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An introduction to Owls

Facts

There are over 200 owl species in the world. Many come from the genus Strix, which is Latin for screech owl, and Bubo, which is Latin for owl.

Features

A relatively large head, facial disc and large eyes make owls unmistakable. They have soft feathers and, in most cases, this helps them fly silently. Unlike diurnal raptors, owls do not have a crop. The food they eat passes directly into the stomach. Despite the similarities to other raptors, such as a hooked beak and sharp powerful talons, owls are more closely related to nightjars. Owls range from the size of a sparrow to huge eagle owls nearly three feet long with wingspans of more than six feet.

General

There are many misconceptions about owls: they only come out at night, they cannot see during the day or they can see in total darkness. None of these are true. Some owls are often most active during the day. Others are more successful hunting at night, and some are called crepuscular. These owls are most active around dawn and dusk. Irrespective of what time of day they are active, most owls have a higher degree of optical sensitivity in low light levels. This is to do with the how the back of the eye (the retina) is constructed. The retina has two major types of sensors - cones and rods. Cones deal with high light levels, sharp contrasts and colour, whilst rods deal with detail in low light levels. Unlike diurnal raptors, which have a high concentration of cones in the retina, owls have a larger amount of rods. This means that their eyes are able to see more detail in low light.
Human eyes contain rods as well, but they are located towards the sides of the retina - this is why we see better out of the corner of our eyes in low light.

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