True owl or
Typical owl (
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Strigidae) are one of the two generally accepted families of
OwlOwls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
s, the other being the
barn owlBarn-owls are one of the two families of owls, the other being the true owls, Strigidae. They are medium to large sized owls with large heads and characteristic heart-shaped faces. They have long, strong legs with powerful talons...
s (Tytonidae). The
Sibley-Ahlquist taxonomyThe Sibley-Ahlquist taxonomy is a bird taxonomy proposed by Charles Sibley and Jon Edward Ahlquist. It is based on DNA-DNA hybridization studies conducted in the late 1970s and throughout the 1980s....
unites the
CaprimulgiformesThe Caprimulgiformes is an order of birds that includes a number of birds with global distribution . They are generally insectivorous and nocturnal...
with the owl
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
; here, the typical owls are a subfamily
Strigidae. This is unsupported by more recent research (see
CypselomorphaeCypselomorphae is a clade of birds. It includes the living families and orders Caprimulgidae , Nyctibiidae , Apodiformes , as well as the Aegotheliformes whose distinctness was only recently realized...
for details), but the relationships of the owls in general are still unresolved. This large family comprises around 189 living
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in 25
generaIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. The typical owls have a
cosmopolitan distributionIn biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
and are found on every continent except
Antarctica.
Morphology
While typical owls (hereafter referred to simply as owls) vary greatly in size, with the smallest species, the
Elf OwlThe Elf Owl is a member of the owl family Strigidae that breeds in the southwestern United States and Mexico. It is the world's lightest owl, although the Long-whiskered Owlet and the Tamaulipas Pygmy Owl are of a similarly diminutive length. The mean body weight of this species is 40 grams...
, being a hundred times smaller than the largest, the Eurasian Eagle-Owl and
Blakiston's Fish OwlBlakiston's Fish Owl, Bubo blakistoni, is a fish owl, a sub-group of eagle owls who specialized in hunting riparian areas. This species is a part of the family known as typical owls, Strigidae, which contains most species of owl...
, owls generally share an extremely similar body plan. They tend to have large heads, short tails, cryptic
plumagePlumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
and round facial discs around the eyes. The family is generally arboreal (with a few exceptions like the
Burrowing OwlThe Burrowing Owl is a tiny but long-legged owl found throughout open landscapes of North and South America. Burrowing Owls can be found in grasslands, rangelands, agricultural areas, deserts, or any other open dry area with low vegetation. They nest and roost in burrows, such as those excavated...
) and obtain their food on the wing. The wings are large, broad, rounded and long. Like other
birds of preyBirds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
many owl species exhibit reverse
sexual dimorphismSexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size, where females are larger than males (as opposed to the more typical situation in birds where males are larger).
Because of their
nocturnalNocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....
habits they tend not to exhibit
sexual dimorphismSexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in their plumage. The feathers are soft and the base of each is downy, allowing for silent flight. The toes and tarsus are feathered in some species, and more so in species at higher latitudes. Numerous species of owl 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
camouflageCamouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
function, breaking up the outline of a roosting bird. The feathers of the
facial discIn ornithology, the facial disc is the concave collection of feathers on the face of some birds—most notably owls—surrounding the eyes. The concavity of the facial disc forms a circular paraboloid that collects sound waves and directs those waves towards the owl's ears...
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 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 fine in the day.
Behaviour
Owls are generally nocturnal and spend much of the day roosting. They are often perceived as tame since they will 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
mobbingMobbing in animals is an antipredator behavior which occurs when individuals of a certain species mob a predator by cooperatively attacking or harassing it, usually to protect their offspring. A simple definition of mobbing is an assemblage of individuals around a potentially dangerous predator...
by small birds.
Systematics
The nearly 200 extant
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
are assigned to a number of
generaGenera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
, which are in taxonomic order:
- Genus Megascops: screech-owls, some 20 species
- Genus Otus
Scops owls are Strigidae belong to the genus Otus. Approximately 45 living species are known, but new ones are frequently recognized and unknown ones are still being discovered every few years or so, especially in Indonesia...
: scops-owls; probably paraphyletic, about 45 species
- Genus Pyrroglaux - Palau Owl
- Genus Gymnoglaux - Bare-legged Owl or Cuban Screech-owl
- Genus Ptilopsis
Ptilopsis is a genus of African owls. Its members are:*Northern White-faced Owl Ptilopsis leucotis *Southern White-faced Owl Ptilopsis granti...
- white-faced owls, 2 species
- Genus Mimizuku - Giant Scops-owl or Mindanao Eagle-owl
- Genus Bubo
The American horned owls and the Old World eagle-owls make up the genus Bubo, at least as traditionally described. This genus, depending on definition, contains about one or two dozen species of typical owls and is found in many parts of the world. Some of the largest living Strigiformes are in...
