Owls are revered and appreciated for their beauty and elegance, strength
and independence, as well as for their perceived wisdom and intelligence.
Owls are an extremely wide-ranging classification of birds, with 134 known
species occurring in almost all parts of the world. Scientists classify
owls as belonging to the order Strigiformes, which is divided into 2
families - the Tytonidae of which there are up to ten species known, according
to which classification source is quoted, and the Strigidae to which
the remaining 124 owl species belong.
Owls are predators which, by and large, specialise in catching ground-
dwelling small mammals: birds, rabbits, reptiles, insects, earth-worms
and even fish are also taken by some species. They are not in any way
related to predators such as eagles, falcons, or hawks. The closest
relatives of the owls are the nightjars and the frogmouths (Caprimulgi-
formes). The family Strigidae represents the main line of owl evolution,
sharing a common ancestor with the group Caprimulgiformes, from a time
before the Palaeocene some 54 to 65 millions years ago, the family
Tytonidae becoming distinct at least since the Miocene some 7 to 26
million years ago.
Owls vary in size from 10 centimetres (4 inches) to over 70 centimetres
(28 inches). There is a general trend for the females to be larger than
the males, in order to reduce competition for food between partners,
particularly during the breeding season. Unique among raptors, the
Australian Hawk Owl species displays a tendency towards larger males.
They boast a wide range of markings,and they share similar characteristics
including the distinctive head, and a flattened forward-facing facial disc,
surrounding relatively large eyes. In most species the plumage appears as
rather subdued shades of brown and grey, with feather patterns that provide
amazingly proficient camouflage for daytime roosts.
Owls are largely a nocturnal bird of prey - more than 60 percent of the
134 known owl species hunt and feed after dark, and of the remaining 40
percent, few are exclusively diurnal, ie. hunt in daylight. The twilight
hours of dawn and dusk are their domain, as well as the dead of night,
when no other avian predators can function.
The members of the Strigidae are closely enough related to be grouped
together in the one family. However, the members of the genus Tyto together
with the two little known bay owls (genus Phodilus), differ considerably
from all the others in a number of ways, and have been placed in the
separate family Tytonidae.
Among all the owls, Tyto species are the supreme night hunters, able to
operate successfully on even the darkest of nights. Tyto owls are capable
of hunting in total darkness. Hearing is their great strength, so acute
that they have almost no need for light to detect prey. It is the nature
of the facial disc that serves most conveniently to distinguish between
the living representatives of the two families of owls. Most strikingly
the facial disc, rather than being rounded, is heart-shaped. Tyto species
do also, of course, have excellent night vision. Interestingly, apart from
the two sooty owls, the eyes are relatively quite small, their size deceptively
enhanced by a combination of dark colour and the radiating facial
disc. Silence of flight is characteristic of most owls, but Tyto species
have the most silent flight of all.
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