Owls
Why owls are special predators?
Owls have evolved as specialised hunters with skills to help them locate and catch their prey. Each species of owl has a range of incredible features and attributes that many other birds do not possess, but which gives owls the ‘tools’ to survive.
Some species have:
- Eyes that can see in almost total darkness.
- Ear tufts to break up their outline and increase camouflage.
- Cryptic plumage to aid camouflage.
- Soft feathers with a comb-like ‘fringe’ on the flight feathers which acts to displace less air when flying, aiding silent flight.
- Round facial discs with special feathers to ‘catch’ sound and direct the sound into the ear openings.
- Asymmetrical ear openings to help ears work independently (ie.not in stereo).
- Different size ear openings that can hear at different frequencies.
- A toe that swivels so talons can be used 2+2 for squeezing prey or 3+1 for gripping a branch.
Owls as Indicator Species
Birds of prey are regarded as ‘Indicator’ species, giving conservationists an early warning of the health of the food chain and the wider environment should they start to decline.
If owls are in decline, it is usually because their rough grassland hunting habitats are declining. This is a warning sign that other wildlife, which depends on these habitats – such as bats, butterflies, insects, and other wildlife – may be under threat.
British Owl Species
There are six species of owl that breed in the UK, plus the snowy owl – which still occurs, but hasn’t been recorded as breeding since the early seventies.
Little Owl (Athene noctua):
Introduced to the UK in the 19th Century, the little owl has become a permanent resident in the UK. Our smallest owl – little owls are found all over England and Wales and have now established themselves over the Scottish border. Little owls are a di-urnal species, often seen out during the day time, sat up on telegraph poles or on the tops of farm buildings.
Estimated breeding population (2009): 6000 – 11,000prs
Size: 21 – 23cm
Wingspan: 54 – 58cm
Habitat: Open country and farmland
Nesting: Nests in hollows in trees, walls, barns etc, rabbit burrows, cliff holes.
Prey: Worms, insects, invertebrates, small mammals, small birds etc
Conservation issues: Little owls have declined heavily in recent years. Loss of habitats and nest sites is an ongoing problem, the use of insecticides in agriculture impacts on the little owl’s insect prey and research is continuing into fledgling mortality rates and the causes.
Tawny Owl (Strix aluco):
The tawny owl is the familiar too-whit too-whoo owl that is nocturnal and mostly heard at night. Found all over the UK, normally in wooded areas, tawnies are highly territorial and defend their ‘patch’ against other tawny owls. They often hunt from a perch, such as a tree branch or post, scanning the ground for signs of prey. Young tawny owls leave the nest after just 3 or 4 weeks and continue their development up in the tree canopy.
Estimated breeding population (2009): 19000 prs
Size: 37 – 39cm
Wingspan: 95 – 100cm
Habitat: Woodland, parks (including in cities), copses, large gardens
Nesting: Tree hollows, abandoned crows nests, squirrel dreys, holes in buildings .
Prey: Small mammals (in particular wood mice) birds, insects, worms and amphibians.
Conservation issues: Tawny owls are quite versatile birds and have held numbers in recent years, but they are always under threat from loss of woodland habitats, road mortality and sometimes from persecution.
Barn Owl (Tyto alba):
The barn owl is the only British owl that has Schedule 1 protection under the Wildlife and Countryside CT OF 1981. This gives this vulnerable species extra protection against disturbance. Therefore, a licence is required to disturb or even photograph breeding barn owls at the nest. Barn owls are heavily dependent on voles for food, and as vole populations have a natural crash every 3 – 4 years, combined with the intensive management of its rough grass habitats, barn owl populations are under regular threat from loss of food resources.
Barn owls usually hunt at dawn and dusk, in low light or darkness. When their small mammal prey is more active and the owl’s hearing capabilities can be most effective. But after periods of rain at night, hungry owls can sometimes be seen hunting in the day.
