Abstract
The spotted owl (Strix occidentalis) is a threatened species in many areas of its western North American range. Concomitant with its decline has been a rapid invasion of its range and habitat by barred owls (Strix varia), a native species that was restricted, until relatively recently, to eastern North America. We assess the theoretical potential for negative interactions between these two owls by examining size dimorphism and ecological relationships within various owl assemblages throughout the world. We then review the anecdotal, natural history, modeling, and experimental evidence that suggest barred owls may negatively affect spotted owls with at least a potential for the competitive exclusion of spotted owls by barred owls throughout all or part of the former’2019;s range. While it is widely accepted that barred owls are either causing or exacerbating declines of spotted owl populations, there are confounding factors, such as habitat loss and bad weather that also may contribute to declines of spotted owls. Both theory and empirical information suggest that barred owls are likely to have negative effects on spotted owl range and density, but the degree of the impact is not predictable. There is a conservation conundrum here, in that the barred owl is a native species that has expanded its range westwards, either naturally or with a degree of human facilitation, and now constitutes a major threat to the viability of another native species, the threatened spotted owl. We propose that only through carefully designed experiments involving removal of barred owls will we be able to determine if recent declines in spotted owl populations are caused by barred owls or by other factors. It is rare in conservation science that replicate study areas exist for which we also have long-standing demographic information, as is the case with the spotted owl. Removal experiments would take advantage of the wealth of data on spotted owls, and allow ecologists to assess formally the impacts of an invasive species on a threatened species, as well as to suggest mitigation measures.
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References
Anderson DR, Bart J, Edwards TC Jr, Kepler CB, Meslow EC (1990) 1990 Status review: northern spotted owl Strix occidentalis caurina. United States Fish and Wildlife Service, Department of the Interior, 95 pp
Anthony RG, Forsman ED, Franklin AB, Anderson DR, Burnham KP, White GC, Schwarz CJ, Nichols J, Hines JE, Olson GS, Ackers SH, Andrews S, Biswell BL, Carlson PC, Diller LV, Dugger KM, Fehring KE, Fleming TL, Gerhardt RP, Gremel SA, Gutiérrez RJ, Happe PJ, Herter DR, Higley JM, Horn RB, Irwin LL, Loschl PJ, Reid JA, Sovern SG (2006) Status and trends in demography of northern spotted owls, 1985–2003. Wildlife Monogr 163
Barrowclough GF, Gutiérrez RJ, Groth JG (1999) Phylogeography of spotted owl (Strix occidentalis) populations based on mitochondrial DNA sequences: gene flow, genetic structure, and a novel biogeographic pattern. Evolution 53:919–931
Carey AB, Horton SP, Biswell BL (1992) Northern spotted owls: influence of prey base and landscape character. Ecol Monogr 62:223–250
Cody ML, Velarde E (2002) The land bird. In: Case TJ, Cody ML, Ezcurra E (eds) New Biogeography of the Islands in the Sea of Cortés. Oxford University Press, NY, pp 271–312
Cook WE (1992) Barred owl feeds on frog in November. The Kingbird 42:84
Courchamp F, Woodroffe R, Roemer G (2003) Removing protected populations to save endangered species. Science 302:1532
Crozier ML, Seamans ME, Gutiérrez RJ, Loschl PJ, Horn RB, Sovern SG, Forsman ED (in review) Does the presence of barred owls suppress the calling behavior of spotted owls? Condor
Dark SJ, Gutiérrez RJ, Gould GI Jr (1998) The barred owl (Strix varia) invasion in California. Auk 115:50–56
del Hoyo J, Elliott A, Sargatal J (eds) (1999) Handbook of the birds of the world. Barn owls to hummingbirds, vol. 5. Lynx Edicions, Barcelona, pp 34–242
