By Alanna Mitchell
A Saskatchewan researcher finds that neonics are devastating Canada’s bug-eating birds as much as they are our pollinators
Being a successful migratory bird depends on a few basics. Among them: being able to figure out where you’re headed and being able to get enough food to fuel the trip. If either of those is missing, it means the journey is in peril and so too is the critical goal of passing on the DNA to the next generation. It’s one of the reasons that migration is one of the riskiest parts of a bird’s life.
Nearly nine in 10 of Canada’s birds spend part of their lives in other countries. And many of them have been in steep decline. The “aerial insectivores,” meaning the ones that snatch bugs out of the air for food, are in the biggest trouble, according to 2012’s State of Canada’s Birds report. Their populations dropped 63.7 per cent from 1970 to 2010. When the report came out five years ago, Christy Morrissey, an ecotoxicologist at the University of Saskatchewan in Saskatoon, wanted to figure out what was going on. Could it be that the wintering grounds were changing? Or that the birds’ food was vanishing? She decided to find out.
I first wrote about Morrissey’s work in 2014 for this column, and then, spurred by my own curiosity, went to the Prairie fields with her that summer. Her focus by then was a relatively new class of insecticide: neonicotinoids, or neonics for short. They had become the most popular insecticide in the world over the previous couple of decades, and were very often used to coat seeds of canola, soybean and corn crops. That means the insecticide is used whether there’s an infestation or not. And it means the insecticide is used in huge volumes.
Over time, the central concern has become how neonics affect bees. The European Commission is considering banning neonics entirely from fields. Health Canada is considering a phased-in ban on one formulation, imidacloprid, in agricultural fields. Ontario and Quebec and the cities of Vancouver and Toronto have voted to limit the chemical’s use. The use of neonics is under review in the United States as well.
Still, while they have been known for some time to be a powerful neurotoxin to insects, they were thought to be safer for warm-blooded animals than earlier pesticides.
Christy Morrissey was testing that assumption: she was wondering how neonics affect the birds that consume prodigious quantities of insects. A surprising early study she did found that neonics persist in the environment far longer than anyone had expected: about 90 per cent of potholes near affected fields still had last-year’s neonics in them in the spring before new crops were laid down. Insects breed in the potholes. Birds need the insects. Morrissey continued to unpack the implications.
Then, in November 2017, Morrissey published the results of a stunning new study, the first of its kind. It looked at the direct effects of the neonic imidacloprid and an older class of pesticide, an organophosphate, on the white-crowned sparrow, a migratory bug-eater.
In just three days, the sparrows that got the low dose of neonic lost 17 per cent of their weight. Those that got the high dose lost more than 25 per cent. About one in five of the neonic-dosed birds died. It was a far more severe reaction than to the older pesticide, a surprise.
She and her co-authors, Margaret Eng and Bridget Stutchbury, caught 51 sparrows as the birds were migrating in the spring and fed some of them with different doses of insecticide. The neonic doses were set to be the equivalent of what a sparrow might easily get in a field. The low dose was about four canola seeds or less than a tenth of a corn seed; the high dose was about nine canola seeds or about two-tenths of a corn seed.
The sparrows’ body weights plummeted after they got the chemicals. In just three days, the sparrows that got the low dose of neonic lost 17 per cent of their weight. Those that got the high dose lost more than 25 per cent. About one in five of the neonic-dosed birds died. It was a far more severe reaction than to the older pesticide, a surprise.
And then there was navigation. The sparrows dosed with either type of pesticide couldn’t find their way. The pesticides are toxic to the birds’ neural networks. The ability to figure out where you are, where you want to go and how to get there — which means sensing the Earth’s magnetic field and reading cues from the sun and stars — is contained within the neural networks. In some cases, their sense of direction was disrupted. In others, it vanished completely. Recovery took weeks if it happened at all. It represented the loss of a critical survival skill during the migration period.
The result is a catastrophe: migrating birds lose their ability to fuel up for the journey, and then lose their way, too. And all for an insecticide that, in many cases, isn’t even needed. It is an object lesson in folly.