Falco columbarius - Linnaeus, 1758
Other English Common Names: merlin
Other Common Names: Esmerilhão
Taxonomic Status: Accepted
Related ITIS Name(s): Falco columbarius Linnaeus, 1758 (TSN 175613)
French Common Names: faucon émerillon
Spanish Common Names: Halcón Esmerejón
Unique Identifier: ELEMENT_GLOBAL.2.105574
Element Code: ABNKD06030
Informal Taxonomy: Animals, Vertebrates - Birds - Raptors
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Falconiformes Falconidae Falco
Genus Size: D - Medium to large genus (21+ species)
Check this box to expand all report sections:
Concept Reference
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: Falco columbarius
Taxonomic Comments: See Olsen et al. (1989) for a study of relationships within the genus Falco based on electrophoretic patterns of feather proteins.
Conservation Status

NatureServe Status

Global Status: G5
Global Status Last Reviewed: 07Apr2016
Global Status Last Changed: 22Nov1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Widespread (Holarctic) distribution; increasing population trends in areas formerly negatively impacted by pesticide pollution; still threatened in some areas by habitat loss; organochlorine use in Central and South America poses a threat.
Nation: United States
National Status: N4B,N4N (05Jan1997)
Nation: Canada
National Status: N5B,N5N,N5M (02Jan2018)

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 Alabama (SNRN), Alaska (S5B,S4N), Arizona (S4N), Arkansas (SNA), California (S3S4), Colorado (SHB,S4N), Connecticut (SNA), Delaware (SNA), District of Columbia (S1N), Florida (S2), Georgia (S3S4), Idaho (S4), Illinois (SXB), Indiana (S1N), Iowa (SXB), Kansas (SNA), Kentucky (SNA), Louisiana (S4N), Maine (S3B), Maryland (S1N), Massachusetts (S4N), Michigan (S3), Minnesota (SNRB,SNRN), Mississippi (SNA), Missouri (SNA), Montana (S4), Navajo Nation (S4N), Nebraska (S1), Nevada (S3N), New Hampshire (S3B), New Jersey (S4N), New Mexico (S4N), New York (S3?B), North Carolina (S3N), North Dakota (S2), Ohio (SX), Oklahoma (SU), Oregon (SHB), Pennsylvania (SNA), Rhode Island (SNA), South Carolina (S4), South Dakota (S3B,S3N), Tennessee (S3N), Texas (S3N), Utah (SHB,S2S3N), Vermont (S2B), Virginia (SNA), Washington (S3B,S4N), West Virginia (S1N), Wisconsin (S3B,S2N), Wyoming (S3B,S4N)
Canada Alberta (S5), British Columbia (S5), Labrador (S5B,S5M), Manitoba (S5B,S2N), New Brunswick (S5B,S5M), Newfoundland Island (S4S5B,SUM), Northwest Territories (S5B), Nova Scotia (S5B), Nunavut (SUB,SUM), Ontario (S5B), Prince Edward Island (S4S5B), Quebec (S5), Saskatchewan (S4B), Yukon Territory (S4B)

Other Statuses

Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Not at Risk (01Apr1985)
Comments on COSEWIC: Reason for designation: This falcon has a widespread distribution and population numbers are large and increasing. 

Status history: Designated Not at Risk in April 1985.

IUCN Red List Category: LC - Least concern
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: Holarctic distribution. BREEDS: from northward tree limit in Alaska, Canada, and Eurasia southward to southern Alaska, Oregon, Idaho, South Dakota, northern Great Lakes region, New York, Maine, Nova Scotia, British Isles, and central Russia. NORTHERN WINTER: southern British Columbia and western and southern U.S. south to Venezuela and Peru, and in Europe, extreme northern Africa, and China. Holarctic distribution.

Number of Occurrences: 81 to >300

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Estimated number of breeding pairs in Canada in the early 1990s was 10,000-100,000 (Kirk et al. 1995).

Overall Threat Impact Comments: Pesticides contributed to a decline, particularly in Europe, in productivity recorded in a 20-year period prior to the early 1970s (Trimble 1974). Primary threats include habitat loss and continued use of organochlorine biocides in Central and South America.

