139 



Genus — Otus. Screech Owls. 



373. Screech Owl. fb. — le hibou macule. Otus asio. L, 9-40. Plate XVI A. 



Distinctions. The species is dichromatic, that is, it occurs in two well-marked colour 

 forms irrespective of sex, age, or season. One form is rich brown with shades of grey and 

 white, and the other has the grey replaced by bright rufous. The plumage pattern of 

 each is the same. Many intermediate stages occur. In apparent size it comes between 

 Richardson's and the Saw-whet Owls, but the presence of well-defined horns from the 

 sides of the crown and the sharply defined figures of its colour pattern are characteristic. 



Field Marks. Size, and the distinct horns are the best field guides. 



Nesting. In hollow trees. 



Distribution. All temperate North America. Breeds in Canada wherever found. 



SUBSPECIES. The Screech Owl is divided into a great number of subspecies, nine 

 geographical races being recognized in North America by the American Ornithologists' 

 Union Check-list. The only one found in eastern Canada, however, is the type form — the 

 Eastern Screech Owl. 



Although called the "Screech Owl", the notes of this bird are melo- 

 dious and soothing with a tinge of melancholy, and contain nothing harsh 

 or grating. The most common call is a long, soft, tremolo whistle on an 

 even descending scale. Occasionally it consists of low croons, gurgles, 

 and other quiet and conversational notes. Although inoffensive, these 

 small birds show surprising courage in defence of their young. At night 

 they will swoop down on the head of an intruder with a startling, hollow- 

 sounding "whoo-whoo" and snapping of the bill. Just before striking, 

 however, they wheel away to gather momentum for a return. Such 

 attacks while disconcerting are far from dangerous. The habit of nesting 

 in old, hollow, apple trees on the farm, where its mousing is of immediate 

 importance, makes this bird most valuable to the husbandman. 



Economic Status. The official finding on the food of the Screech Owl 

 is warrant for its protection. Of 212 stomachs examined, 1 contained 

 poultry; 38, other birds; 91, mice; 11, other mammals; 2, lizards; 4, frogs 

 and toads; 1, fish; 100, insects; 5, spiders; 9, crawfish; 7, miscellaneous; 

 22, scorpions; and 2, earthworms. The poultry item must be regarded as 

 an accidental occurrence, as the bird represented, a Pigeon, would be 

 exceedingly large prey for this Owl. 



Genus — Bubo. Horned Owls. 



375. Great Horned Owl. cat owl. fh. — le duc de vieginie. Bubo virginianus. 

 L, 22. Plate XVI B. 



Distinctions. Our only Owl over 15 inches in length wearing horns. Its ochraceous 

 and black and white coloration is distinctive. 



Field Marks. Large size, ochraceous colour, and prominent ear-tufts. 



Nesting. Usually in abandoned Hawks' nests or in hollow trees. 



Distribution. In various subspecies the Great Horned Owl ranges over all of North 

 America. The ranges of the subspecies in Canada are sufficiently indicated by their 

 names. 



SUBSPECIES. The Great Horned Owls of North America are split up into a 

 great number of geographical races or subspecies, some of which occur as migrants in 

 eastern Canada. The Arctic form B. v. subarcticus is nearly white in colour with the 

 ochre and rufous of the common variety almost absent and the black pattern much reduced. 

 The Western Horned Owl B. v. pallescens is about intermediate between the Arctic and 

 the Eastern Horned Owl, the type form shown in the illustration. The Labrador Horned 

 Owl B. v. heterocnemis is a very dark form. As these intergrade with each other indis- 

 tinguishably and overlap in range in migration, exact subspecies designations should be 

 made only with great care and, except in extreme plumages, only after comparison with 

 duly authenticated specimens. 



28587—10 



