Strix occidentalis caurina

(Merriam, 1898)

Northern Spotted Owl

T3T3 (G3G4T3) Found in 283 roadless areas NatureServe Explorer →
T3T3Global Rank
HighThreat Impact
Northern spotted owl (Strix occidentalis caurina). Photo by U.S. Fish & Wildlife Service, Public Domain (U.S. Government Work), via ECOS.
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.104619
Element CodeABNSB12011
Record TypeSPECIES
ClassificationSubspecies
Classification StatusStandard
Name CategoryVertebrate Animal
CITESAppendix II
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassAves
OrderStrigiformes
FamilyStrigidae
GenusStrix
Other Common Names
Chouette tachetée de la sous-espèce caurina (FR)
Concept Reference
American Ornithologists' Union (AOU). 1957. The AOU check-list of North American birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.
Conservation Status
Rank MethodExpertise without calculation
Review Date2016-04-10
Change Date1996-11-27
Edition Date2011-02-17
Edition AuthorsHammerson, G.
Threat ImpactHigh
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences81 - 300
Rank Reasons
Fairly large range (British Columbia to northern California) but relatively few occurrences are of high quality, and population trend is downward, so this owl remains of significant conservation concern; decline is due to past and continuing loss and/or fragmentation of habitat resulting from timber harvest, effects of barred owls, and other factors.
Range Extent Comments
Range extends from southwestern British Columbia (Dunbar et al. 1991) southward through the Coast Ranges and Cascade Range (both west and east sides) of Washington and Oregon to northwestern California north of San Francisco (Marin County) and northwest of the Pit River in northeastern Shasta County (the Pit River boundary between subspecies caurina and occidentalis is based on biogeographic considerations, rather than on adequate taxonomic data from that area) (Thomas et al. 1990). The population on the Olympic Peninsula appears to be reproductively isolated (by nonforested lands of the Puget Trough) from owls in the Cascade Range. The Columbia River may constitute an isolating barrier between the Cascades populations in Washington and Oregon. Population size and density are relatively low at the northern and southern ends of the range.
Occurrences Comments
This subspecies is represented by a large number of occurrences (subpopulations).
Threat Impact Comments
In a major range-wide analysis, Lint et al. (2005) concluded that presence of barred owls (Strix varia), weather, past and present harvest of habitat, and wildfire and insect infestations that alter habitat are all possible contributors to declines in northern spotted owl populations. Lint et al. (2005) determined that barred owls, West Nile virus (Flavivirus sp.), and management of owl habitat in high-fire-risk areas are topics for future management consideration.

Habitat continues to be lost or degraded by logging and/or forest fragmentation, but the rate of loss has slowed. A perhaps conservative estimate is that habitat has been reduced by about 60% since 1800; habitat loss (including that due to fragmentation) has been due primarily to logging, but natural disturbances also have played a role (Thomas et al. 1990).

Spotted owls may be threatened by the recent expansion of the range of the barred owl into the Pacific Northwest; barred owls possibly could compete with or displace spotted owls. For example, Kelly et al. (2003) found that occupancy of spotted owl territories in Oregon and Washington declined after barred owls were detected within 0.80 kilometers of the territory center. Between 1974 and 1998, the authors estimated that 706 different barred owl territories were located in Oregon. From 1989-1998, an average of 60 new barred owl territories were located in Oregon each year. USFWS (2007) concluded that the most important threat currently facing the spotted owl is competition from the barred owl. Hybridization between spotted owls and barred owls has been detected but is relatively rare (Thomas et al. 1993, Hamer et al. 1994, Seamans et al. 2004) and has been recorded most often in Oregon.

Based on data from all three spotted owl subspecies, Bond et al. (2002) hypothesized that "wildfires may have little short-term impact on survival, site fidelity, mate fidelity, and reproductive success of spotted owls. Further, prescribed burning could be an effective tool in restoring habitat to natural conditions with minimal short-term impact on resident spotted owls."
Ecology & Habitat

Description

A large, dark-eyed, round-headed, dark brown owl with white spotting on the head, back, and underparts (spotted breast, barred belly).

Diagnostic Characteristics

Differs from other subspecies in being darker, with lighter markings more reduced in size, and with the legs and feet more heavily mottled (Ridgway 1914).

