Top Line: The barred owl has invaded the range of the northern spotted owl and needs to be stopped before driving the latter to extinction.
Figure 1. The northern spotted owl (Strix occidentalis caurina), on the left, and the barred owl (Strix varia), on the right. Source: Marin Group Sierra Club.
Barred owls are very cool.
I have heard the call of a barred owl (“Who cooks for you? Who cooks for you-all?”) in woods in the American East.
When Henry David Thoreau encountered an injured barred owl (then known as Strix nebulosa) at Derby’s shop in Concord, Massachusetts, on December 14, 1858, he noted in his journal, “Solemnity is what they express, —fit representatives of the night.”
However, my love for the barred owl (Strix varia) is geographically limited. Barred owls (BOs) have expanded their range across the continent and are now killing enough northern spotted owls (NSOs) to eventually result in the latter’s extinction.
While the NSO is dependent upon old-growth Douglas-fir forests, the barred owl is quite the generalist and is at home in a variety of habitats from the wild to the urban. In 2017, a barred owl carrying a meal of a partially eaten (and nonnative) rat collided with the glass façade of the Apple Store in downtown Portland. Other BOs, aggressive avifauna that they are, have made several Portlandians scurry out of the bird’s territory.
I have no problem with (actually I rather enjoy) BOs harassing human citizens of the Rose City, but I do have a problem with BOs killing off the threatened NSO. This inter-genus conflict is relatively recent and human caused, and it needs to be addressed.
Strixicide Among the Old Growth
It’s bad out there in the fragmented old-growth Douglas-fir forests.
BOs are not only more adaptive, they are also bigger and badder than NSOs. Notes the US Geological Survey (USGS):
The barred owl is an apex predator and a fiercely territorial invader from eastern North America. Unlike the northern spotted owl, barred owls can thrive in a wider variety of forest conditions and they aggressively push northern spotted owls out of their established territories. Invasive barred owls will eat anything they can catch, having what is called a “generalist” appetite.
The USGS (mission: “ . . . to monitor, analyze, and predict current and evolving dynamics of complex human and natural Earth-system interactions and to deliver actionable intelligence at scales and timeframes relevant to decision makers) and partner scientists recently published three peer-reviewed studies that depict a grim future for NSOs (links to the studies are found in “For More Information” below). The USGS says the combined results of the studies “show that even while forest management policies and practices maintained NSO habitat across their range, barred owls pose a very serious threat to remaining populations of northern spotted owl.”
Study #1: Northern Spotted Owls in Decline
The USGS summarizes the first study this way:
[N]orthern spotted owl populations have experienced significant yearly declines, translating to a 65–85% population decrease on many of the study areas between 1995 and 2017. Barred owl presence on northern spotted owl territories was the primary factor negatively affecting apparent survival, recruitment, and ultimately, rates of population change. Without removal or reduction of barred owl populations, it’s likely northern spotted owls will become locally extinct from portions of their range. The species would possibly linger on as small populations in other areas until those populations are eliminated by catastrophic events, such as wildfire, resulting in its extinction. [emphasis added]
Study #2: Northern Spotted Owls on the Move
NSOs are homebodies. If they are in high-quality (unfragmented older forest) habitat, they have little reason to go elsewhere. Historically, approximately 5 percent of spotted owls were on the move, the major cohort being young males looking to get laid. In the study area, breeding dispersal has increased four to five times—and it’s not just young males. The increased dispersal directly correlates with increased barred owl numbers. Increased dispersal of NSOs means fewer NSOs in the future.
“Our study further shows that increasing rates of breeding dispersal associated with population declines contribute to population instability and vulnerability of NSOs to extinction,” said Julianna Jenkins, U.S. Forest Service wildlife biologist and lead author of the study.
Study #3: Barred Owl Removal
In recent years, several controlled experiments have tested whether “removal” (pronounced “SHOO-ting”) of BOs in NSO habitats improves the chances for the latter (Figures 2 and 3). The USGS notes:
Removal of barred owls had a strong, positive effect on the survival of northern spotted owls, stopping their long-term population declines. After removals, northern spotted owl population declines stabilized in areas with removals but continued to decrease sharply in areas without removals. [emphasis added]
Figure 2. Before an experiment in lethal removal of barred owl pairs within areas historically occupied by northern spotted owls. Source: US Geological Survey.
Figure 3. After the experiment. Source: US Geological Survey.
