Oreoscoptes montanus - (Townsend, 1837)
Sage Thrasher
Other English Common Names: sage thrasher
Taxonomic Status: Accepted
Related ITIS Name(s): Oreoscoptes montanus (Townsend, 1837) (TSN 178654)
French Common Names: moqueur des armoises
Spanish Common Names: Cuitlacoche de Chías
Unique Identifier: ELEMENT_GLOBAL.2.101963
Element Code: ABPBK04010
Informal Taxonomy: Animals, Vertebrates - Birds - Perching Birds
Image 10738

© Dick Cannings

 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Passeriformes Mimidae Oreoscoptes
Genus Size: A - Monotypic genus
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Concept Reference
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Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online: http://www.aou.org/.
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Oreoscoptes montanus
Taxonomic Comments: Placed in Sturnidae in Sibley and Ahlquist (1984).
Conservation Status
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NatureServe Status

Global Status: G4
Global Status Last Reviewed: 09Apr2016
Global Status Last Changed: 12Aug2015
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G4 - Apparently Secure
Reasons: Large range in western North America; large population size; still widespread and numerous but declining in most of range; required sagebrush habitat is being lost, degraded, and fragmented as a result of ongoing conversion for human uses, effects of non-native plants, and climate change.
Nation: United States
National Status: N5B,N5N (05Jan1997)
Nation: Canada
National Status: N1B,N1M (08Dec2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Arizona (S5), California (SNR), Colorado (S5), Idaho (S3B), Kansas (SNA), Montana (S3B), Navajo Nation (S3S4B), Nebraska (S1B), Nevada (S5B), New Mexico (S3B,S4N), Oregon (S4B), South Dakota (S2B), Texas (S3N), Utah (S4B), Washington (S3B), Wyoming (S5)
Canada British Columbia (S1B), Saskatchewan (S1B)

Other Statuses

Canadian Species at Risk Act (SARA) Schedule 1/Annexe 1 Status: E (05Jun2003)
Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Endangered (26Nov2010)
Comments on COSEWIC: Reason for designation: In Canada, this species occurs in British Columbia, Alberta and Saskatchewan. Its Canadian population is extremely small, ranging from 7 to 36 individuals depending on the year. Populations in adjacent parts of the U.S., which are a likely source of birds for Canada, are declining. In addition, the sagebrush habitat necessary for breeding is decreasing, particularly in British Columbia, where the species is a regular breeder.

Status history: Designated Endangered in April 1992. Status re-examined and confirmed in November 2000 and November 2010.

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: Breeding range extends from southern British Columbia, central Idaho, and south-central Montana southward through the Great Basin to eastern California, northeastern Arizona, and west-central and northern New Mexico (AOU 1983, Reynolds et al. 1999). Sage thrashers breed at least irregularly in southern Alberta and southern Saskatchewan (Cannings 1992). Nonnreeding range extends from central California, southern Nevada, central Arizona, central New Mexico, and central Texas south to southern Baja California, northern Sonora, Chihuahua, Durango, Guanajuato, northern Nuevo Leon, and northern Tamaulipas (AOU 1983, Reynolds et al. 1999).

Number of Occurrences:  
Number of Occurrences Comments: The number of distinct occurrences has not been determined using standardized criteria, but this species is represented by a large number of recent observation sites (e.g., see eBird data) and locations (as defined by IUCN).

Population Size: >1,000,000 individuals
Population Size Comments: Partners in Flight (PIF 2013) estimated global populartion size at 5,900,000.

Overall Threat Impact: High - medium
Overall Threat Impact Comments: HABITAT LOSS, DEGRADATION, FRAGMENTATION: Large scale reduction and fragmentation of sagebrush habitats is occurring in many areas due to land conversion to tilled agriculture, urban and suburban development, and road and power-line rights of way. Range improvement programs remove sagebrush by burning, herbicide application, and mechanical treatment, replacing sagebrush with annual grassland to promote forage for livestock. Burning can result in longer-lasting sagebrush control than chaining (Castrale 1982). Range management practices such as mowing, burning, herbicide treatments, and residential and agricultural development have reduced the quantity and quality of sagebrush habitat (Braun et al. 1976, Cannings 1992, Reynolds 1999). In Wyoming, an increase in energy development (well density) did not result in a decline in sage thrasher populations, though possibly a decline might occur over a longer time frame (Gilbert and Chalfoun 2011).

