Newly published research says two of Canada’s most commonly used pesticides cause migrating songbirds to lose weight and their sense of direction.
“This is very good evidence that even a little dose — incidental, you might call it — in their feeding could be enough to have serious impacts,” said University of Saskatchewan biologist Christy Morrissey, whose paper was published Thursday in the journal Scientific Reports.
Morrissey studied the effect of two widely used pesticide types — neonicotinoids and organophosphates. Both are used on more than 100 different crops, including wheat and canola, and are found in dozens of commercial products.
The so-called neonics are often applied to seeds before they’re planted in the ground. Organophosphates are applied in tiny granules.
Both are known to be lethal to birds in large doses, but Morrissey wanted to study the impact of smaller amounts.
She and her colleagues took three groups of white-crowned sparrows, a common migratory songbird found throughout North America, and exposed them to a small dose, a somewhat larger dose, or no dose at all.
All doses were kept deliberately small. The low neonic dose was the equivalent of four treated canola seeds per day for three days — about one per cent of the bird’s diet.
The results were dramatic.
After three days, the low-dose birds lost 17 per cent of their weight. The high-dose birds lost 25 per cent.
“That’s a lot,” said Morrissey. “At that point, those birds were on life support.”
The birds exposed to organophosphates kept their weight, but they lost something else — their ability to find north. Both the high-dose and low-dose group lost all orientation and didn’t get it back after the tests ended.
The neonics also disoriented the sparrows, but the effect faded when the exposure stopped.
A 2016 survey suggested that migratory songbird populations have fallen by 1.5 billion since 1970. Morrissey suggests that pesticides might be one reason why.
“In the real world, any bird that experiences these effects is pretty much a dead bird,” she said.
Morrissey points out that pesticides are often applied just as birds are increasing their food intake to get ready to migrate.
Pierre Petelle, head of the agricultural chemical industry association CropLife Canada, said the paper is being considered.
“We’ll be looking closely at the study, including how realistic the exposure scenarios were, among other elements,” he said.
“Like any new study on pesticides, this one will be thoroughly reviewed by both industry and regulators and it will need to be looked at in the context of other extensive studies.”
Neonics have already been blamed for steep drops in bee populations.
Health Canada is considering a ban on the neonic used in Morrissey’s study. The European Union strictly regulates its use.
Morrissey said her study has been made available to Health Canada.
There may be ways to keep the popular pesticide on the market and reduce its environmental impact, she suggested. Instead of being applied universally to seeds, it may be wiser to use neonics only when they’re needed.
“That’s where we have to consider how we’re doing agriculture, whether we should be applying very toxic pesticides when they may or may not need to be used.”
The Canadian Press