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1 September 2010 Killing Barred Owls to Help Spotted Owls I: A Global Perspective
Kent B. Livezey
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Barred Owls (Strix varia) expanded their range to include western North America and have been competing with federally threatened Northern Spotted Owls (S. occidentalis caurina) for the past few decades. To help protect Spotted Owls, the US Fish and Wildlife Service is considering conducting a 3- to 10-y study in which as many as 2150 to 4650 Barred Owls would be killed and, possibly, conducting long-term management of Barred Owls. To help give these considerations a global perspective, I gathered information concerning instances of negative effects between native (non-introduced) birds worldwide (n  =  194) and how managers address these effects. I found reports for 15 species of native birds of concern negatively affected by hybridization, 22 by brood parasitism, 58 by competition, and 99 by predation. Control commonly is used to address brood parasitism by cowbirds (Molothrus spp.), and predation by gulls (Larinae) and corvids (Corvidae), whereas control rarely is used to address competition and is never used to address hybridization. Globally, very few raptors are killed for any of these threats. If the precedent-setting removal study as described here is implemented, it would, during its 1st year, result in the death of 36 times more raptors than in all other conservation-based projects combined in the United States and its territories, and 84 times more raptors than in the largest ongoing effort worldwide. This study could cost $1 million annually; simplifying the cost to dollars per Barred Owl killed approximates $700 per Barred Owl for the 1st year and $2800 per Barred Owl for each subsequent year.

Kent B. Livezey "Killing Barred Owls to Help Spotted Owls I: A Global Perspective," Northwestern Naturalist 91(2), 107-133, (1 September 2010).
Received: 20 November 2009; Accepted: 1 April 2010; Published: 1 September 2010

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