A synopsis of suggested approaches to address potential competitive interactions between Barred Owls (Strix varia) and Spotted Owls (S. occidentalis)

Joseph B. Buchanan, R. J. Gutiérrez, Robert G. Anthony, Tim Cullinan, Lowell V. Diller, Eric D. Forsman, Alan B. Franklin

Research output: Contribution to journalReview articlepeer-review

20 Scopus citations


The conservation of Spotted Owl (Strix occidentalis) populations has been one of the most controversial and visible issues in United States conservation history. Coincident with declines in Spotted Owl populations over the last three decades has been the invasion of Barred Owls (Strix varia) throughout the range of the Northern Spotted Owl (S. o. caurina) and into the range of the California Spotted Owl (S. o. occidentalis). This invasion has confused the reasons behind recent Spotted Owl declines because anecdotal and correlative information strongly suggests that Barred Owls are a new factor influencing the declines. There is great uncertainty about all aspects of the invasion, and this has sparked discussion about appropriate management and research responses regarding the effects of this invasion on Spotted Owls. We present a set of possible responses to address the issue, and we discuss the relative merits of these with regard to their efficacy given the current state of knowledge. We recommend that research specifically aimed at learning more about the interspecific relationships of these two owls throughout the range of sympatry should begin immediately. Approaches that seem unlikely to be useful in the short-term either because they do not facilitate knowledge acquisition, are relatively costly, or would be technically less feasible, should not be considered viable at this time. We believe the consequences of the invasion are potentially dire for the Spotted Owl and that research and management actions, including the use of adaptive management, are required to inform the near- and long-term decision-making process for conservation of Spotted Owls.

Original languageEnglish (US)
Pages (from-to)679-691
Number of pages13
JournalBiological Invasions
Issue number6
StatePublished - Aug 2007

Bibliographical note

Funding Information:
Acknowledgments We thank Steven Courtney for organizing and facilitating the workshop that prompted the initial development of this manuscript. The workshop was held in conjunction with the 2005 meeting of the Cooper Ornithological Society in Arcata, California. Workshop attendees contributed thoughtful discussion on various aspects of the ecology of the two owl species. The U. S. Forest Service (Contract #53-91S8-5-EC15) and the Minnesota Agricultural Research Station supported the work of RJG and ABF. James W. Watson and Lorelle I. Berkeley made helpful comments that improved this manuscript.


  • Barred Owl
  • Review of potential approaches to respond to Barred Owl invasion
  • Spotted Owl
  • Strix occidentalis
  • Strix varia


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