GRAZING: Grazing can increase sagebrush density, positively affecting thrasher abundance. Dense stands of sagebrush, however, are considered degraded range for livestock and may be treated to reduce or remove sagebrush. Grazing may also encourage the invasion of non-native grasses, which escalates the fire cycle and converts shrublands to annual grasslands. West (1988, 1996) estimated that less than 1% of sagebrush steppe habitats remained untouched by livestock; 20% is lightly grazed, 30% moderately grazed with native understory remaining, and 30% heavily grazed with understory replaced by invasive annuals. The effects of grazing in sagebrush habitats are complex, and depend on intensity, season, duration and extent of alteration to native vegetation.

INVASIVE GRASSES: Cheatgrass readily invades disturbed sites and has come to dominate the grass-forb community of more than half the sagebrush region in the West, replacing native bunchgrasses (Rich 1996). Cheatgrass can create a more continuous grass understory than native bunchgrasses. Dense cheatgrass cover can possibly affect foraging ability for ground foragers, and more readily carries fire than native bunchgrasses. Crested wheatgrass and other non-native annuals have also altered the grass-forb community in many areas of sagebrush shrub-steppe.

FIRE: Cheatgrass has altered the natural fire regime on millions of acres in the western range, increasing the frequency, intensity, and size of range fires. Fire kills sagebrush and where non-native grasses dominate, the landscape can be converted to annual grassland as the fire cycle escalates (Paige and Ritter 1998).

Breeding range is projected to decrease by 78 percent between 2010 and 2099 as a result of ongoing climate change (van Riper et al. 2014).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Multi-decade decline indicated by Breeding Bird Survey continued during 2003-2013.

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: Long-term trend (i.e., past 200 years) is uncertain but distribution and abundance likely have declined to a significant degree as a result of habitat changes. North American Breeding Bird Survey (BBS) data indicate a multi-decade survey-wide decline (almost 50 percent, 1968-2013), with substantial declines in most areas and increases in smaller areas.

Other NatureServe Conservation Status Information

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) Breeding range extends from southern British Columbia, central Idaho, and south-central Montana southward through the Great Basin to eastern California, northeastern Arizona, and west-central and northern New Mexico (AOU 1983, Reynolds et al. 1999). Sage thrashers breed at least irregularly in southern Alberta and southern Saskatchewan (Cannings 1992). Nonnreeding range extends from central California, southern Nevada, central Arizona, central New Mexico, and central Texas south to southern Baja California, northern Sonora, Chihuahua, Durango, Guanajuato, northern Nuevo Leon, and northern Tamaulipas (AOU 1983, Reynolds et al. 1999).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AZ, CA, CO, ID, KS, MT, NE, NM, NN, NV, OR, SD, TX, UT, WA, WY
Canada BC, SK

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: NatureServe, 2002; WILDSPACETM 2002


