NOCTUKNAL BIEDS OF PREY. 575 



sun, the action of which upon colour of plumage cannot be 

 doubted, they are not arrayed in those splendid hues which 

 clothe diurnal birds of tropical regions. 



Owing to the structure and nature of their feathers, nocturnal 

 birds of prey fly without making the least noise. They can, there- 

 fore, pounce unawares on their victims, seizing them before they 

 have any idea of necessity -for escape. "When they lay hold of 

 their prey it is immediately devoured an easy matter on account 

 of the enormous expansion of their bills. Their stomach afterwards 

 separates the indigestible parts, such as bones, hair, and feathers, 

 and when these are rolled together in the shape of a ball or pellet, 

 they are ejected by vomiting. Diurnal birds of prey which sub- 

 sist on living animals possess the same power. 



With the exception of the Barn Owl, nocturnal birds of prey 

 all lay eggs of a spherical shape. They live in couples, only 

 assembling in flocks at the epoch of migration ; they never, how- 

 ever, hunt in common. They do not build any nest, but deposit 

 their eggs in cavities in old trunks of trees or ruined habita- 

 tions. They exhale a disagreeable and unwholesome smell, which 

 is no doubt owing to their exclusively animal diet. 



A nocturnal bird of prey, unless forced, never comes out of its 

 lurking-place during day. When compelled by circumstances to 

 do so, it is assailed by all the Passerines of the neighbourhood, 

 which resent its intrusion, and avenge the oppression exercised 

 over them during the night, by combined attacks. It places itself 

 in the strangest postures, ruffles up its feathers, and balances its 

 head with a stupid look, making its bill crack, when so assaulted. 

 It does not, however, try to defend itself, and passively receives 

 the blows of its feathered enemies, which do it but little harm. 

 This natural antipathy of small birds for their nocturnal destroyers 

 has been taken advantage of for purposes of sport. The method 

 of catching birds by calling is founded upon it. Imitating the voice 

 of an Owl, the birds flock together and perch on the trees or 

 bushes in the suspected neighbourhood, where twigs covered with 

 birdlime have been abundantly scattered. This operation must 

 take place about an hour before sunset ; if later, it would not be 

 successful. This way of catching birds was in use in the days of 

 antiquity, for Aristotle has given us a description of it. 



