NESTS AND NEST-BUILDING IN BIRDS 337 



leads to the most eccentric forms of behavior, such as pulHng 

 down feathers from the young or offering them strings or similar 

 objects when the parent is prematurely seized b}^ the building 

 instinct, as explained more fully in earlier papers. We are 

 now ready to consider what logically comes first, the actual 

 building of the nest. 



6. NIDIFICATION: THE BUILDERS AT WORK 



After having criticised the literature of nest building, I wish 

 to point out a difficulty with which all students, who must 

 heed the clock, will have to contend. We are dealing here with 

 a strictly field problem, to which the motto, "Strike while the 

 iron is hot" admits of no exception; it is always " Now or never," 

 and no part of the subject can be taken to the laboratory for 

 leisurely study. In this latitude the best period for studying 

 the building beha\-ior of birds is from mid April until mid June. 

 Accordingly, the student should be able to devote many suc- 

 cessive days to continuous observation whenever the subject 

 demands it. 



In spite of such drawbacks, however, it would be difficult 

 to name a field in the province of behavior where the right 

 kind of study promises more interesting results the world over, 

 and where some of the phenomena to be witnessed close to 

 your door, may be as worthy of record as anything observed 

 in the forests of Brazil or of Africa. 



Without any doubt all builders of elaborate statant nests 

 go through the molding and turning movements in a fairly 

 uniform and stereotyped fashion, but it is safe to predict that 

 all which fashion pendent nests, or which smooth or garnish 

 the walls of their homes, especially when the sexes cooperate 

 effectively in the work, will prove well worth watching. 



Nest Building in the Robin. — The American robin of the 

 eastern states (Merula migratoria or Planesticus migratorius) 

 is an excellent exponent of the builders of statant nests of the 

 increment type, molding a perfect cup of characteristic form 

 and size, and commonly using mud or wet earth in such a way 

 that a consistent mortar is produced. When sun dried and 

 securely placed such nests long outlast the season. 



Choice of Nest Site. — So far as I have observed, the selection 

 of nesting site is a simple affair, and unattended with any im- 



