U of S researchers say songbirds that eat seeds coated with imidacloprid lose weight and delay their migration
The findings of a University of Saskatchewan study may affect the fate of insecticide seed treatments in Canada.
The study, published Sept. 13 in Science, has concluded that imidacloprid is a threat to songbirds.
When white-crowned sparrows consumed seeds coated with the insecticide, the birds lost weight and the exposure halted their migration, the scientists found.
“We saw these effects using doses well within the range of what a bird could realistically consume in the wild — equivalent to eating just a few treated seeds,” said Margaret Eng, a post-doctoral fellow in the U of S’s Toxicology Centre and lead author of the study.
“Both of these results seem to be associated with the appetite suppression effect of imidacloprid. The dosed birds ate less food, and it’s likely that they delayed their flight because they needed more time to recover and regain their fuel stores.”
Imidacloprid is a neonicotinoid, a class of insecticides used on tens of millions of acres in Canada.
Neonics are applied to almost every corn and canola seed in Canada and a portion of soybean seeds. They are also applied as sprays on fruit, vegetables and berry crops.
The study on songbirds comes at a time when Health Canada is making a final decision on the safety of neonicotinoids.
Health Canada has proposed to phase out all agricultural uses of neonics because the insecticides were accumulating in ponds, creeks and other water bodies near agricultural land.
Health Canada has argued that neonics are reducing the population of midges and mayflies in water bodies, potentially harming birds and other animals that depend on those insects for food.
“Current research shows that these pesticides are detected frequently in water bodies at levels that could be harmful to certain aquatic organisms,” Health Canada said earlier this year. “The department expects to report on its findings at the end of 2019.”
Normally, proposed decisions on pesticides usually become final decisions at Health Canada.
However, water-testing data carried out in 2017 and 2018 indicated that researchers were finding tiny amounts of neonics in waterbodies. Based on that new data, some observers believe Health Canada might back away from its neonic ban.
However, the U of S study on songbirds may force Health Canada to think longer and harder about neonicotinoid safety.
“Migration is a critical period for birds, and timing matters. Any delays can seriously hinder their success in finding mates and nesting, so this (study) may help explain, in part, why migrant and farmland bird species are declining so dramatically worldwide,” said Christy Morrissey, University of Saskatchewan toxicologist and senior author of the study.
Scientists from the U of S and York University studied sparrows at a location in southern Ontario, a stopover during the spring migration.
They exposed the sparrows to small doses of imidacloprid and used a tagging technology to evaluate the impact on the birds. The sparrows’ body composition was measured before and after exposure. They also tracked the sparrows’ movements in the wild.
“Birds given the higher dose of the pesticide lost six percent of their body mass within just six hours. That one dose also caused birds to stay 3.5 days longer, on average, at the stopover site before resuming their migration, compared to control birds,” the U of S said in a news release.
Canada’s crop protection industry says it supports research into product safety, but this study exaggerates the risk to birds.
“It appears that the doses administered in this most recent study are … well above what songbirds might realistically be exposed to under real world conditions,” said Pierre Petelle, CropLife Canada president and chief executive officer.
If pesticide research is not based on real world situations, it distorts the truth about pesticide safety, he added.
“Without (realistic exposures), these studies create unnecessary confusion within the industry, for regulators and for the public.”
Science, Nature and PNAS are known as a “high-impact” academic journals. Consequently, a number of media outlets covered the U of S study on neonics and songbirds, which was published in Science. Those include National Geographic, the Australian Broadcasting Corp. Scientific American and Bloomberg.