Owl

Owl
Fossil range: Late Paleocene–Recent
The rare Northern Spotted Owl
Strix occidentalis caurina
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Subclass: Neornithes
Infraclass: Neognathae
Superorder: Neoaves
Order: Strigiformes
Wagler, 1830
Families

Strigidae
Tytonidae
Ogygoptyngidae (fossil)
Palaeoglaucidae (fossil)
Protostrigidae (fossil)
Sophiornithidae (fossil)
Synonyms

Strigidae sensu Sibley & Ahlquist

Owls are the order Strigiformes, comprising 200 extant bird of prey species. Most are solitary and nocturnal with some exceptions (e.g. the Northern Hawk Owl). Owls hunt mostly small mammals, insects, and other birds though a few species specialize in hunting fish. They are found in all regions of the Earth except Antarctica, most of Greenland and some remote islands. Though owls are typically solitary, the literary collective noun for a group of owls is a parliament.

Living owls are divided into two families: the typical owls, Strigidae; and the barn-owls, Tytonidae.

Contents

Description

Owls have large forward-facing eyes and ear-holes, a hawk-like beak, a flat face, and usually a conspicuous circle of feathers, a facial disc, around each eye. Most birds of prey sport eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits a greater sense of depth perception necessary for low-light hunting. Although owls have binocular vision, their large eyes are fixed in their sockets, as with other birds, and they must turn their entire head to change views. Owls can rotate their heads and necks as much as 270 degrees in either direction.[1][2][3] Owls are farsighted and are unable to see anything clearly within a few centimeters of their eyes. Caught prey can be felt by owls with the use of filoplumes, which are small hair-like feathers on the beak and feet that act as "feelers". Their far vision, particularly in low light, is exceptionally good.

Eagle Owl

The smallest owl is the Elf Owl (Micrathene whitneyi), at as little as 31 g (1.1 oz) and 13.5 cm (5.3 inches). Some of the pygmy owls are scarcely larger. The largest owls are two of the eagle owls; the Eurasian Eagle Owl (Bubo bubo) and Blakiston's Fish Owl (Bubo blakistoni)—which may reach a size of 60 – 71 cm (28.4 in) long, have a wingspan of almost 2 m (6.6 ft), and an average weight of nearly 4.5 kg (10 lb).

Different species of owls make different sounds; the wide range of calls aids owls in finding mates or announcing their presence to potential competitors, and also aids ornithologists and birders in locating these birds and recognizing species. The facial disc helps to funnel the sound of prey to their ears. In many species, these are placed asymmetrically, for better directional location.[4]

The plumage of owls is generally cryptic, but many species have facial and head markings, including face masks, ear tufts and brightly coloured irises. These markings are generally more common in species inhabiting open habitats, and are thought to be used in signalling with other owls in low light conditions.[5]

Owl eggs usually have a white colour and almost spherical shape, and range in number from a few to a dozen, depending on species. Eggs are laid at intervals of 1 to 3 days and do not hatch at the same time. This accounts for the wide variation in the size of sibling nestlings. Owls do not construct nests, but rather look for a sheltered nesting site or an abandoned nest in trees, underground burrows, or in buildings, barns and caves.

Behaviour

Most owls are nocturnal, actively hunting for prey only under the cover of darkness. Several types of owl, however, are crepuscular, active during the twilight hours of dawn and dusk; one example is the pygmy owl (Glaucidium). A few owls are also active during the day; examples are the Burrowing Owl (Speotyto cunicularia) and the Short-eared Owl (Asio flammeus).

The serrations on the leading edge of an owl's flight feathers reduce noise.

Much of the owls' hunting strategy depends on stealth and surprise. Owls have at least two adaptations that aid them in achieving stealth. First, the dull coloration of owls' feathers can render them almost invisible under certain conditions. Secondly, serrated edges on the leading edge owls' remiges muffle an owl's wing beats, allowing its flight to be practically silent. Some fish-eating owls, for which silence is of no evolutionary advantage, lack this adaptation.

An owl's sharp beak and powerful talons allow it to kill its prey before swallowing it whole (unless it is too big). Scientists studying the diets of owls are helped by their habit of regurgitating the indigestible parts of their prey (such as bones, scales and fur) in the form of pellets. These "owl pellets", which are plentiful and easy to interpret, are often sold by companies to schools for dissection by students as a lesson in biology and ecology.[6]

Evolution and systematics

A Great Horned Owl (Bubo virginianus) sleeping at daytime in a hollow tree.

The systematic placement of owls is disputed. For example, the Sibley-Ahlquist taxonomy finds that, based on DNA-DNA hybridization, owls are more closely related to the nightjars and their allies (Caprimulgiformes) than to the diurnal predators in the order Falconiformes; consequently, the Caprimulgiformes are placed in the Strigiformes, and the owls in general become a family Strigidae. A recent study indicates that the drastic rearrangement of the genome of the accipitrids may have obscured any close relationship of theirs with groups such as the owls .[7] In any case, the relationships of the Caprimulgiformes, the owls, the falcons and the accipitrid raptors are not resolved to satisfaction; currently there is an increasing trend to consider each group (with the possible exception of the accipitrids) a distinct order.