Devereux JG, Mosher JA (1984) Breeding ecology of barred owls in the central Appalachians. J Raptor Res 18:49–58
Dodd CK Jr, Griffey ML (1997) Scincella lateralis (ground skink) predation. Herpetological Rev 28:89
Dunbar DL, Booth BP, Forsman ED, Hetherington AE, Wilson DJ (1991) Status of spotted owl, Strix occidentalis, and barred owl, Strix varia, in southwestern British Columbia. Can Field-Nat 105:464–468
Earhart CM, Johnson NK (1970) Size dimorphism and food habits of North American owls. Condor 72:251–264
Enriquez-Rocha PL, Rangel-Salazar JL (2001) Owl occurrence and calling behavior in a tropical rain forest. J Raptor Res 35:107–114
Enriquez-Rocha P, Rangel-Salazar JL, Holt DW (1993) Presence and distribution of Mexican owls: a review. J Raptor Res 27:154–160
Evens J, LeValley R (1982) The spring migration, middle pacific coast region. Am Birds 36:889–892
Forsman ED, Meslow EC, Wight HM (1984) Distribution and biology of the spotted owl in Oregon. Wildlife Monogr 87:1–64
Forsman, ED, Anthony RG, Meslow EC, Zabel CJ (2004) Diets and Foraging Behavior of Northern Spotted Owls in Oregon. J Raptor Res 38:214–230
Franklin AB, Anderson DR, Gutiérrez RJ, Burnham KP (2000) Climate, habitat quality, and fitness in northern spotted owl populations in northwestern California. Ecol Monogr 70:539–590
Franklin AB, Gutiérrez RJ (2002) Spotted owls, forest fragmentation, and forest heterogeneity. Stud Avian Biol 25:203–220
Garrido OH, Kirkconnell A (2000) Birds of Cuba. Comstock Publishers and Cornell University Press, Ithaca NY
Gee JM (2003) How a hybrid zone is maintained: behavioral mechanisms of interbreeding between California and Gambel′s quail (Callipepla californica and C. gambelii). Evolution 57:2407–2415
Gehlbach FR (1995) Eastern screech-owl. In: Poole A, Gill F (eds) The Birds of North America No. 165. The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists’ Union, Washington, DC
Gerhardt RP, Gerhardt DM, Flatten CJ, Gonzalez NB (1994) The food habits of sympatric Ciccaba owls in northern Guatemala. J Field Ornithol 65:258–264
Graves GR (1985) Elevational correlates of speciation and intraspecific geographic variation in plumage in Andean forest birds. Auk 102:556–579
Gutiérrez RJ, Franklin AB, LaHaye WS (1995) Spotted owl (Strix occidentalis). In: Poole A, Gill F (eds) The Birds of North America No. 179. The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists’ Union, Washington, DC
Gutiérrez R, Cody M, Courtney S, Kennedy D (2004) Assessment of the potential threat of the northern barred owl. In: Final report: scientific evaluation of the status of the northern spotted owl. Sustainable Ecosystems Institute, Portland, OR
Hamer TE (1988) Home range size of the northern barred owl and northern spotted owl in western Washington. MS Thesis, Western Washington University, Bellingham, WA, 86 pp
Hamer TE, Hays DL, Senger CM, Forsman ED (2001) Diets of northern barred owls and northern spotted owls in an area of sympatry. J Raptor Res 35:221–227
Hamer TE, Forsman ED, Fuchs AD, Walters ML (1994) Hybridization between barred and spotted owls. Auk 111:487–492
Hamer TE, Seim SG, Dixon KR (1989) Northern spotted owl and northern barred owl habitat use and home range size in Washington: preliminary report. Washington Department of Wildlife, Olympia WA
Herter DR, Hicks LL (2000) Barred owl and spotted owl populations and habitat in the central Cascade Range of Washington. J Raptor Res 34:279–286
Howell SNG (1999) A bird-finding guide to Mexico. Comstock Publishing Associates, A Division of Cornell University Press, Ithaca, NY, pp 104-106
Howell SNG, Webb S (1995) A guide to the birds of Mexico and Northern Central America. Oxford University Press, Oxford England, pp 353–370
Ibañez C, Ramo C, Busto B (1992) Notes on food habits of the black and white owl. Condor 94:529–531
Iverson WF (1993) Is the barred owl displacing the spotted owl in western Washington? MS Thesis, Western Washington University, Bellingham, WA.
