EDWARD BURGESS. 65 



ing that somehow they could note the recurrence of every 

 fourteenth day, and to do this they must have had some 

 idea of time. 



The instinct of nest building is very curious, not the 

 mere fact of building a nest, but that the different kinds 

 of birds should have such different ways of doing this. 

 Wallace says that nest building is not an inherited in- 

 stinct but comes from imitation. The young birds 

 observe the nest in which they are reared, and after they 

 have left it, construct one like it when the proper 

 time comes around. But Romanes very truly says that 

 if this were so, nests of the same varieties would differ 

 widely, since, if they were reproduced by imitation alone, 

 there would be continual variations, which if copied in 

 turn, would eventually quite alter the style of the nest. 

 It is well-known that the nests of each variety remain 

 substantially the same, although it is perfectly true that 

 birds do profit by experience in this, and that the nests 

 of older birds are much better made than those of younger 

 ones. No ! nest building is in the main an inherited in- 

 stinct, but capable of being improved upon by experience. 

 But why they should vary so with the different kinds of 

 birds is quite curious. 



The petrel, kingfisher and land marten, make their 

 nests in burrows in the earth. Grulls, sand-pipers and 

 plovers lay their eggs in shallow pits, excavated in the 

 soil ; partridge and quail build upon the ground also. 

 The house martin builds its nest of clay, which it fastens 

 to the side of the wall ; only the forenoon is devoted to 

 this work, for the reason that if the nest is built too fast, 

 being made of soft material, it would crumble with its 

 own weight, unless it were allowed to harden. The 

 woodpecker and tom-tit dig a hole in a tree, and care- 

 fully carry away the chips to conceal their home. The 

 woodpecker's hole is sometimes five feet deep and of a 

 tortuous form to keep out the wind and rain. 



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