Conservation

Conservation Update

Lethal Barred Owl Removal…by Janice Reid

 

There are several opinions on the proposal by the US Fish and Wildlife Service to lethally remove barred owls within the range of the Northern and California Spotted Owl populations.¹ Spotted owls are a specialized species with narrow habitat and prey requirements. Work continues to protect the old forest ecosystem, the preferred habitat for the spotted owl, but the populations are still in peril. The invasive barred owl has been implicated as an impediment to stabilizing spotted owl populations.² A pilot project to determine if lethal barred owl removal would be successful and feasible was conducted in a few areas within the range of the Northern Spotted Owl, including right here in Douglas County, Oregon, near Myrtle Creek. Evidence indicated that lethally removing barred owls increased the occupancy of spotted owls within those areas.^3,4 In Northern California, lethal removals of the barred owl on the Hoopa Nation and Green Diamond Timber Resource Company lands also resulted in a rebounding of spotted owl populations. The barred owl is not native to Oregon, or the West Coast, for that matter. The range expansion is well documented and shows that the barred owl is a recent arrival to our area facilitated by European settlement as colonists moved west.⁵ Once in the west, where the main competition for resources was the smaller and more specialized spotted owl, the barred owl quickly began to overtake the territories of the spotted owl and oust its western cousin from their preferred habitat. The smaller, more specialized spotted owl cannot defend itself against the more aggressive barred owl. Exploiting this new niche and the ability to reproduce more quickly made the barred owl an

emerging threat to the spotted owl in the 1980s. The Oregon Department of Fish and Wildlife writes, “The Barred owl expanded its range from the eastern United States. It was first reported in Oregon in the early 1970s and has since spread to forested areas throughout most of the state.” ⁶ The Oregon Invasive Species Council indicates that “Invasive species are defined by Oregon Statute as ‘nonnative organisms that cause economic or environmental harm and are capable of spreading to new areas of the state.'” ⁷ It is clear that the barred owl is considered invasive and, therefore, subject to rules and regulations about invasive species at the state and federal level.

 

Management actions to deal with invasive species can take on many forms. It is not new that agencies have to choose one species over another. An example similar to the barred owl/spotted owl interaction is the interaction between the American Bullfrog and the Oregon Spotted Frog, an endangered species. The American Bullfrog is a nonnative invasive frog that not only consumes Oregon Spotted Frogs but also

aggressively competes for food and habitat. In addition, the young western pond turtles are consumed by the bullfrog. The Western Pond Turtle was recently proposed for listing as a threatened species under the Endangered Species Act. Proposals to lethally control American bullfrogs, a native of the eastern US, parallel the barred owl’s lethal removal. “Without management to reduce these threats, Oregon spotted frog populations will likely continue to decline.” ⁸  There are many examples of efforts to lethally eliminate a nonnative to restore a native species. The eradication of nonnative Brook Trout through lethal means to restore Bull Trout Populations in a stream near Crater Lake National Park is another example of the lethal removal of a nonnative species to favor the native species.⁹ There may be less opposition to these management actions because frogs and fish are not as charismatic as owls.

 

It is not always that a non-native species is outcompeting a native species when we need to intervene. It can be that our naïve actions in the past have resulted in changes to the environment that have resulted in favoring one native species to the detriment of another. On our 13 acres, we are embarking on a project to restore the native Oregon White Oak habitat. Oaks have declined due to several human activities, including cattle grazing, development, and fire suppression. We happen to have some oak habitat where native species are competing for resources. Removal of native species to favor the Oregon White Oak is a process that the Umpqua Oak Partnership promotes for some areas within the Umpqua Valley.¹⁰

 

With the barred owl and other nonnative species, we have to think about how they are impacting the ecosystem that did not evolve with them. Naturalist John Muir said, “When we try to pick out anything by itself, we find it hitched to everything else in the universe.” Barred owls are such voracious predators that they are consuming native species in quantities so large that the impact on those prey species is likely to trigger a trophic cascade within the ecosystem.¹¹

 

We are just learning about the effect that the extirpation of the passenger pigeon has had on our health. Lymes disease has increased and is linked to increased chipmunks, voles, and mice. Passenger Pigeons consumed enormous amounts of grain, including acorns that mice and other small mammals thrive on.

