Great Horned Owl
Bubo virginianus
Summary 7
The Great Horned Owl, (Bubo virginianus), also known as the Tiger Owl, is a large owl native to the Americas. It is an adaptable bird with a vast range and is the most widely distributed true owl in the Americas.
Distribution 8
Great horned owls are native to a large geographic range that covers most of North America and extends south into Central and South America. Their latitudinal range is from 68 degrees north latitude (around the northern tip of Alaska) to 54 degrees south latitude (near the southern tip of Brazil).
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Morphology 9
Like similar owl species, great horned owls have a rounded facial structure and forward-facing eyes which allow for binocular vision. They have distinctive horn-like feather tufts on the tops of their heads. The tufts are usually darker than the rest of the head, improving camouflage. They have a distinctive white spot on their throat. Their underbellies are white with brown and black 'bars' distributed throughout. They are white or tan colored around a black bill. Their back is darker in color, featuring a mottled blacks and browns. Their eyes are different shades of yellow in color.
The size and of great horned owls varies by their geographic location and their sex. They exhibit reverse sexual dimorphism, where females are slightly larger than males. Females average about 1.7 kg, while males average 1.3 kg. Evidence suggests this dimorphism is not influenced by environmental factors. This conclusion comes from the observation that great horned owls generally do not migrate sufficient distances to cross-breed with subspecies which may differ in size. In northern latitudes, they tend to have larger core bodies and a longer wingspan. Their overall length is 45.7 to 63.5 cm and their wingspan is 127 to 152.4 cm. This is consistent with Bergmann's rule, which states that in broadly-distributed genuses, larger individuals of species are found in northern latitudes, while smaller individuals are found in southern latitudes. Variations in color also exist depending on geographic location. For example, Bubo virginianus saturatus, a woodland-inhabiting subspecies of great horned owl, may have darker, browner coloration. Bubo virginianus elachistus, which lives in desert habitats in Baja California, may have a lighter, grayer coloration.
Average mass: 1.3 (males) 1.7 (females) kg.
Range length: 45.7 to 63.5 cm.
Range wingspan: 127 to 152.4 cm.
Other Physical Features: endothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: female larger
Average mass: 1450 g.
Average basal metabolic rate: 5.2442 W.
Chihuahuan desert habitat 10
This taxon is found in the Chihuahuan Desert, which is one of the most biologically diverse arid regions on Earth. This ecoregion extends from within the United States south into Mexico. This desert is sheltered from the influence of other arid regions such as the Sonoran Desert by the large mountain ranges of the Sierra Madres. This isolation has allowed the evolution of many endemic species; most notable is the high number of endemicplants; in fact, there are a total of 653 vertebrate taxa recorded in the Chihuahuan Desert. Moreover, this ecoregion also sustains some of the last extant populations of Mexican Prairie Dog, wild American Bison and Pronghorn Antelope.
The dominant plant species throughout the Chihuahuan Desert is Creosote Bush (Larrea tridentata). Depending on diverse factors such as type of soil, altitude, and degree of slope, L. tridentata can occur in association with other species. More generally, an association between L. tridentata, American Tarbush (Flourensia cernua) and Viscid Acacia (Acacia neovernicosa) dominates the northernmost portion of the Chihuahuan Desert. The meridional portion is abundant in Yucca and Opuntia, and the southernmost portion is inhabited by Mexican Fire-barrel Cactus (Ferocactus pilosus) and Mojave Mound Cactus (Echinocereus polyacanthus). Herbaceous elements such as Gypsum Grama (Chondrosum ramosa), Blue Grama (Bouteloua gracilis) and Hairy Grama (Chondrosum hirsuta), among others, become dominant near the Sierra Madre Occidental. In western Coahuila State, Lecheguilla Agave (Agave lechuguilla), Honey Mesquite (Prosopis glandulosa), Purple Prickly-pear (Opuntia macrocentra) and Rainbow Cactus (Echinocereus pectinatus) are the dominant vascular plants.
Because of its recent origin, few warm-blooded vertebrates are restricted to the Chihuahuan Desert scrub. However, the Chihuahuan Desert supports a large number of wide-ranging mammals, such as the Pronghorn Antelope (Antilocapra americana), Robust Cottontail (Sylvilagus robustus EN); Mule Deer (Odocoileus hemionus), Grey Fox (Unocyon cineroargentinus), Jaguar (Panthera onca), Collared Peccary or Javelina (Pecari tajacu), Desert Cottontail (Sylvilagus auduboni), Black-tailed Jackrabbit (Lepus californicus), Kangaroo Rats (Dipodomys sp.), pocket mice (Perognathus spp.), Woodrats (Neotoma spp.) and Deer Mice (Peromyscus spp). With only 24 individuals recorded in the state of Chihuahua Antilocapra americana is one of the most highly endangered taxa that inhabits this desert. The ecoregion also contains a small wild population of the highly endangered American Bison (Bison bison) and scattered populations of the highly endangered Mexican Prairie Dog (Cynomys mexicanus), as well as the Black-tailed Prairie Dog (Cynomys ludovicianus).
