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Humans to blame for majority of raptor deaths in Ontario, Guelph study finds

Humans encroaching on natural habitats is killing off Ontario's at-risk birds of prey, a new study from the University of Guelph has found. It is the first study of its kind to look at common causes of death in the province's raptors.

'These birds are solitary and territorial, so they need a lot of space to survive'

A great horned owl is released back into the wild in 2014. A new study from the University of Guelph has found humans encroaching on natural habitats is killing off Ontario's at-risk birds of prey - including the great horned owl. (John Gaudi/CBC)

Humans encroaching on natural habitats is killing raptors in Ontario, a University of Guelph study has found.

Pathobiology professor Nicole Nemeth led the study, which is the first to look at common causes of deaths of raptors in the province.

The researchers looked at death reports from the Canadian Wildlife Health Co-operative from between 1991 and 2014. In all, 1,500 birds were studied and the most common were red-tailed hawks and great horned owls.

Nemeth and her team found 49 per cent of the birds were killed by trauma. That included collisions with vehicles or other stationary objects, such as buildings.

The second most common cause was emaciation, which happened in 17 per cent of the birds.

That "often occurs when the landscape changes in a way that hinders them from successfully hunting and finding shelter," Nemeth said in a release about her study.

"We recognize that these causes in great part are related to human encroachment into these birds habitat and affecting their ability to survive," Nemeth said in a video about her research.

The causes of death in the other 34 per cent of cases included infection — most commonly West Nile Virus — and exposure to toxic substances.

Need a lot of space to survive

"Based on these findings, it is apparent that urban expansion into natural areas and other types of anthropogenic landscape alterations are behind many of these deaths," Nemeth said. "These birds are solitary and territorial, so they need a lot of space to survive."

She said raptors need a certain amount of space, cover and other resources to survive.

"When they can't find cover, are exposed to the elements and unable to rest, they will struggle to find food resources. Add to that a long hard winter and it's enough to kill them," she said.

Nemeth said she hopes the research brings more awareness to the plight of Ontario's at-risk birds of prey.

The study was published online in the Journal of Wildlife Diseases.

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