Jaksic FM, Carothers JH (1985) Ecological, morphological, and bioenergetic correlates of hunting mode in hawks and owls. Ornis Scandinavica 16:165–172
Johnsgard PA (1988) North American owls. Biology and natural history. Smithsonian Institution Press, Washington, pp 176–193
Johnsgard PA (2002) North American owls. Biology and natural history, 2nd edn. Smithsonian Institution Press, Washington
Kelly EG (2001) The range expansion of the northern barred owl: an evaluation of the impact on spotted owls. MS Thesis, Oregon State University, Corvallis, OR, 92 pp
Kelly EG, Forsman ED (2004) Recent records of hybridization between barred owls (Strix varia) and northern spotted owls (S. occidentalis caurina). Auk 121:806–810
Kelly EG, Forsman ED, Anthony RG (2003) Are barred owls displacing spotted owls? Condor 105:45–53
König C, Weick F, Becking JH (1999) Owls: a guide to the owls of the world. Yale University Press, New Haven, pp 325-328
Korschgen LJ, Stuart HB (1972) Twenty years of avian predator-small mammal relationships in Missouri. J␣Wildlife Manage 36:269–282
Land HC (1963) A collection of birds from the Caribbean lowlands of Guatemala. Condor 65:49–65
Langrand O (1990) Guide to the birds of Madagascar. Yale University Press, New Haven CT
Languy M, Motombe FN (2003) Birds of Takamanda Forest Reserve, Cameroon. Ch. 7, pp 95-110 in Takamanda: The biodiversity of an African Rainforest. SI/MAB: Smithsonian Institution/Monitoring and Assessment of Biodiversity Series #8. Washington DC.
Leskiw T, Gutiérrez RJ (1998) Possible predation of a spotted owl by a barred owl. Western Birds 29:225–226
Lloyd H (2003) Bird diversity and abundance in Amazon forest communities. J Field Ornithol 74:127–192
Loyn RH, McNabb EG, Volodina L, Willig R (2001) Modelling landscape distributions of large forest owls as applied to managing forests in north-east Victoria, Australia. Biol Conserv 97:361–376
Marcot BG, Johnson DH (2003) Owls in mythology and culture. In: Duncan JR (ed) Owls of the World, Chap 2, pp 89–105. Firefly Books, Buffalo NY
Marks JS, Hendricks DP, Marks VS (1984) Winter food habits of barred owls in western Montana. Murrelet 65:27–28
Marshall JT Jr (1957) Birds of pine-oak woodland in southern Arizona and adjacent Mexico. Pacific Coast Avifauna 31:1–125
Mazur KM, James PC (2000) Barred owl (Strix varia). In: Poole A, Gill F (eds) The birds of North America No. 508. The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists’ Union, Washington, DC
McCallum DA (1994) Flammulated owl. In: Poole A, Gill F (eds) The birds of North America No. 93. The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists’ Union, Washington, DC
Mikkola H (1983) Owls of Europe. Buteo Books, Vermillion SD
Olson GS, Glenn EM, Anthony RG, Forsman ED, Reid JA, Loschl PJ, Ripple WJ (2004) Modeling demographic performance of northern spotted owls relative to forest habitat in Oregon. J Wildlife Manage 68:1039–1053
Olson GS, Anthony RG, Forsman ED, Ackers S H, Loschl PJ, Reid JA, Dugger KM, Glenn EM, Ripple WJ (2005) Modeling of site occupancy dynamics for northern spotted owls, with emphasis on the effects of barred owls. J Wildlife Manage 69:918–932
Ortega CP, Chace JF, Peer BD (eds) (2005) Management of cowbirds and their hosts: balancing science, ethics, and management mandates. Ornithological Monographs 57. American Ornithologists’ Union, Washington DC
Parker IM, Simberloff D, Lonsdale WM, Goodell K, Wonham M, Kareiva PM, Williamson MH, Von Holle B, Moyle PB, Byers JE, Goldwasser L (1999) Impact: toward a framework for understanding the ecological effects of invaders. Biol Inv 1:3–19
Pearson RR, Livezey KB (2003) Distribution, numbers, and site characteristics of spotted owls and barred owls in the Cascade Mountains of Washington. J Raptor Res 37:265–275
Petersen J (2006) Owls be dammed. Wall Street Journal Abstracts. February 18, 2006; Page A9
Peterson AT, Robins CR (2003) Using ecological-niche modeling to predict barred owl invasions with implications for spotted owl conservation. Conserv Biol 17:1161–1165
