238 NATURAL HISTORY OF SELBORNE. 



struction, would often vary and do that by many methods which 

 instinct effects by one alone. Now this maxim must be taken in 

 a qualified sense ; for there are instances in which instinct does 

 vary and conform to the circumstances of place and convenience. 



It has been remarked that every species of bird has a mode of 

 nidification peculiar to itself ; so that a school-boy would at once 

 pronounce on the sort of nest before him. This is the case 

 among fields and woods, and wilds ; but, in the villages round 

 London, where mosses and gossamer, and cotton from vegetables, 

 are hardly to be found, the nest of the chaffinch has not that 

 elegant finished appearance, nor is it so beautifully studded with 

 lichens, as in a more rural district : 

 and the wren is obliged to construct 

 its house with straws and dry grasses, 

 which do not give it that rotundity 

 and compactness so remarkable in 

 the edifices of that little architect. 

 Again, the regular nest of the house- 

 martin is hemispheric ; but where a w re n. 

 rafter, or a joist, or a cornice, may happen to stand in the way, 

 the nest is so contrived as to conform to the obstruction, and 

 becomes flat or oval, or compressed. 



In the following instances instinct is perfectly uniform and 

 consistent. There are three creatures, the squirrel, the field- 

 mouse, and the bird called the nut-hatch (sitta EuropceaJ, which 

 live much on hazle-nuts ; and yet they open them each in a dif- 

 ferent way. The first, after rasping off the small end, splits the 

 shell in two with his long fore-teeth, as a man does with his 

 knife ; the second nibbles a hole with his teeth, so regular as if 

 drilled with a wimble, and yet so small that one would wonder 

 how the kernel can be extracted through it ; while the last picks 

 an irregular ragged hole with its bill : but as this artist has no 

 paws to hold the nut firm while he pierces it, like an adroit 

 workman, he fixes it, as it were in a vice, in some cleft of a tree, 

 or in some crevice ; when, standing over it, he perforates the 

 stubborn shell. We have often placed nuts in the chink of a 

 gate-post where nut-hatches have been known to haunt, and have 

 always found that those birds have readily penetrated them. 

 While at work they make a rapping noise that may be heard at a 

 considerable distance. 



You that understand both the theory and practical part of 



