California Spotted Owl (Strix occidentalis occidentalis)
Update...April 2012...Owl populations studied from 1992 to 2010 show steady declines in the Lassen, Eldorado, and Sierra National Forests. Scroll down to "Status" to learn more, with links to online webinars and video.
The California spotted owl is closely associated with old forests and according to studies, old-growth forests in the Sierra Nevada have declined by as much as 90 percent. Such habitat loss is believed to be a factor in the poor survival of adult California spotted owls, which were found by a Forest Service study to be dying at a faster rate than the listed Northern spotted owl. The owl population trend in the northern Sierra Nevada is currently in decline and measures taken by Federal land managers over the last decade have failed to show marked improvement in its status. The mature forest stands favored by the owl are generally at lower risk of crown fire than younger forests, because the dense, older forest canopies maintain relatively moist conditions within the stand. Also, the large trees favored by the owl for nesting and foraging do not generally contribute greatly to wildfire risk.
California spotted owl inhabits the Sierra Nevada from approximately 3,000 to 7,000 feet in elevation. Ninety-nine percent of the total known owl sites on Forest Service land occur within the seven west-slope national forests, from the Plumas to the Sequoia. The forests that once provided habitat for the owl have been decimated by over a century of logging, road-building and development.
The 2001 Sierra Nevada Framework Plan paid particular attention to the spotted owl decline by crafting a set of standards to protect its habitat. The Forest Service’s 2004 revisions to the Framework eliminated key protection measures for medium and large trees, canopy cover, home-range core areas and weakened protections near nests. The original Framework provided protection for the owl, while at the same time allowing for substantial progress towards reducing risk of destructive forest fires, by protecting fire resistant medium and large trees across the landscape, and focusing fuel treatments around communities where they are needed most.
The U.S. Fish and Wildlife Service’s original decision (In 2003, see below) not to list the owl under the Endangered Species Act was based on the assumption that the owl’s habitat in the Sierra Nevada would be largely protected by the Clinton Administration’s Sierra Nevada Framework, a plan that restricted logging to protect the owl’s habitat. Once the Bush Administration’s revisions of the Sierra Nevada Framework were adopted in 2004, promising to triple logging in the Sierra Nevada, the Fish and Wildlife again denied endangered status to the owl while the threats to the owl's survival had increased dramatically thanks to the watering down of the original Framework and its protections.
The Sierra Campaign (Sierra Forest Legacy) and the Center for Biological Diversity filed a petition to list the California Spotted Owl under the Endangered Species Act in April 2000. In 2003 the U.S. Fish and Wildlife Service denied that listing, stating that it was warranted but that they were precluded from listing the owl due to administrative restraints. A second petition to list was filed in 2004 after the revisions to the Sierra Nevada Framework were adopted and the Fish and Wildlife Service once again denied listing based upon a “warranted but precluded” finding. The California Spotted owl is consider a “sensitive” species by the Forest Service though this status has done little to stop projects and plans which greatly impact the habitat of the owl and its survivability in the Sierra Nevada.
Currently, the Forest Service is committed to monitor the California spotted owl under the terms of the 2004 Framework Appeal decision that established an adaptive management program incorporating Appendix E, the monitoring program established for the new Framework (2001 and 2004). The Region's committments include funding on-going monitoring of the Pacific fisher, American marten, and the California spotted owl.
Monitoring in the Plumas Lassen Study Area now reports owl declines over the last 20 years, and in October 2012, the Sierra Nevada Adaptive Management Program owl research team reported steady declines in the Eldorado Study Area and the Sierra National Forest as well. This was despite earlier reports that the owl was not in decline--suggesting that data had been misinterpreted during the period when F&WS was evaluating the owl for potential listing under the Endangered Species Act.
Don't miss this: click here to view an online webinar presented by owl scientist John Keane (April, 2012). This webinar is sponsored by the California Fire Science Consortium. Keane discusses recent research investigating the effects from fuels treatments and wildfires on California spotted owls and their habitat in the Plumas-Lassen Study Area, as well as other related topics. Researchers are attempting to monitor the effects of fuels treatments implemented under the Herger-Feinstein Quincy Library Group Act in the northern Sierra Nevada. Keane reports the decline of the California spotted owl in three of the four study areas: Plumas-Lassen, Eldorado, and Sierra National Forest Study Areas; while the owls are holding steady on the Sequoia Kings Canyon National Park study area.
Click here to view a slide show presentation by owl scientist Doug Tempel, documenting the serious decline of the owl in the El Dorado Study Area.
Below, you can watch a video created by the SNAMP owl team that highlights ongoing California spotted owl research.
