306 U. S. NATIONAL MUSEUM BULLETIN 211 



be feeding there also. Although the flock may be all together, pairs 

 can be detected within the group walking together and maintaining a 

 fairly constant interval between the male and the female, which is less 

 than the distance to the next pair. Suddenly they all flush and the 

 pairs bunch together into a flock and fly off. Often the flock circles 

 about and alights on the wires. If the members of a pair do not 

 happen to light together individuals shift their positions on the wire 

 until the flock is sorted pair by pair. Thereupon mutual display 

 starts again. 



Individual pairs vary as to the date when they commence to act as 

 a pair. Also there is a gradual increase in the time that pairs spend 

 in segregation and a corresponding decrease in the time spent in the 

 flock. Although pairing behavior may start as early as the end of 

 January, there are brief intervals in the day when the birds revert to 

 flock formation even as late as April. 



Constancy in pairing behavior with the same mates is also arrived at 

 gradually. Members of old pairs are less frequently involved in pair- 

 ing behavior with individuals other than the "proper" mate and thus 

 they tend to be constant from the beginning. New pairs, however, 

 perform pairing behavior with other birds in many instances until 

 finally the "true" pair forms and remains constant through the re- 

 mainder of Phase 1. This is not to say, however, that after pairs are 

 formed, mated males do not respond to the displays of a neighbor's 

 female, as indeed they do. Females perform the generalized display 

 more and more frequently as Phase 1 progresses, even though copula- 

 tion is in the future. The intruding male responds to this display by 

 approaching in the ruff-out or even pre-coitional display, or he may 

 just walk or fly toward the female. But the female is constantly 

 guarded by her mate, who drives off the intruder, either by flying 

 directly at him, or walking deliberately head-up, between the female 

 and the intruder. The latter responds with the head-up display and 

 both, still holding this posture, walk stiffly abreast of each other away 

 from the female. Sometimes both males shift to the ruff-out and re- 

 main facing each other, exchanging this display. When they do, this 

 the action looks very like a pair in mutual display (there is no head-up 

 in mutual display, however). Rarely, a fight occurs when both males 

 flutter up together and peck and claw at each other. 



After the pair is formed the members are almost always together, 

 becoming separated only for brief intervals. The male guards his 

 mate from the approaches of other males with increasing constancy. 



In Phase 1 there is some toying with nesting material by both sexes 

 and even carrying it to a site. The male of the pair is sometimes the 

 first to hold nesting material in the bill, but he rarely places it at a 

 nest site. Actual nest construction is accomplished almost entirely 



