490 U.S. NATIONAL RIUSEUM BULLETIN 23 7 part i 



One nest on the Hastings Reservation was 20 feet up in a slender 35- 

 foot blue oak on a steep east-facing slope. Observations were made 

 here on the mornings of May 19 and 20. The nest was supported by 

 small twigs and it was partly exposed. Building was by the female 

 only, but the male was nearly always close by singing while she worked. 

 The two birds seemed markedly aware of each other. The male ap- 

 peared distressed when the female was not close b}'^, and he nearly 

 always followed her when she left the nest tree, but not when she 

 collected material nearby. Her trips were in a different direction 

 each time. Much of the material was lichen {Ramalina reticulata) 

 picked from tree branches. 



The second morning the female brought only small pieces of plant 

 material, but she spent much time working around the nest and pres- 

 sing her body against the sides. In midmorning she brought feathers. 

 Throughout the nest building the male continued to sing while the 

 female worked. He sang in flight when following her, but more 

 persistently when perched near her at the nest. On the first morning 

 the song was spontaneous, not in answer to any other male, and was 

 usually delivered from one of several particular branches in the tree. 



During this period each member of the pair often drove off strange 

 goldfinches. The male was quick to chase other males, and the female 

 pursued other females and sometimes strange males. Yet once another 

 pair stayed in the vicinity of the nest for 5 minutes undisturbed, and 

 another time a strange male followed the pair in and perched and 

 sang within 3 feet of the nest while its owners paid no attention. 

 Later the nestmg pair followed a strange pair into the tree; the strange 

 female drove off the female owner while the two males perched 9 

 inches apart without apparent antagonism. 



The flocking habit is so strong in Lawrence's goldfinch that a late 

 nest-building pair was regularly followed to the nest by one or more 

 goldfinches, usually of the same species, but sometimes by a green- 

 backed. While the nesting pair usually made some attempt to drive 

 out the strangers, their pursuits tended to be mild and did not extend 

 far. Evidently the impulse to follow other birds in fUght and to join 

 other individuals in a flock prevented the establishment of rigid 

 isolation by the nesting pair to the exclusion of all other birds of the 

 same species or even of the same sex. 



Eggs. — The number of eggs runs from three to six with four or five 

 most frequently comprising the set. They are ovate in shape with 

 some tendency to rounded ovate, and have very little lustre. They 

 are very pale bluish-white and unmarked, although an occasional 

 egg may be found with a few very small reddish brown spots. 