There are some 220 to 225 extant species of owls, subdivided into two families: typical owls (Strigidae) and barn-owls (Tytonidae). Some entirely extinct families have also been erected based on fossil remains; these differ much from modern owls in being less specialized or specialized in a very different way (such as the terrestrial Sophiornithidae). The Paleocene genera Berruornis and Ogygoptynx show that owls were already present as a distinct lineage some 60 - 57 mya (million years ago), and, hence, possibly also some 5 million years earlier, at the extinction of the non-avian dinosaurs. This makes them one of the oldest known groups of non-Galloanserae landbirds. The supposed "Cretaceous owls" Bradycneme and Heptasteornis are apparently non-avialan maniraptors.[8]

During the Paleogene, the Strigiformes radiated into ecological niches now mostly filled by other groups of birds. The owls as we know them today, on the other hand, evolved their characteristic morphology and adaptations during that time, too. By the early Neogene, the other lineages had been displaced by other bird orders, leaving only barn-owls and typical owls. The latter at that time were usually a fairly generic type of (probably earless) owl similar to today's North American Spotted Owl or the European Tawny Owl; the diversity in size and ecology found in typical owls today developed only subsequently.

Around the Paleogene-Neogene boundary (some 25 mya), barn-owls were the dominant group of owls in southern Europe and adjacent Asia at least; the distribution of fossil and present-day owl lineages indicates that their decline is contemporary with the evolution of the different major lineages of typical owls, which for the most part seems to have taken place in Eurasia. In the Americas, there was rather an expansion of immigrant lineages of ancestral typical owls.

The supposed fossil herons "Ardea" perplexa (Middle Miocene of Sansan, France) and "Ardea" lignitum (Late Pliocene of Germany) were more probably owls; the latter was apparently close to the modern genus Bubo. Judging from this, the Late Miocene remains from France described as "Ardea" aureliensis should also be restudied.[9] The Messelasturidae, some of which were initially believed to be basal Strigiformes, are now generally accepted to be diurnal birds of prey showing some convergent evolution towards owls. The taxa often united under Strigogyps[10] were formerly placed in part with the owls, specifically the Sophiornithidae; they appear to be Ameghinornithidae instead.[11]

For fossil species and paleosubspecies of extant taxa, see the genus and species articles.

Unresolved and basal forms (all fossil)

Ogygoptyngidae

Protostrigidae

Sophiornithidae

Strigidae: Typical owls

A Long-eared Owl, Asio otus, in erect pose

Fossil genera

Placement unresolved

Masked Owl, Tyto novaehollandiae.

Tytonidae: Barn-owls

Fossil genera

Placement unresolved

Relationship with humans

A Burrowing Owl, Athene cunicularia.

Africa

Among the Kikuyu of Kenya it was believed that owls were harbingers of death. If one saw an owl or heard its hoot, someone was going to die. In general, owls are viewed as harbingers of bad luck, ill health, or death. The belief is widespread even today.[14]

The Americas

In the culture of the Uto-Aztec tribe, the Hopi, taboos surround owls, which are associated with sorcery and other evils. The Aztecs and Maya, along with other Natives of Mesoamerica, considered the owl a symbol of death and destruction. In fact, the Aztec god of death, Mictlantecuhtli, was often depicted with owls. There is an old saying in Mexico that is still in use[15]: Cuando el tecolote canta, el indio muere ("When the owl cries/sings, the Indian dies"). The Popol Vuh, a Mayan religious text, describes owls as messengers of Xibalba (the Mayan "Place of Fright").[16] The belief that owls are messengers and harbingers of the dark powers is also found among the Hočągara (Winnebago) of Wisconsin.[17] When in earlier days the Hočągara committed the sin of killing enemies while they were within the sanctuary of the chief's lodge, an owl appeared and spoke to them in the voice of a human, saying, "From now on the Hočągara will have no luck." This marked the beginning of the decline of their tribe.[18] An owl appeared to Glory of the Morning, the only female chief of the Hočąk nation, and uttered her name. Soon afterwards she died.[19] People often allude to the reputation of owls as bearers of supernatural danger when they tell misbehaving children, "the owls will get you." [20]

Western culture

The modern West generally associates owls with wisdom. This link goes back at least as far as Ancient Greece, where Athens, noted for art and scholarship, and Athena, Athens' patron goddess and the goddess of wisdom, had the owl as a symbol.[21] Marija Gimbutas traces veneration of the owl as a goddess, among other birds, to the culture of Old Europe, long pre-dating intrusive Indo-European cultures.[22]

Owls were considered funerary birds among the Romans.

