We human beings are essentially diurnal creatures, but this is not true of many of the birds and animals that inhabit this planet with us. As the sun sinks low on the horizon and the long shadows of evening creep through the woods, various mice, rabbits, raccoons, opossums, flying squirrels, deer, and other creatures emerge from their daytime concealment and begin their nightly forays.
In this world of darkness, predatory birds and mammals are also on the prowl, assuring that nature's intricate system of checks and balances shall not be disrupted and that no essential job--for example, curbing the rodent hordes--is left undone. Chief among these nocturnal predators is a specialized order of birds called Strigiformes, the owls, which are characterized by extraordinary powers of vision, together with a soft downy plumage enabling practically soundless flight. If hawks, in their function of keeping within bounds the populations of mammals and birds, are on the "day shift," owls may be said to be on the "night shift."
Perhaps the most outstanding and controversial member of this tribe of night flyers is the celebrated "'Tiger of the Air," the great horned owl, Bubo virginianus. Often described as the fiercest and most savage of all predatory birds, it has been shot, trapped, and discriminated against for years throughout its wide range, by farmers, sportsmen, gamekeepers, and even some naturalists, but it continues to survive as one of our commonest large owls.
The great horned owl is the classic representative of a "hoot owl" to the layman, for its low, melancholy--often booming--notes are probably more familiar than the voices of any other of the eighteen species of North American owls. Moreover, it is most often the bird that people envision whenever the expression "wise old owl" is used: the owl's flat, feathered facial disks and wide-set eyes give it an almost human expression, and the presence of "ear" tufts (from which the bird gets its name) tends to increase its scholarly appearance and magnificent bearing.
The great horned owl is one of our largest owls, measuring 18 to 25 inches in length and with a wingspread of more than four feet. It weighs about three pounds and is comparable in size and weight to the snowy owl of the sub-arctic tundra regions. Only the great gray owl of the Canadian wilderness-surpasses it in over-all length and wingspread: this bird, however, is deceptive in appearance, having long wings and tail, a large round head, and long fluffy plumage. These give the great gray owl an appearance of immense size, but in weight and actual body measurements it is exceeded by both the snowy owl and the great horned owl, both of which are substantially more powerful birds, capable of killing larger animals.
Most great horned owls tend to live in the same general vicinity more or less continuously throughout the year; this is called maintaining a permanent home range. Simply defined, the home range of a bird or other animal is a portion of land or water fulfilling the biological requirements of the species. For a horned owl, such a place must contain suitable nesting sites for raising its young, roosting cover for daytime concealment, and fairly open hunting territory. Above all, the home range must support enough wildlife to provide an adequate, annual food supply for the owl and its family.