The Chihuahuan Desert herpetofauna typifies this ecoregion.Several lizard species are centered in the Chihuahuan Desert, and include the Texas Horned Lizard (Phrynosoma cornutum); Texas Banded Gecko (Coleonyx brevis), often found under rocks in limestone foothills; Reticulate Gecko (C. reticulatus); Greater Earless Lizard (Cophosaurus texanus); several species of spiny lizards (Scelopoprus spp.); and the Western Marbled Whiptail (Cnemidophorus tigris marmoratus). Two other whiptails, the New Mexico Whiptail (C. neomexicanus) and the Common Checkered Whiptail (C. tesselatus)occur as all-female parthenogenic clone populations in select disturbed habitats.
Representative snakes include the Trans-Pecos Rat Snake (Bogertophis subocularis), Texas Blackhead Snake (Tantilla atriceps), and Sr (Masticophis taeniatus) and Neotropical Whipsnake (M. flagellum lineatus). Endemic turtles include the Bolsón Tortoise (Gopherus flavomarginatus), Coahuilan Box Turtle (Terrapene coahuila) and several species of softshell turtles. Some reptiles and amphibians restricted to the Madrean sky island habitats include the Ridgenose Rattlesnake (Crotalus willardi), Twin-spotted Rattlesnake (C. pricei), Northern Cat-eyed Snake (Leptodeira septentrionalis), Yarrow’s Spiny Lizard (Sceloporus jarrovii), and Canyon Spotted Whiptail (Cnemidophorus burti).
There are thirty anuran species occurring in the Chihuahuan Desert: Chiricahua Leopard Frog (Rana chircahuaensis); Red Spotted Toad (Anaxyrus punctatus); American Bullfrog (Lithobates catesbeianus); Canyon Treefrog (Hyla arenicolor); Northern Cricket Frog (Acris crepitans); Rio Grande Chirping Frog (Eleutherodactylus cystignathoides); Cliff Chirping Frog (Eleutherodactylus marnockii); Spotted Chirping Frog (Eleutherodactylus guttilatus); Tarahumara Barking Frog (Craugastor tarahumaraensis); Mexican Treefrog (Smilisca baudinii); Madrean Treefrog (Hyla eximia); Montezuma Leopard Frog (Lithobates montezumae); Brown's Leopard Frog (Lithobates brownorum); Yavapai Leopard Frog (Lithobates yavapaiensis); Western Barking Frog (Craugastor augusti); Mexican Cascade Frog (Lithobates pustulosus); Lowland Burrowing Frog (Smilisca fodiens); New Mexico Spadefoot (Spea multiplicata); Plains Spadefoot (Spea bombifrons); Pine Toad (Incilius occidentalis); Woodhouse's Toad (Anaxyrus woodhousii); Couch's Spadefoot Toad (Scaphiopus couchii); Plateau Toad (Anaxyrus compactilis); Texas Toad (Anaxyrus speciosus); Dwarf Toad (Incilius canaliferus); Great Plains Narrowmouth Toad (Gastrophryne olivacea); Great Plains Toad (Anaxyrus cognatus); Eastern Green Toad (Anaxyrus debilis); Gulf Coast Toad (Incilius valliceps); and Longfoot Chirping Toad (Eleutherodactylus longipes VU). The sole salamander occurring in the Chihuahuan Desert is the Tiger Salamander (Ambystoma tigrinum).
Common bird species include the Greater Roadrunner (Geococcyx californianus), Burrowing Owl (Athene cunicularia), Merlin (Falco columbarius), Red-tailed Hawk (Buteo jamaicensis), and the rare Zone-tailed Hawk (Buteo albonotatus). Geococcyx californianus), Curve-billed Thrasher (Toxostoma curvirostra), Scaled Quail (Callipepla squamata), Scott’s Oriole (Icterus parisorum), Black-throated Sparrow (Amphispiza bilineata), Phainopepla (Phainopepla nitens), Worthen’s Sparrow (Spizella wortheni), and Cactus Wren (Campylorhynchus brunneicapillus). In addition, numerous raptors inhabit the Chihuahuan Desert and include the Great Horned Owl (Bubo virginianus) and the Elf Owl (Micrathene whitneyi).
Migration 11
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Northern populations partially migratory; some individuals, especially young, found in winter up to a few hundred km south of banding site. Band recoveries indicate that most individuals remain within 80 km of banding site (Johnsgard 1988).
Sources and Credits
- (c) Minette, some rights reserved (CC BY-NC), http://www.flickr.com/photos/7232133@N08/2925340745
- (c) Cláudio Dias Timm, some rights reserved (CC BY-NC-SA), http://farm4.static.flickr.com/3519/3793977534_7dd087bb61.jpg
- Original uploader was ZeWrestler at en.wikipedia, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/9/9c/Great_horned_owl_chick_3w.jpg
- (c) Blake Matheson, some rights reserved (CC BY-NC), http://farm4.static.flickr.com/3430/3204975685_45b74bac80_o.jpg
- (c) Billy Hunt, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Great_Horned_Owl_in_Winter.jpg/460px-Great_Horned_Owl_in_Winter.jpg
- (c) brendan.lally, some rights reserved (CC BY), https://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/Bubo_virginianus_-Canada-6.jpg/460px-Bubo_virginianus_-Canada-6.jpg
- (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Bubo_virginianus
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31381444
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31381446
- (c) C. Michael Hogan & World Wildlife Fund, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/27287678
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28823307