Habitat

Thomas et al. (1990) found that typical habitat characteristics include: "moderate to high canopy closure; a multilayered, multispecies canopy dominated by large overstory trees; a high incidence of large trees with large cavities, broken tops, and other indications of decadence; numerous large snags; heavy accumulations of logs and other woody debris on the forest floor; and considerable open space within and beneath the canopy." Generally these conditions are found in old growth (at least 150-200 years old), but sometimes they occur in younger forests that include patches of older growth; in Washington and Oregon, conifer forests begin to develop conditions suitable for spotted owls about 80-120 years after clearcutting; coastal redwood forests are exceptional in that stands that are 50-80 years old or so may provide suitable conditions. Can tolerate some degree of habitat fragmentation (e.g., as on BLM lands in western Oregon) (Thomas et al. 1990). In southwestern Oregon, almost all owls consistently selected old forest for foraging and roosting (Carey et al. 1992). In northwestern California, nest and roost sites had more old-growth and mature forest and were less fragmented than were random sites (Hunter et al. 1995).

Recent landscape-level analyses in portions of the California Klamath and Oregon Coast Province suggest that a mosaic of mid-seral and late-successional nesting habitat interspersed with other seral conditions may result in high fitness for spotted owls (see USFWS 2007), but other studies have not found that correlation (e.g., Dugger et al. 2005).

Nests on broken tree top, cliff ledge, in natural tree cavity, or in tree on stick platform, often the abandoned nest of hawk or mammal; sometimes in cave. In western Oregon, the proportion of old-growth and mature forest was significantly greater at nest sites than at random sites (Ripple et al. 1991). Pairs tend to occupy the same nesting territories in successive years, as long as habitat remains suitable (Thomas et al. 1990).

Ecology

In southwestern Oregon, density ranged from 0.190 pairs/sq km in old unfragmented mixed-conifer forest to 0.046 pairs/sq km in old fragmented Douglas-fir forest (Carey et al. 1992).

Population density estimates range from 0.09/sq km in Washington to 0.36/sq km in Oregon (Johnsgard 1988); 0.24/sq km in northwestern California (about 0.6/sq km of suitable habitat) (Franklin et al. 1990). Density estimates for 12 study areas during 1985-1992 ranged up to 0.27 adults and subadults/sq km (Thomas et al. 1993).

Reproduction

The spotted owl is relatively long-lived, has a long reproductive life span, invests significantly in parental care, and exhibits high adult survivorship relative to other North American owls (USFWS 2007).

USFWS (2007) summarized life history as follows. Courtship behavior usually begins in February or March, and females typically lay eggs in late March or April. The timing of nesting and fledging varies with latitude and elevation. Breeding females lay 1-4 four eggs per clutch, with the average clutch size being two eggs; however, most pairs do not nest every year, nor are nesting pairs successful every year. Renesting (in different nest) after nest failure is infrequent. Incubation, by the female (fed by male), lasts about 30 days. Young leave the nest at about 5 weeks, fly at about 6 weeks. After they leave the nest in late May or June, juveniles depend on their parents until they are able to fly and hunt on their own. Parental care continues after fledging into September. During the first few weeks after the young leave the nest, the adults often roost with them during the day. By late summer, the adults are rarely found roosting with their young and usually only visit the juveniles to feed them at night. Spotted owls are sexually mature at 1 year of age, but rarely breed until they are 2 to 5 years of age. See USFWS (2007) for specific sources of this information.
Terrestrial Habitats
Forest - ConiferForest - Mixed
Palustrine Habitats
Riparian
Other Nations (2)
United StatesN3
ProvinceRankNative
WashingtonS1Yes
OregonS1Yes
CaliforniaS2Yes
CanadaN1
ProvinceRankNative
British ColumbiaS1Yes
Threat Assessments
ThreatScopeSeverityTiming
5 - Biological resource useUnknownExtreme - moderateHigh (continuing)
5.3 - Logging & wood harvestingUnknownExtreme - moderateHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesLarge - restrictedSerious - moderateHigh (continuing)
8.2 - Problematic native species/diseasesLarge - restrictedSerious - moderateHigh (continuing)