Short-term Trend Comments: Declined in the 1960s due to the effects of pesticides. In the 1980s, prairie populations in North America were increasing (e.g., see Sodhi et al. 1992). Fall migration counts in the eastern U.S. and Christmas bird counts in Washington indicate increasing abundance in recent decades (Palmer 1988, Titus and Fuller 1990). Increasing in Michigan, in part due to greater availability of nesting sites resulting from increased crow and raven populations (Evers 1992). In Canada, widespread with populations apparently increasing in the mid-1980s (De Smet, 1985 COSEWIC report). Stable or increasing in Canada in the early 1990s (Kirk et al. 1995).

Other NatureServe Conservation Status Information

Inventory Needs: Obtain current information on rangewide distribution and abundance.

Protection Needs: Limit pesticide use to levels that do not affect reproduction. Protect habitat.

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Holarctic distribution. BREEDS: from northward tree limit in Alaska, Canada, and Eurasia southward to southern Alaska, Oregon, Idaho, South Dakota, northern Great Lakes region, New York, Maine, Nova Scotia, British Isles, and central Russia. NORTHERN WINTER: southern British Columbia and western and southern U.S. south to Venezuela and Peru, and in Europe, extreme northern Africa, and China. Holarctic distribution.

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 AK, AL, AR, AZ, CA, CO, CT, DC, DE, FL, GA, IAextirpated, ID, ILextirpated, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NN, NV, NY, OHextirpated, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, LB, MB, NB, NF, NS, NT, NU, ON, PE, QC, SK, YT

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; NatureServe, 2005; WILDSPACETM 2002

