U of S researcher says common insecticides make birds lose their way

Exposure to two insecticides often used to control agricultural pests led the migratory songbirds studied by University of Saskatchewan researchers to lose their sense of direction.

Dr. Christy Morrissey, a biology professor, and Margaret Eng, a postdoctoral fellow, studied 51 whitecrowned sparrows. At first, all of them were able to find their way northward, as migratory birds do in the spring. But after test groups were dosed with imidacloprid and chlorpyrifos, the birds were unable to orient themselves. Some of the birds exposed to imidacloprid began to fly east; others, along with the birds exposed to chlorpyrifos, began to fly in random directions.

“These are two of the most widely used insecticides in the world, so in terms of numbers of crops and areas of treated land, these are extremely common,” Morrissey said. “Also the timing of when farmers are seeding the crops and using the chemicals directly overlaps the ... spring migration of these millions of songbirds.”

The study, published online on Thursday in the journal Scientific Reports, also found that exposure to one of the insecticides led to the songbirds losing body mass and having significant reductions in their fat stores.

Morrissey said they started their research in part because of ongoing controversy about the use of imidacloprid, a neonicotinoid, which is used as a treatment to coat seeds, and chlorpyrifos, one of the older organophosphate chemicals. Both neonicotinoids and organophosphates are used in agricultural settings to ward off crop-damaging pests, but they have also been linked to the decline of bee populations.

In 2016, Health Canada announced it would re-evaluate allowing the use of neonicotinoid insecticides. Its Pest Management Regulatory Agency is reviewing comments received during a consultation phase earlier this year, and scientific data is still under review.

Much of the debate right now is over what happens if imidacloprid is removed from use through a proposed ban and older organophosphate chemicals are used instead, Morrissey said. In particular, what would be the risk to exposed species, such as songbirds?

“So a bird that stops along its journey in its agricultural habitats where they very commonly feed ... routinely will use these crop seeds as they’re migrating just to fuel up their journey, will not only experience the impaired migration orientation but will also experience severe weight loss that can delay

The timing of when farmers are seeding the crops and using the chemicals directly overlaps the ... spring migration …

their overall journey or put them off course,” she said.

After the dosing ended, the birds began to regain their body mass at the rate they lost it. The birds exposed to chlorpyrifos didn’t regain their ability to orient themselves within the two weeks after the dosing period in which the researchers continued to observe them.

Scott Hartley, an insect specialist with the Ministry of Agriculture, said both insecticides are permitted for use in Saskatchewan. He said imidacloprid is not widely used in the province, but is used as a seed treatment. Chlorpyrifos is sprayed onto crops.