Roadless Areas (283)
California (106)
AreaForestAcres
BackboneShasta-Trinity National Forest11,466
Bakeoven RidgeShasta-Trinity National Forest46
Bell QuinbyShasta-Trinity National Forest11,556
Big Butte ShinboneMendocino National Forest4,265
Big Butte ShinboneSix Rivers National Forest1,102
BlackKlamath National Forest6,530
Black ButteMendocino National Forest15,461
Blue Creek Rare ISix Rivers National Forest12,134
Board CampSix Rivers National Forest4,527
Bonanza KingShasta-Trinity National Forest16,402
BoulderKlamath National Forest435
Box CampKlamath National Forest858
BriscoeMendocino National Forest7,212
Burnt Lava FlowModoc National Forest8,387
Callahan FlowKlamath National Forest3,231
Callahan FlowModoc National Forest6,618
Castle Crags AShasta-Trinity National Forest113
Castle Crags BShasta-Trinity National Forest1,619
ChanchelullaShasta-Trinity National Forest3,915
China Springs AShasta-Trinity National Forest25
China Springs BShasta-Trinity National Forest568
ChinquapinShasta-Trinity National Forest22,040
Condrey Mtn.Klamath National Forest2,923
Cow CreekShasta-Trinity National Forest22,627
Cow CreekSix Rivers National Forest1,271
CrapoKlamath National Forest1,487
Cub (fs)Klamath National Forest135
CypressLassen National Forest3,380
Deer MountainMendocino National Forest11,716
Devils RockShasta-Trinity National Forest16,209
Dog CreekShasta-Trinity National Forest5,001
EagleShasta-Trinity National Forest6,553
East BeegumShasta-Trinity National Forest8,425
East ForkShasta-Trinity National Forest6,201
East GirardShasta-Trinity National Forest27,894
Elk CreekMendocino National Forest23,182
Fisher Gulch BShasta-Trinity National Forest4,791
Granite PeakShasta-Trinity National Forest122
GriderKlamath National Forest10,647
GrindstoneMendocino National Forest26,031
Hobo GulchShasta-Trinity National Forest88
Indian CreekKlamath National Forest5,011
Jacobs (fs)Klamath National Forest577
JohnsonKlamath National Forest10,652
KangarooKlamath National Forest40,617
KellySix Rivers National Forest5,195
KelseyKlamath National Forest3,237
Kettle Mtn.Shasta-Trinity National Forest4,589
Lake EleanorShasta-Trinity National Forest397
LavaLassen National Forest5,978
LavasModoc National Forest25,864
Little French CShasta-Trinity National Forest11,529
MayfieldLassen National Forest14,444
Monkey CreekSix Rivers National Forest9,017
Mt. EddyShasta-Trinity National Forest7,232
Mt. HoffmanModoc National Forest9,780
Mt. HoffmanKlamath National Forest802
Mt. LassicSix Rivers National Forest6,643
Mt. Shasta AShasta-Trinity National Forest676
Mt. Shasta BShasta-Trinity National Forest2,809
Mt. Shasta CShasta-Trinity National Forest292
Murphy GladeShasta-Trinity National Forest1,015
MuseKlamath National Forest238
North Fork SmithSix Rivers National Forest37,898
Orleans Mtn.Shasta-Trinity National Forest57
Orleans Mtn.Klamath National Forest49,090
Orleans Mtn. BSix Rivers National Forest17,183
Orleans Mtn. CSix Rivers National Forest15,589
PacksaddleSix Rivers National Forest3,862
PantherShasta-Trinity National Forest12,016
PattisonShasta-Trinity National Forest29,299
Penney RidgeShasta-Trinity National Forest5,226
Pilot CreekSix Rivers National Forest9,192
PortugueseKlamath National Forest18,915
Redcap Addition Rare ISix Rivers National Forest489
Reister CanyonMendocino National Forest5,897
RussianKlamath National Forest21,771
Salt CreekSix Rivers National Forest9,505
Salt GulchShasta-Trinity National Forest6,511
ShacklefordKlamath National Forest1,679
Ship MountainSix Rivers National Forest11,936
SiskiyouKlamath National Forest54,039
Siskiyou ASix Rivers National Forest1,017
Siskiyou BSix Rivers National Forest18,871
Skeleton GladeMendocino National Forest9,237
Slate CreekShasta-Trinity National Forest6,636
Slide CreekSix Rivers National Forest11,458
SnoozerKlamath National Forest23,414
Snow MountainLassen National Forest2,165
Snow MountainMendocino National Forest14,457
SoliderSix Rivers National Forest14,918
South ForkShasta-Trinity National Forest16,786
South KalmiopsisSix Rivers National Forest321
Stoveleg GapShasta-Trinity National Forest61
ThatcherMendocino National Forest16,652
Thomes CreekMendocino National Forest16,616
Timbered CraterLassen National Forest4,096