Expansion of Barred Owl Range Across North America
The BO was once confined to the eastern United States (Figure 4). BOs now range across the continent, including the entire range of the northern spotted owl (Figure 5).
Figure 4. The expanding range of the barred owl over the last couple of centuries. The bird has moved from the eastern United States to span the continent. Source: US Geological Survey.
Figure 5. Current range of the barred owl. Expansion into the range of the northern spotted owl has been severely detrimental to the latter. Source: US Geological Survey.
Kent B. Livezey of the US Fish and Wildlife Service has published extensively on barred owl expansion and interaction with spotted owls (both northern and California subspecies). In a couple of his papers, cited under “For More Information” below, he focuses on how BOs expanded their range from forests east of the Great Plains (Figure 6) to forests throughout most of central and western North America during the past century. By mapping more than 12,500 records of BOs in their expanded range from the earliest records to the present, he was able to infer the general timing and flow of the BO’s range expansion. In the first of those two papers he reports:
Evidently, Barred Owls originally traveled across the northern Great Plains via the forested riparian corridors of the Missouri, Yellowstone and Musselshell rivers into east-central Montana by 1873. From there, they accessed western forests in southwestern Montana (1909), moved to northwestern Montana (1922) and then expanded their range in two general directions. They moved north and east to northern Alberta (1934) and Saskatchewan (1948) where they apparently encountered other Barred Owls coming westward from Manitoba. They also moved north to northern British Columbia (1943), southeastern Alaska (1967) and Northwest Territories (1977), and west and south to Washington (1965), Idaho (1968), Oregon (1972) and California (1976). [emphasis added]
Figure 6. The barred owl at home within its original range in a mixed-hardwood forest in the East. Source: US Fish and Wildlife Service.
In the second of those papers, he explores what prevented BOs from expanding their range westward during recent millennia and what allowed them to do so during the past century. He concludes:
Overall, it appears the historical lack of trees in the Great Plains acted as a barrier to the range expansion and recent increases in forests broke down this barrier. Increases in forest distribution along the Missouri River and its tributaries apparently provided Barred Owls with sufficient foraging habitat, protection from the weather, and, possibly, concealment from avian predators to allow Barred Owls to move westward. Decades later, increases in forests in the northern Great Plains allowed Barred Owls to connect their eastern and western distributions across southern Canada. These increases in forests evidently were caused by European settlers excluding fires historically set by Native Americans, suppressing fires and planting trees. They apparently were caused, to lesser degrees, by European settlers extirpating bison (Bison bison), overhunting elk (Cervus elaphus) and deer (Odocoileus spp.) and, in some areas, extirpating beaver (Castor canadensis) and replacing native ungulates with livestock. Accordingly, it appears the range expansion was prohibited for millennia by actions of Native Americans and recently facilitated by actions of European settlers. [emphasis added]
We can ask if the expansion of the range of the barred owl from eastern North America to western North America was natural or unnatural. It seems to me that the expansion was facilitated by a combination of both natural and unnatural factors. The ultimate cause of the containment of BOs to the East was the “historical lack of trees in the Great Plains,” which “acted as a barrier.” The BOs took advantage of an increase in tree cover along the Missouri River and its tributaries. The increased tree cover resulted from the relatively recent invasion of North America by humans from Europe, who (1) disrupted Native American burning practices, (2) extirpated bison and beaver, (3) overhunted elk and deer, and (4) replaced native ungulates with domestic livestock.
While European settlers are clearly to blame for all four of these unnatural factors, their actions only introduced the latter three unnatural acts while ending the first unnatural act—that of Native American burning. Though done for millennia, the traditional—though nonetheless unnatural—Native American burning was a result of an earlier human invasion of North America from Asia.
To Control or Not to Control the BO Within the Range of the NSO?
The Friends of Animals (FoA) has opposed killing barred owls to protect spotted owls from the beginning. FoA sued to prevent the Fish and Wildlife Service experimental program but lost the case. FoA notes that “logging companies’ economic interests in old-growth forests has historically been, and still is, the NSO’s greatest threat to survival, not barred owls.” FoA further notes, “Even amid this lethal experimentation, U.S. government agencies acknowledge the most crucial factor for NSO survival is habitat conservation. In the meantime, FWS’ short sightedness in its experiments could cost thousands of animals their lives as climate change continues to press species from their natural range.”
In contrast, I favor killing BOs within the range of the NSO. The evidence is clear and convincing. BOs are killing NSOs because of the unnatural actions of modern humans. Without human intervention to prevent BOs from continuing to kill NSOs, the latter are not long for this planet. We have a moral duty to reverse the extinction crisis, and killing BOs to protect NSOs is part of that duty.
