The sexes are alike, the female being larger than the male. The young resemble the adults, but, at least in certain cases, are more rufous or buff; further information is, however, needed as to the successive stages. All Owls exhibit a certain similarity, while their ample plumage creates an erroneous impression of bulk; the feathers–most compact in Surnia–are soft, with an admixture of hairs and with weak, brittle shafts, to which facts the noiseless flight is largely due. An erectile tuft decorates each side of the crown in Bubo, Asio, Scops, and Ketupa; but the most striking outward characteristic is the ruff of several series of small, stiff-shafted, recurved feathers, originating from a fold of the skin round the cheek, which support the larger feathers of the overlying disc around the eye. The latter is very complete in Strix, Syrnium, and Asio, being in the first-named rather triangular than circular; but in Surnia, Speotyto, Bubo, and Scops, not to mention other cases, it is far less perfect.
Syrnium cinereum, one of the largest members of the Family, is thirty inches long, though Bubo possesses species that are perhaps more powerful; on the other hand, Micrathene whitneyi and Glaucidium cobanense measure about five inches. Omitting the white or yellowish-white forms, the coloration of Owls may be stated to be a mixture of black, brown, rufous, grey, yellow, and white, while barring is frequent on the wings and tail. The pattern is always difficult to describe, nor can more than an indication of it be given in the space available below. Permanent rusty-red and grey phases occur in many species, or more rarely a brown phase; such species as exhibit two of these being termed dimorphic, though dichromatic would better express the meaning. The bill is blackish, dusky, or yellowish. The moult in the Strigidae appears to be very gradual.
Owls are an exceptionally cosmopolitan group of birds, a large proportion of the genera being common to both hemispheres; Ketupa, Scotopelia, Ninox, Heteroglaux, Sceloglaux, Carine, Photodilus and Heliodilus are, however, peculiar to the Old World, Speotyto, Gymnasio and Micrathene to the New. The Short-eared Owl (Asio accipitrinus) is found at various seasons throughout the globe, except, it would seem, in West Africa, Australia, the Moluccas, Papuasia, and Oceania; it occurs even in the Sandwich, Galápagos, and Falkland Islands. The Screech-Owl (Strix flammea) has an even wider range, but is not met with in Norway, the north of North America, or New Zealand. Authorities differ as to the genera and species to be recognised, but certainly many more of the latter are now known than the one hundred and ninety at which Dr. Sharpe put the total in 1875.[[232]]
The members of this Family frequent districts of the most varied description, whether they be wooded highlands, rocky ravines, or cultivated lowlands; the Snowy Owl (Nyctea scandiaca) nests chiefly on the fjelds and barren lands towards the North Pole; while the Burrowing Owl (Speotyto cunicularia), which is equally at home on the sandy plains of North or South America, is exceptional as an instance of gregarious habits in the group. The majority, being nocturnal, are ill at ease in sunlight, a fact which may explain the apparent discrepancy between their habitual shyness and their bold conduct at the nest or when wounded; many are then positively dangerous, and prove worse adversaries than Falcons or Eagles. In the perpetual day of the Arctic summer the Snowy Owl and the Hawk-Owl (Surnia ulula) cannot of course be nocturnal, while to a limited extent various species of Bubo, Scops, Ninox, Glaucidium, Carine, Nyctala, and Asio may be seen abroad in the hours of light; so that in many cases sight may aid in the capture of prey as much as hearing.
The noiseless flight is buoyant, but usually slow and somewhat wavering, with frequent beats of the wing; occasionally it is more direct, and in Surnia ulula almost Hawk-like. Owls apparently prefer to perch with the first and fourth toes behind, and on a level surface to stand with three toes in front; their gait on the ground is awkward, and being arboreal birds–with the exception of Speotyto and Sceloglaux–they rarely walk to any extent.
The food consists of small mammals, such as lemmings, rats, voles, and mice; of insects, with perhaps beetles in especial; and to a less degree of birds, reptiles, bats, worms, slugs, and snails. The stronger forms even capture young fawns, rabbits, hares, large grouse, and so forth, Ninox connivens being a great enemy of the young of the Koala (an Australian marsupial); while the Snowy, Mottled, Screech-, and Wood-Owls occasionally take fish, which, with crabs, constitutes the chief diet of Ketupa. The manner of procuring sustenance varies with the object sought. Insects are frequently caught upon the wing, but ordinarily the ground is quartered after the manner of Harriers, and a pounce made upon the prey, which is secured in the long curved talons. The smaller creatures are swallowed entire or carried in the bill; the bigger are conveyed, hanging between the feet, to some convenient spot, where they are torn to pieces and sometimes plucked. Bones, fur, feathers, beetles' elytra, and the like are ejected as round or cylindrical pellets, which commonly lie thickly around the nests or feeding-places, and clearly shew the nature of the food.
