370 FRANCIS H. HERRICK 



intelligence. As to the " prudence " of the house martin we 

 should compare the contrary notice of its stupidity mentioned 

 earlier (see Part II, p. 255). 



Cooperation in Nest-Building. — In the building of a nest to 

 be used by a single pair of birds, the work may be performed 

 by one or both sexes, though commonly devolving upon the 

 female alone. So far as I have observed, when both sexes co- 

 operate effectively, they act alone, and usually in silence. The 

 occasional bringing of materials by the male, as in the case of 

 the red-eyed vireo, as noticed above, to be immediately taken 

 and used by his more active mate, may be compared to the 

 bringing of food by the cock after the young are hatched, and 

 its prompt service by the hen, a fact which we have recorded 

 in a number of species. That swallows or any other birds 

 which are gregarious during the nesting period cooperate in 

 such a degree that several adults unite in the effort of building 

 a single nest for the use of a single pair, as has been reported 

 by various writers, is undoubtedly an error. 



7. INTELLIGENCE IN NEST BUILDING 



There is no doubt either that instinct furnishes the springs 

 of action in birds, or that their instincts are extremely complex 

 and in a high degree adaptive. Nor is it to be further ques- 

 tioned that this innate equipment takes the place in large 

 measure of mind or intelligence. We have used the latter term 

 in the sense of the power of learning by individual experience, 

 or of forming habits, by which we designate fixed ways of action, 

 not innate. We know that by the aid of intelligence an animal 

 can lead a fuller and more successful life, and we assume that 

 in some unknown way its more A^ariable intelligent responses 

 have arisen from its more uniform instincts. 



Do birds display exceptional intelligence in building their 

 nests? The answer is No, but if the impression has been con- 

 veyed that at this time birds are more the slaves of instinct 

 than at any other, it is probabh^ erroneous. No time or period 

 is favored in this respect, except to the extent that the keener 

 the impulses to action, the more uniform the conduct. In 

 nest-building instinct boldly outlines behavior, and may in- 

 deed be responsible for many of its complex details, while certain 

 shadings and variants of no mean import, are as surely the 



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