Number of jays in southern Ontario shrinking due to climate change, study finds
The number of jays in southern Ontario is declining due to more frequent freeze-thaw days due to climate change, according to a recently published study.
The birds’ winter food supply was compromised when fall temperatures fluctuated. The food would thaw, grow bacteria and in some cases become inedible.
And it had an effect on reproduction and the number of bird populations, researchers at the University of Guelph found in a study recently published in the scientific journal Global Change Biology.
“If your food is spoiled, you have less food than you can spend on survival and reproduction,” said Alex Sutton, who was a doctoral student at the University of Guelph when he co-led the study with Ryan Norris, Associate Professor. at the university’s integrative biology department.
“What seems to be happening is that they have to decide whether to survive or reproduce,” said Sutton, now a post-doctoral fellow at Kansas State University.
If the warming pattern in the fall continues to affect breeding and food supply, birds could become locally extirpated from Algonquin Provincial Park and other ranges in southern Ontario, said Sutton, who is based in Manhattan, Kansas, approximately 94 kilometers west of the capital, Topeka. .
Number of chicks refused
Canada jays are known to keep their food – which can be anything from berries to road meat – in nearby trees for the winter.
However, when their food supply deteriorated over freeze-thaw weather, non-migratory birds produced fewer young or less healthy hatchlings, Sutton said.
“On average, the number of chicks has decreased over time, or at least in years when falling conditions are unfavorable,” he said.
And that has long-term implications, according to the study with data spanning nearly 40 years.
The study looked at the birds in a small part of the park, about 280 kilometers northeast of Toronto. However, the Canadian jay population that has been studied in the park has ranged from a high of 85 to now between 40 and 50 depending on the year, Sutton said.
“Breeding was really the key factor driving this decline in Algonquin,” he said.
The study used bird population numbers from 1980 to 2018, as well as environmental data recorded in Algonquin Provincial Park since 1977 to examine the effects of temperature fluctuations on the bird population and their diet.
Between 1980 and 1996, which experienced 10 years of above-average freeze-thaw cycles, researchers found that the number of birds had declined significantly.
Although there were fewer above-average freeze-thaw cycles and more reproductive success in subsequent years, bird numbers never rebounded after “a period of poor environmental conditions over several years. decades ago, ”according to the study.
David Bird, a retired professor of wildlife biology at McGill University in Montreal, said the amount of detailed data included in the study is impressive but the results are disturbing.
“There are still a lot of challenges to overcome,” he said. “Climate change is very worrying.”
The birds could go north
Sutton and Bird believe the effects of climate change on bird food supplies could eventually push the species further north.
The Northern Jay is found in every province and territory, but little is known about the effects of climate change on northern populations.
The study said that citizen science databases, such as Christmas Bird Counts, “help fill this knowledge gap and are used to estimate population trends in more northern latitudes.” The bird is important to many Canadians, so much so that there is a campaign by Bird and others, like Norris, to name the Canadian jay the national bird of the country.
Sutton said it was important to learn more about the Canadian jay.
“I think it’s really important that we try to understand how this species actually responds to climate change across its range,” Sutton said.
“This could be a really key point in understanding how future population declines or even changes could occur with climate change.”