True owl

The true owls or typical owls (family Strigidae) are one of the two generally accepted families of owls, the other being the barn owls (Tytonidae). The Sibley-Ahlquist taxonomy unites the Caprimulgiformes with the owl order; here, the typical owls are a subfamily Striginae. This is unsupported by more recent research (see Cypselomorphae for details), but the relationships of the owls in general are still unresolved. This large family comprises nearly 220 living species in 25 genera. The typical owls have a cosmopolitan distribution and are found on every continent except Antarctica.

True owl
Temporal range: Early Eocene to present
Eastern Screech Owl
Eastern screech owl
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Strigiformes
Family: Strigidae
Leach, 1820
Genera

some 25, see text

Synonyms

Striginae sensu Sibley & Ahlquist

Morphology

Strix nebulosa plumage
Cross sectioned great grey owl specimen showing the extent of the body plumage, Zoological Museum, Copenhagen

While typical owls (hereafter referred to simply as owls) vary greatly in size, with the smallest species, the elf owl, being a hundredth the size of the largest, the Eurasian eagle-owl and Blakiston's fish owl, owls generally share an extremely similar body plan.[1] They tend to have large heads, short tails, cryptic plumage, and round facial discs around the eyes. The family is generally arboreal (with a few exceptions like the burrowing owl) and obtain their food on the wing. The wings are large, broad, rounded, and long. As is the case with most birds of prey, in many owl species females are larger than males.[2]

Because of their nocturnal habits, they tend not to exhibit sexual dimorphism in their plumage. The feathers are soft and the base of each is downy, allowing for silent flight. The toes and tarsi are feathered in some species, and more so in species at higher latitudes.[3] Numerous species of owls in the genus Glaucidium and the northern hawk-owl have eye patches on the backs of their heads, apparently to convince other birds they are being watched at all times. Numerous nocturnal species have ear-tufts, feathers on the sides of the head that are thought to have a camouflage function, breaking up the outline of a roosting bird. The feathers of the facial disc are arranged in order to increase sound delivered to the ears. Hearing in owls is highly sensitive and the ears are asymmetrical allowing the owl to localise a sound in multiple directions. In addition to hearing, owls have massive eyes relative to their body size. Contrary to popular belief, however, owls cannot see well in extreme dark and are able to see well in the day.[1]

Behaviour

Owls are generally nocturnal and spend much of the day roosting. They are often perceived as tame since they allow people to approach quite closely before taking flight, but they are instead attempting to avoid detection. The cryptic plumage and inconspicuous locations adopted are an effort to avoid predators and mobbing by small birds.[4]

Systematic

Squelette de Strigidae MHNT
Skeleton of Strigidae. Muséum de Toulouse

The family Strigidae was introduced by the English zoologist William Elford Leach in a guide to the contents of the British Museum published in 1820.[5][6]

The nearly 220 extant species are assigned to a number of genera, which are in taxonomic order:

  • Genus Megascops – screech-owls, some 20 species
  • Genus Otus – scops owls; probably paraphyletic, about 45 species
  • Genus Pyrroglaux – Palau owl
  • Genus Margarobyas – bare-legged owl or Cuban screech-owl
  • Genus Ptilopsis – white-faced owls, two species
  • Genus Bubo – horned owls, eagle-owls and fish-owls; paraphyletic with Nyctea, Ketupa and Scotopelia, some 25 species
  • Genus Strix – earless owls, some 19 species, including four that were previously classified as Ciccaba
  • Genus Ciccaba – the four species have been transferred to Strix
  • Genus Lophostrix – crested owl
  • Genus Jubula – maned owl
  • Genus Pulsatrix – spectacled owls, three species
  • Genus Surnia – northern hawk-owl
  • Genus Glaucidium – pygmy owls, about 30–35 species
  • Genus Xenoglaux – long-whiskered owlet
  • Genus Micrathene – elf owl
  • Genus Athene – two to four species (depending on whether Speotyto and Heteroglaux are included or not)
Forest Owlet Athene blewitti by Ashahar alias Krishna Khan.jpeg
The forest owlet, one of the critically endangered owls found in Central Indian Forest

Recently extinct

  • Genus Mascarenotus – Mascarene owls, three species (extinct around 1850)
  • Genus Sceloglaux – laughing owl (extinct around 1914)

