Most populations strongly associate with either old-growth conifer or pine-oak forests (Johnsgard 1988, Gutiérrez et al. 1995), but some lucida also occur in heavily logged secondary pine-oak forest, warmer and drier conditions and on bare rocky cliffs and canyons (Lammertink et al. 1996,  J. M. Lammertink in litt. 1998, U. S. Fish and Wildlife Service 2012, Bowden et al. 2015). It occurs from sea-level to 1,200 m in the northern part of its range, and to 2,700 m in the southern part. Nests are generally in trees within closed-canopy forest, (usually in cavities or on stick platforms constructed originally by raptors, wood rats or squirrels) on cliff-ledges in steep-walled canyons (and occasionally in caves (Wilk et al. 2018). Eggs are laid from March to May. Young birds are obligate dispersers, whilst unpaired birds or those that have failed to breed previously also disperse (Forsman et al. 2002, Blakesley et al. 2006, Ganey et al. 2014a); this may help to sustain some sink populations. It may make some movements in winter, including to recently burnt areas as these can have greater food availability (Ganey et al. 2014b). It feeds principally on nocturnal mammals.

Strix occidentalis has five subspecies: caurina ('Northern Spotted Owl') is estimated to number 3,778 pairs and 1,001 territorial individuals from south-west British Columbia, Canada, to north California, USA, although this number may have declined in recent years; the nominate ('California Spotted Owl') has a minimum of 3,050 individuals in central and south California, USA, and (formerly) Baja California, Mexico; and lucida, juanaphillipsae and huachucae ('Mexican Spotted Owl') (see del Hoyo and Collar 2014). Subspecies huachuacae occurs from Utah and Colorado to Arizona, New Mexico and extreme west Texas, USA, while lucida occurs in Sonora, Chihuahua and Nuevo León to Jalisco, Durango, Michoacán and Guanajuanto, Mexico (Johnsgard 1988, Sibley and Monroe 1990, Gutiérrez et al. 1995, Lammertink et al. 1996, AOU 1998, del Hoyo and Collar 2014), and juanaphillipsae has been recently described from the State of Mexico (Dickerman 1997). Mexican Spotted Owl may be considered to be declining (U. S. Fish and Wildlife Service 2012), although Mexican populations may be stable because forestry activities there typically modify rather than destroy habitat (Lammertink et al. 1996, J. M. Lammertink in litt. 1998) and at least locally in New Mexico some subpopualations may be increasing (Ganey et al. 2014b). Most other populations are declining and, in some, the decline is accelerating because of clear-felling and selective logging (Gutiérrez et al. 1995, Noon and McKelvey 1996). Subspecies caurina is estimated to be in significant decline, at 3.8% per year range-wide and 8.4% per year in Washington State (1985-2013; Dugger et al. 2016), and is close to extinction in Canada. California Spotted Owl is declining in the Sierra Nevada, apart from at one site in a National Park (see Tempel et al. 2014b, Gutiérrez et al. 2017).

Conservation Actions Underway
CITES Appendix II. The Northern (caurina) and Mexican (lucida) subspecies are listed as Threatened under the U.S. Endangered Species Act, and are the subject of recovery plans (U. S. Fish and Wildlife Service 2011, 2012). The Northwest Forest Plan was created to provide protection and reduce rates of timber harvest leading to habitat destruction. Protected Activity Centres are advocated for as an effective mechanism of conserving the species in parts of its range (Verner et al. 1992, Willey and van Riper III 2007). In 2012 9.6 million acres of habitat was designated as critical habitat for the Northern Spotted Owl by U. S. Fish and Wildlife Service (Society for Conservation Biology 2012, Dunk et al. 2019). A captive breeding programme was started at the Mountain View Conservation and Breeding Centre, British Columbia, with a second attempt in Woodland Park Zoo in Seattle. Neither have so far had much success (Moore 2013). Experimental removal of Barred Owls is underway (Oregon Fish and Wildlife Service and U. S. Fish and Wildlife Service 2013, A. Franklin in litt. 2016, Wiens et al. 2019b).

Conservation Actions Proposed
Continue to monitor population trends across its range, and monitor the effects of conservation actions (U. S. Fish and Wildlife Service 2012), including Barred Owl control. Conduct research into broad areas of the species's biology such as interspecific interactions, population structure and habitat relationships (U.S. Fish and Wildlife Service 2012). Maintain and restore habitat; large reserves, encompassing suitable habitat and widely distributed are needed to retain the owl's current range and a halt to logging operations throughout parts of its range are required to prevent local extinctions. Use analyses to inform habitat management decisions, and ensure appropriate habitat management, which may involve habitat restoration and recovery (U. S. Fish and Wildlife Service 2011, 2012, Peery et al. 2017). Large-scale Barred Owl control efforts are likely to be needed, especially for the Northern Spotted Owl, but may also be required within the range of the California Spotted Owl to prevent local extinctions in parts of the species's range. Calls have been made for captive breeding of birds from the tiny remaining British Columbian population. Investigate the threats posed by West Nile virus, avian malaria, water management and climate change, and research the effect of wildfires and controlled burning on spotted owls (Gutiérrez et al. 2017). Counter unfavourable management policies designed to reduce wildfire risk in order to effectively minimise the likelihood of large-scale stand-replacing wildfires. Attempt to get Californian Spotted Owl listed under the US Endangered Species Act.