Tom MartinKlamath National Forest9,031
Ukonom CreekKlamath National Forest4,621
UnderwoodSix Rivers National Forest6,591
UnderwoodShasta-Trinity National Forest3,046
Weaver BallyShasta-Trinity National Forest829
Wells MountainShasta-Trinity National Forest5,919
West BeegumShasta-Trinity National Forest5,198
West GirardShasta-Trinity National Forest37,516
Wilderness ContiguousMendocino National Forest3,606
Idaho (1)
AreaForestAcres
Bear CreekCaribou-Targhee National Forest118,582
Oregon (92)
AreaForestAcres
AspenWinema National Forest1,107
Badger CreekMt. Hood National Forest847
BadlandsWinema National Forest822
BearwallowsDeschutes National Forest7,317
Bend WatershedDeschutes National Forest14,829
Bitter LickUmpqua National Forest179
Brown Mt.Winema National Forest3,117
Bull Of The WoodsWillamette National Forest53
Bull Of The WoodsMt. Hood National Forest8,843
Bulldog RockUmpqua National Forest6,056
Bulldog RockWillamette National Forest559
Calf - Copeland CreekUmpqua National Forest15,696
Canton CreekUmpqua National Forest6,721
Castle Rock AppendageUmpqua National Forest4,649
CharltonDeschutes National Forest7,047
Charlton ButteWillamette National Forest3,031
Chucksney MountainWillamette National Forest15,369
CloverWinema National Forest365
CornpatchWillamette National Forest7,346
Cougar BluffUmpqua National Forest5,574
DoneganUmpqua National Forest5,914
Drift CreekSiuslaw National Forest6,333
EagleMt. Hood National Forest16,841
Echo MountainWillamette National Forest8,098
ElkhornWillamette National Forest9,380
FairviewUmpqua National Forest7,417
Fish Creek AppendageUmpqua National Forest1,377
French Pete (a)Willamette National Forest1,668
French Pete (b)Willamette National Forest1,186
Frog CampWillamette National Forest491
Gold CreekWillamette National Forest1,364
Gordon MeadowsWillamette National Forest9,463
Hardesty MountainUmpqua National Forest2,597
Hardesty MountainWillamette National Forest3,754
Hebo 1aSiuslaw National Forest13,930
HuckleberryWillamette National Forest793
Jackson Creek AppendageUmpqua National Forest4,673
LakeMt. Hood National Forest1,327
LarchMt. Hood National Forest12,961
LastUmpqua National Forest7,666
Limpy RockUmpqua National Forest6,782
Lonesome Meadow AppendageUmpqua National Forest930
Maiden PeakWillamette National Forest9,627
Maiden PeakDeschutes National Forest26,432
MarshWinema National Forest1,226
Mclennon MountainWillamette National Forest8,085
Medicine Creek AppendageUmpqua National Forest745
Menagerie (rooster Rock)Willamette National Forest374
Metolius BreaksDeschutes National Forest11,141
Middle SantiamWillamette National Forest7,316
Moose LakeWillamette National Forest5,013
Mosquito CreekWillamette National Forest335
Mt. JeffersonDeschutes National Forest2,282
Mt. BaileyUmpqua National Forest18,401
Mt. HagenWillamette National Forest6,406
Mt. Hood AdditionsMt. Hood National Forest13,061
Mt. Jefferson AdditionMt. Hood National Forest162
Mt. ThielsenWinema National Forest1,153
N. BoundaryWinema National Forest769
North KalmiopsisSiskiyou National Forests91,560
OdessaWinema National Forest146
OlallieMt. Hood National Forest7,607
Opal CreekWillamette National Forest5,417
Rainbow FallsWillamette National Forest65
Roaring RiverWillamette National Forest2,128
Roaring RiverMt. Hood National Forest27,316
Rolling Grounds AppendageUmpqua National Forest1,987
Salmon - HuckleberryMt. Hood National Forest17,570
Shasta CostaSiskiyou National Forests14,420
SherwoodUmpqua National Forest2,449
Skimmerhorn AppendageUmpqua National Forest1,820
Sky Lakes AWinema National Forest3,940
Sky Lakes BWinema National Forest9,615
Smith UmpquaSiuslaw National Forest7,622
South KalmiopsisSiskiyou National Forests104,477
TahkenitchSiuslaw National Forest5,799
TenmileSiuslaw National Forest10,818
Thirsty Creek AppendageUmpqua National Forest2,255
Twin LakesMt. Hood National Forest6,055
Umpqua SpitSiuslaw National Forest2,090
W. BoundaryWinema National Forest2,345
WaldoDeschutes National Forest4,973
Waldo - FujiWillamette National Forest15,273
Waldo - KochWillamette National Forest245
Waldo - LakeWillamette National Forest2,993
Waldo - Many PrariesWillamette National Forest2,585
Waldo - MoolackWillamette National Forest1,183
