Architecture in the Animal Kingdom. 119 



Operation under the most different circumstances, and 

 is even to a certain degree improved by sensitive 

 experience, i. e., it is rnodified according to new per- 

 ceptions. True, many birds, too, are able to adapt to 

 changing circumstances^ the places and the materials 

 they choose for their nests ; nor can their instinct be 

 called mechanical automatism, because its activities 

 are governed by the sensitive cognition of the animal. 

 Many species of birds change the place and the 

 material of their nests according to locality; besides,' 

 the single individuals are not rigidly bound to a cer- 

 tain material for building their nests, but they fre- 

 quently employ scraps of paper, horse hair, cotton and 

 other materials, which happen to come in their way. 

 Those birds that build nests more or less open to view, 

 instinctively avoid materials the coloring of which 

 would set their nest into striking contrast with the 

 surroundings. In this they are evidently governed by 

 their power of sense-perception. Sometimes this pro- 

 tective resemblance of the nest with its background is 

 effected quite of itself, when birds use the material 

 for their nests, which is usual and natural to them; 

 but sometimes also unusual materials found by chance 

 serve the same purpose. Thus I was informed by a 

 friend:^ *Tn Blyenbeck (in the northern part of Dutch 

 Limburg) I had occasion to observe how chaffinches in 

 building their nest 'ingeniously' imitated the greyish- 

 white color of lichen which covered the tree on which 

 they built. They used small scraps of paper, and thu€ 



^) Several examples of the same are found in "Westfalens TTiier- 

 leben," Vol. II. Besides also in Darwin's posthumous essay on instinct 

 (Romanes, "Evolution in the Animal Kingdom," appendix). 



2) Rev. L. Dressel, S. J. 



