Western Barn Owl

Western Barn Owl

Derivation of scientific name: Tyto is onomatopoeic Greek for ‘owl’ and alba is Latin for ‘white’.

Common names: Western Barn Owl, barn owl, ghost owl (Eng.); nonnetjie-uil (Afr.); lerubise (Setswana); sephooko (Sesotho); isikhova (isXhoza); umZwelele (isiZulu); xinkhovha (Xitsonga).

With its ghostly appearance, spine-chilling shrieks and habit of roosting in abandoned builds, the Western Barn Owl has earned itself the nickname ‘ghost owl’. This mystical creature is the most widely distributed bird species in the world and it has been incorporated into folklore, with superstitions being passed from generation to generation.

Description/How to recognise a Western Barn Owl?

Western Barn Owls are medium-sized, measuring 30–33 cm in length, with long wings and a short, squarish tail. Females (weighing around 365 g) are slightly smaller than males, which weigh up to 410 g, but both sexes are similar in plumage colouration. The upper body is golden brown, vermiculated (marked with sinuous or wavy lines) with grey, and spotted black and white. The white, heart-shaped facial disk is contrasted by small, brown to black eyes and a beak that varies from a pale pink to a brownish horn. Underparts are white, with fine brown spots, which make the bird look ghost-like in flight. Legs are greyish-brown and are densely covered with feathers (Hockey et al. 2005).

Getting around

Flight is the main form of locomotion used by barn owls. They fly by moving their wing up and down, which thrusts them into the air and propel them forward. Western Barn Owls are adapted to silent flight – comb-like structures at the edges of the wings, called serrations, play a vital role in air-flow control and noise-reduction during flight (Bachmann & Wagner 2011).

Communicating

Western Barn Owls communicate by using a complex variety of sounds, with the most common being an eerie ‘schreeeee’ screech, usually made while in flight. During courtship, a loud hissing scream with a marked shaking or quivering effect is given in flight. A low wailing and purring sound is also used to attract the female (Bunn et al. 2010).

When there is a predator lurking in their midst, a warning scream is used to denote fear and warn others. A mobbing note might also be made, which symbolises a combination of fear and anger towards the predator. A defensive hiss is made with an open bill to intimidate and frighten the predator (Bunn et al. 2010).

Chicks make ‘sib-sib’ sounds when begging for food from their parent upon their return from hunting. This sound is also made when siblings are fighting over food and it is called ‘sibling negotiation’ (Van den Brink et al. 2011).

Distribution

Barn owls have a cosmopolitan distribution, however, they are not found in Antarctica and on many islands. In addition, they do not occur in parts of the West Indies, Indonesia and New Zealand. Barn owls are seldom found at extreme northern altitudes (Martin et al. 2005). In South Africa, the Western Barn Owl occurs throughout the country (Hockey et al. 2005).

Habitat

This species prefers open areas such as grasslands, wooded savannas and deserts. They inhabit tree cavities, fissures in cliff, and man-made structures (such as mine shafts and abandoned buildings) and their nests are created on the floors of these structures from regurgitated pellets (Smith et al. 1979; Hockey et al. 2005; Martin et al. 2016).

Western Barn Owl with mouse

Food

Western Barn Owls are nocturnal predators. They habitually start hunting after sunset and return to the roosting site before sunrise. The bird hunts by flying slowly over objects that might obscure prey and uses trees and high structures as a look-out to scan for prey. Their feather-structure promotes silent flight (Orlowski et al. 2012). They also have great low-light vision and they are able to localise sound with extreme accuracy (Konishi 1973). The facial disk is used to channel sound to their ear holes located beneath feathers on each side of their face (Martin et al. 2016). The difference in the total sound intensity detected by the two ears is used to determine the elevation of the sound source and this enables the bird to catch its prey (Knuden & Masakazu 1979).

Western Barn Owls feed mainly on small rodents such as hares, rats, mice and shrews (and they are therefore an excellent, environmentally friendly form of pest control), as well as on small birds, insects, lizards, frogs and termites The prey is usually swallowed whole and indigestible material such as bones and fur are regurgitated in the form of a pellet (Smith et al. 1979; Martin et al. 2016).

Sex and life cycles

Sex:

Western Barn Owls are monogamous and territorial in nature (Gibbon 2012–2016); breeding pairs are solitary nesters. They mate for life, except if one of the pair dies off. The male and female may roost separately outside the breeding season (Martin et al. 2016). When the breeding season approaches, the pair moves back to the area that they selected for the nest to roost. The same nest/roost site is often used repeatedly over years. Copulation begins with courtship, which starts from August to December in the Western Cape and from February to May in other parts of South Africa (Hockey et al. 2005).

Courtship starts with the female flying in circles around an area that the pairs established as a roosting site. The male will fly behind the female emitting high-pitched sounds. Courtship usually takes place for 30 to 120 minutes and copulation takes place on high perches within in the breeding site. Females are able to lay up to 13 eggs, and one egg is laid every two days (Smith et al. 1979). Eggs are incubated by the female for 29 to 34 days (Hockey et al. 2005) and they hatch in the same sequence in which they were laid.

Family life

During the incubation period, the male goes hunting and brings food for the female and the extra food is piled up next to her to ensure that there is enough food for the chicks after hatching. Once the eggs have hatched, both partners are responsible for feeding their chicks (Smith et al. 1979). Within a week after their arrival, the chicks are able to hold their heads up and move around the nest. Fledging (flying) begins after 45 to 55 days, when the chicks are as big as their parents (Hockey et al. 2005). Once the chicks become adept flyers, parents terminate post-fledging dependency by reducing the amount of food given to them.

