NESTS AND NEST-BUILDING IN BIRDS 



359 



Building operations ceased on the first da}^ at 6.27 p. m., 

 after they had been watched for 17 minutes, and after proceeding 

 for possibly an hour or more. The behavior was essentially the 

 same at each visit, the bird bringing of ten but a single fiber, carry- 

 ing it around the support and working it into the nest-mass by 

 what we shall call " shuttle movements " of the bill. Standing 

 upon the twig or clinging to it in any position, and holding the 



Figure 21. The same oriole's nest after about ten hours of constructive work, 

 showing rim formed, and nest-wall blocked out with the exception of one 

 open side. Bottom and upper web between second and third points of attach- 

 ment very thin; outer wall characterized by long streamers which are later 

 withdrawn and worked into the wall from the inside. Sketch made at 1 p. m.. 

 May 15. 



thread, the bird, makes a series of rapid thrust-and-draw move- 

 ments with the bill. With the thrust the first fiber is pushed 

 through the mass; at a second thrust either that fiber or 

 another is drawn back. IVIost of the threads brought at a later 

 time are treated in this way, that is, the}^ are worked 

 into the primary nest mass by one end, and left with the other 

 hanging free. But again one end of a strand being fixed in 

 the way described, like a flash the other end is picked up, passed 



