VI STRIGIDAE 399 



eyes are directed obliquely forwards, but those of Ninox are said 

 to have a less staring look ; Owls, moreover, have little power of 

 turning the eye -ball, and consequently add to their grotesque 

 appearance by constantly moving the head from side to side. 

 The upper eye-lid shuts over the eye, aixl not the lower, as in 

 birds generally ; the iris is extremely sensitive, contracting and 

 expanding continually. The external ear varies in an extra- 

 ordinary way, the " conch," or large shell-like aperture, often 

 having its ample membranous margin developed into an elevated 

 operculum or flap which stretches partially or entirely down the 

 anterior side. In Asio and Syrnium the ear-openings are asym- 

 metrical, those of the former reaching nearly the whole height 

 of the skull and being directed respectively upwards and down- 

 wards ; in Nyctcda this asymmetry extends to the bones of the 

 skull itself. The large ear is apparently correlated with a keen 

 sense of hearing in some cases, but not in all. 



The furcula, when complete, is U-shaped; the tongue is fleshy, 

 and somewhat horny below ; the nostrils, placed towards the 

 front of the cere, are rather large, and usually concealed by 

 bristles ; the syrinx is bronchial ; the after-shaft is absent or 

 rudimentary ; down occurs in the adults only on the unfeathered 

 spaces, but in the nestlings forms a woolly coating, which may be 

 brown or dusky, as in the Snowy Owl, white as in the Screech - 

 Owl, yellowish or grey, as in many species. 



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 admix- 

 ture of hairs and with weak, brittle shafts, to which facts the noise- 

 less flight is largely due. An erectile tuft decorates each side of 

 the crown in Bubo, Asio, Scops, and Ketupa ; but the most strik- 

 ing outward characteristic is the ruff of several series of small, 

 stiff-shafted, recurved feathers, originating from a fold of the skin 

 round the cheek, wiiich support the larger feathers of the over- 

 lying " 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 S^crnia, Speotyto, Buho, and Sco2JS, not to 

 mention other cases, it is far less perfect. 