THE BIG PICTURE

Friends and foes

Western Barn Owls are birds-of-prey and usually feed on small mammals; however, they occasionally feed on other birds, lizards and amphibians. Nestlings and eggs are sometimes preyed on by snakes or other birds-of-prey. Their main enemy is humans, who put out poisoned bait for rodents and if an owl happens to eat a poisoned rodent, it may eventually die of secondary poisoning.

Smart strategies

Western Barn Owls have evolved mechanisms that enable them to survive predation. When a predator is lurking nearby, these birds start hissing loudly to scare the predator away. The predator becomes confused by the noise that the owls make and mistakes it for another animal. Western Barn Owls also survive predation through tonic immobility, were the bird lies still and pretend to be dead. The predator loses interest and walks away (Van den Brink et al. 2016).

The ability of Western Barn Owls to survive predation has been linked to the size of the spots on the plumage of the birds. Bird with large spots have been found to be better at frightening predators, faking their death, and are more resistant to parasites than those with small spots (Roulin et al. 2001; Van den Brink et al. 2016). Chicks raised by heavily spotted females are less prone to parasite attacks than those raised by lightly spotted females. Males select to form monogamous relationships with heavily spotted females so that they can pass on genes that make their offspring more fecund in nature (Roulin et al. 2001).

Poorer world without me

Rat and mice are notorious for destroying agricultural crops and can cause ill-health to their human neighbours through some zoonotic diseases of which rodents are carriers. Western Barn Owls are predators of rats and mice, and they play an important role in preventing famine and epidemics of zoonotic diseases.

People & I

Throughout history, Western Barn Owls have been associated with superstitious beliefs. They are thought to symbolise death, bring bad luck to humans, and they have been allied to witchcraft. It is believed that when a Western Barn Owl is seen perching on the roof of a house, a family member will pass on the next day.

These birds are also believed not to be natural birds, but creatures created by witches and wizards to bring bad omens at night. Seeing a Western Barn Owl crossing the street while driving is thought to indicate that something terrible is about to happen (Mikkola & Mikkola 1997). Superstitions and prejudice towards Western Barn Owls have led to the senseless and cruel killing of these birds. They have also been brutally killed for the noise they make, to protect cats, and for trophy hunting.

However, farmers as well as more enlightened city dwellers hold these magnificent birds in high regard, because they primarily feed on rats, mice and birds, hence protecting the famer’s crops. People nowadays even install owl boxes on their farms or in their suburban gardens to encourage these birds to nest there – since Western Barn Owls reuse nesting sites year after year, the lucky home owner who gets a breeding pair to live on his property has free pest control for life! (Birdlife South Africa 2016). Western Barn Owls are furthermore important for the bioremediation of rat-infested areas such as slumps and dumping sites.

Conservation status and what the future holds

Barn owls are not threatened in South Africa, although it they are occasionally victims of senseless killings, car accidents (road kill) and secondary poisoning from eating poisoned rats.

Relatives

There are nearly 35 species of barn owls and they are all different in colour. Barn owls are widely distributed. There are at least three major lineages of barn owl, one in Europe, western Asia and Africa (the Western Barn Owl, Tyto alba affinis), one in East Asia and Australasia (Eastern Barn Owl) and one in the Americas (American Barn Owl) (Gibbon 2012–2016). Some experts believe there are more than three species or sub-specific taxa, but this needs further investigation. Barn owls are closely related to the African Grass-Owl (Tyto capensis) and the Madagascan Red Owl (Tyto soumagnei).

References and further reading:

Birdlife South Africa. 2016. Build your own owl house. Internet 1 pp. www.birdlife.org.za/get-involved/owl-boxes

Buchmann, T. & Wagner. H. 2011. The three-dimensional shape of serrations at barn owl wings: towards a typical natural serration as a role model for biomimetic applications. Journal of Anatomy 219: 192–202.

Gibbon, G. 2012–2016. Roberts VII Multimedia Birds of Southern Africa. iPhone and iPad Edition, version 2.4. Southern African Birding, Westville, South Africa

Hockey, P.A.R., Dean, W.R.J. & Ryan, P.G. 2005. Birds of southern Africa, 7th ed. The trustees of the John Voelcher Bird Book Fund, Cape Town.

Martin, J.M., Richard, N.R. & Branch, L.C. 2016. Barn Owl (Tyto alba). University of Florida: Department of Wildlife Ecology and Conservation. Retrieved from: http//edis.ifas.ufl.edu. Accessed on 15 November 2015.

Mikkola, H., & Mikkola, H. 1997. General public owl knowledge in Malawi. The Society of Malawi Journal 50,1: 13–35.

Roulin, A., Riols, C., Dijkstra, C. & Ducrest, A.L. 2001. Female plumage spottiness signals parasite resistance in the barn owl (Tyto alba). Behavioral Ecology 12,1: 103–110.

Smith, D.G., Wilson, C.R., & Frost, H.H. 1974. History and ecology of a colony of barn owls in Utah. The Condor 76 (2): 131-136.

Van den Brink, V., Dolivo, V., Falourd, X., Dreiss, A.N. & Roulin, A. 2012. Melanic color-dependent antipredator behavior strategies in barn owl nestlings. Behavioral Ecology 23,3: 473–480.

By Lerato Hoveka and Zwelakhe Zondi

Images by Jonathan Haw.

July 2017.

Official Common Name: Western Barn Owl 

Scientific Name and Classification:

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Strigiformes

Family: Tytonidae

Genus: Tyto

Species: T. alba affinis (Scopoli, 1769)

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