Who-oo-oo's out there? A closer look at owls
Their large eyes, silencing presence and contented nature make them a symbol of wisdom for many people. But underneath this honourable facade lies the instinct of a merciless hunter.
As silent as the night, owls hunt when it is dark. They have special adaptations which make this possible. Large eyes collect all available traces of light, sensitive ears pick up the tiniest of sounds and soft wings allow them to stalk silently. Their hunting tactic is surprise; combined with dull colouration and a muffled wing beat, they are able to sneak up on their prey with little effort.
Unlike other birds of prey, owl eyes are not situated on the side of their head but directly in front. The reason for this is greater sense of depth when hunting in the low-light of night. Owls have fantastic far vision, but cannot see close objects clearly. They therefore have special feathers known as filoplumes around their beak and feet which act to ‘feel’ their prey once it has been caught.
Other specially adapted feathers, known as facial discs, are situated around each eye. The feathers making up the discs can be adjusted to direct and sharply focus sound onto the ear cavities, which are also found on the front of the face. In some species the ear cavities are placed asymmetrically for better directional location.
After the ears and eyes have located the prey, they are able to swoop down unnoticed. The wing feathers of owls are soft and edged with fine hair-like filaments that deaden the sound of their flight, making them successful at sneaking up on their prey. The final work is done by their sharp talons and hooked-beak which crush the skull and tenderise the body. All these adaptations make owls extremely effective hunters.
Most owls feed on insects, birds and small mammals, but their diet is also species specific (the Pel’s fishing owl, for example, feeds on fish). A few hours after consuming the entirety of their prey, the indigestible bits are regurgitated as a pellet and collected in their nest. These act as cushioning in the roost for the eggs; owls do not therefore need to go out to collect material for their home.
Each species of owl has a unique call which is used for communication, particularly when finding mates and announcing their presence. Whilst there is the well-known “who-oo-oo who-oo-oo” call of some, others whistle, hiss, click or even chatter to each other.
The most cryptic aspect of these already mysterious birds is their plumage. Owls generally mimic their environmental colouration in an attempt to remain camouflaged while they sit inactively during the day. However, head and facial markings, ear tufts and coloured irises make them identifiable. These are thought to be used to signal to other owls in low light. Some species have ear tufts, nothing more than feathers, which are also used as camouflage to break their outline as well as to communicate their mood through their posture.
Most owls use their defensive posture to intimidate enemies. This usually involves lowering the head while the wings are spread. To warn off threats, this action is often accompanied by swaying, hissing and bill clicking.
In terms of conservation, all owls are listed in Appendix II of the international CITES treaty (Convention on Illegal Trade in Endangered Species of Wild Fauna and Flora). This comes after a long history of hunting, poaching and declining population numbers worldwide. A huge threat to owls, like most animals, is habitat destruction. Although owls have been recognised as a natural form of pest control, especially amongst rodents, many traditions believe owls to be a bad omen, bringing ill health, bad luck and even death.
Owls found in South African parks and reserves include the marsh owl, spotted eagle-owl, Verreaux’s eagle-owl (former giant eagle-owl), Cape eagle-owl, African barred owlet, pearl-spotted owlet, African scops-owl, southern white-faced scops-owl, Pel’s fishing-owl, barn owl, African wood-owl and African grass-owl.
Did you know?
• Owls cannot move their eyes from side to side, but they make up for this by being able to turn their head 270 degrees.
• Owls are far-sighted and struggle to see objects up close, but they have binocular vision and are able to see in the dark exceptionally well.
• There are about 200 different species of owl occurring across a range of habitats worldwide.
• Owls are birds of prey and the majority are nocturnal, being active at night. For classification purposes owls are divided into two main families, the typical owls (Strigidae) and the barn-owls (Tytonidae).
• Even though owls are solitary birds, the collective noun for a group is a ‘parliament of owls’.
• The smallest owl is the elf owl, weighing only 31 grams and measuring 13,5cm. The smallest in Southern Africa is the pearl-spotted owlet, which measures 17cm.
• The largest owl is the great grey owl which can get up to 84cm in length! However, the heaviest and largest winged owls are in the eagle-owl category. In Southern Africa, Verreaux's eagle-owl measures is the biggest and measures up to 66cm.
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