Bernie Solymar, coordinator of the Ontario Barn Owl Recovery Project, really thought the birds would come back. He worked for years to make it happen, enlisting hundreds of volunteers to build more than 300 nest boxes and hang them up across the province. But in more than a decade, not a single barn owl was seen using the nests.

“It was a big project. These were all built by local scout groups and volunteers,” Solymar says. “We wouldn't have done it if we didn't think it would work. We thought that by providing the housing, they would be sheltered.”

Barn owls are a farmer’s friend, keeping rodents at bay: a family of barn owls can eat as many as 4,000 mice and other small mammals in a single year. That’s why it was so easy to convince farmers in southwestern Ontario to put the nests up: build it, the hope was, and they will come. But species become endangered for many reasons, and sometimes addressing just one concern fails to make a difference.

Solymar says barn owls were likely more plentiful in the mid-20th century: “That was a time when a lot of the farms had a lot of stuff going on, there were different crops grown, every farm had livestock, and people stored their grain at home, so there were lots of mice around for barn owls.”

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Although barn owls live on every continent except Antarctica, it’s rare to see them in Ontario, partly because they don’t do well in extreme cold. It’s estimated that there are fewer than five nesting pairs in the province (and just two have been reported this year). Part of the problem is Ontario’s disappearing grasslands, most notably the tallgrass prairie ecosystem that once covered 1,000 square kilometres and provided barn owls with fertile hunting grounds. Today, just 21 square kilometres remain, scattered throughout the province.

“Barn owls have adapted to be grassland hunters worldwide,” says James Cowan, director of the Canadian Raptor Conservancy and a founder of the owl recovery project. “We thought originally we were going to find out it was lost nesting habitat, like trees and cavities of old barns [that was causing owls to die off], but we soon learned it was the foraging habitat where mice are found.”

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That habitat hasn’t completely disappeared from Ontario, but the locations it exists have become closely guarded secrets according to Don Sutherland, a zoologist with the province’s Natural Heritage Information Centre: “There are at least two farms in the southwest and these landowners do not want the locations known by anybody … they're afraid of that news getting out and being besieged with well-wishers — birders and that.”

Nest boxes, which offer owls a space to breed, are relatively easy to put up — but restoring grassland is complex, costly, and requires farmers to relinquish valuable land to the cause.

The charity ALUS Canada is dedicated to restoring natural ecosystems where farming has taken over, including in Norfolk County, where the organization established a tallgrass prairie on three acres that couldn’t be profitably farmed.

“I think people think it's too late to do anything about it, but it's never too late,” Cowan says. “There's always something we can do. We do have bordering states that have populations of them, so I think if we put grasslands back into place that they would spill over into our climactic zone.”