U.S. Distribution by County Help
State County Name (FIPS Code)
CA Butte (06007), Fresno (06019), Imperial (06025), Kern (06029), Los Angeles (06037), Merced (06047), Riverside (06065), Sacramento (06067), San Benito (06069), San Bernardino (06071), San Joaquin (06077), San Luis Obispo (06079), San Mateo (06081), Stanislaus (06099), Yolo (06113)
FL Bay (12005), Charlotte (12015), Franklin (12037), Gulf (12045), Martin (12085), Miami-Dade (12086), Monroe (12087), Nassau (12089), Okeechobee (12093), Palm Beach (12099), St. Lucie (12111)
ID Ada (16001), Adams (16003), Bannock (16005), Bingham (16011), Blaine (16013), Boise (16015), Bonner (16017), Bonneville (16019), Boundary (16021), Butte (16023), Camas (16025), Canyon (16027), Caribou (16029), Cassia (16031), Clearwater (16035), Custer (16037), Elmore (16039), Fremont (16043), Gem (16045), Gooding (16047), Idaho (16049), Jefferson (16051), Jerome (16053), Kootenai (16055), Latah (16057), Lemhi (16059), Lincoln (16063), Madison (16065), Minidoka (16067), Nez Perce (16069), Oneida (16071), Owyhee (16073), Power (16077), Shoshone (16079), Teton (16081), Twin Falls (16083), Valley (16085), Washington (16087)
MI Alger (26003), Charlevoix (26029), Chippewa (26033), Delta (26041), Dickinson (26043), Huron (26063), Kalamazoo (26077), Keweenaw (26083), Luce (26095), Mackinac (26097), Mecosta (26107), Ottawa (26139), Sanilac (26151), Schoolcraft (26153), St. Clair (26147)
MS Adams (28001), Bolivar (28011)*, Hancock (28045), Harrison (28047), Jackson (28059), Warren (28149)*
ND Billings (38007), Bowman (38011), McKenzie (38053), Slope (38087)
NE Dawes (31045), Sioux (31165)
NH Coos (33007)
SD Custer (46033)*, Fall River (46047)*, Harding (46063), Sanborn (46111)*
UT Davis (49011)*, Garfield (49017)*, Kane (49025)*, Morgan (49029)*, Summit (49043)*, Weber (49057)*
VT Addison (50001), Chittenden (50007), Lamoille (50015), Orleans (50019), Rutland (50021)
WA Chelan (53007), Clallam (53009), Clark (53011), Ferry (53019), Grant (53025), Grays Harbor (53027), Jefferson (53031), King (53033), Kittitas (53037), Okanogan (53047), San Juan (53055), Skagit (53057), Snohomish (53061), Spokane (53063), Stevens (53065)
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)
01 Upper Androscoggin (01040001)+
03 Cumberland-St. Simons (03070203)+, Florida Bay-Florida Keys (03090203)+, Caloosahatchee (03090205)+, Florida Southeast Coast (03090206)+, Lower Ochlockonee (03120003)+, New (03130013)+, Apalachicola Bay (03130014)+, St. Andrew-St. Joseph Bays (03140101)+, Pascagoula (03170006)+, Mississippi Coastal (03170009)+, Lower Pearl. Mississippi (03180004)+
04 Keweenaw Peninsula (04020103)+, Betsy-Chocolay (04020201)+, Waiska (04020203)+*, Menominee (04030108)+, Cedar-Ford (04030109)+, Black-Macatawa (04050002)+, Kalamazoo (04050003)+, Manistique (04060106)+, Brevoort-Millecoquins (04060107)+, Lake Michigan (04060200)+, St. Marys (04070001)+, Carp-Pine (04070002)+, Pigeon-Wiscoggin (04080103)+, Birch-Willow (04080104)+, Pine (04080202)+, St. Clair (04090001)+, Otter Creek (04150402)+, Winooski River (04150403)+, Lamoille River (04150405)+, Lake Champlain (04150408)+, St. Francois River (04150500)+
08 Lower Mississippi-Helena (08020100)+*, Big Sunflower (08030207)+*, Lower Mississippi-Natchez (08060100)+*, Homochitto (08060205)+
10 Yellowstone Headwaters (10070001)+, 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)+, Little Bighorn (10080016)+, Upper Tongue (10090101)+, 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 Yellowstone (10100004)+, Upper Little Missouri (10110201)+, Middle Little Missouri (10110203)+, Lower Little Missouri (10110205)+, Antelope (10120101)+, Dry Fork Cheyenne (10120102)+, Upper Cheyenne (10120103)+, Angostura Reservoir (10120106)+, Beaver (10120107)+, Hat (10120108)+, Middle Cheyenne-Spring (10120109)+*, Upper Belle Fourche (10120201)+, Lower Belle Fourche (10120202)+, Redwater (10120203)+, Upper Cannonball (10130204)+, North Fork Grand (10130301)+, South Fork Grand (10130302)+, South Fork Moreau (10130304)+, Upper Moreau (10130305)+, Upper White (10140201)+, Niobrara Headwaters (10150002)+, Lower James (10160011)+*, 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)+, Cache La Poudre (10190007)+, Lone Tree-Owl (10190008)+, Crow (10190009)+, Upper Lodgepole (10190015)+, Lower Lodgepole (10190016)+
14 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)+, Great Divide closed basin (14040200)+, Little Snake (14050003)+, Muddy (14050004)+, Paria (14070007)+*
15 Imperial Reservoir (15030104)+
16 Upper Bear (16010101)+, Central Bear (16010102)+, Upper Weber (16020101)+*, Lower Weber (16020102)+*, Curlew Valley (16020309)+, Upper Sevier (16030001)+*, East Fork Sevier (16030002)+*
17 Upper Kootenai (17010101)+, Lower Kootenai (17010104)+, Lower Clark Fork (17010213)+, Pend Oreille Lake (17010214)+, Priest (17010215)+, Pend Oreille (17010216)+, Coeur D'alene Lake (17010303)+, Upper Spokane (17010305)+, Colville (17020003)+, Sanpoil (17020004)+, Methow (17020008)+, Wenatchee (17020011)+, Lower Crab (17020015)+, Upper Yakima (17030001)+, Snake headwaters (17040101)+, Gros Ventre (17040102)+, Greys-Hobock (17040103)+, Palisades (17040104)+, Salt (17040105)+, Idaho Falls (17040201)+, Upper Henrys (17040202)+, Lower Henrys (17040203)+, Teton (17040204)+, 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)+, Boise-Mores (17050112)+, Lower Boise (17050114)+, Middle Snake-Payette (17050115)+, Middle Fork Payette (17050121)+, Payette (17050122)+, North Fork Payette (17050123)+, Weiser (17050124)+, Brownlee Reservoir (17050201)+, Lower Snake-Asotin (17060103)+, Palouse (17060108)+, Upper Salmon (17060201)+, Middle Salmon-Panther (17060203)+, Lemhi (17060204)+, Upper Middle Fork Salmon (17060205)+, Middle Salmon-Chamberlain (17060207)+, South Fork Clearwater (17060305)+, Clearwater (17060306)+, Lower North Fork Clearwater (17060308)+, Lower Willamette (17090012)+, Hoh-Quillayute (17100101)+, Queets-Quinault (17100102)+, San Juan Islands (17110003)+, Lower Skagit (17110007)+, Snohomish (17110011)+, Lake Washington (17110012)+, Dungeness-Elwha (17110020)+
18 Lower American (18020111)+, Upper Cache (18020116)+, Butte Creek (18020158)+, Lower Sacramento (18020163)+, Upper Dry (18030009)+, Tulare-Buena Vista Lakes (18030012)+, Middle San Joaquin-Lower (18040001)+, Middle San Joaquin-Lower (18040002)+, San Joaquin Delta (18040003)+, Upper Stanislaus (18040010)+, Upper Mokelumne (18040012)+, San Francisco Coastal South (18050006)+, Pajaro (18060002)+, Salinas (18060005)+, San Gabriel (18070106)+, Santa Ana (18070203)+, Antelope-Fremont Valleys (18090206)+, Salton Sea (18100204)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: Merlin, pigeon hawk, Falconidae.
General Description: A small falcon with pointed wings, a strongly barred tail, a hooked bill, and heavy streaking below; upperparts are gray-blue in males, dark brown in females; overall, plumage is much darker in the Pacific Northwest than in central Canada and the Midwest; average length 31 cm, wingspan 64 cm (NGS 1983).
Diagnostic Characteristics: Differs from American kestrel, prairie falcon, and peregrine falcon in lacking a strong facial pattern. Differs from kestrel also in lacking russet back and tail. Only about half as big as a gyrfalcon (average length 31 cm vs. 51-64 cm).
Reproduction Comments: Laying generally is completed in southeastern Montana by May 20, which is the peak date in Saskatchewan, where clutches were initiated between mid-April and late May (Sodhi et al. 1992); clutches were completed by late May in Denali Park, Alaska. Clutch size is 2-7 (average 3-5). Incubation, primarily by the female, lasts 31-32 days (male brings food). Young fledge in 25-35 days, remain dependent on parents for food 2-5 more weeks (young remained in vicinity of nest 7-19 days after fledging in southeastern Montana, Becker and Sieg 1985). First breeds at 1-2 years (occasionally 1 year). Yearling male may help nesting pair (James and Oliphant 1986). See Sodhi et al. (1992) for information on an expanding Saskatchewan population characterized by very high reproductive success.
Ecology Comments: At Saskatoon, Saskatchewan, breeding density was 25.4 pairs/100 sq km, the highest recorded for this species (Sodhi et al. 1992). Hunting range sizes (May-July) in Saskatoon varied from about 2-14 sq km (average 6-7 sq km) in residents to 0.6-64 sq km (average 9 sq km in females, 34 sq km in males) in immigrants; neighboring hunting ranges overlapped by 0-77% (Sodhi and Oliphant 1992).