U.S. Distribution by County Help
State County Name (FIPS Code)
ID Ada (16001), Bannock (16005), Bear Lake (16007), Bingham (16011), Blaine (16013), Boise (16015), Bonneville (16019), Butte (16023), Camas (16025), Canyon (16027), Caribou (16029), Cassia (16031), Clark (16033), Custer (16037), Elmore (16039), Fremont (16043), Gem (16045), Gooding (16047), Jefferson (16051), Jerome (16053), Latah (16057), Lemhi (16059), Lincoln (16063), Madison (16065), Minidoka (16067), Oneida (16071), Owyhee (16073), Power (16077), Twin Falls (16083), Valley (16085), Washington (16087)
MT Beaverhead (30001), Big Horn (30003), Broadwater (30007), Carbon (30009), Carter (30011), Chouteau (30015), Custer (30017), Fallon (30025), Gallatin (30031), Garfield (30033), Golden Valley (30037), Jefferson (30043), Lewis and Clark (30049), Madison (30057), Musselshell (30065), Park (30067), Petroleum (30069), Phillips (30071), Powder River (30075), Prairie (30079), Richland (30083), Rosebud (30087), Sanders (30089), Silver Bow (30093), Stillwater (30095), Sweet Grass (30097), Valley (30105), Wheatland (30107), Yellowstone (30111)
NE Kimball (31105), Sioux (31165)
NM Otero (35035)
SD Butte (46019), Fall River (46047), Meade (46093)*, Pennington (46103)*, Shannon (46113)*
UT Box Elder (49003), Juab (49023), San Juan (49037), Tooele (49045)
WA Adams (53001), Douglas (53017), Grant (53025), Kittitas (53037), Lincoln (53043), Yakima (53077)
WY Albany (56001), Big Horn (56003), Campbell (56005), Carbon (56007), Converse (56009), Crook (56011), Fremont (56013), Goshen (56015), Hot Springs (56017), Johnson (56019), Laramie (56021), Lincoln (56023), Natrona (56025), Niobrara (56027), Park (56029), Platte (56031), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041), Washakie (56043), Weston (56045)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
10 Red Rock (10020001)+, Beaverhead (10020002)+, Ruby (10020003)+, Big Hole (10020004)+, Jefferson (10020005)+, Boulder (10020006)+, Madison (10020007)+, Gallatin (10020008)+, Upper Missouri (10030101)+, Arrow (10040102)+, Fort Peck Reservoir (10040104)+, Big Dry (10040105)+, Upper Musselshell (10040201)+, Middle Musselshell (10040202)+, Flatwillow (10040203)+, Box Elder (10040204)+, Middle Milk (10050004)+, Lower Milk (10050012)+, Beaver (10050014)+, Rock (10050015)+, Charlie-Little Muddy (10060005)+, Yellowstone Headwaters (10070001)+, Shields (10070003)+, Upper Yellowstone-Lake Basin (10070004)+, Clarks Fork Yellowstone (10070006)+, Upper Wind (10080001)+, Little Wind (10080002)+, Popo Agie (10080003)+, Muskrat (10080004)+, Lower Wind (10080005)+, Badwater (10080006)+, Upper Bighorn (10080007)+, Nowood (10080008)+, Greybull (10080009)+, Big Horn Lake (10080010)+, Dry (10080011)+, North Fork Shoshone (10080012)+, South Fork Shoshone (10080013)+, Shoshone (10080014)+, Upper Tongue (10090101)+, Lower Tongue (10090102)+, Middle Fork Powder (10090201)+, Upper Powder (10090202)+, South Fork Powder (10090203)+, Salt (10090204)+, Crazy Woman (10090205)+, Clear (10090206)+, Middle Powder (10090207)+, Little Powder (10090208)+, Lower Powder (10090209)+, Mizpah (10090210)+, Lower Yellowstone-Sunday (10100001)+, Big Porcupine (10100002)+, O'fallon (10100005)+, Upper Little Missouri (10110201)+, Boxelder (10110202)+, Antelope (10120101)+, Dry Fork Cheyenne (10120102)+, Upper Cheyenne (10120103)+, Lance (10120104)+, Lightning (10120105)+, Angostura Reservoir (10120106)+, Beaver (10120107)+, Hat (10120108)+, Rapid (10120110)+*, Middle Cheyenne-Elk (10120111)+*, Upper Belle Fourche (10120201)+, Lower Belle Fourche (10120202)+, Upper White (10140201)+*, Upper North Platte (10180002)+, Pathfinder-Seminoe Reservoirs (10180003)+, Medicine Bow (10180004)+, Little Medicine Bow (10180005)+, Sweetwater (10180006)+, Middle North Platte-Casper (10180007)+, Glendo Reservoir (10180008)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Lower Laramie (10180011)+, Horse (10180012)+, Pumpkin (10180013)+, Cache La Poudre (10190007)+, Lone Tree-Owl (10190008)+, Crow (10190009)+, Upper Lodgepole (10190015)+
