Barred Owl Removal Necessary to Save Spotted Owls
The northern spotted owl is moving quickly towards extinction. The most recent demographic study shows that the owl is in steep decline across its entire range and that rate of decline is increasing in many areas. The culprits? Habitat loss and barred owls. While habitat loss was the prime cause for the species listing as threatened under the Endangered Species Act in 1990, invasive barred owl incursion into northern spotted owl territory is driving the species ever closer to extinction. If left unchecked, the northern spotted owl will be functionally extinct in the wild in the next 50 years. To prevent the extinction of the northern spotted owl, we need to retain existing habitat, plan for the growth of future habitat, and remove barred owls from key locations within the range of the northern spotted owl.
Barred owls are native to eastern North America. European-American settlement of the Great Plains, which resulted in forest growth in historic prairies maintained by fire, is theorized to have allowed for the expansion of the range of the barred owl, reaching British Columbia first (recorded in 1943), Washington (1965), Oregon (1972) and California (1976). Recent decades have shown a dramatic increase in the number of barred owls throughout the West. Compared to spotted owls, barred owls are bigger, have more diverse diets (that allow them to have a greater density on the landscape and smaller home ranges), and are able to utilize a broader range of forest conditions for nesting and foraging. As barred owls occupy new areas, they typically push out existing spotted owls, causing them to become non-territorial “floaters”—no longer reproducing but still present on the landscape.
Barred owls don’t just impact spotted owls. Researchers worry that barred owls may cause large-scale ecosystem impacts too. Barred owls did not coevolve with the wildlife of western forests and so its prey base in the Pacific Northwest did not develop adequate defensive mechanisms and behaviors to avoid predation. Barred owls are also generalist predators, eating a wider variety of species than the northern spotted owl, which is primarily a rodentivore. As a result, barred owls are at much higher densities in our forests than spotted owls could ever achieve and are eating far more prey From salamanders to crayfish and from frogs to brush rabbits, predation pressure could result in population declines and even push species toward extinction. As this occurs, a “trophic cascade” could affect entire ecosystems. Through increased pressure on seed dispersers, like Douglas’ squirrel, northern flying squirrel, western gray squirrel, and Steller’s jay—all known prey species of the barred owl—we may see a decline in tree and shrub development. By predating on burrowing animals, soil processing may diminish and impact forest health.
Because of the pronounced impacts of barred owl occupation in historic northern spotted owl habitat, researchers identified barred owl removal—effectively hunting barred owls—as a potential conservation strategy for spotted owls as part of the 2011 “Revised Recovery Plan for the Northern Spotted Owl.” To research this potential, scientists set up a removal study across the Pacific Northwest, with five study sites consisting of a treatment area (where barred owls would be removed) and five control areas where no barred owl management would occur. The results of this study were clear: barred owl removal was effective at stabilizing population declines. In areas where barred owls were removed, the mean annual rate of population decline stabilized (0.2% decline per year) but in areas without removal, declines continued dramatically (12.1% decline per year). The results also reinforce earlier research from California’s redwoods which likewise found that barred owl removal was effective and resulted in increased occupancy of northern spotted owls in treatment areas.
From the existing research, this appears clear: to save the northern spotted owl from extinction, some amount of barred owl removal is necessary. EPIC understands that the U.S. Fish and Wildlife Service is in discussions with other federal land management agencies to begin discussions of a multi-agency, multi-state barred owl management program. EPIC supports barred owl removal together with the protection of existing habitat and development of new habitat.