Low food availability and the predatory pressure from foxes kept the rodent population in check. Without the Passenger Pigeon, mice, voles, and chipmunks, prominent hosts for the nymph stage of ticks, increased due to increased food availability. The increased rodent population led to an increase in ticks and a subsequent increase in Lyme disease, a tick-borne illness affecting wildlife and human health.¹³

The effort to save the spotted owl may not have the desired result, but in my opinion, we have to try. We won’t run out of barred owls, but as we did with the passenger pigeon, we could very well run out of spotted owls, and that is a gamble we cannot afford to risk without making our very best attempt at keeping them in the system. There is more than one species at risk, and if we do not take action sooner rather than later, it may be too late to manage the barred owl by the time we find out what those impacts are. Changes to the forest could make the future forest look very different or disappear altogether. The decision to act or not act comes with consequences. Not acting has a higher consequence.

1. Draft Environmental Impact Statement for the Barred Owl Management Strategy; Washington, Oregon, and California, US Fish and Wildlife Service, 88 FR 80329, 2024
2. Dugger, K. M., Forsman, E. D., Franklin, A. B., Davis, R. J., White, G. C., Schwarz, C. J., Burnham, K. P., Nichols, J. D., Hines, J. E., Yackulic, C. B., Doherty, P. F., Bailey, L., Clark, D. A., Ackers, S. H., Andrews, L. S., Augustine, B., Biswell, B. L., Blakesley, J., Carlson, P. C., . . .  Sovern, S. G. (2016). The effects of habitat, climate, and Barred Owls on long-term demography of Northern Spotted Owls. The Condor, 118(1), 57-116.
3. Effects of Barred Owl (Strix varia) Removal on Population Demography of Northern Spotted Owls (Strix occidentalis caurina) in Washington and Oregon—2019 Annual Report. Open-File Report 2020-1089. Prepared in cooperation with the U.S. Fish and Wildlife Service, Bureau of Land Management, and U.S. Forest Service By: J. David Wiens, Katie M. Dugger, Damon B. Lesmeister, Krista E. Dilione, and David C. Simon
4. Wiens, J. D., Dugger, K. M., Higley, J. M., Lesmeister, D. B., Franklin, A. B., Hamm, K. A., White, G. C., Dilione, K. E., Simon, D. C., Bown, R. R., Carlson, P. C., Yackulic, C. B., Nichols, J. D., Hines, J. E., Davis, R. J., Lamphear, D. W., McCafferty, C., McDonald, T. L., & Sovern, S. G. (2021). Invader removal triggers competitive release in a threatened avian predator. Proceedings of the National Academy of Sciences, 118(31), e2102859118.
5. Livezey, Kent B. “Range expansion of barred owls, Part I: chronology and distribution.” The American Midland Naturalist, vol. 161, no. 1, Jan. 2009, pp. 49+. Gale Academic OneFile, link.gale.com/apps/doc/A192898767/AONE?u=oregon_oweb&sid=googleScholar&xid=627fe169. Accessed 21 Feb. 2024.
6. Oregon Department of Fish and Wildlife website.
7. Oregon Invasive Species Council website
8. Draft Recovery Plan for Oregon Spotted Frog (Rana pretiosa), US Fish and Wildlife Service, Portland, OR. 2023. 36pp.
9. Buktenica, M. W., Hering, D. K., Girdner, S. F., Mahoney, B. D., & Rosenlund, B. D. (2013). Eradication of Nonnative Brook Trout with Electrofishing and Antimycin-A and the Response of a Remnant Bull Trout Population. North American Journal of Fisheries Management, 33(1), 117-129. .Pacific Birds Website
10. Holm, S. R., Noon, B. R., Wiens, J. D., & Ripple, W. J. (2016). Potential trophic cascades triggered by the barred owl range expansion. Wildlife Society Bulletin, 40(4), 615-624. 
11. Koske, A. K., Austin, E., Boehmer, J., Lindemayer, M., Stormer, D., & Juanes, F. (2011). Trophic Cascades: Predators, Prey and the Changing Dynamics of Nature.. J. Terborgh and J. A. Estes, editors. Integrative and Comparative Biology, 51(4), 644-646.
12. Kilpatrick AM, Dobson ADM, Levi T, Salkeld DJ, Swei A, Ginsberg HS, Kjemtrup A, Padgett KA, Jensen PM, Fish D, Ogden NH, Diuk-Wasser MA. Lyme disease ecology in a changing world: consensus, uncertainty and critical gaps for improving control. Philos Trans R Soc Lond B Biol Sci. 2017 Jun 5;372(1722):20160117. doi: 10.1098/rstb.2016.0117. PMID: 28438910; PMCID: PMC5413869.