GENERAL ADAPTIVENESS. 367 



prey. When it approaches the birds, having estimated their 

 exact position and distance, it wholly submerges itself quietly, 

 comes up under the unwary prey, and drags them by the 

 legs under water. It is also said to kill wild pigs by half 

 burying itself in the ground in the forests on the same river- 

 banks (Belt). 



The construction of nests or other forms of dwelling 

 affords in relation to site and material, for instance many 

 illustrations of adaptiveness. As to site or position, it has 

 first to be noted that water-hens and swans raise the level of 

 their nests with the rising of the water of ponds or lakes, of 

 streams or rivers, in flood, constructing pillars for them 

 (Watson). 



Various birds expose their nests or their openings to the 

 sun, and shelter them from the wind, or they seek the shade, 

 avoiding the sun, according to climate. In other words, they 

 select a proper locality as to exposure or shelter (Houzeau)- 

 They sometimes provide double openings, for egress as well 

 as access, using the former in case of intrusion or sur- 

 prise by enemies. Watson mentions a wren opening a new 

 entrance to its nest simply to escape publicity or notice. 

 As to size, the beaver, for instance, adapts the size of its 

 private dwelling to the increase of its family (Watson, 

 6 Percy Anecdotes '). 



The selection of material for nest building is even more 

 apparent. In general terms it may be said that many, if 

 not most, birds make choice of that material which is at 

 once most accessible and most suitable, including manufac- 

 tured material of man's. Thus in the southern United 

 States, in the weaving or lining of their nests, birds make 

 appropriate use of ' vegetable hair ' the Tillandsia usneoides 

 of botanists. On the other hand, Mr. Schwendler of the 

 telegraph department of India, in a communication to the 

 Asiatic Society of Bengal in 1874, describes crows' nests as 

 made of fragments of thin telegraph wire, or (in one case) 

 of the wire used in corking soda-water bottles; and he 

 contrasts the ingenuity or sagacity of the bird with the 

 mental status of the human natives 'who, in the con- 

 struction and arrangement of their houses, had not ad- 



