Barn owls suffer amid long, harsh winter

B.C.’s barn-owl population is falling with the snow.

Delta’s OWL Orphaned Wildlife Rehabilitation Society has taken in 43 barn owls since Jan. 1, compared with just five barn owls over the same period last winter, according to raptor care manager Rob Hope. Many of the rescued owls have died.

Winter is a tough time for many birds, but “it’s the barn owls that have been the hardest hit this year,” said Hope.

B.C.’s barn owls are at the northern limit of their range in the Lower Mainland and have been identified as a threatened species for many years. Wildlife biologist Sofi Hindmarch estimated there are between 600 and 1,200 barn owls in B.C., but the birds’ nocturnal habits make it hard to say for sure.

Harsh winters are known to reduce population size — the birds can’t store body fat and don’t have warm feathering on their feet — and starvation is a common cause of death. Hindmarch recently found a dead chick at one of the nesting sites she monitors and assumed its parents had abandoned it during the last big snowstorm.

“I would expect that after a tough winter, we’d see some population decrease,” she said, explaining that the deep snow provides cover for the small rodents the owls rely on for food.

But B.C.’s barn owls are also facing threats that have nothing to do with Mother Nature.

Rat poison and other rodenticides are often fatal to the birds, which arrive at OWL anemic and bruised after eating mice and other small rodents that have ingested blood-thinning poison, said Hope. “The poison just travels down the line.”

In 2009, Environment Canada scientists looked at the livers of 164 barn, barred and great-horned owls from B.C. and Yukon and found evidence of at least one anticoagulant rodenticide in 70 per cent of the birds. Health Canada has since restricted the use of some poisons, but the carnage continues.

Newer rodenticides take longer to work, but they’re still fatal to barn owls, said Hope. When the poisoned raptors are close to death the vitamin K injections that can help with blood coagulation aren’t effective.

“If they come in early enough, we can save them,” he said, “but that’s quite rare.”

GERRY KAHRMANN Karen Wheatley, president and CEO of the OWL Orphaned Wildlife Rehabilitation Society, holds Sarah, a barn owl that lives at the facility, in Delta on Thursday.