An Owl with a Parachute

I never knew a northern spotted owl could parachute vertically through the forest.

This delightful image came from a researcher who spent eight years studying the owls in the Oregon Cascades. He had personally witnessed a descent and could hardly contain his excitement when he told us about it.

To find the reticent Strix for their study, the researchers walked through the forest with a bucket of mice, sending out their best imitation owl calls across the old growth timbers. If an owl replied, they came as close to the sound as they could and deposited a mouse on a nearby log.

These lab-bred mice, the researcher assured us, were “fat, white, and stupid.” They displayed none of the caution a forest-born mouse would exhibit. After watching the mouse take several lazy laps back and forth across the log, the owl could no longer resist and would swoop down silently through the trees to grab the hapless rodent in its talons. That was when the hard work began.

cjp

The researcher’s job was to set off after the owl, keeping their eyes on it as it headed into the higher branches towards its nest. The chase could go on for several hundred yards, sometimes almost vertically up a hillside, always through shrubs and the downed trunks of Douglas fir and western hemlock. If all went right, they would see the owl enter a nest high up in a tree. The next time they glimpsed it, the mouse would be gone, indicating to the researchers there were some chicks to feed. At this point, they took careful note of the location of the nest tree.

This is where the parachuting comes in. The survey protocol allowed them to feed up to four mice to each owl, offering up more data as the owl moved back and forth from its nest to the forest floor. The researchers typically served the owls’ second and third courses on nearby logs or rocks but sometimes, to add variety, they experimented.

One of the scientists discovered if you placed a mouse at the foot of the nest tree an owl would sometimes simply step out of the nest and drop vertically to the ground, with only a slight opening of its feathered limbs to cushion the freefall. The owl had the avian aplomb to brake at just the right moment to slow its descent and grasp its prey from the forest floor.  Winged flight, it appears, is not always necessary for a spotted owl to get a good meal.

Parachuting vertically is a neat trick but not enough, unfortunately, to save the spotted owl from a different menace. Nesting pairs of northern spotteds have declined from fourteen to just one over the last two decades in this particular portion of the Cascades due to the encroachment of the barred owl. Encouraged to move cross country by land use changes, the larger and more cosmopolitan barred owls have been making short work of any spotteds standing in their way. They outcompete them for food, hybridize with them, and occasionally kill their smaller cousins. In some areas, more than 80% of the spotted owls have disappeared since the barred owl arrived. It may not be long before the barred owl causes the extinction of the northern spotted owl, a species whose protection took many years of work, considerable political wrangling, and millions of dollars of investment.

The US Fish and Wildlife Service has been experimenting with removing barred owls from areas where spotted owls breed. Some evidence suggests the elimination of barred owls can be effective. Lowell Diller, one of the people tasked with shooting barred owls in spotted owl habitat reports a spotted owl pair returned to a previously occupied territory just thirteen days after the barred owls were removed. Not only are they quick to recolonize, they also have long memories. A female spotted owl returned to a patch of forest cleared of barred owls six years after she was last seen there.

Even if it can be effective, the practice of shooting owls to save owls creates a difficult ethical dilemma. The barred owls are native to North America. They are also in spotted owl habitat through no fault of their own. They are a charismatic and highly-adapted species. Does the planet need spotted owls more than it needs barred owls? Do the barred owls really deserve to be shot just because they are more successful?

US FWS
Two Northern spotted owl fledglings

It is a classic dilemma for the Anthropocene epoch. Human influence creates a habitat change. A native species struggles. An invader, helped along by more habitat disruption, provides an existential threat. Wildlife managers have to decide who to save and whether there are effective ways to do so.

If I claimed to have an answer to this conundrum I would be fooling you. Even though I am an environmental ethicist by trade who specializes in this kind of ethical challenge, it is easy to see both sides of the coin. Practical considerations, money, and sunk costs all weigh into the moral calculus. It is not clear the dilemma can be resolved, even by ethical experts.

In the absence of a clear answer to the question, I can only note how painful such dilemmas are, dilemmas certain to increase in frequency as habitat impacts together with climate change put more and more species under pressure.

There is one thing, however, I do know with certainty….and it is this. A world without an owl parachuting, feet first, down the front of a two hundred and fifty foot Douglas fir tree would be a poorer world indeed.

 

Forest picture by author
Owls by US Fish and Wildlife Service

 

 

 

 

 

 

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