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Northern Spotted Owl (Strix occidentalis caurina)
Global:G3 Provincial:S1 COSEWIC: E (May 2000) BC List: Red Identified Wildlife under the Forest & Range Practices Act
Potential South Coast Occurrence Range
Distribution: The Northern spotted owl subspecies represents the northern end of this
species group in North America. The species is a permanent resident throughout its North
American range, following old growth and mature coastal forests from southwestern British
Columbia to southern California, and along the southern Rocky Mountains from central
Colorado to central Mexico. The range in BC is restricted to the South Coast mainland, as far
north as Anderson Lake, east to Manning Park and west to the Squamish watershed. In Metro
Vancouver, it may still occur in the drinking watersheds (Capilano, Seymour, Coquitlam).
The caurina subspecies is extremely imperiled in BC and in 2006 was down to at least 22
individuals (6 breeding pairs). The species as a whole is facing significant declines in the
extent of its range in North America (Chutter et al 2006).
Description: The northern spotted owl is a medium-sized, round-headed owl lacking ear
tufts. Plumage is generally brown interlaced with buff tipped (spotted) with white. Sexes are
alike; however, females are slightly larger than males. Juveniles can have somewhat less
distinctive markings.
Diet: Spotted owls feed primarily on small mammals associated with old-growth and mature
coastal forests such as northern flying squirrels, bushy-tailed woodrat, red-backed voles and
deermice.
Look’s Like? This species is most likely to be confused with the more common naturalized
barred owl, a close, competitive relative with which it may be hybridizing (Sutherland et al
2007). The barred owl lacks the characteristic white tipped breast and belly plumage, instead
feathers are streaked (barred) over a light buff breast and belly. Juveniles between the two
species can have somewhat less distinctive markings. Members of the Strix genus have large
dark brown eyes, a key difference from the other owls that they may co-occur with which
generally have yellow eyes.
Primary Habitat: As with its prey species the spotted owl is an old growth-mature forest
specialist, and forages and roosts in late seral (older successional) stands that have >50%
canopy closure. In wet forest areas, this species generally uses stands dominated by conifers,
though they may use mixed conifer-hardwood stands. Pure hardwood stands are not used in
the winter, but they may be used for foraging and roosting in the summer. In drier forest
areas, the owls use pure fir or mixed conifer forests containing at least 20% fir. These
preferences reflect the availability of their most important prey species, the flying squirrel,
which feeds on fungi growing on Douglas-firs.
Secondary Habitat: While this species is primarily old-growth forest dependent, mature
second growth features are utilized where sufficient prey base and structural diversity are
present.
Field Guide to Select Species of Conservation Concern for the South Coast of British Columbia
Northern Spotted owl - Draft 2008
Critical feature: The northern spotted owl nests in large (>30 cm dbh, but preferably >50 cm
dbh) trees in old growth stands within tree cavities or abandoned hawk or crow nests. Trees
with broken tops, tree cavities resulting from heart rot, and platform nests built by other
species are important habitat features. Breeding begins at two or three years of age. This
species usually mates for life and uses the same nest site in subsequent years, though they do
not breed every year. Spotted owls are easily subjected to heat stress and respond to
variations in temperature by moving within the canopy to more favourable microclimates. In
summer, when temperatures are warmer, roosts tend to be in cool, shady areas. Their narrow
preferred range of ambient temperature may be one of the reasons they strongly select mature
and old forest habitats (Gutiérrez et al. 1995).
Seasonal Life Cycle
Jan Feb Mar
Apr
Breeding /
Nesting.
Clutch size
1-3 eggs
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Chick’s in nest
Young of the year, Juveniles & adults active all year. Breeding begins at two or three years of
age, birds usually mate for life and use the same nest site in subsequent years. Breeding is usually every
other year.
Habitat Guild: Upland and riparian old growth and late mature coniferous forests, mature
deciduous and mixed forests.
Threats (based on Chutter et al 2004 and Sutherland et al 2007)
 Fragmentation of forest habitats, loss of preferred nesting features and prey availability
(tied to forest structure) are considered the most significant threats.
 Spotted Owl populations naturally have low fecundity and low juvenile survivorship
(normally offset by high survivorship of adults). Effects of low recruitment on
population growth rate may be exaggerated because of the small population and its
increasingly fragmented distribution. These effects may hinder chances of the
population’s recovery.
 Disturbance (especially due to industrial activity like road building and logging) may
exacerbate low juvenile survival and breeding success.
 Predation on chicks by other raptors (e.g. great horned owl) and inter species
competition and hybridization with barred owl.
 Bio-accumulative impacts on breeding success from use of pesticides in forest
management (eggshell thinning).
 Potential impacts from disease vectors (i.e. West Nile virus).
Conservation Objectives
Field Guide to Select Species of Conservation Concern for the South Coast of British Columbia
Northern Spotted owl - Draft 2008
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Identify and conserve critical habitat - support habitat features that provide for widely
dispersed breeding territories and nesting preferences for remote forested regions with
extensively forested canopies.
