TAWNY OWLS
ABOUT TAWNY OWLS
"Tawnies" are the most numerous of the owls found on the UK mainland. The characteristic "twit-twoo" of the male and "kewick" of the female are familiar to many but, being a largely nocturnal species, they are seldom seen.
GENERAL
CALLS
DESIGN FEATURES
BREEDING
DIET
GALLERY
GENERAL ECOLOGY
DISTRIBUTION AND HABITAT
Tawny owls are found in much of Europe, in parts of North Africa and throughout most of the UK mainland. Their preferred habitat is broad-leafed woodland but they can be found in mixed and coniferous woodland, parks and large gardens. Where there is adequate prey and suitable nest sites, they can frequent relatively built environments.
LIFESPAN AND PAIRING
Tawny owls have been known to live 20 years in the wild. One individual having had a ring put on it as a chick was recaptured 20 years later.
TERRITORIES
Tawny owls are strictly territorial, established pairs remaining in their breeding territories throughout the year. Territories vary in size from 12 to 20 hectares (30 to 50 acres) depending on habitat type and food availability. Resident pairs advertise their ownership of a territory with regular calling at certain times of year (see Calls).
CONSERVATION STATUS
The Tawny Owl was moved onto the Amber List of Birds of Conservation Concern in 2015 because of worries that it may have be undergoing a long-term population decline.
CALLS
The calls below represent the typical calls of male and female tawny owls but there is likely to be some overlap, both males and females can on occasion sound more like each other.
MALE
(typical call)
FEMALE
(typical call)
FEMALE then MALE
MALE ("warbling") and FEMALE in September
On seeing a cat (presumed alarm or threatening call made by an adult tawny owl)
8-12 weeks old chicks
CHICK
16 weeks old chick
DESIGN FEATURES
SIZE AND WEIGHT
As with most birds of prey, female tawny owls tend to be 25% bigger than the males (females average 520g as opposed to 420g for males). The wingspan can vary from 80 to 100cm. There is no significant difference in colouration between the two sexes.
EYESIGHT
With large, forward facing eyes tawny owls have excellent eyesight with which to see and hunt at night. Their ability to see in very low light is enhanced by an eye that has a large lens, a large cornea and a short distance from the lens to the retina. The retina has far more of the light-sensitive rods than the cones that are better suited to detailed daytime vision. 70% of a tawny owl's skull is occupied by its eyes, compared to 50% in birds more generally.
Unlike the spherical eyes of mammals, birds have semi-tubular shaped eyes (probably as an adaption to minimise weight)
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X-ray of RTA tawny owl
to show the size and shape of the eye
HEARING
The hearing of a tawny owl is said to be 10 times more sensitive than that of humans. The disc-shaped face of tawny and other owls helps to focus sound onto their ears lying to the side of and just behind the facial disc. As with humans, tawny owls can detect the direction from which sound is coming by the difference in time at which sounds arrives at each ear.
FEATHERS
Owls need to be able to fly as quietly as possible both to avoid being detected by their prey and to make it as easy as possible for them to hear their prey. Tawny owl feathers are soft to the touch and their wing feathers have adaptions on their leading edge (the fimbriae/flutings) and "feathered" tips. These adaptions allow air to move over the feathers with the minimum of turbulence. It is the turbulence generated by moving through the air that generates sound. Another theory is that these adaptions shift the sound generated to a frequency inaudible to prey species.
Feathering
Fimbriae or flutings
Buzzard for comparison
WINGS
Tawny owls have relatively large and broad wings compared to their weight (a feature known as low wing loading). This allows them to fly buoyantly and effortlessly with the minimum of flapping and noise creation. Short, broad wings make them very manoeuverable, a useful adaption for a bird that tends to live and hunt in woodland.
BREEDING
Whilst some tawny owls may start to breed at one year old if conditions are right, most do not breed until they are two years old.
WARNING
Extreme caution is required approaching tawny owl nest sites as the female may well attack an intruder. In 1937 Eric Hosking, a famous bird photographer, lost an eye to a tawny owl whose nest he was photographing at the time.
