking at data from radio-tagged birds given even smaller doses of neonicotinoid, but even this appears to affect their migration.