In Montana, nestling-period home range of 3 telemetered males was 13-28 sq km; moved up to 8-9 km from nest site (Becker and Sieg 1985).

Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: Most boreal birds of all ages migrate; in southern breeding range, sometimes resident or migration shorter (Palmer 1988). Northward migrants reach northern U.S. and northern Eurasia in April-May, males generally before females. Migrates southward for northern winter; migration begins in north in late August, peaks in central latitudes of U.S. September-October; migrants reach southwestern Ecuador October-November (Palmer 1988). In Puerto Rico, begins to arrive in October, departs by end of April (Rodriguez-Duran and Lewis 1985). Migrants may cross large bodies of water.
Estuarine Habitat(s): Herbaceous wetland, Tidal flat/shore
Palustrine Habitat(s): Bog/fen, HERBACEOUS WETLAND, Riparian
Terrestrial Habitat(s): Cliff, Cropland/hedgerow, Desert, Forest - Conifer, Forest - Hardwood, Forest - Mixed, Grassland/herbaceous, Savanna, Suburban/orchard, Woodland - Conifer, Woodland - Hardwood, Woodland - Mixed
Special Habitat Factors: Standing snag/hollow tree
Habitat Comments: NONBREEDING: a wide variety of habitats including marshes, deserts, seacoasts, near coastal lakes and lagoons, open woodlands, fields, etc. May roost in conifers in winter.

BREEDING: In southeastern Montana, breeding males appeared to prefer patchy shrub/grassland habitats for hunting (Becker and Sieg 1987). Urban-breeding Merlins in Saskatchewan avoided hunting in agricultural areas where prey abundance was low (Sodhi and Oliphant 1992).

Nests in conifer woodland or wooded prairie (e.g., groves of deciduous trees along rivers), including planted shelterbelts; often near water; in towns in some areas (e.g. Alberta, Manitoba, Saskatchewan). Nests in trees in abandoned crow, magpie, hawk, or squirrel nest; also in natural tree cavity or abandoned woodpecker hole, on bare cliff ledge, or scrape on ground (arctic, heather moor of U.K.). Not infrequently returns to same nesting area in successive years.