Life is one large and long benefit-cost analysis. In this case, the BOs should lose out (in a portion of their range where they have not long been present) and the NSOs should win out (in the relic portions of what once was a larger range, but a small fraction of the range of the BO). Reducing some of the numbers of a species that is increasing its range to help a species that is declining in numbers is—in the end—a no-brainer to me. The answer is clear and easy, though simultaneously hurtful and sad.
While I see the value of the humane treatment of animals, our long-term humanity is increased by not allowing other species to go extinct due to human actions. Yes, our short-term humanity takes a hit with the shooting of a bunch of innocent BOs. Whether you call it control or killing, my choice to favor NSOs over BOs within the range of the NSO is a brutal choice and should be recognized as such. A lot of innocent BOs will be routinely shotgunned out of the sky or off of perches to help save NSOs. It will not be pretty.
The USGS notes: “Their [barred owls’] sheer numbers and generalist appetite threaten not only the northern spotted owl, but other native wildlife throughout the region.” How ironic this all is for my friends in Big Timber! If only the European invasion had started a half century earlier, perhaps the barred owl would have wiped out the spotted owl before the onset of the Pacific Northwest Forest War. Still, this wouldn’t have stopped the war. While the NSO was the proximate cause of the timber battles, it was never the ultimate cause.
Finally, I must declare a conflict of self-interest. I cannot rule out that part of my reasoning may stem from the fact that I have dedicated most of the decades of my life to conserving the NSO (and the habitat upon which it depends). One never likes to have a significant portion of one’s life work be for naught. I come to this conclusion/recommendation not with relish but with resolution. The US Fish and Wildlife Service should undertake a large-scale and long-lived program of barred owl “control” within the range of the NSO. The agency should eschew timidity and embrace resolve.
Habitat Protection and Restoration Still Vital for the NSO
The studies indicate that NSOs fare better against BOs in areas of excellent NSO habitat—intact old-growth forest (Figure 7). In this case “better” is not good enough. NSOs are still losing out. Nonetheless, NSO habitat conservation and restoration continues to be a vital requirement to conserve the NSO across the landscape and over time.
Figure 7. The northern spotted owl at home within its range in an old-growth Douglas-fir forest in the West. Source: US Fish and Wildlife Service.
“The results of the study showed that long-term survival of NSOs will depend heavily on reducing the negative impacts of barred owls while simultaneously addressing other threats such as habitat loss,” notes David Wiens, USGS research biologist.
“Our analyses indicated that northern spotted owl populations potentially face extirpation if the negative effects of barred owls are not ameliorated while maintaining northern spotted owl habitat across their range,” say Alan B. Franklin et al.
“Removing one species to save another is a difficult decision and one that the USFWS did not take lightly. These studies and others show that it is very likely the northern spotted owl would go extinct in large portions of its range if the threat from invasive barred owls and management of spotted owl habitat are not addressed simultaneously,” says Robin Bown, USFWS lead for the Barred Owl Project.
While the Fish and Wildlife Service deals with barred owls, the Forest Service and Bureau of Land Management should stop the logging of any older (mature and old-growth) forests within the range of the northern spotted owl.
Bottom Line: On balance, reducing the numbers and range of a native species of owl to help save one native species of owl from extinction is rational, possible, and in the public interest.
For More Information
Franklin, Alan B., et al. 2021. Range-wide Declines of Northern Spotted Owl Populations in the Pacific Northwest: A Meta-analysis. Biological Conservation 259(7).
Jenkins, Julianna M. A., et al. 2021. Conspecific and Congeneric Interactions Shape Increasing Rates of Breeding Dispersal of Northern Spotted Owls. Ecological Applications 31(7).
Livezey, Kent B. 2009. Range Expansion of Barred Owls, Part I: Chronology and Distribution. American Midland Naturalist 161(1).
———. 2009. Range Expansion of Barred Owls, Part II: Facilitating Ecological Changes. American Midland Naturalist 161(4).
US Fish and Wildlife Service. Northern Spotted Owl (webpage).Oregon Fish and Wildlife Office
US Geological Survey. October 6, 2021. Northern Spotted Owl Still Fights for Survival (webpage).
Wiens, J. David, et al. 2021. Invader Removal Triggers Competitive Release in a Threatened Avian Predator. Proceedings of the National Academy of Sciences 188(31).