Estimated breeding population (2009): 3000 – 5000 prs
Size: 33 – 35cm
Wingspan: 85 – 93cm
Habitat: Open farmland.
Nesting: Tree hollows, farm buildings.
Prey: Small mammals (in particular field vole) sometimes small birds.
Conservation issues: The long-winged barn owl has evolved as a field vole specialist, and in an ideal world 85% of a barn owl’s diet should consist of voles. However, due to variation of vole availability due intensive grass cutting regimes, barn owls often struggle to find food. Long periods of wet weather can limit how long a barn owl can hunt for, as soft feathers for silent flight are not waterproof. Increased road traffic accounts for over 5,000 barn owl deaths every year, caused by collisions with vehicles whilst flying low over busy roads. 75% of barn owl chicks born every year are unlikely to survive to breed the following year. These young birds have a steep learning curve for survival and many starve to death in the early weeks of independence. Nest site loss as a result of development, such as barn conversions, can affect barn owls, but with Schedule 1 status, developers are required by law to comply with conditions to ensure breeding or roosting barn owls are not disturbed, and that nest boxes are installed as part of the planning process to offer the owls an alternative nest site.
Short-eared owl (Asio flammeus):
The short-eared owl is a diurnal species of owl, often see hunting during the day in it’s moorland and heathland habitats. Due to this specific habitat requirement, most breeding short-eared owls in the UK are found in northern Britain and some parts of Wales but in the winter, when hunting habitats can be covered by snow, or food is scarce, this nomadic species will travel south and spend winter in the milder coasts, heathlands and farmland of southern Britain, returning north to breed in the spring.
Estimated breeding population (2009): 1000 – 3500 prs
Size: 37 – 39cm
Wingspan: 95 – 100cm
Habitat: Moorland, heathland, sand dunes.
Nesting: Nests of the ground
Prey: Small mammals, small birds, reptiles, insects
Conservation issues: Short-eared owls can suffer in their moorland breeding habitats as a result of moorland management regimes, including the planting of commercial forests. Vole-rich rough grassland habitats created for barn owls in southern England can be of great value to wintering short-eared owls.
Long-eared owl (Asio otus)
The secretive long-eared owl is rarely heard and very seldom seen due to its secretive habits. Small and highly camouflaged, long-eared owls are active during the hours of darkness, hunting over farmland or between forest rides in its favoured coniferous forest habitat.
Estimated breeding population (2009): 2000-5000 prs
Size: 35 – 37cm
Wingspan: 90 – 100cm
Habitat: Coniferous forest, hawthorn hedges in farmland
Nesting: Uses the abandoned nests of other birds, such as crows and magpies.
Prey: Small mammals, small birds, reptiles, insects
Conservation issues: Long-eared are under-recorded due to their shy nature, but steps can still be taken to ensure meet their breeding and hunting requirements. When planting forests, the creation of 20m rough grassland rides through the plantation gives long-eared owls hunting corridors. Farmers and landowners are also advised to check that crows nests are not occupied by long-eared owls or other birds of prey when shooting out stick nests as part of corvid control measures.
European Eagle Owl (Bubo bubo):
The European eagle owl is the largest owl in the world and in recent years has been found breeding in small numbers in the UK. There are debates continuing as to whether these birds are wild birds that have made their way across to the UK from Europe or Scandinavia, or indeed if they are the result of keepers either losing of intentionally releasing these birds from captivity.
Estimated breeding population (2009): 25 prs+
Size: 60 -75cm
Wingspan: 138 – 200cm
Habitat: Mainly rocky areas, ravines plus open forest
Nesting: Cliff ledge, crevice in ground.
Prey: Mainly mammals from mice through to foxes and young deer. Will also take birds, reptiles and amphibians.
Conservation issues: There are some bodies now calling for a cull of this species in the UK to protect other species of owls, raptors and other birds that would be easy prey for this powerful and highly capable predator.