Postupalsky S, Papp JM, Scheller L (1997) Nest sites and reproductive success of barred owls (Strix varia) in Michigan. In: Duncan JR, Johnson DH, Nicholls TH (eds) Biology and conservation of owls of the northern hemisphere. United States Department of Agriculture, Forest Service, GTR-NC-190
Randler C (2002) Avian hybridization, mixed pairing and female choice. Anim Behav 63:103–119
Ridgeway (1914) Birds of Middle and North America VI, Bulletin 50, pp 648-654. United States National Museum
Rignall JA (1973) Owls of the world. EP Dutton and Company, Incorporated, New York NY
Riley SPD, Shaffer HB, Voss SR, Fitzpatrick BM (2003) Hybridization between a rare, native tiger salamander (Ambystoma californiense) and its introduced congener. Ecol Appl 13:1263–1275
Roberts TJ (1991) The birds of Pakistan. Regional studies and non-passeriformes, vol. 1. Oxford University Press, Oxford England
Root RB (1969) The behavior and reproductive success of the blue-gray gnatcatcher. Condor 71:16–31
Romesburg CH (1981) Wildlife science: gaining reliable knowledge. J Wildlife Manage 45:293–313
Rosenberg DK, Swindle KA, Anthony RG (2003) Influence of prey abundance on northern spotted owl reproductive success in western Oregon. Can J Zool 81:1715–1725
Schaldach WJ Jr (1963) The avifauna of Colima and adjacent Jalisco. Proc Western Foundation Vertebrate Zool 1:1–100
Seamans ME, Corcoran JC, Rex AG (2004) Southernmost record of a spotted owl-barred owl hybrid in the Sierra Nevada. Western Birds 35:173–174
Simberloff D (2003) How much information on population biology is needed to manage introduced species? Conserv Biol 17:83–92
Simberloff D, Gibbons L (2004) Now you see them, now you don’2019;t!–population crashes of established introduced species. Biol Inv 6: 161-172
Smith DG, Devine A, Devine D (1983) Observations of fishing by a barred owl. J Field Ornithol 54:88–89
Taylor AL Jr, Forsman ED (1976) Recent range extensions of the barred owl in western North America, including the first records for Oregon. Condor 78:560–561
Terborgh J, Robinson SK, Parker TA III, Munn CA, Pierpont N (1990) Structure and organization of an Amazonian forest bird community. Ecol Monogr 60:213–238
United States Department of the Interior (1990) Endangered and threatened wildlife and plants, determination of threatened status for the northern spotted owl; final rule. United States Fish and Wildlife Service, Federal Register Part VI, vol. 55, No. 123, Tuesday, June 26, 1990
United States Department of the Interior (1992) Final draft recovery plan for the northern spotted owl. Unpublished report, United States Department of the Interior, Washington DC
Voous KH (1966) The distribution of owls in Africa in relation to general zoogeographical problems. Ostrich Supplement 6:499–506
Vrezec A (2003) Breeding density and altitudinal distribution of the ural, tawny, and boreal owls in North Dinaric Alps (Central Slovenia). J Raptor Res 37:55–62
Weidemeier DJ, Horton SP (2000) Trends in spotted owl and barred owl detections in the Olympic Experimental State Forest from 1991 to 1999. Northwestern Nat 81:93
Winter J (1986) Status, distribution, and ecology of the great gray owl (Strix nebulosa) in California. MS Thesis, San Francisco State University, San Francisco, CA, 121 pp
Acknowledgements
We thank Lisa Sztukowski for logistical support. D. Kennedy provided some relevant references and reports. Funding was provided by the U.S. Fish and Wildlife Service through The Sustainable Ecosystem Institute. The U.S. Forest Service (Contract #53-91S8-5-EC15) provided funding to RJG and ABF, with additional funding provided by the Minnesota Agricultural Experiment Station to RJG.
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Gutiérrez, R.J., Cody, M., Courtney, S. et al. The Invasion of Barred Owls and its Potential Effect on the Spotted Owl: a Conservation Conundrum. Biol Invasions 9, 181–196 (2007). https://doi.org/10.1007/s10530-006-9025-5
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DOI: https://doi.org/10.1007/s10530-006-9025-5