Late Quaternary prehistoric extinctions

  • Genus Grallistrix – stilt-owls, four species
    • Kaua‘i stilt-owl, Grallistrix auceps
    • Maui stilt-owl, Grallistrix erdmani
    • Moloka‘i stilt-owl, Grallistrix geleches
    • O‘ahu stilt-owl, Grallistrix orion
  • Genus Ornimegalonyx – Caribbean giant owls, one or two species
    • Cuban giant owl, Ornimegalonyx oteroi
    • Ornimegalonyx sp. – probably subspecies of O. oteroi
  • Genus Asphaltoglaux

Fossil record

  • Mioglaux (Late Oligocene? – Early Miocene of WC Europe) – includes "Bubo" poirreiri
  • Intulula (Early/Middle Miocene of WC Europe) – includes "Strix/Ninox" brevis
  • Alasio (Middle Miocene of Vieux-Collonges, France) – includes "Strix" collongensis

Placement unresolved:

  • "Otus/Strix" wintershofensisfossil (Early/Middle Miocene of Wintershof West, Germany) – may be close to extant genus Ninox[7]
  • "Strix" edwardsifossil (Middle Miocene of Grive-Saint-Alban, France)
  • "Asio" pygmaeusfossil (Early Pliocene of Odessa, Ukraine)
  • Strigidae gen. et sp. indet. UMMP V31030 (Rexroad Late Pliocene of Kansas, USA) – Strix/Bubo?[8]
  • Ibiza owl, Strigidae gen. et sp. indet. – prehistoric (Late Pleistocene/Holocene of Es Pouàs, Ibiza)[9]

The supposed fossil heron "Ardea" lignitum (Late Pliocene of Germany) was apparently a strigid owl, possibly close to Bubo.[10] The Early–Middle Eocene genus Palaeoglaux from west-central Europe is sometimes placed here, but given its age, it is probably better considered its own family for the time being.

References

  1. ^ a b Marks, J. S.; Cannings, R.J. and Mikkola, H. (1999). "Family Strigidae (Typical Owls)". In del Hoyo, J.; Elliot, A. & Sargatal, J. (eds.) (1999). Handbook of the Birds of the World. Volume 5: Barn-Owls to Hummingbirds. Lynx Edicions. ISBN 84-87334-25-3
  2. ^ Earhart, Caroline M. & Johnson, Ned K. (1970). "Size Dimorphism and Food Habits of North American Owls". Condor. 72 (3): 251–264. doi:10.2307/1366002.
  3. ^ Kelso L & Kelso E (1936). "The Relation of Feathering of Feet of American Owls to Humidity of Environment and to Life Zones". Auk. 53 (1): 51–56. doi:10.2307/4077355.
  4. ^ Geggel, Laura (September 19, 2016). "Are All Owls Actually Night Owls?".
  5. ^ Leach, William Elford (1820). "Eleventh Room". Synopsis of the Contents of the British Museum (17th ed.). London: British Museum. pp. 65–70. OCLC 6213801. Although the name of the author is not specified in the document, Leach was the Keeper of Zoology at the time.
  6. ^ Bock, Walter J. (1994). History and Nomenclature of Avian Family-Group Names. Bulletin of the American Museum of Natural History. Number 222. New York: American Museum of Natural History. p. 142.
  7. ^ Olson, p. 131
  8. ^ Feduccia, J. Alan; Ford, Norman L. (1970). "Some birds of prey from the Upper Pliocene of Kansas" (PDF). Auk. 87 (4): 795–797. doi:10.2307/4083714.
  9. ^ Sánchez Marco, Antonio (2004). "Avian zoogeographical patterns during the Quaternary in the Mediterranean region and paleoclimatic interpretation" (PDF). Ardeola. 51 (1): 91–132.
  10. ^ Olson, p. 167

Bibliography

  • Olson, Storrs L. (1985). The fossil record of birds. In: Farner, D.S.; King, J.R. & Parkes, Kenneth C. (eds.): Avian Biology 8: 79–238. Academic Press, New York.

External links

Abyssinian owl

The Abyssinian owl or African long-eared owl (Asio abyssinicus) is a medium-sized true owl.

