254 WILD TRAITS IN TAME ANIMALS. 



method of intimidation. A mere glance at 

 this very incomplete list proves at once that 

 neither blood-relationship nor geographical pro- 

 pinquity can account for the common posses- 

 sion of the habit. Indeed the only thing 

 which most of these sibilant youngsters have 

 in common seems to be the character of the 

 nurseries in which their parents deposit them. 

 So widespread a defensive method can only 

 have arisen from a common need of protec- 

 tion from one kind of danger. Now we know 

 that many beasts of prey are keen searchers 

 for nests, and make a habit of exploring any 

 hole likely to contain tender and defenceless 

 morsels which may be won without much 

 exertion or risk. When a family of young 

 kittens or owlets is left by its natural pro- 

 tectors, it is in a position of most imminent 

 peril if the nose or eye of a proAvling foe 

 should chance to detect its hiding - place. I 

 do not know of anything which more em- 

 phasises the greatness of the danger which 

 often threatens dwellers in hollow trees than 

 the habit common to hornbills in various parts 

 of the world of walling up the hole in which 

 the female bird is sitting, so that only a small 



