Killing owls to save owls

Yesterday, we brought you one of the longest stories we’ve ever published: an in-depth look at the fight for the survival of northern spotted owls in British Columbia.

We wrote about the decades long process that led to three of the owls being returned to the Spuzzum area, where local Indigenous people consider them to be the “messenger of the forest.” If you haven’t read that story yet, you can do so here.

Sometimes to save a few owls, you apparently have to kill a few owls (of a different sort).

Fifteen years ago, as BC officials considered how to help the province’s northern spotted owl population rebound, they hoped to stop the encroachment of a species of larger and meaner owls. That led biologists to begin removing barred owls, which aren’t endangered, from the territory of existing northern spotted owls, which are. That has been done both through relocating the owls and, sometimes, by killing them.

The details of those relocations and killings—somewhat euphemistically called “removal”—shed light on a fascinating inter-bird war in North America’s forests, and the difficulties humans face when attempting to intervene.

Owl vs. owl

Unlike the northern spotted owl, the barred owl is not endangered and has spread its territory across North America in recent years. Some of that expansion has come at the expense of northern spotted owls. The expansion is not wholly natural: northern spotted owls thrive in old growth forests, but as those forests have become sparser, barred owls have found themselves more able to adapt and thrive.

Efforts to reverse the demise of the northern spotted owls failed, with only one bird surviving in the wild. But today, with the owl’s future dependent on the success of a breeding-and-release program, the removal of barred owl is still seen as important to the bird’s future.

Biologists need to ensure that the precious northern spotted owls released into the wild aren’t immediately killed by aggressively territorial barred owls. So officials have sought to ensure that the precious few owls bred in captivity and released into the wild wouldn’t be placed in areas where barred owls were present.

So how was that accomplished? A 2016 report by provincial biologists details a decade’s worth of owl-removal efforts. You can read the report yourself here.

Between 2007 and 2016, 150 barred owls were removed from 32 different sites. If biologists looking for northern spotted owls spotted a barred owl in the vicinity, it was removed either as soon as possible or after breeding season. During the breeding season, only one of a breeding pair was removed.

Biologists used two sharply different strategies: “soft removal” and “lethal removal.”

Eliminating an owl wasn’t the first choice.

‘Soft removal’ involved trapping the birds and relocating them at least 50 kilometres from any northern spotted owl territory. Almost all were taken to a single watershed “outside the southwestern boundary” of the range. (The specific place isn’t revealed. But the identification of the boundaries suggests birds were released on Vancouver Island and other areas along the southern BC coast.)

Two-thirds of birds were removed by this method.

The lethal option was, well, lethal. It involved shooting and killing the owls using a Remington shotgun loaded with BB shot. Of the 150 owls removed, about one-third—42 birds—were killed.

Barred owls were killed if: A) biologists were unable to capture the bird on two occasions; B) if one capture attempt failed and the bird posed an imminent threat to a spotted owl; or C) if the site was deemed too remote to allow for relocation. The dead owls were then collected for research purposes.

Lethal removal was easier and more effective than the softer alternative, the biologists wrote. It took around three site visits to capture and relocate the average barred owls. It took two visits on average to shoot an owl dead.

If funding permitted, biologists returned to the sites each year to survey them for both northern spotted owls and barred owls.

There was one other issue with relocating barred owls: a handful kept coming back.

In the United States, work is also underway to help the northern spotted owl population rebound. Biologists there had stopped capturing and relocating barred owls because of concerns that the barred owls would return to the northern spotted owl areas.

And in BC, at least three different owls that were relocated returned within the 50-plus-kilometres to their previous site. One bird was particularly persistent. He was relocated, returned to his previous territory, was relocated again, returned again, and was then relocated a third time.

“These returns of translocated owls suggest that the success of soft removal rates could be overestimated,” the report declared.

The study’s authors said their findings showed that helping the northern spotted owls re-establish their territories will require humans to keep removing barred owls.

“Due to ongoing recolonization by barred owls, a consistent annual removal effort would be required to achieve effective control and provide habitat for northern spotted owl re-establishment that is not occupied by barred owls,” they write. And on that front, killing the owls may be more effective than moving them. “Lethal removal may be more effective than soft removal because it improves efficiency (cost and removals per visit).”