NESTING
Tawny owls use a variety of nest sites that include holes in trees and the old stick nests of birds such as crows. Occasionally they nest in buildings and have been known to nest on the ground. They take readily to nest boxes (both those designed for tawny owls and those designed for barn owls).
One to five (usually two to three) eggs are laid and the four-week incubation starts immediately which leads to asynchronous hatching and staggered development of the chicks. Breeding starts relatively early in the year, often in early or mid-March but can be as early as February or as late as May. Fed by the male, apart from brief absences, the female remains at the nest through incubation and on to two weeks after the eggs hatch.
Nest site in hollow tree
Nesting in a box designed for barn owls
Chicks (reared in the tree on the left) at about 2 weeks of age
FLEDGING
Tawny owl chicks fledge after 4-5 weeks. In a process known as branching, with limited feathering and a poor ability to fly, tawny chicks leave the nest and enter the nearby branches. They quickly gain more feathers enabling them to fly confidently within 2 weeks of fledging. If grounded, they are excellent climbers and soon return to the safety of the trees.
Close to fledging
24hrs after fledging
DEVELOPMENT
Tawny owl chicks will hide during the day but as darkness falls they move into the open where they can be seen more easily by their parents. The asynchronous hatching is very apparent a few weeks after fledging.
Soon after fledging illustrating good feather development on the wings but not elsewhere
At about 3 months of age
DISPERSAL
Tawny owl chicks are dependent on their parents for food and remain in their parents' territory for 10 to 12 weeks following fledging. Fledging and dispersal are times of high mortality.
Tawny owls are relatively sedentary, chicks dispersing on average only 4km (with half likely to remain within 10km of their place of hatching).
There are no tawny owls in Ireland nor on many of the islands around the UK mainland. None are recorded as having crossed the English Channel.
4-5 months old and approaching dispersal.
DIET
Tawny owls have a wide ranging diet, something that has probably allowed them to occupy a varied range of habitats.
Small mammals (especially voles and mice) are the mainstay of many tawny owls' diet. Other commonly taken prey are shrews, frogs, birds, insects (including cockchafers) and earthworms. Carrion, such as roadkill, is also eaten. There are even records of tawny owls eating fish, including one record of an owl taking a goldfish from a garden pond. What they are feeding on will depend on their habitat, the time of year and the weather conditions.
Wood mouse delivered to chicks 3-4 weeks old
Frog delivered to a young chick
ME AND THE TAWNIES
Inspired by Johnathan Scott's image of a vulture, "undercarriage" extended, dropping out of the sky with eyes fixed on a carcass, in 2005 I set out to photograph and capture a similar image here in rural mid-Devon. In the absence of any local vultures, I hoped to attract in a buzzard as a friend had done, placing a day-old chick on his wall each afternoon when he fed his snakes. I installed a feeding table in my field and within seven days the food started to disappear on a regular basis but, seemingly, at night. Not sure who was taking it, I set up a camera and tied a cotton thread to the chick's leg and onto an improvised remote switch made of two pieces of aluminium foil.
22nd April 2006
.... and so began a fascination and close relationship with my local tawny owls that persists to this day.
The original "tawny" continued to come to the feeding table (and have his photograph taken) until he stopped appearing in June 2018. For me, it was 12 magical years. Both he and a subsequent pair of owls have not only given me and over 100 friends and contacts enormous pleasure, they have given me a window into their fascinating lives. Not only this, along the way they have afforded me some wonderful photographic opportunities.
Feeding time
At all times I have been very careful with how I stage the in-flight photographs so as not risk blinding the owls with the flash -guns and having them hit an object soon after having had their photograph taken.
The day old cockerel chicks fed to the owls are a by-product of the poultry industry. Being the brothers of layer chicks, these chicks would never fatten. In order that the owls don't become dependent on the supplementary food, the amount that I feed is judged to be a small fraction of their daily requirement.
