Saturday, January 24, 2009

Mr. Owl...

The January 2009 issue of Smithsonian Magazine has an interesting article about the spotted owl. Here's some information I picked up from the article and elsewhere on these owls, their connection to the conservation movement, and the new threat they're facing.

Spotted Owls

The spotted owl (strix occidentalis), is a member of the strix genus (sometimes referred to as "earless owls"), and as such it lacks the horn-like tufts of feathers that some other owls have near their ears. As the Latin name "occidentalis" suggests, this species is native to the American West, and as you may have gathered from its English name it has spotted plumage. Another distinguishing characteristic is that its eyes are all black.

There are three subspecies of spotted owl: the Mexican spotted owl (strix occidentalis lucida) whose feathers are the lightest brown, the California spotted owl (strix occidentalis occidentalis), and the northern spotted owl (strix occidentalis caurina) which is the darkest. The three subspecies have a lot in common: their habitat is made up of forested mountains and canyons (with old growth forests being particular important), their diet is comprised mainly of rodents, and they are all threatened by shrinking habitat due to logging and wildfires.

The Mexican spotted owl's range stretches from the Southern Rockies and Colorado Plateau of southern Utah/Colorado to the Sierra Madres of Mexico extending through Arizona, New Mexico and west Texas. It was declared an endangered species in 1993, and it is estimated that around 2,100 Mexican spotted owls currently live in the US.

The California spotted owl lives in the Sierra Nevadas and the mountains of southern California. Although it faces all the same challenges as other spotted owls, it is currently the only breed not protected under the Endangered Species Act.

The Northern Spotted Owl (the environmentalists' darling)



The bird at the center of the controversy in the 1990s was the northern spotted owl. It lives in the mountains along the Pacific coast from southern British Columbia to northern California. Its habitat is made up almost exclusively of old growth forest where it likes to nest in the hollows of old trees and in broken-limbed canopies and eat flying squirrels, red tree voles, wood rats and deer mice.

In 1990, the northern spotted owl was listed as an endangered species. After a series of conflicting regulations from different federal agencies, federal court cases brought by conservation groups (cf. Robertson v. Seattle Audubon Society), and Congressional legislation, it was decided that logging would be all but halted on federally-owned national forests in the Pacific Northwest in order to preserve the owl's habitat.

This reduced logging in the region by 80% and resulted in a loss of jobs and closure of mills, which in turn sparked a backlash from loggers and the logging industry. The forest service estimated that this move would cost up to 30,000 jobs, but subsequent studies have questioned how much the northern spotted owl conservation effort is really to blame for job losses citing the fact that the region's logging industry had been in steady decline since WWII.

Some opponents point to this big action taken to protect a few owls from extinction as environmentalism gone mad, but – on the other hand – many scientists would argue that the northern spotted owl acts as a "flagship species" and that it has indirectly helped preserve a whole ecosystem which is home to a great variety of flora and fauna (these are the temperate rainforests of the Pacific Northwest). In other words, its worthwhile conserving our nation's forests anyway, and the spotted owl was just a good excuse.

The Barred Owl (the invasive species)



In addition to the usual suspects of deforestation at the hands of man and wildfires, the northern (and, increasingly, the California) spotted owl are now facing a new threat represented by an invasive species of closely related birds. The Barred Owl (strix varia), which has streaks on its feathers instead of spots, is native to eastern North America but over the years it has expanded its range. Making its way westward across the forests of Canada, it is now creeping down the Pacific coast.

The barred owl is bigger and stronger than its western cousin and it is a bully, pushing spotted owls out of their nesting areas and into hiding and sometimes killing them in turf wars. It's also simply a fitter species in evolutionary terms: barred owls are less picky about where they nest (they've adapted to suburban areas and even city parks while spotted owls are confined to old growth forests) and what they eat. Barred owls also produce more offspring.

The Sparred Owl (the hybrid)



As an aside, it's interesting to note that there's been documented cases of interspecies mating between barred and spotted owls producing hybrid offspring who seem to be popularly called "sparred owls." This seems to happen when barred owls first enter an area populated by spotted owls and they cannot find a member of their own species to mate with. All the documented pairings have involved a male barred owl mating with a female spotted owl and thus I guess we should technically be calling them "botted owls" (I'm sure everyone remembers our post on hybrids).

The sparred owl's markings combine its father's streaks and its mother's spots. Moreover, at least some of these hybrids are fertile; they invariably end up mating with barred owls (regardless of sex) which results in the diminution of the spotted owl genes over generations.

Here's a video I found on YouTube of one sparred owl doing its thing.



The Future

Is there anything we can do to shelter spotted owls from competition by this invasive species? Some people have proposed hunting barred owls. But putting aside the ethical concerns this would raise (killing members of one species to save another, "playing God"...), Eric Forsman, the US Forest Service's expert on the northern spotted owl, says that "you could shoot barred owls until you're blue in the face, but unless you're willing to do it forever it's not going to work." On the other hand, some interested parties have proposed that the government lift its protection of the spotted owl's habitat given that its main threat now comes from the barred owl and not from logging. Obviously, this wouldn't be doing the owls any favors.

The problem is currently the most severe in the northern part of the spotted owl's range (they're thought to have all but vanished from British Columbia), but that will change as barred owls continue to fly southward. Forsman says that the most optimistic outlook for the species is that the area may eventually become dominated by barred owls but scattered pairings of spotted owls will remain.

Links

In addition to the Smithsonian article there's an accompanying video and slideshow. Also, here's a short NPR piece from 2005.


Images: Photo of female spotted owl and 3-week-old spotted owl hatchlings by Gary Braasch from Smithsonianmag.com; photo of barred owl by Collin Tanner, and sparred owl by Janice Reid taken from owlpages.com.

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