When avifauna collide: the case for lethal control of barred owls in western North America

Abstract

Forest avifauna in eastern North America have expanded their range across the Great Plains to the West, likely due to anthropogenic changes. The barred owl (Strix varia) is a focal example of the negative effects that these intracontinental range expansions can have, with this invasive species becoming a major threat to the northern spotted owl (Strix occidentalis caurina) and potentially larger biological communities. If barred owl populations are not managed immediately, northern spotted owl populations will likely be extirpated from large parts of their range and, ultimately, may become extinct. Of available management options, lethal control of barred owls has the greatest potential to rapidly benefit spotted owls and other impacted species. We argue that immediate action is necessary to buy time while other management options are explored and developed and that lethal control is an ethical management option. The barred owl conundrum exemplifies the challenges of managing native invasive species.

Full text

© 2024 e Ecological Societ y of America. is article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
When avifauna collide: the case for lethal control
of barred owls in western North America
John P Dumbacher1*† and Alan B Franklin2†
Forest avifauna in eastern North America have expanded their range across the Great Plains to the West, likely due to anthropo-
genic changes. The barred owl (Strix varia) is a focal example of the negative effects that these intracontinental range expansions
can have, with this invasive species becoming a major threat to the northern spotted owl (Strix occidentalis caurina) and poten-
tially larger biological communities. If barred owl populations are not managed immediately, northern spotted owl populations
will likely be extirpated from large parts of their range and, ultimately, may become extinct. Of available management options,
lethal control of barred owls has the greatest potential to rapidly benefit spotted owls and other impacted species. We argue that
immediate action is necessary to buy time while other management options are explored and developed and that lethal control is
an ethical management option. The barred owl conundrum exemplifies the challenges of managing native invasive species.
Front Ecol Environ 2025; 23(3): e2817, doi:10.1002/fee.2817
Historically, the North American Great Plains were a bar-
rier separating the eastern forest avifauna from their
western counterparts in North America (Mengel1964; Engle
et al.2008; Livezey2009b). However, in the past century, this
once almost impenetrable barrier has become freckled with
forest patches and corridors created by anthropogenic changes,
including fire suppression, planting of urban shade trees, pro-
motion of riparian woodlands after the removal of bison
(Bison bison) and beaver (Castor canadensis), and establishing
windbreaks after the Dust Bowl (Engle et al. 2008;
Livezey 2009b; Currey et al. 2022). These changes allowed
forest- dependent eastern avifauna to “island hop” or follow
riparian forest corridors across the once treeless expanse of
grasslands to interact and compete with ecologically similar
forest species of the West, which had been separated from their
eastern counterparts for millennia (DeSante and George1994;
La Sorte and Boecklen2005).
An invasive species is an organism that causes ecological or
economic harm in an environment where it is not native,
whereas native invaders are species that have become invasive by
expanding their range into new areas through anthropogenic
modifications (Carey et al.2012). The perception is usually that
an invasive species on one continent originated from a different
continent; however, increasingly, invasive species are native to a
continent but expanded their historical geographic range into
new environments in response to anthropogenic changes. These
shifts in species’ geographic ranges may result in a collision
course with native species that are naïve to the invading species.
For example, the blue jay (Cyanocitta cristata) expanded its
range from eastern to western North America within approxi-
mately the past 70 years (Figure1). Although their impacts on
western forest avifauna are largely unknown, invasive blue jays
are predicted to have negative effects on several native avian
species because they are aggressive nest predators of many spe-
cies, especially songbirds (Danielson et al.1997), and could be
potential competitors with native corvids. For instance, in
Massachusetts, Kluza et al.(2000) found that blue jay popula-
tions increased with human housing density, which correlated
with declines in open- cup- nesting bird populations. Invasive
blue jays have also been implicated in the local extirpation of
endangered golden- cheeked warbler (Setophaga chrysoparia)
populations in Texas (Engels and Sexton 1994). In addition,
invasive blue jays may impact the ecology of West Nile virus in
western North America because they are considered a compe-
tent amplifying host for the virus (LaDeau et al.2008), account-
ing for 22% of viral amplification in some areas (Levine
et al.2016).
Range expansions can also lead to “conservation conun-
drums” for impacted species that are already threatened or
1Institute for Biodiversity Science and Sustainability,California Academy
of Sciences, San Francisco, CA*(jdumbacher@calacademy.org);2US
Department of Agriculture, Wildlife Services,National Wildlife Research
Center, Fort Collins, CO
†these authors contributed equally to this work.
In a nutshell:
• In response to anthropogenic climate change and habitat
alteration, animals are shiing their geographic ranges,
sometimes with negative eects on the ecological com-
munities therein
• Barred owls (Strix varia) from the eastern US have ex-
panded to the West and will need to be managed eec-
tively to prevent the extinction of the federally listed
northern spotted owl (Strix occidentalis caurina)
• In North America, as the fauna mix, dicult decisions
on management will need to be made
CONCEPTS AND QUESTIONS 1 of 8