1298 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



Courtship. — Courtship behavior includes both pairing and copula- 

 tion. The two processes may be separated by several weeks. Like 

 territory establishment, the elements of behavior involved in court- 

 ship are the same for all races. Such variations as occur involve the 

 duration of courtship behavior, its relation to the stage of the repro- 

 ductive cycle, and the length of time elapsing between pairing and 

 copulation. Except in Nuttall's sparrow, I have little or no evidence 

 of the permanence of the bond between mates. 



As with few exceptions the Nuttall's sparrows I watched at Berkeley 

 remained paired for life, only the immature and bereft adults sought 

 mates in the spring. The rising intensity of the male's song and of 

 the female's trilling and posturing thus may serve two different 

 purposes in courtship: either they bring together two unmated birds 

 and result in pairing, or they intensify the permanent bond between 

 members of a pair that bred together the previous year. In either 

 case the elements of behavior are the same. I shall describe them in 

 adults already paired. 



In January the female's interest in her mate gradually intensifies, 

 expressed by low metallic trills and wing fluttering. At first her 

 trilling is sporadic and seems to be called forth only by the loud song 

 of a male (not necessarily her mate) or by a chase or fight in which 

 the mate is involved ; it may or may not be accompanied by fluttering 

 of the wings. As the season advances, trilling and posturing are 

 almost invariably linked, and more and more often occur independent- 

 ly of any apparent external stimulus. Both actions increase in 

 intensity and frequency until the peak is reached some 6 to 8 weeks 

 later, just before copulation, in early to late March, depending upon 

 the year. As the female becomes engaged in nesting, both trilling 

 and posturing cease, to be resumed in lesser degree prior to copulation 

 for the second brood. 



The intensification of the male's interest in his mate, insofar as I 

 can judge from his behavior, is much more sudden. During January 

 and February he seems indifferent to her trilling and posturing. He 

 pays no special attention to her other than to forage with her and to 

 utter location notes as he has done throughout the fall and winter. 

 From early March, however, he punctuates long periods of indiffer- 

 ence by "attacks" upon the female. Suddenly, with no warning 

 that I can detect, his indifference changes to aggression. He chases 

 the female and jabs her with his beak. Such "attacks" take place 

 as much as 18 days before, and also a few days after, the first observed 

 copulation. Another change that precedes coition by from 1 to 3 

 weeks is the beginning of evening song. During the half-hour before 

 dark the male intersperses periods of foraging with faint singing, 

 which seems directed at his mate rather than at neighboring males. 



