tawny owl (Strix Aluco) is a medium-sized raptor, it is an owl the size of a wood pigeon. It has a rounded body and head, with a ring of dark feathers around the face surrounding the dark eyes.

Although the tawny owl is often said to have exceptional night vision, its retina is no more sensitive than a human's, but its asymmetrically positioned ears give the owl excellent directional hearing. Their nocturnal habits and the mysterious and easily imitated call have led to an association in myth with bad luck and death.

The tawny owl's wings allow it to fly silently.

The tawny owl's wings allow it to fly silently.

Features

The tawny owl is a robust bird, its large, rounded head lacks ear tufts, and the facial disc surrounding the dark brown eyes is usually quite smooth. The female is much larger than the male, 5% longer, and more than 25% heavier.

Flight

The tawny owl flies with rounded, less wavy wings and with fewer wingbeats than other Eurasian owls, and typically higher. Like most owls, their flight is quiet due to the soft, furry surface of their feathers and a fringe on the leading edge of the outer primaries. Its size, rugged shape, and wide wings distinguish it from other owls found within its range; gray owls, eagles, and urals are similar in shape, but much larger.

Eyes and vision

The eyes of the tawny owl are placed on the front of the head and have a 50-70% field overlap, giving it better binocular vision than daytime raptors (30-50% overlap).

The owl's retina has about 56.000 light-sensitive rod cells per square millimeter (36 million per square inch); Although previous claims that it could see in the infrared part of the spectrum have been discarded, it is often said to have 10 to 100 times better vision than humans in low light conditions. However, the experimental basis for this claim is probably inaccurate by at least a factor of ten. The true visual acuity of the owl is only slightly superior to that of the man, and any increase in sensitivity is due to optical factors rather than increased retinal sensitivity; both humans and owls have reached the resolution limit for the retinas of terrestrial vertebrates.

Unlike diurnal raptors, they normally only have one fovea (part of the retina that allows us to see clearly), which is poorly developed, except in diurnal hunters such as the Little Owl.

Hearing

Hearing is important for a nocturnal bird of prey, and as with other owls, the two auditory openings differ in structure and are positioned asymmetrically to improve directional hearing.

A passage through the skull joins the eardrums, and small differences in the time of arrival of a sound to each ear allow locating its source. The left ear opening is higher on the head than the larger right ear and slopes downward, improving sensitivity to sounds from below. Both atrial openings are concealed under the facial disc feathers, which are structurally specialized to be transparent to sound, and are supported by a movable fold of skin (the preauricular flap).

The retina of a tawny owl has only one fovea. The internal structure of the ear, which has a large number of auditory neurons, provides a better ability to detect low-frequency sounds at a distance, which could include whispers caused by prey moving in vegetation.

The owl's hearing is ten times better than that of a human, and it can hunt using this sense only in the dark of a forest on a cloudy night, but the pattern of raindrops makes it difficult to detect faint sounds, and humid weather. Prolonged can lead to starvation if you cannot hunt effectively.

Claims and calls

The commonly heard contact call is a screech, kew-wick, but the male has a shaky publicity song. The call is easily imitated by blowing into cupped hands through slightly spread thumbs, and a study in Cambridgeshire found that this mimicry produced an owl response in 30 minutes in 94% of trials. A male's response to a transmitted song appears to be indicative of his health and vigor; tawny owls with higher blood parasites use fewer high frequencies and a more limited range of frequencies in their responses to an apparent intruder.

Taxonomy

This species was first described by Linnaeus at their Systema in 1758 under its current scientific name. The binomial derives from the Greek strix "owl" and the Italian allocco (from the Latin ulucus).

The tawny owl is a member of the genus Strix, part of the typical owl family Strigidae, which contains all species of owls except barn owls. Within its genus, the closest relatives of the tawny owl are the hume's owl, Strix butleri, (formerly considered conspecific), its larger northern neighbor, the Royal Owl, S. uralensis, And the north american long-eared owl, S. varia. The Strix intermedia of the Early Middle Pleistocene is sometimes considered a paleosubspecies of the tawny owl, which would make it its immediate ancestor.