Snowy Owl (Bubo scandiaca):
This large owl is actually an arctic eagle owl, and as the name implies, it is more at home in colder regions of the world. Although it can still be found in small numbers in northern Britain, the last recorded breeding snowy owls were a pair on Fetlar, in the Shetlands that bred for the last time in the early seventies.
Estimated breeding population (2009): 0 prs – single birds only
Size: 55 – 66cm
Wingspan: 45 – 60cm
Habitat: Arctic tundra
Nesting: Lays egg in a scrape on the ground.
Prey: Mainly mammals, especially lemmings, hares, rabbits etc where available, plus birds up to the size of ducks.
Conservation issues: Globally this species is not threatened, but with warming temperatures, UK sightings may decline in the years to come.
Habitat creation and conservation for owls
Most owls depend heavily on short-tailed field voles for food. This small, vegetarian mammal eats the juicy stalks of grass and lives in the cover of grass that has been left to grow and fold, creating a warm, dark thatch that is out of the sight of predators (except those that can smell or hear the voles under the grass). A field that has been left unmanaged for 6 months or more can soon be populated by thousands of voles offering a rich source of food for birds of prey.
Insect eating owls like the little owl benefit from these vole habitats, where they may also eat grasshoppers, moths, crane fly and other insects, but little owls also will forage piles of rotting wood for beetles and compost heaps and muck piles for worms and bugs.
Can I put up an owl nest box?
In the absence of suitable natural sites, some species of owl can be offered an artificial nest site in the form of a wooden nest box. These boxes can be installed on a tree or building and provide a safe, dry nesting or roost site for owls and their young.
Wildlife World produce three designs of solid timber, hand made FSC nesting boxes for owls that have been developed to suits the needs of tawny owls (TOB) barn owls (BOB) and little owls (LOB).
Where to site owl nest boxes?
Each species has slightly different nest site requirements and so this should be taken into consideration when installing a wooden nest box.
Tawny owl box:
Installed in a woodland or copse, approximately 8 – 12ft off the ground, with a flight path into the box, preferably facing NE – SE, away from the prevailing weather. Tawny owl chicks leave the nest site before they are fully developed, so the box should be installed in a large tree that has branches around or above it where branching chicks can exit and clamber higher up into the tree canopy, where they will stay and continue with their development.
Barn owl box:
Installed in a single tree in a field, a large tree in the woodland edge or hedgerow, on the side of a farm building or inside a farm building or barn (two means of entrance/exit for the owls is recommended). On external boxes, box hole should be visible to attract passing owls and box should be installed facing NE – SE, away from the prevailing weather. Additional perches can be added around the box to give growing chicks additional roosting areas.
Little owl box:
Installed in a tree within hedgerow, either in the crown of the tree or on the trunk, in a solitary tree in a field. Boxes can also be installed on the side of a farm building or inside barns, cow sheds etc. Locate 6 – 10ft off the ground and install box facing NE – SE and in a position where there are branches nearby for emerging chicks to reach. Additional perches can be added if installing in a building if beams are not close to the box.
Other considerations when installing nest boxes for owls:
- Boxes should not be installed close to busy roads, and in the case of barn owls, not within 1km of any major roads.
- When choosing site of box, and installation height, consideration should be given to the risk of interference if boxes are being installed in areas accessible to the public.
- All Wildlife World nest boxes come fitted with a camera clip enabling the easy installation of an optional infra-red camera for monitoring purposes. This can be of particular value with boxes for barn owls, that cannot be physically disturbed without the appropriate licence.
- Owl boxes put up for one species may attract another species of owl, or indeed a kestrel. Other birds, such as the threatened stock dove may also make an owl box it’s home, as well as grey squirrels.
Useful Contacts
Wild OwlInformation on identifying British owls, calls, habitat advice and other resources from freelance owl conservationist, Ian McGuire.
The Barn Owl TrustThe Barn Owl Trust is dedicated to the conservation and education of the barn owl and it’s environment. An excellent resource for advice on helping all owls plus drawings and downloads for making owl boxes at home.