Use as rodent control

Encouraging natural predators to control rodent population is a natural form of pest control, along with excluding food sources for rodents. Placing a new box for owls on a property can help control rodent populations (one family of hungry barn owls can consume more than 3,000 rodents in a nesting season) while maintaining the naturally balanced food chain.[23]

Owl conservation issues

Laughing Owl (Sceloglaux albifacies)- last seen 1914

All owls are listed in Appendix II of the international CITES treaty (the Convention on Illegal Trade in Endangered Species of Wild Fauna and Flora). Although owls have long been hunted, a 2008 news story from Malaysia indicates that the magnitude of owl poaching may be on the rise. In November 2008, TRAFFIC reported the seizure of 900 plucked and "oven-ready" owls in Peninsular Malaysia. Said Chris Shepherd, Senior Programme Officer for TRAFFIC's Southeast Asia office, "This is the first time we know of where 'ready-prepared' owls have been seized in Malaysia, and it may mark the start of a new trend in wild meat from the region. We will be monitoring developments closely." Traffic commended the Department of Wildlife and National Parks in Malaysia for the raid that exposed the huge haul of owls. Included in the seizure were dead and plucked Barn Owls, Spotted Wood Owls, Crested Serpent Eagles, Barred Eagles, and Brown Wood Owls, as well as 7,000 live lizards.[24]

Footnotes

  1. ↑ "San Diego Zoo Birds: Owl". San Diego Zoo. http://www.sandiegozoo.org/animalbytes/t-owl.html. Retrieved 2010-08-24. 
  2. ↑ "A Parliament of Owls". Colorado Division of Wildlife. http://wildlife.state.co.us/Education/TeacherResources/ColoradoWildlifeCompany/OwlsCWCWin9293.htm. Retrieved 2010-8-24. 
  3. ↑ "The Owls of Big Bend". National Park Service U.S. Department of the Interior. http://www.nps.gov/bibe/naturescience/owls.htm. Retrieved 2010-08-24. 
  4. ↑ Cotty, 2008.
  5. ↑ Galeotti, Paolo; Diego Rubolini (2007). "Head ornaments in owls: what are their functions?". Journal of Avian Biology 38 (6): 731–736. doi:10.1111/j.0908-8857.2007.04143.x. 
  6. ↑ "Owl Pellets in the Classroom: Safety Guidelines".
  7. ↑ See Haaramo (2006). In reality, the presumed distant relationship of the accipitrids - namely, the "Accipitriformes" according to Sibley and Ahlquist (1990) - with owls (and most other bird lineages) is most likely due to systematic error. Accipitrids have undergone drastic chromosome rearrangement and thus appear in DNA-DNA hybridization generally unlike other living birds.
  8. ↑ Mortimer (2004)
  9. ↑ Olson (1985): pp.131, 267
  10. ↑ Mayr (2005)
  11. ↑ Alvarenga & Höfling (2003), Peters (2007)
  12. ↑ 12.0 12.1 Olson 1985: p.131
  13. ↑ Sánchez Marco (2004)
  14. ↑ "Owls in Lore and Culture - The Owl Pages". Owlpages.com. http://www.owlpages.com/articles.php?section=Owl+Mythology&title=Owls+Lore+Culture&page=8. Retrieved 2009-07-29. 
  15. ↑ "La Cronica". http://www.cronica.com.mx/especial.php?id_tema=1010&id_nota=375192. Retrieved 2009-03-21. 
  16. ↑ "The Popol Vuh". http://www.meta-religion.com/World_Religions/Ancient_religions/Central_america/popol_vuh.htm. Retrieved 2008-07-23. 
  17. ↑ See the article "Owls" in the Hočąk Encyclopedia. Retrieved: 4/21/09.
  18. ↑ Paul Radin, The Winnebago Tribe (Lincoln: University of Nebraska Press, 1990 [1923]) 7-9.
  19. ↑ David Lee Smith, Folklore of the Winnebago Tribe (Norman: University of Oklahoma Press, 1997) 160. See also "Glory of the Morning" in the Hočąk Encyclopedia. Retrieved: 4/21/09.
  20. ↑ E. W. Lenders, "The Myth of the 'Wah-ru-hap-ah-rah,' or the Sacred Warclub Bundle," Zeitschrift für Ethnologie 46 (1914): 404-420, p. 409.
  21. ↑ Deacy, Susan, and Alexandra Villing. Athena in the Classical World. 1st ed. Koninklijke Brill NV,Leiden, The Netherlands: Brill, 2001. Print.
  22. ↑ The living goddesses, Marija Gimbutas, University of California Press, 2001, p 158.
  23. ↑ "The Hungry Owl Project". Hungryowl.org. http://www.hungryowl.org/. Retrieved 2009-07-29. 
  24. ↑ Wednesday (2008-11-12). "Wildlife Trade News - Huge haul of dead owls and live lizards in Peninsular Malaysia". Traffic. http://www.traffic.org/home/2008/11/12/huge-haul-of-dead-owls-and-live-lizards-in-peninsular-malays.html. Retrieved 2009-07-29. 

References

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