BIRDS OF PREY. 137 



mit a great deal of light; they are also surrounded with 

 a disk of feathers of a light color, which serves to direct 

 the light, striking it in upon the eye. The nictitating 

 membrane is very conspicuous, it being needed to shut 

 out some of the light in broad day ; to open its eyes 

 widely then, and without the covering of this membrane, 

 would dazzle the Owl exceedingly. Its head is very 

 large and round, which is owing mostly to some cells 

 that are connected with the organ of hearing, rendering 

 that sense very acute ; this is of essential service to it in 

 taking its prey by night. Owls are the only birds that 

 have an external ear, 206. It is covered by feathers, 

 and in some species by a sort of lid, which the bird can 

 open or shut at pleasure. 



232. The plumage of the Owls is very peculiar. It is 

 downy, partly to keep them warm, but mostly to enable 

 them to approach their prey noiselessly. Their flight is 

 so noiseless that they seem borne along on the air like 

 a tuft of down. The food of the larger species consists 

 of hares, rabbits, fawns, birds, etc., and that of the smaller, 

 of mice, rats, moles, small reptiles, and the larger insects. 

 They take these either by night or in the twilight ; and 

 we find this family most abundant in those portions of 

 the globe where the twilight is most prolonged the 

 cold and temperate regions. There are some aberrant 

 species in which the habits are diurnal more than noc- 

 turnal, and, consequently, the characteristics mentioned 

 are not fully developed in them. The typical species, in 

 which the development of these peculiarities is complete, 

 scarcely move during the day. They remain at rest upon 

 their perch, with eyes half closed, and an amusing air of 

 gravity ; and when aroused in any way they do not fly 

 off, but raise themselves up, and assume grotesque atti- 

 tudes, making ludicrous motions. 



233. The Barn Owl, Fig. 114 (p. 138), is widely dif- 

 fused through the temperate regions of Europe and this 

 country. It is a very useful animal in destroying rats 