- horned owls, eagle-owls and fish-owls; paraphyletic with Nyctea, Ketupa and Scotopelia, some 25 species
- Genus Strix
Strix is a genus of owls. They belong to the typical owl family Strigidae, one of the two generally accepted living families of owls, with the other being the barn-owls . Common names are earless owls or wood owls though they are not the only owls without ear tufts, and "wood owl" is also used as a...
- earless owls, some 15 species
- Genus Ciccaba
Ciccaba is a small genus of typical owls. It contains 4 species:* Mottled Owl, Ciccaba virgata* Black-and-white Owl, Ciccaba nigrolineata* Black-banded Owl, Ciccaba huhula* Rufous-banded Owl, Ciccaba albitarsis...
- 4 species
- Genus Lophostrix - Crested Owl
- Genus Jubula
The Maned Owl is a species of owl in the Strigidae family that is endemic to Africa. It is the only species in genus Jubula....
- Maned Owl
- Genus Pulsatrix
Pulsatrix is a genus of owl in the Strigidae family. They are called spectacled owls because of their prominent facial pattern.It contains the following species:* Spectacled Owl, Pulsatrix perspicillata...
- spectacled owls, 3 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
Athene is a genus of owls, containing two to four living species, depending on classification. These birds are small, with brown and white speckles, yellow eyes, and white eyebrows...
- 2-4 species (depending on whether Speotyto and Heteroglaux are included or not)
- Genus Aegolius
Aegolius is a small genus of owls. Three of the species are restricted to the New World, but th Boreal Owl has a circumpolar range through North America, Eurasia, the Alps and the Rockies.The species are:...
- saw-whet owls, 4 species
- Genus Ninox
Ninox is a genus of owls comprising about 20 species found in Asia and Australasia. Many species are known as hawk owls or boobooks...
- Australasian hawk-owls, some 20 species
- Genus Uroglaux - Papuan Hawk-owl
- Genus Pseudoscops - Jamaican Owl and possibly Striped Owl
The Striped Owl is a medium-sized owl with large ear tufts and a brownish-white facial disk rimmed with black. Its beak is black, and it has cinnamon-colored eyes. It has shorter, rounder wings than most of its close relatives. The upperparts are cinnamon with fine black vermiculation and heavy...
- Genus Asio
Asio is a genus of typical owls, or true owls, in family Strigidae. The genus Asio contains the eared owls, which are characterised by feather tufts on the head which have the appearance of ears...
- eared owls, 6-7 species
- Genus Nesasio - Fearful Owl
Recently extinct
- Genus Mascarenotus - Mascarene owls, 3 species (extinct c.1850)
- Genus Sceloglaux - Laughing Owl (extinct 1914?)
Late Quaternary prehistoric extinctionsPrehistoric birds are various taxa of birds that became extinct before recorded history, or more precisely, before they could be studied alive by bird scientists...
- Genus Grallistrix
The stilt-owls are a genus of true owls which contains four species, all of which lived on the Hawaiian Islands but are now extinct....
- Stilt-owls, 4 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, 1-2 species
- Cuban Giant Owl, Ornimegalonxy oteroi
- Ornimegalonyx sp. - probably subspecies of O. oteroi
FossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record
- Mioglaux (Late Oligocene? - Early Miocene of WC Europe) - includes "Bubo" poirreiri
- Intutula (Early/Middle Miocene of WC Europe) - includes "Strix/Ninox" brevis
- Alasio (Middle Miocene of Vieux-Collonges, France) - includes "Strix" collongensis
Placement unresolved:
- "Otus/Strix" wintershofensis - fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
(Early/Middle Miocene of Wintershof West, Germany) - may be close to extant genus Ninox (Olson 1985:131)
- "Strix" edwardsi - fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
(Middle Miocene of Grive-Saint-Alban, France)
- "Asio" pygmaeus - fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
(Early Pliocene of Odessa, Ukraine)
- Strigidae gen. et sp. indet. UMMP V31030 (Rexroad Late Pliocene of Kansas, USA) - Strix/Bubo? (Feduccia 1970)
- Ibiza Owl, Strigidae gen. et sp. indet. - prehistoric
Prehistoric birds are various taxa of birds that became extinct before recorded history, or more precisely, before they could be studied alive by bird scientists...
(Late Pleistocene/Holocene of Es Pouàs, Ibiza) - see Sánchez Marco 2004
The supposed fossil
heronThe herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
"Ardea" lignitum (Late Pliocene of Germany) was apparently a strigid owl, possibly close to
Bubo (Olson 1985:167). The Early–Middle
EoceneThe Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
genus
PalaeoglauxPalaeoglaux is a genus of fossil owl from the Eocene epoch. There are two known species, P. perrierensis from the Upper Eocene of Quercy, France and P. artophoron from the Middle Eocene Messel shales, Germany. The holotype of P. perrierensis is a partial left coracoid in the Collection Université...
from west-central Europe is sometimes placed here, but given its age it is probably better considered its own family for the time being.
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