13 Tularosa Valley (13050003)+
14 Upper Colorado-Kane Springs (14030005)+, Upper Green (14040101)+, New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Muddy (14040108)+, Vermilion (14040109)+, Great Divide closed basin (14040200)+, Little Snake (14050003)+, Muddy (14050004)+
16 Upper Bear (16010101)+, Central Bear (16010102)+, Bear Lake (16010201)+, Lower Bear-Malad (16010204)+, Upper Weber (16020101)+, Utah Lake (16020201)+, Skull Valley (16020305)+, Northern Great Salt Lake Desert (16020308)+, Curlew Valley (16020309)+
17 Upper Clark Fork (17010201)+, Lower Flathead (17010212)+, Franklin D. Roosevelt Lake (17020001)+, Chief Joseph (17020005)+, Upper Columbia-Entiat (17020010)+, Moses Coulee (17020012)+, Upper Crab (17020013)+, Banks Lake (17020014)+, Lower Crab (17020015)+, Upper Yakima (17030001)+, Snake headwaters (17040101)+, Gros Ventre (17040102)+, Greys-Hobock (17040103)+, Idaho Falls (17040201)+, Upper Henrys (17040202)+, Lower Henrys (17040203)+, Willow (17040205)+, American Falls (17040206)+, Blackfoot (17040207)+, Portneuf (17040208)+, Lake Walcott (17040209)+, Raft (17040210)+, Goose (17040211)+, Upper Snake-Rock (17040212)+, Salmon Falls (17040213)+, Beaver-Camas (17040214)+, Medicine Lodge (17040215)+, Birch (17040216)+, Little Lost (17040217)+, Big Lost (17040218)+, Big Wood (17040219)+, Camas (17040220)+, Little Wood (17040221)+, C. J. Idaho (17050101)+, Bruneau (17050102)+, Middle Snake-Succor (17050103)+, Upper Owyhee (17050104)+, East Little Owyhee. Nevada, (17050106)+, Middle Owyhee (17050107)+, Jordan (17050108)+, Boise-Mores (17050112)+, South Fork Boise (17050113)+, Lower Boise (17050114)+, Payette (17050122)+, North Fork Payette (17050123)+, Weiser (17050124)+, Upper Salmon (17060201)+, Pahsimeroi (17060202)+, Lemhi (17060204)+, Lower Middle Fork Salmon (17060206)+, Clearwater (17060306)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: Medium-sized songbird, 20-23 cm long with a wingspan of 32 cm (Reynolds et al. 1999). Males and females brownish gray on the back with indistinct streaking, especially on the crown. Whitish underside with dark streaking. Outer tail feathers tipped white, wings with thin, white wingbars.
Reproduction Comments: Clutch size four to seven (usually three to five). Incubation about 15 days, by both sexes. Nestlings altricial and downy. Nestling period about 13 days. Probably can raise two broods per season, but probably only one brood per year in British Columbia (Cannings 1992). In Oregon, reproductive parameters were not associated with climatic variation (Rotenberry and Wiens 1989).
Ecology Comments: Density rarely exceeds 30 per square kilometer (Rotenberry and Wiens 1989). In eastern Washington sagebrush shrub-steppe, mean densities reported at 0.09 to 0.2 individuals per hectare (Dobler et al 1996). Breeding density 0.05 individuals per hectare or less in shadscale habitat in eastern Nevada (Medin 1990). Territory size in eastern Idaho averaged 8 territories per 1.86 hectares in one year, 11 territories per 1.14 hectares the following (Reynolds 1981).

