Finding a home among humans
Vehicles, lack of hunting and nesting sites threaten urban barn owls: report
VANCOUVER — One of Canada’s largest populations of barn owls may be more aptly named bridge or overpass owls because they’re losing normal roosting spaces and struggling to adapt to urbanization, a new study says.
It was based on owls around Metro Vancouver and found that habitat loss, road deaths and rodent poison have a lethal impact on the birds but changes to green-space policies and public education could mitigate the loss.
Wildlife biologist and lead researcher Sofi Hindmarch said the original focus of the study was on the impact of rodenticide, but that changed when the owls were seen to be dependant on hunting along grass growing next to highways. Barn owls’ hunting behaviour usually involves flying within a metre of the ground, making them especially vulnerable to being hit by vehicles, said the study contracted by Environment Canada and published in the journal Landscape and Urban Planning.
The research was conducted between 2010 and 2014, when 11 adult barn owls were radio tagged and followed for five to 12 months, until the transmitter fell off or the battery died.
She followed one pair to an industrial building, other birds to overpasses and another pair to a busy commuter bridge over the Fraser River.
“A lot of these areas were predominately grass, marsh and farmland not that long ago. I suspect these are kind of remnant individual populations that are still persisting in an environment that is becoming increasingly urban.”
In the Lower Mainland and Fraser Valley, where blueberries and greenhouse-grown vegetables are the region’s fastest-growing crops, the birds’ grassland habitats are disappearing.
High-density human developments and farming also draw rats and mice, which the study said prompt the need for rodent control.
“Threats from the loss of habitat and nest sites were the main reasons barn owls were recommended to be upgraded in 2014 to ‘threatened’ in Western Canada,” it said.
The Canadian Species at Risk Act lists the Western barn owl population as a special concern, while the Eastern population found in southern Ontario is listed as endangered.
But Hindmarch said the owls she studied were highly adaptive and could coexist with humans.