Waldo - Salmon CreekWillamette National Forest3,195
West - South BachelorDeschutes National Forest25,994
Williams CreekUmpqua National Forest5,844
Wind CreekMt. Hood National Forest5,438
WoahinkSiuslaw National Forest5,309
South Dakota (1)
AreaForestAcres
Indian CreekBuffalo Gap National Grassland24,666
Washington (83)
AreaForestAcres
Alpine Lakes Adj.Wenatchee National Forest57,104
Angry MountainGifford Pinchot National Forest445
BackboneGifford Pinchot National Forest1,201
Bear CreekGifford Pinchot National Forest7,980
Big Lava BedGifford Pinchot National Forest19,043
Black CanyonOkanogan National Forest9,681
Blue LakeGifford Pinchot National Forest11,359
Blue SlideWenatchee National Forest17,505
Boulder RiverMt Baker-Snoqualmie National Forest32,563
BourbonGifford Pinchot National Forest4,512
Canyon CreekWenatchee National Forest7,983
Carlton RidgeGifford Pinchot National Forest2,190
ChambersGifford Pinchot National Forest2,006
ChelanWenatchee National Forest74,650
Coal Creek BluffGifford Pinchot National Forest1,164
CortrightGifford Pinchot National Forest3,462
Dark DivideGifford Pinchot National Forest52,483
Deer CreekGifford Pinchot National Forest882
Devils GulchWenatchee National Forest24,419
Dixon MountainGifford Pinchot National Forest6,339
Eagle RockMt Baker-Snoqualmie National Forest34,064
EntiatWenatchee National Forest72,617
Glacier Peak BMt Baker-Snoqualmie National Forest19,328
Glacier Peak IMt Baker-Snoqualmie National Forest15,175
Glacier Peak JMt Baker-Snoqualmie National Forest26,482
Glacier Peak KMt Baker-Snoqualmie National Forest47,269
Glacier Peak LMt Baker-Snoqualmie National Forest14,084
Goat Rocks AdjWenatchee National Forest6,108
Gotchen CreekGifford Pinchot National Forest7,518
Green MountainOlympic National Forest4,617
Heather LakeWenatchee National Forest10,628
Higgins MountainMt Baker-Snoqualmie National Forest13,185
HorseshoeGifford Pinchot National Forest7,579
Hungry RidgeOkanogan National Forest8,708
Jefferson RidgeOlympic National Forest6,512
Jupiter RidgeOlympic National Forest10,148
Laughing WaterGifford Pinchot National Forest1,167
Liberty BellOkanogan National Forest108,495
LightningOlympic National Forest7,179
Lion RockWenatchee National Forest4,692
Long SwampOkanogan National Forest66,344
Madison CreekOlympic National Forest1,223
ManastashWenatchee National Forest11,155
McdonaldOlympic National Forest501
Moonlight DomeOlympic National Forest4,919
Mt. Baker MaMt Baker-Snoqualmie National Forest24,847
Mt. Baker Noisy - DiobsudMt Baker-Snoqualmie National Forest56,039
Mt. Baker NorthMt Baker-Snoqualmie National Forest16,873
Mt. Baker WestMt Baker-Snoqualmie National Forest25,390
Mt. BaldyOlympic National Forest3,557
Mt. ZionOlympic National Forest3,544
Myrtle LakeWenatchee National Forest11,133
NaneumWenatchee National Forest4,508
Nason RidgeWenatchee National Forest19,329
Norse PeakWenatchee National Forest10,169
Packwood LakeGifford Pinchot National Forest1,084
Pasayten RimOkanogan National Forest17,074
PompeyGifford Pinchot National Forest23,985
PressentinMt Baker-Snoqualmie National Forest14,545
QuartzWenatchee National Forest8,550
QuilceneOlympic National Forest18,656
Red LakeGifford Pinchot National Forest2,162
Red MountainGifford Pinchot National Forest2,992
Rock CreekWenatchee National Forest32,239
Rugged RidgeOlympic National Forest4,358
SawtoothOkanogan National Forest122,194
Silver StarGifford Pinchot National Forest7,779
SiouxonGifford Pinchot National Forest12,773
Slide RidgeWenatchee National Forest11,430
South MidwayGifford Pinchot National Forest2,384
South QuinaultOlympic National Forest11,081
Spencer RidgeGifford Pinchot National Forest5,880
Stormy Mtn.Wenatchee National Forest32,612
StrawberryGifford Pinchot National Forest5,244
TaneumWenatchee National Forest26,140
TeanawayWenatchee National Forest72,849
Thorp Mtn.Wenatchee National Forest22,717
TumwaterGifford Pinchot National Forest8,676
Twin LakesWenatchee National Forest22,496
Upper SkokomishOlympic National Forest9,311
West AdamsGifford Pinchot National Forest2,238
White PassGifford Pinchot National Forest1,145
WobblyGifford Pinchot National Forest6,335
References (55)
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