Relative abundance significantly positively correlated with the following species in western U.S., based on North American Breeding Bird Survey data (T.D. Rich, unpubl. data): Brewer's Sparrow (SPIZELLA BREWERI; r = 0.87, P < 0.001), Sage Sparrow (AMPHISPIZA BELLI; r = 0.73, P < 0.001), Gray Flycatcher (EMPIDONAX WRIGHTII; r = 0.73, P P < 0.001), Sage Grouse (CENTROCERCUS UROPHASIANUS; r = 0.71, P < 0.001), Rock Wren (SALPINCTES OBSOLETUS; r = 0.61, P < 0.001), Vesper Sparrow (POOECETES GRAMINEUS; r = 0.53, P < 0.001), Prairie Falcon (FALCO MEXICANUS; r = 0.53, P < 0.001), and Green-tailed Towhee (PIPILO CHLORURUS; r = 0.51, P < 0.001).

Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: Y
Mobility and Migration Comments: Departs from northern breeding areas by end of September, returns in April, May, or June.
Terrestrial Habitat(s): Desert, Shrubland/chaparral
Habitat Comments: BREEDING: Sagebrush plains, primarily in arid or semi-arid situations, rarely around towns (AOU 1998). Usually breeds between 1300 and 2000 meters above sea level (Reynolds and Rich 1978). In eastern Washington, showed strongest correlation to amount of sagebrush cover of all shrub-steppe birds; most abundant where sagebrush percent cover was 11% which is similar to estimated historic sagebrush cover (Dobler 1992, Dobler et al. 1996). In northern Great Basin, breeds and forages in tall sagebrush/bunchgrass, juniper/sagebrush/bunchgrass, mountain mahogany/shrub, and aspen/sagebrush/bunchgrass communities (Maser et al. 1984).

Positively correlated with shrub cover, shrub height, bare ground, and horizontal heterogeneity (patchiness); negatively correlated with spiny hopsage, budsage, and grass cover (Rotenberry and Wiens 1980, Wiens and Rotenberry 1981). In Idaho, more likely to occur in sites with higher sagebrush cover and greater spatial similarity within 1-kilometer radius (Knick and Rotenberry 1995). In Nevada, found most often on plots with taller, more dense sagebrush (Medin 1992).

Usually nests within 1 meter of ground in fork of shrub (almost always sagebrush); sometimes nests on ground (Harrison 1978, Reynolds 1981, Rich 1980). In southeastern Idaho, nested in clumps of tall big sagebrush, with dense foliage overhead, invariably a depth of 0.5 meter from nest to shrub crown, and nests tending to be on the southeast side of the shrub (Petersen and Best 1991). Reynolds (1981) recorded mean nest shrub height 89 centimeter, mean nest height 18 centimeter, and mean distance between nest and shrub crown 58 centimeter. For nests placed within shrubs, Rich (1980) observed mean nest shrub height 83 centimeters, mean nest height 23 centimeters, and mean distance between nest and shrub crown 60 centimeters (n = 114 nests). Distance between nest and shrub crown nearly always the same (58 to 60 centimeters) whether nest placed on ground or within shrub, presumably for optimum shading and shelter (Reynolds 1981, Rich 1980).

NONBREEDING: In winter, uses arid and semi-arid scrub, brush and thickets.

Adult Food Habits: Frugivore, Invertivore
Immature Food Habits: Frugivore, Invertivore
Food Comments: Feeds on a wide variety of insects, including grasshoppers, beetles, weevils, ants, bees, etc. Also feeds on fruits and berries.
Adult Phenology: Diurnal
Immature Phenology: Diurnal
Length: 22 centimeters
Weight: 46 grams
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Appears to be stable or increasing in much of range. Can likely persist with moderate grazing and other land management activities that maintain sagebrush cover, tall vigorous shrubs, and the quality and integrity of native vegetation. Vulnerable where sagebrush habitats are severely degraded or converted to annual grasslands or to other land uses. Sagebrush habitats may be very difficult to restore where non-native grasses and other invasive weeds are pervasive, leading to an escalation of fire cycles that permanently convert sagebrush habitats to annual grassland.
Species Impacts: May be beneficial. Reportedly can help control Mormon crickets and other grasshoppers (Knowlton and Harmston 1943).
Restoration Potential: There is a high probability of sustaining thrashers wherever native sagebrush habitats are maintained with high shrub vigor, tall shrubs, horizontal shrub patchiness, and an open understory of bare ground and native bunchgrasses and forbs. However, sagebrush habitats can be very difficult to restore once invaded by cheatgrass and other noxious non-natives, leading to an escalation of fire frequency and fire intensity that permanently converts shrub-steppe to annual grassland. There are no simple prescriptions for eliminating cheatgrass, medusahead, and other noxious weeds. Restoration of native vegetation at severely degraded sites may be expensive and require long-term dedication that includes continuous weed control, control of disturbances, and repeated reseeding of sagebrush and native understory plants (see Paige and Ritter 1998).
Preserve Selection & Design Considerations: In Idaho, Knick and Rotenberry (1995) found the probability of occupancy increased with increasing homogeneity of the surrounding habitat within a 1-kilometer radius, and with greater percent sagebrush cover. Also, positively correlated with shrub patch size, and negatively correlated with disturbance.
Management Requirements: Will thrive where sagebrush habitat is maintained, with shrubs occurring in tall, clumped, and vigorous stands. Prefers tall shrubs for nesting or song perches and low percent grass cover to facilitate foraging on ground.

