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Each year, snowy owls spread their wings and migrate to the prairies, where they have access to large numbers of rodents in vast open spaces.
But this year's migration is the first of its kind and is marked recent classification of snowy owls as a critically endangered species.
The designation was announced in May by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), which assesses the status of endangered native species and makes recommendations to the federal government.
Louise Blythe, associate professor at Victoria University's School of Environmental Studies and co-chair of COSEWIC's bird specialist subcommittee, says the decision to designate snowy owls as a critically endangered species was not an easy one. But, she said, their population has declined by about 40 percent over the past 24 years.
Snowy owls face many challenges, including loss of habitat in their Arctic breeding grounds due to climate change, Blythe said. Warming temperatures are melting sea ice, reducing the number of platforms on which owls can perch while hunting.
Snowy owls also suffer from avian flu, becoming infected with it and losing winter prey to the virus, Blythe said. According to the data, 15 cases of avian influenza have been identified in snowy owls in Canada since 2021. data compiled by the Canadian Food Inspection Agency.
Snowy owls face even greater challenges when they embark on their long migration south. On wintering grounds they may be hit vehicles, electrocuted along power lines, confused in human structures and become poisoned after eating exposed prey rodenticide.
Colin Weir, managing director of the Alberta Birds of Prey Foundation's wildlife rehabilitation center in Coaldale, has dealt with raptors affected by all of these phenomena.
“Oftentimes snowy owls come from the Arctic … they end up in new areas that have a lot of man-made hazards around them,” Weir said.
The center treats injured birds from across Canada and is currently home to two snowy owls that could not be freed after being hit by a car.
“The thing to remember about roads is that they have ditches that collect a lot of moisture and attract a lot of ground rodents,” Weir said. “So that’s why birds get hit by cars. Roadside ditches are like buffet restaurants for them.”
Weir said the busiest time for bird strikes in Alberta is from May to September because most migratory birds of prey return from wintering grounds further south during this time, but that is not the case for snowy owls.
“Just watching wildlife in general is probably the number one thing,” Weir said. “Not only for the safety of the creatures themselves, but also for the personal safety of people.”
Snowy owls can be found in every province in Canada following their winter migration. NatureCounts, a biodiversity data platform managed by Birds Canada, estimates there are 15,000 snowy owls in the country – more than half of the estimated global population of 29,000.
The International Union for Conservation of Nature classifies the global population of snowy owls as vulnerable.
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Snowy owls are particularly difficult to observe due to their nomadic nature, Lisa Takac Priestley said.
“They don't have direct corridors,” said Priestley, a wildlife biologist who has been studying owl populations and movement patterns for more than 20 years. “They are very difficult to work with in terms of trapping and banding.”
According to her, installing transmitters on snowy owls has allowed us to better understand their movement patterns, but this does little to confirm changes in the population.
Most data on snowy owl abundance comes from Christmas birdsan annual citizen science initiative in which thousands of volunteers across Canada count all the birds they see in a given area.
Because snowy owl movement patterns tend to be unpredictable, trying to track population trends based on visual counts may not be enough, Priestley said.
Because they have recently been designated as a critically endangered species in Canada, there may be increased interest and effort on the part of researchers to better understand snowy owl numbers.
“Now that the snowy owl is listed, we will be looking to use more data collected from different sources to help us understand where there may be more problems in certain parts of the owl's range,” Priestley said.