The note varies from a loud hoot to a low, muffled sound or a clear, musical cry; the utterance of both young and adults being in some cases a cat-like mew, while the Screech-Owl snores when stationary. The "hoot" is said to be produced by closing the bill, puffing out the throat, and then liberating the air, a proceeding comparable to that of the Bitterns (p. [88]). On the whole the voice is mournful and monotonous, but occasionally it resembles a shrill laugh. If a nest be made, it is commonly placed in a hole in a tree or on a ledge of rock, but many species simply deposit their eggs on the débris naturally found in cavities.
To descend to a few particulars, the Snowy and Short-eared Owls, certain other species of Asio, and in some cases the Eagle-Owls (Bubo) breed upon the ground, often near some sheltering tuft, and use little or no bedding; Speotyto collects a mass of grass, dry leaves, feathers, and rubbish in burrows; the Wood-Owls (Syrnium), the Long-eared Owl (Asio otus), and several other forms utilize deserted nests of Pies, Crows, Squirrels, and the like, commonly adding a fresh lining; the first-named alternatively choose holes in trees or in the ground; while Carine glaux has been known to breed in ant-hills. The Screech-Owl (Strix) and most of the smaller members of the Family deposit their eggs in crevices in rocks or banks, in natural cavities in trees, or even at the junction of two large branches; towers, lofts, dovecots, and belfries being well-known sites for the former. Apparently none of the above excavate their own holes in the wood, or do more than clear them out; a few, however, decorate the nests they usurp with green foliage, as do so many Buzzards and Eagles. The habits sometimes undergo a decided change, as when the Short-eared Owl in the Aleutian Islands, and the Screech-Owl in Texas and India take to fairly deep burrows.
The Strigidae are exceptionally early breeders; for instance, Long-eared Owls' eggs have been found in England at the end of February, and those of Bubo virginianus in that month in the United States; it is true the Screech-Owl is later in this country, but this does not seem to be the case with its American race. Where fresh sets are found late in the year, the first have generally been destroyed, and a second brood is uncommon, though the contrary holds true during vole- or lemming-plagues, when food is unusually abundant; at such times, moreover, the number of eggs is abnormally large for the species. The usual tale varies from two to ten, while the bigger forms as a rule do not deposit so many. Much has been made of the fact that the Screech-Owl (with the Eagle-Owl and other forms) lays at considerable intervals of time; but this is certainly not always true, and in many cases the varying size of the embryo is easily accounted for by supposing the parent to sit as soon as the first egg is deposited. On the other hand, occasional breaks certainly occur in the laying, and pairs of eggs are often produced almost simultaneously; yet the bird has no regular habit of allowing the subsequent eggs to be hatched by the warmth of the oldest nestlings; and the reader may be reminded that in other groups, such as the Harriers and Divers, a very similar inequality in the development of the eggs may be observed. Exceptionally the white shell is said to be tinted with blue or yellow, or to be even marked with lilac and brown in Bubo coromandus.[[233]] The shape is normally oval or nearly spherical, but longer or even pointed specimens are not uncommon, while the larger the size the less glossy is the texture. The male is generally to be found near at hand if the nest is disturbed, and undoubtedly assists in some cases in incubation, which lasts about four weeks. The hen hisses when caught in a hole, and invariably sits closely; while both parents frequently remain near an intruder, and "click" their beaks at him in exactly the same manner as the pugnacious nestlings do.
Owls are constantly mobbed by other birds, especially when dazed by sunlight, the Little Owl being used as a lure on the Continent. They migrate to a greater or less extent, the autumnal visits of the Short-eared Owl being especially well-known in Britain; yet the Snowy Owl often remains in the far north in winter. The flesh is not generally reckoned palatable, but Bubo, Asio, Nyctea, Carine and Scops at least are eaten by the natives of various countries; superstition, however, usually prevents the murder of an Owl, which is usually supposed to entail evil, though in a few places good luck. In Andalucia the Scops- and Screech-Owls are believed to be the devil's birds, and to drink the oil from the lamps in saints' shrines; the Malagasy consider the members of the Family embodiments of the spirits of the wicked; and country folks' belief in their connection with death and the churchyard dates back at least to the time of Shakespeare, who makes one of his characters call the owl's hoot or screech a "song of death." Many species are well-adapted for aviaries, and breed freely; and the Little Owl (Carine noctua) has done so when liberated in Britain.