BO BIRDS IMPROVE IN NEST-B.UIBB1NG ? 487 



to shut up in an enclosure, with a wire screen overhead, a pair of birds 

 brought up in isolation from their kind, with a view to find out what 

 manner of nest their inexperienced efforts would produce. But, even 

 though we have not such evidence, there are plenty of other proofs 

 which confirm Mr. Wallace's theory. 



The form and structure of birds'-nests are more dependent than 

 is usually supposed upon external conditions, and consequently they 

 vary in proportion as these conditions are changed. Each separate 

 species employs the materials it has at hand, chooses sites most 

 agreeable to its habits ; and the shape given to the nests often betrays 

 very definite purposes, which are not to be detected without some de- 

 gree of discernment. The wren, which dwells in hedge-rows and 

 thickets, commonly builds its nest of the moss in which it is accus- 

 tomed to search for insects ; but at times it departs from this custom, 

 and employs feathers and hay, when they are to be had. The raven, 

 which feeds on carrion, frequenting pasture-grounds and warrens, 

 builds its nest of wool and fur ; the lark builds in a furrow, employ- 

 ing dry twigs, interwoven with fine blades of grass, which it collects 

 when looking for worms ; the kingfisher uses the bones of fishes he 

 has eaten. The long-legged and big-beaked flamingo, which stalks 

 about in wet flats, builds a conical hillock of mud, and in this de- 

 posits her eggs, so as to sit easily upon them, and to keep them out of 

 the water. 



In what respect are these animals, which avail themselves of the 

 circumstances around them for a perfectly determinate object, inferior 

 to the Patagonian, who builds for himself a rude shelter of foliage ; or 

 to the African negro, who scoops out a hole in the ground ? It will 

 be said that man progresses : but that is not universally the case. 

 What progress is shown in the palm-leaf huts of American savages, 

 the tent of the Arab, the Irish mud-cabin, the stone hovel of the Scot- 

 tish peasant, which appear to belong to primitive times ? The art of 

 house-building remains stationary, if it is in conformity with tastes* 

 and habits which are unalterable, because the physical conditions 

 which determine them are ever the same. Sometimes even a habit 

 once engendered persists, though the exterior conditions be changed. 

 The Malays from time immemorial built their houses on piles, after 

 the manner of the lacustrine dwellings of ancient Europe ; and this 

 mode of building has sunk so deep into the manners of tribes which 

 have penetrated into the interior of the islands and settled on arid 

 plains, or on rocky mountains, that they still go on prudently raising 

 their houses above the surface of the ground. And yet, no one ima- 

 gines that in these inveterate habits we have a case of instinct ; and 

 certainly no one would suppose that an Arab infant brought up in 

 France would feel the need of dwelling in a tent of skins, or that a 

 young Malay, if brought to Europe, would bring with him his habit 

 of building on piles. The unvarying processes of barbarous tribes are 