Asian barred owlet

The Asian barred owlet (Glaucidium cuculoides) is a species of true owl, resident in northern parts of the Indian Subcontinent and parts of Southeast Asia. It ranges across north central and northeast India, Nepal Bhutan, north Bangladesh, and southeast Asia (Myanmar, Thailand, Cambodia, Laos, Vietnam). Its natural habitat is temperate forest.

Asphaltoglaux

Asphaltoglaux cecileae is an extinct species of true owl which existed in what is now California, U.S.A. during the Late Pleistocene age. Its osteology suggests a close relation to the owls of the genus Aegolius.

Barred owl

The barred owl (Strix varia), also known as northern barred owl or hoot owl, is a true owl native to eastern North America. Adults are large, and are brown to grey with barring on the chest. Barred owls have expanded their range to the west coast of North America, where they are considered invasive. Mature forests are their preferred habitat, but they are also found in open woodland areas. Their diet consists mainly of small mammals, but they are also known to prey upon other small animals such as birds, reptiles, and amphibians.

Chocolate boobook

The chocolate boobook (Ninox randi) is species of bird in the true owl family, Strigidae. Formerly considered to be a subspecies of the brown hawk-owl, it is endemic to the Philippines, where it is found on all major islands except Palawan.

Fauna of Toronto

The fauna of Toronto include a variety of different species that have adapted to the urban environment, its parks, its ravine system, and the creeks and rivers that run throughout Toronto. Many other animals from outside the city limits have been known to straddle inside on from time to time.

Fulvous owl

The fulvous owl (Strix fulvescens), or Guatemala barred owl, is a resident of the cloud forests of Central America. A medium-sized true owl, it has a round head, lacking ear tufts. It is generally a warm dark brown or reddish brown on the back and lighter brown on the front with darker barring. Adults weigh approximately 600 grams (21 oz), with females being heavier. Its distribution is limited to highland regions of Guatemala, Honduras, and El Salvador. It inhabits elevations from 1,200 to 3,100 meters (3,900 to 10,200 ft), and is fairly common within its range. Its behavior is poorly known, as are its population size and distribution. It is classified as a species of least concern by the International Union for Conservation of Nature, although it is considered endangered in Mexico.

Gargano

Gargano (Italian pronunciation: [gar'gaːno]) is a historical and geographical sub-region in the province of Foggia, Apulia, southeast Italy, consisting of a wide isolated mountain massif made of highland and several peaks and forming the backbone of the Gargano Promontory projecting into the Adriatic Sea, the "spur" on the Italian "boot". The high point is Monte Calvo at 1,065 m (3,494 ft). Most of the upland area, about 1,200 km2 (460 sq mi), is part of the Gargano National Park, founded in 1991.

The Gargano peninsula is partly covered by the remains of an ancient forest, Foresta Umbra, the only remaining part in Italy of the ancient oak and beech forest that once covered much of Central Europe as well as the Apennine deciduous montane forest biome. The Latin poet Horace spoke of the oaks of Garganus in Ode II, ix.

Great horned owl

The great horned owl (Bubo virginianus), also known as the tiger owl (originally derived from early naturalists' description as the "winged tiger" or "tiger of the air") or the hoot owl, is a large owl native to the Americas. It is an extremely adaptable bird with a vast range and is the most widely distributed true owl in the Americas. Its primary diet is rabbits and hares, rats and mice, and voles, although it freely hunts any animal it can overtake, including rodents and other small mammals, larger mid-sized mammals, birds, reptiles, amphibians, and invertebrates. In ornithological study, the great horned owl is often compared to the Eurasian eagle-owl (Bubo bubo), a closely related species, which despite the latter's notably larger size, occupies the same ecological niche in Eurasia, and the red-tailed hawk (Buteo jamaicensis), with which it often shares similar habitat, prey, and nesting habits by day, thus is something of a diurnal ecological equivalent. The great horned owl is one of the earliest nesting birds in North America, often laying eggs weeks or even months before other raptorial birds.

Johann Hurlinger

Johann Hurlinger was an Austrian man who walked on his hands from Paris to Vienna in 1900. Hurlinger walked on his hands for 10 hours a day for 55 days. He averaged 1.58 miles per hour and traversed 870 miles.