Determine the minimum amount and distribution of critical habitat needed
to maintain a stable, self-sustaining population distributed throughout the species’
natural range.
Enhance wild populations through a captive breeding program to re-establish
distribution throughout that range to a level (250 individuals) that permits the removal of
the endangered status. (This would entail either removing all or some of the remaining
Spotted Owls from the wild or to remove four adults of each sex and all known juveniles
from the wild – yet to be determined).
Undertake control measures to reduce inter-species competition and predation (e.g.
barred and possibly great-horned owl).
Re-evaluate seral structure needs (e.g. dependency on old-growth and mature second
growth stands and amend harvest plans accordingly. Under IWMS, a limited number of
Wildlife Habitat Areas may be established on provincial Crown forest and/or range land,
including such areas not covered by the SOMP (Province of British Columbia 2003).
Wildlife Habitat Areas of sufficient size and quality have the potential to protect owl
territories.
Management Practices Check List
Assess, inventory and monitor using methodology setout in the RISC standards # 11
Inventory Methods for Raptors (Version 2.0
http://ilmbwww.gov.bc.ca/risc/pubs/tebiodiv/raptors/version2/rapt_ml_v2.pdf
Apply methods as set out in Best Management Practices for Raptor Conservation during
Urban and Rural Land Development in British Columbia.
http://www.env.gov.bc.ca/wld/documents/bmp/raptor_bmp_final.pdf
Territory establishment by Spotted Owls appears to be limited by the amount, quality,
and distribution of habitat found within the landscape. Higher fecundity and adult
survivorship is associated with larger amounts of suitable habitat in areas surrounding
the nest area (Bart 1995; see Meyer et al. 1998).
Avoid activities that result in a reduction in stem density, canopy volume and habitat
quality in forested stands (e.g. under storey brushing, patch cutting and clear-cutting).
Spotted Owls are non-migratory, home ranges, particularly in the northern parts of their
distribution, are very large (Gutiérrez et al. 1995). Preliminary home range size
estimates from telemetry studies in British Columbia appear to be consistent with
estimates from Washington i.e. 2100 to 4000 ha (reviewed by Gutiérrez et al. 1995).
During breeding season owls concentrate activities closer to their nests, than in the nonbreeding season (Carey et al. 1990). Natal rearing areas were assessed at 400 ha
(Sutherland et al 2007).
Connectivity among subpopulation clusters is considered essential to maintain a
population’s viability (Lamberson et al. 1994.)
Field Guide to Select Species of Conservation Concern for the South Coast of British Columbia
Northern Spotted owl - Draft 2008
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Sightings, specimens, or observations of activities threatening its habitat should be
reported to the regional Species at Risk Biologist at the Ministry of Environment office.
Mitigating Impacts
 Maintain the hierarchical structure of core zones and home range zones e.g. nest sites,
nest areas, post-fledging area and foraging areas. Core zones should have limited access
and no disturbance.
 The general wildlife measures (GWMs) for the northern spotted owl (as an identified
wildlife) include recommendations to maintain or restore at least 67% of the gross
forested area within a designated Wildlife Habitat Area for this species, of which 75%
should be maintained or restored as superior habitat ( >140 years, >19.4 m tall and 1370
m).
 Distribute the 67% suitable habitat into large non-fragmented patches >500 ha that are
connected by movement corridors of suitable habitat that are a minimum of 1 km wide.
Main References & Literature Cited:
A Field Guide to Species at Risk in the Coast Forest Region of British Columbia: Published by:
International Forest Products Limited and Ministry of Water, Land and Air Protection. 2003.
Accounts and Measures for Managing Identified Wildlife – Accounts V. 2004 –
http://www.env.gov.bc.ca/wld/frpa/iwms/accounts.html
Recovery Strategy For The Northern Spotted Owl (Strix occidentalis caurina) in BC. Chutter, M.J. et al.
2004. http://www.sararegistry.gc.ca/virtual_sara/files/plans/rs_spotted_owl_caurina_1006_e.pdf
A Framework to Support Landscape Analyses of Habitat Supply and Effects on Populations
of Forest-dwelling Species: A Case Study Based on the Northern Spotted Owl. G.D. Sutherland et al.
B.C. Min. For. Range, Res. Br., Victoria, B.C. Tech. Rep. 038. 2007
http://www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr038.pdf
Northern Spotted Owl Population Enhancement and Recovery in British Columbia. Proposed Five-Year
Action Plan. SOPET. March 2007.
http://ilmbwww.gov.bc.ca/sarco/so/files/SOPET_Proposed_5year_Action_Plan-20070330.pdf
BC Species & Ecosystems Explorer (BC Conservation Data Center Summary Report)
http://www.env.gov.bc.ca/atrisk/toolintro.html
NatureServe Explorer - http://www.natureserve.org
Committee on the Status of Endangered Wildlife in Canada: http://www.cosewic.gc.ca/
Image credits:
SO – Rod Gilbert
Habitat – Alex Isenberg
Field Guide to Select Species of Conservation Concern for the South Coast of British Columbia
Northern Spotted owl - Draft 2008