Adult Food Habits: Carnivore, Invertivore
Immature Food Habits: Carnivore, Invertivore
Food Comments: Bulk of diet usually consists of small to medium-sized birds, often flocking species. Large flying insects (e.g., dragonflies) may be important for young learning to hunt. Also eats toads, reptiles, and mammals (including bats in the West Indies). Uses inconspicuous perches and searching flights when hunting. May cache prey in various seasons. Prey requirements for adults and young during 120-day breeding/rearing period: several hundred sparrow-size birds (see Palmer 1988).
Adult Phenology: Diurnal
Immature Phenology: Diurnal
Phenology Comments: Preyed on emerging bats around sunset in Puerto Rico (Rodriguez-Duran and Lewis 1985).
Length: 31 centimeters
Weight: 244 grams
Economic Attributes Not yet assessed
Management Summary Not yet assessed
Population/Occurrence Delineation
Group Name: Hawks and Falcons

Use Class: Breeding
Subtype(s): Feeding Area, Nest Site
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: If nest site is separated from feeding area by more than 100 meters, map as separate polygons.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance a compromise between usually relatively small home ranges and obvious mobility of these birds. Home ranges variable, ranging from about 0.5 to about 90 square kilometers; the latter figure refers to nests where birds commuted some distance to feeding grounds. A number of studies give mean home ranges on the order of 7 square kilometers, which equates to a circle with a diameter of about 3 kilometers; three times that home range gives a separation distance of about 10 kilometers. Home ranges: Ferruginous Hawk, mean 5.9 square kilometers in Utah (Smith and Murphy 1973); range 2.4 to 21.7 square kilometers, mean 7.0 square kilometers in Idaho (Olendorff 1993); mean 7.6 square kilometers in Idaho (McAnnis 1990); mean 90 square kilometers in Washington (Leary et al. 1998); Red-tailed Hawk, most forage within 3 kilometers of nest (Kochert 1986); mean spring and summer male home ranges 148 hectares (Petersen 1979); Hawaiian Hawk, 48 to 608 hectares (n = 16; Clarkson and Laniawe 2000); Zone-tailed Hawk, little information, apparent home range 1-2 kilometers/pair in west Texas (Johnson et al. 2000); White tailed Kite, rarely hunts more than 0.8 kilometers from nest (Hawbecker 1942); Prairie Falcon, 26 square kilometers in Wyoming (Craighead and Craighead 1956), 59 to 314 square kilometers (reported by Steenhof 1998); Aplomado Falcon, 2.6 to 9.0 square kilometers (n = 5, Hector 1988), 3.3 to 21.4 square kilometers (n = 10, Montoya et al. 1997). Nest site fidelity: high in Zone-tailed Hawk; all seven west Texas nesting territories occupied in 1975 were reused in 1976 (Matteson and Riley 1981). Swainson's Hawk: In California, dispersal distances from natal sites to subsequent breeding sites ranged from 0 to 18 kilometers, mean 8.8 kilometers (Woodbridge et al. 1995); in contrast, none of 697 nestlings in Saskatchewan returned to the study area; three were found 190, 200 and 310 kilometers away (Houston and Schmutz 1995).
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 3 km
Inferred Minimum Extent Justification: Foraging range variable; 3 kilometers is the mean diameter in several species.
Date: 13Mar2001
Author: Cannings, S.

Use Class: Nonbreeding
Subtype(s): Foraging area, Roosting area
Minimum Criteria for an Occurrence: Evidence of recurring presence of wintering birds (including historical); and potential recurring presence at a given location, usually minimally a reliable observation of 5 birds (this can be reduced to 1 individual for rarer species). 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 20 days annually. Be cautious about creating EOs for observations that may represent single events.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance somewhat arbitrary; set at 10 kilometers to define occurrences of managable size for conservation purposes. However, occurrences defined primarily on the basis of areas supporting concentrations of foraging birds, rather than on the basis of distinct populations.
Date: 15Apr2002
Author: Cannings, S.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 27Dec1994
Element Ecology & Life History Edition Date: 30Mar1995
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).

  • Alabama Ornithological Society. 2006. Field checklist of Alabama birds. Alabama Ornithological Society, Dauphin Island, Alabama. [Available online at http://www.aosbirds.org/documents/AOSChecklist_april2006.pdf ]

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