SAGEBRUSH CONTROL: Sensitive to sagebrush control; abundance declines with the loss of shrubs. In Wyoming, abundances lower on 22-year old herbicide-treated site (shrub cover approximately 15 percent) than on untreated site (shrub cover > 35 percent), and was not present on 9-year old burned site (shrub cover < 10 percent) (Kerley and Anderson 1995). Castrale (1982) found thrashers persisting in sagebrush islands with tall shrubs within a burned site (10.2 percent shrub cover in islands; max height = 59.0 centimeters), but found no territories within the burn itself (0.0 percent shrub cover), or within plowed (11.8 percent shrub cover; max height = 44.8 centimeters) or chained (5.8 percent shrub cover; max height = 41.4 centimeters) sites reseeded with grasses. In southern Oregon, densities declined following herbicidal spraying and removal of sagebrush and reseeding with crested wheatgrass, where sagebrush cover decreased from 19-24 percent to 4-12 percent (Wiens and Rotenberry 1985). In Idaho, crested wheatgrass seedings did not support sage thrashers (Reynolds and Trost 1980).

FIRE: Fire that kills and completely removes sagebrush cover over large areas would be detrimental. In Idaho, densities remained stable over three years following a prescribed burn that left 50 percent of the sagebrush in a mosaic pattern of burned and unburned sage (sagebrush cover was reduced from an average 21 percent to an average 12 percent) (Petersen and Best 1987).

GRAZING: Not likely affected where livestock grazing regime maintains native vegetation composition and densities. Reported responses to grazing are generally positive, particularly where grazing increases sagebrush cover. In Nevada, positive response to heavy grazing reported in greasewood and Nevada bluegrass habitats (Page et al. 1978, cited in Saab et al. 1995). Reynolds (1980, cited in Saab et al. 1995) reported a positive response to moderate grazing in big sage. In Idaho, Reynolds and Trost (1980) found more nests in sheep-grazed sagebrush with denser cover (14 nests; sage cover = 25 percent) than in ungrazed sagebrush (8 nests; sage cover = 17 percent). Nest success was slightly higher on a site grazed by sheep in spring (big sagebrush cover = 25 percent) than on an ungrazed site (big sagebrush cover = 22.5 percent; Reynolds and Rich 1978).

GRASS COVER: Abundance is negatively correlated with grass cover (Rotenberry and Wiens 1980). Not present in crested wheatgrass plantings (Reynolds and Trost 1980). Primarily a ground forager, foraging success may be reduced by continuous cover of crested wheatgrass, cheatgrass or other non-native grasses (Paige and Ritter 1998).

PESTICIDES: In southern Idaho shrub-steppe, aerial application of Malathion (applied at 585 grams per hectare ultra-low volume, in single-day applications in each of two successive years) reduced food base; nestling foot length was smaller on treated site although there were no observable direct effects on nestling survival (Howe et al. 1996).

Monitoring Requirements: Male readily detectable during courtship: sings loudly and conspicuously from the tops of shrubs, and will perform song flights low over shrubs. Otherwise, relatively shy and will drop to ground when approached. Singing drops off after eggs are laid (Ryser 1985). Preferred habitats are generally in accessible terrain, and should be adequately detected on point count, transect, spot map, or other standard census methods.
Management Research Needs: Understanding of minimum patch sizes, fragmentation effects, spatial juxtaposition of habitat patches and other aspects of landscape ecology needed. Study of the effects of grazing and impact of predation in relation to habitat changes would be useful. Further study of direct and indirect impacts of herbicides and pesticides typically used in sagebrush shrub-steppe rangelands needed. Study of factors that may be differentially affecting sagebrush bird populations might shed light on why sage thrashers appear stable while Brewer's sparrows are widely decreasing (e.g., brood parasitism, effects on wintering grounds, productivity).
Population/Occurrence Delineation
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Group Name: Passerines

Use Class: Breeding
Subtype(s): Foraging Area, Nest Site, Nesting Colony
Minimum Criteria for an Occurrence: Evidence of historical breeding, or current and likely recurring breeding, at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Mapping Guidance: Breeding occurrences include nesting areas as well as foraging areas.

