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Overview

Brief Summary

Owls have sharp claws and a hooked beak. They often fly noiselessly through the night in search of mice or othe small animals. However, not all owls are nocturnal. The short-eared owl and the snowy owl hunt during the day. Owls have long round wings, a short tail and feathers on their feet and legs. Their eyes are located on the disc-like face. So in order to look in other directions, they have to rotate their entire head. They're very good at doing that. In fact, they can almost rotate their head in a complete circle.
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Wings allow for silent flight: owls
 

The wings of owls allow for silent flight thanks to several types of specialized feathers.

       
  "Serrated feathers on the front edges of owl wings funnel air smoothly over the wings, reducing the noise of rushing air. Each wing has a scarflike, fringed back edge that prevents the abrupt air-pressure changes--and noise--produced by rigid wings." (Courtesy of the Biomimicry Guild)


"Owl can almost fly silently when it is hunting at night, and it has been known as the natural nighttime "stealth craft". Biologists have found three reasons why the owl can fly silently. The first one, the primary feather of the owl’s wings was separated from each other, and the feather’s edges was serrated.

"In flight, the wings resolved the sound wave, which was produced after air passed the wings, changed the air flow status of its surface boundary layer, and inhibited the formation of air turbulence. This form has excellent performance in noise elimination; The second, the smear feather at the end of wings are spiciform and have no regular arrangement; the third one, the soft feather on owl’s wings can absorb surplus sound whose rate was over 2000 Hz. That is why prey cannot hear the owl.

"It was just because of the surface of owl’s body have a lot of coupling interaction such as special surface morphology, unique wing configuration, special internal structure and highly flexible material. They can delay the separation of turbulent boundary layer around the airfoil profile, reduce pulsating pressure of the surface of wings, and reduce the production of Sound energy. Above all the feature make the surface have  function of noise elimination." (Liang et al. 2010:193-194)
  Learn more about this functional adaptation.
  • Liang G-Q; Wang J-C; Chen Y; Zhou C-H; Liang J; Ren L-Q. 2010. The study of owl's silent flight and noise reduction on fan vane with bionic structure. Advances in Natural Science. 3(2): 192-198.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
Specimen Records: 668
Specimens with Sequences: 486
Specimens with Barcodes: 473
Species: 88
Species With Barcodes: 73
Public Records: 336
Public Species: 54
Public BINs: 68
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Barcode data

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Wikipedia

True owl

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Life

True owl or Typical owl (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 Strigidae. 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 around 189 living species in 25 genera. The typical owls have a cosmopolitan distribution and are found on every continent except Antarctica.

Contents

Morphology

While typical owls (hereafter referred to simply as owls) vary greatly in size, with the smallest species, the Elf Owl, being a hundred times smaller than 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. Like other birds of prey many owl species exhibit reverse sexual dimorphism in size, where females are larger than males (as opposed to the more typical situation in birds where males are larger).[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 tarsus are feathered in some species, and more so in species at higher latitudes.[3] 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 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 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.[1]

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 mobbing by small birds.

Systematics

The nearly 200 extant species are assigned to a number of genera, which are in taxonomic order:

Recently extinct

  • Genus Mascarenotus - Mascarene owls, 3 species (extinct c.1850)
  • Genus Sceloglaux - Laughing Owl (extinct 1914?)

Late Quaternary prehistoric extinctions

Fossil 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 (Early/Middle Miocene of Wintershof West, Germany) - may be close to extant genus Ninox (Olson 1985:131)
  • "Strix edwardsi - fossil (Middle Miocene of Grive-Saint-Alban, France)
  • "Asio" pygmaeus - fossil (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 (Late Pleistocene/Holocene of Es Pouàs, Ibiza) - see Sánchez Marco 2004

The supposed fossil heron "Ardea" lignitum (Late Pliocene of Germany) was apparently a strigid owl, possibly close to Bubo (Olson 1985:167). 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 J. S. Marks, R. J. Cannings & H. Mikkola (1999) "Family Strigidae (Typical Owls)". In del Hoyo, J.; Elliot, A. & Sargatal, J. (editors). (1999). Handbook of the Birds of the World. Volume 5: Barn-Owls to Hummingbirds. Lynx Edicions. ISBN 8487334253
  2. ^ Caroline M. Earhart and Ned K. Johnson (1970) "Size Dimorphism and Food Habits of North American Owls" Condor 72 (3): 251-264
  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
  • Feduccia, J. Alan (1970): Some birds of prey from the Upper Pliocene of Kansas. Auk 87(4): 795-797. PDF fulltext
  • 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.
  • Sánchez Marco, Antonio (2004): Avian zoogeographical patterns during the Quaternary in the Mediterranean region and paleoclimatic interpretation. Ardeola 51(1): 91-132. PDF fulltext
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