Little owl

The little owl (Athene noctua) is a bird that inhabits much of the temperate and warmer parts of Europe, Asia east to Korea, and north Africa. It was introduced into Britain at the end of the nineteenth century and into the South Island of New Zealand in the early twentieth century.

This owl is a member of the typical or true owl family, Strigidae, which contains most species of owl, the other grouping being the barn owls, Tytonidae. It is a small, cryptically coloured, mainly nocturnal species and is found in a range of habitats including farmland, woodland fringes, steppes and semi-deserts. It feeds on insects, earthworms, other invertebrates and small vertebrates. Males hold territories which they defend against intruders. This owl is a cavity nester and a clutch of about four eggs is laid in spring. The female does the incubation and the male brings food to the nest, first for the female and later for the newly hatched young. As the chicks grow, both parents hunt and bring them food, and the chicks leave the nest at about seven weeks of age.

Being a common species with a wide range and large total population, the International Union for Conservation of Nature has assessed its conservation status as "least concern".

Lord Howe boobook

The Lord Howe boobook (Ninox novaeseelandiae albaria), also known as the Lord Howe morepork, was a bird in the true owl family endemic to Lord Howe Island in the Tasman Sea, part of New South Wales, Australia. It is an extinct and little-known subspecies of the Southern boobook (Ninox novaeseelandiae).

Norfolk boobook

The Norfolk boobook (Ninox novaeseelandiae undulata), also known as the Norfolk Island boobook, Norfolk Island owl or Norfolk Island morepork, was a bird in the true owl family endemic to Norfolk Island, an Australian territory in the Tasman Sea between Australia and New Zealand. It is an extinct subspecies of the morepork (Ninox novaeseelandiae). However, although the taxon is extinct, its genes live on in the descendants of the hybrid offspring of the last female bird, which was sighted for the last time in 1996.

Northern boobook

The northern boobook (Ninox japonica) is a species of bird in the true owl family. It was split from the brown hawk-owl (Ninox scutulata). It is found in eastern Russia (Ussuriland), North Korea, South Korea, northern and central China, and Japan.

Northern hawk-owl

The northern hawk-owl (Surnia ulula) is a medium sized true owl of the northern latitudes. It is non-migratory and usually stays within its breeding range, though it sometimes irrupts southward. It is one of the few owls that is neither nocturnal nor crepuscular, being active only during the day. This is the only living species in the genus Surnia of the family Strigidae, the "typical" owls (as opposed to barn owls, Tytonidae). The species is sometimes called simply the hawk owl; however, many species of owls in the genus Ninox are also called "hawk owls".

The genus name Surnia appears to be a word made up by A. M. C. Duméril, the creator of the genus, and ulula is Latin for a screech owl.

Owl

Owls are birds from the order Strigiformes, which includes about 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers adapted for silent flight. Exceptions include the diurnal northern hawk-owl and the gregarious burrowing owl.

Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish. They are found in all regions of the Earth except polar ice caps and some remote islands.

Owls are divided into two families: the true (or typical) owl family, Strigidae, and the barn-owl family, Tytonidae.

Snowy owl

The snowy owl (Bubo scandiacus) is a large, white owl of the true owl family. Snowy owls are native to Arctic regions in North America and Eurasia. Males are almost all white, while females have more flecks of black plumage. Juvenile snowy owls have black feathers until they turn white. The snowy owl is a ground nester that primarily hunts rodents and waterfowl, and opportunistically eats carrion. Most owls sleep during the day and hunt at night, but the snowy owl is active during the day, especially in the summertime.

Spotted owl

The spotted owl (Strix occidentalis) is a species of true owl. It is a resident species of old-growth forests in western North America, where it nests in tree holes, old bird of prey nests, or rock crevices. Nests can be between 12 and 60 metres (39 and 197 ft) high and usually contain two eggs (though some contain as many as four). It is a nocturnal owl, which feeds on small mammals and birds. Three subspecies are recognized, ranging in distribution from British Columbia to Mexico. The spotted owl is under pressure from habitat destruction throughout its range, and is currently classified as a near-threatened species.

São Tomé scops owl

The São Tomé scops owl (Otus hartlaubi) is a species of owl in the true owl (a.k.a. Strigidae) family. Within that family, this owl is in the genus Otus, the scops owls; this is the genus of owls having the largest number of species.

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