For swallows and other species that have separate nesting and foraging areas, separations are based on nest sites or nesting areas, not to locations of foraging individuals. For example, nesting areas separated by a gap larger than the separation distance are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Mean foraging radius (from nesting area) of Brown-headed Cowbird females was 4.0 kilometers in California, 1.2 kilometers in Illinois-Missouri (Thompson 1994). Yellow-headed Blackbirds, Brewer's Blackbirds, and probably Red-winged Blackbirds all forage up to 1.6 kilometers away from breeding colony (Willson 1966, Horn 1968). In one study, Brewer's Blackbirds were found as far as 10 kilometers from nesting area (Williams 1952), but this may be unusual.

For swallows and other parrerines with similar behavioral ecology, separation distance pertains to nest sites or nesting colonies, not to locations of foraging individuals. For example, nesting areas separated by a gap of more than 5 km are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.

Use Class: Migratory stopover
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: For most passerines: Evidence of recurring presence of migrating individuals (including historical) and potential recurring presence at a given location; minimally a reliable observation of 25 birds in appropriate habitat.

For swallows: Evidence of recurring presence of migrating flocks (including historical) and potential recurring presence at a given location; minimally a reliable observation of 100 birds in appropriate habitat (e.g., traditional roost sites).

Occurrences should be locations where the species is resident for some time during the appropriate season; it is preferable to have observations documenting presence over at least 7 days annually.

EOs should not be described for species that are nomadic during nonbreeding season: e.g., Lark Bunting.

Be cautious about creating EOs for observations that may represent single events.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance somewhat arbitrary but intended to define occurrences of managable size for conservation purposes. Occurrences defined primarily on the basis of areas supporting concentrations of birds, rather than on the basis of distinct populations.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G., and S. Cannings

Use Class: Nonbreeding
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: Any area used traditionally in the nonbreeding season (used for populations that are not resident in a location year-round). Minimally, reliable observations of 10 or more individuals in appropriate habitat for 20 or more days at a time. For G1-G3 species, observations of fewer individuals could constitute an occurrence of conservation value. Sites used during migration should be documented under the 'migratory stopover' location use class.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance is necessarily arbitrary but attempts to balance the high mobility of birds with the need for occurrences of reasonable spatial scope. Note that a population's roost sites and foraging areas are parts of the same occurrence, even if they are more than 5 km apart.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G.

Use Class: Nonmigratory
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a particular location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in or near appropriate habitat.

These occurrence specifications are used for nonmigratory populations of passerine birds.

Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and breeding-season foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Blue jays have small summer home ranges but fly up to 4 kilometers to harvest mast (Tarvin and Woolfenden 1999). Flocks of pinyon jays range over 21-29 square kilometers (Ligon 1971, Balda and Bateman 1971); nesting and foraging areas may be widely separated. Tricolored blackbirds forage in flocks that range widely to more than 15 kilometers from the nesting colony (Beedy and Hamilton 1999).

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.
Notes: These specs pertain to nonmigratory species.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 12Aug2015
NatureServe Conservation Status Factors Author: Hammerson, G., and C. Paige
Management Information Edition Date: 05Jan1999
Management Information Edition Author: PAIGE, C; REVISIONS BY M. KOENEN, D. KWAN, AND D.W. MEHLMAN
Management Information Acknowledgments: Support for the preparation of this abstract was provided by the National Fish and Wildlife Foundation's Neotropical Migratory Bird Conservation Initiative, through challenge grant number 97-270 to The Nature Conservancy, Wings of the Americas program. Matching funds for this grant were donated by Canon U.S.A., Inc.
Element Ecology & Life History Edition Date: 20Dec1993
Element Ecology & Life History Author(s): HAMMERSON, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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