Blakesley, J.A. 2003. Ecology of the California Spotted Owl: Breeding Dispersal and Associations With Forest Stand Characteristics in Northeastern California. Ph.D. Dissertation, Colorado State University, 69 Pp. (12.35MB PDF)
Blakesley, J.A., B.R. Noon and D.R. Anderson. 2005. Site Occupancy, Apparent Survival, and Reproduction of California Spotted Owls in Relation to Forest Stand Characteristics. Journal of Wildlife Management 69(4)1554–1564. (118KB PDF)
Blakesley, J.A., D.W.H. Shaw and B.R. Noon. 2005. Ecology of the California Spotted Owl on The Lassen National Forest, 1990-2004; Final Report. Colorado State University. Fort Collins, Colorado. (242KB PDF)
Bond, M.L., M.E. Seamans, and R.J. Guitierrez. 2004. Modeling Nesting Habitat Selection of California Spotted Owls (Strix occidentalis occidentalis) in the Central Sierra Nevada Using Standard Forest Inventory Metrics. Forest Science, 56(6) 773-780. (89KB PDF)
Chatfield, A.H. 2005. Habitat Selection by a California Spotted Owl Population: A Landscape Scale Analysis Using Resource Selection Functions. Master of Science Thesis, University Of Minnesota. St. Paul, Minnesota. (1.12MB PDF)
Franklin, A.B., D. R. Anderson, R. J. Gutierrez, and K.P. Burnham. 2000. Climate, Habitat Quality, and Fitness in Northern Spotted Owl Populations in Northwestern California. Ecological Monographs,70(4) 539–590. (679KB PDF)
Keane, J. Gallagher, C.V., Gerrard, R. A., Jehle, G., and Shaklee, P. A. 2011. Chapter 5: Spotted Owl Module. In: Plumas Lassen Study. 2010 Annual Report. USDA Forest Service Pacific Southwest Research Station. (5.33 MB PDF)
LaHaye, W.S., R. J. Gutierrez, and G.S. Zimmerman. 2004. Temporal Variation in the Vital Rates of an Insular Population of Spotted Owls (Strix Occidentalis Occidentalis): Contrasting Effects of Weather. The Auk121(4) 1056–1069. (160KB PDF)
Munton, T.E., K.D. Johnson, G.N. Steger, and G.P, Eberlin. 2002. Diets of California Spotted Owls in the Sierra National Forest. Proceedings of a Symposium on The Kings River Sustainable Forest Ecosystem Project: Progress and Current Status. Gen. Tech. Rep. PSW-GTR-183, Albany, CA: Pacific Southwest Research Station, U.S. Forest Service. Pp. 99-106. (264KB PDF)
Noon, B.R., and A.B. Franklin. 2002. Scientific Research and the Spotted Owl (Strix Occidentalis): Opportunities for Major Contributions to Avian Population Ecology. The Auk 119(2) 311–320. (94KB PDF)
North, M., G. Steger, R. Denton, G. Eberlin, T. Munton, and K. Johnson. 2000. Association of Weather and Nest-Site Structure with Reproductive Success in California Spotted Owls. Journal of Wildlife Management 64(3) 797-807. (942KB PDF)
Peterson, A.T., and C.R. Robins. 2003. Using Ecological-Niche Modeling to Predict Barred Owl Invasions with Implications for Spotted Owl Conservation. Conservation Biology 17(4) 1161-1165. (1.23MB PDF)
Steger, G.N., T.E. Munton, K.D. Johnson, and G.P Eberlin. 2002. Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Park. Proceedings of a Symposium on The Kings River Sustainable Forest Ecosystem Project: Progress And Current Status. Gen. Tech. Rep. PSW-GTR-183, Albany, CA: Pacific Southwest Research Station, U.S. Forest Service. 107-116. (637KB PDF)
Steger, G.N., T.E. Munton, K.D. Johnson, and G.E. Eberlin. 1997. Characteristics of California Spotted Owl Nest Sites in Foothill Riparian and Oak Woodlands of the Southern Sierra Nevada, California. U.S. Forest Service Gen. Tech. Rep. PSW-GTR-160. (133KB PDF)
Steger, G.N., T.E. Munton, K.D. Johnson, and G.E. Eberlin. 1997. Characteristics of Nest Trees and Nest Sites of California Spotted Owls in Coniferous Forests of the Southern Sierra Nevada. Transactions of the Western Section of the Wildlife Society 33:30-3. (954KB PDF)
Temple, D.J., and R.J. Gutierrez. 2004. Factors Related to Fecal Corticosterone Levels in California Spotted Owls: Implications for Assessing Chronic Stress. Conservation Biology 18(2) 538-547. (211KB PDF)
Verner, J., K.S. McKelvey, B.R. Noon, R. J. Gutiérrez, G.I. Gould, Jr., and T.W. Beck. 1992. The California Spotted Owl: A Technical Assessment of Its Current Status. Pacific SW Research Station U.S. Forest Service. (URL)
2004 Updated petition to list as Endangered (1.13MB PDF)
California Department of Fish and Game Natural History Information --This California state website contains rather limited and old information but is a good basic background composite for the species. Choose from a drop-down list to select the animal you are interested in.