IV. 



BIRD ARCHITECTURE. 



A DEFICIENCY IN FACTS. 



Certain classes of data are needed in respect to all 

 our birds, — even the commonest, — relating to their 

 breeding season. Among these may be suggested 

 memoranda through successive seasons and at various 

 localities, of the dates when nest-building is first 

 begun by every species brought under observation. 

 Out of such memoranda would grow a better knowl- 

 edge than we now hold of how far differences of 

 latitude, altitude or other physical situations, and the 

 conditions of weather (as a late or an early spring) 

 affect the breeding habits of the bird. Much, per- 

 haps, is asserted in regard to all these points in our 

 books, but little is actually known and guaranteed. 



Then there is the enquiry into the diversity ob- 

 servable in the method of nest-building and in the 

 use of material. An example of this variability has 



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