Habitat

This species is found in deciduous and mixed forests, and sometimes in mature coniferous plantations, preferring places with access to water. Cemeteries, gardens and parks have allowed it to spread to urban areas, including downtown. The tawny owl is primarily a lowland bird in the colder parts of its range.

Distribution

The tawny owl has a distribution that spans discontinuously across temperate Eurasia from Great Britain and the Iberian Peninsula east to Korea and south to Iran and the Himalayas. The subspecies S. a. Mauritanica extends the range into northwestern Africa. This essentially non-migratory owl is absent from Ireland, and is only a rare vagrant to the Balearic and Canary Islands.

The tawny owl has a geographic range of at least 10 million km² and a large population that includes some 970.000-2.000.000 individuals in Europe alone. Demographic trends have not been quantified, but there is evidence of an overall increase.

Food

The tawny owl's diet is based primarily on small mice, its favorite coda. It hunts almost entirely at night, observing from a perch before silently falling or gliding towards its victim, but very occasionally it hunts in daylight when it has young to feed.

This species captures a wide range of prey, mainly forest rodents, but also other mammals the size of a young rabbit, as well as birds, earthworms and beetles. In urban areas, birds make up a larger proportion of the diet, and species as unlikely as mallard and tern have been killed and eaten.

We can see a tawny owl resting after hunting.

We can see a tawny owl resting after hunting.

Prey are usually swallowed whole, and the indigestible parts are regurgitated in the form of granules or plaster. They are medium-sized and gray in color, consisting mainly of rodent skins and often with protruding bones, and are found in groups under trees used for resting or nesting.

Less powerful forest owls such as the long-eared owl do not usually coexist with the stronger tawny owl, which can take them for food, and they are found in different habitats. Similarly, when the owl has moved into urbanized areas, it tends to displace the barn owl from its traditional nesting sites in buildings.

Predators

Tawny owl predators include large birds such as the eagle and uralian owls, the northern goshawk, and the common buzzard. There have been several cases of Eurasian rooks building nests on top of a female owl that causes the death of the adult and the chicks. A Danish study showed that predation by mammals, especially red foxes, was a major cause of mortality in young newborn infants, with 36% dying between flight and independence. The risk of mortality increased with the fledgling date from 14% in April to more than 58% in June, and increased predation by late hatchlings may be an important selective agent for early reproduction in this species.

Reproduction

Tawny owls mate from the age of one year, and remain together in a generally monogamous relationship for life. The territory of an established couple is defended throughout the year and is maintained with little or no border change from year to year. The pair sit under cover on a branch near a tree trunk during the day, and usually perch separately from July to October. They can be spotted and "harassed" by small birds during the day, but they usually ignore the disturbance.

The tawny owl typically nests in a hole in a tree, but it also uses old European magpie nests, squirrel droughts, or holes in buildings, and easily leads to nest boxes. Nests from February in the south of its range, but rarely before mid-March.

The bright white eggs are 48 x 39 mm in size and weigh 39.0 grams of which 7% is shell. The typical clutch of two or three eggs is incubated by the female alone for 30 days until hatching, and the altricial and hairy chicks hatch in another 35-39 days. Young often leave the nest up to ten days before flying and hide in nearby branches.

This species is fearless in defense of its nest and its young and, like other Strix owls, it attacks the intruder's head with its sharp claws. Because its flight is silent, it may not be detected until it is too late to avoid danger. Dogs, cats and humans can be attacked, sometimes without provocation.
The parents care for the young birds for two to three months after they leave the nest, but from August to November the young disperse to find their own territory to occupy. If they don't find empty territory, they usually starve.

The juvenile survival rate is unknown, but the annual survival rate for adults is 76,8%. The typical life expectancy is 5 years, but an age of more than 18 years has been recorded for the wild owl and more than 27 years for the captive.

State of conservation

This owl is believed not to meet the IUCN Red List criteria of declining more than 30% in ten years or three generations and is therefore assessed as Least Concern. This species has expanded its range in Belgium, the Netherlands, Norway and Ukraine, and populations are stable or increasing in most European countries. There have been declines in Finland, Estonia, Italy and Albania.

Popular culture

It has often been seen as an omen of bad luck and death, William Shakespeare he used it as such in Julius Caesar (Act 1 Scene 3) "And yesterday the night bird sat / Even at noon in the market place / Noises and screeches."

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