1054 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



become active and increase in size at a faster rate than those of the 

 migrants. 



Courtship. — References in the literature to courtship are sparse and 

 fragmentary. Perhaps this is because courtship often begins in the 

 flock, and unless an observer has long acquaintance with a particular 

 flock he hesitates to record the actions of a lively group of small birds 

 that look quite alike superficially. 



A. H. Miller (1941b) describes a male junco courting a female 

 with young, replacing a male that had been collected. While the 

 particular reference pertains to the race mearnsi, I can find nothing 

 to indicate the other Oregon junco races act differently. Miller 

 writes: "A new male was on hand, singing, following her with tail 

 fanned, and twittering in characteristic mating behavior." Miller 

 also had some pairs of juncos in an aviary, and in an additional 

 comment, he writes (pers. comm,): "What was observed there, of 

 course, may have been more a matter of pair formation than actual 

 courtship prior to copulation. However, the tail spreading and twit- 

 tering certainly comes in at that early stage of pair relations. In 

 the cage I saw copulation at least once, and there was no conspicuous 

 behavior preceding it — that is, no special notes or performance." 



Just when the mating process began in the flock Winifred S. Sabine 

 (1955) studied was not learned; but she did notice an increasing 

 tendency for the two mated birds to arrive and depart from the feed- 

 ing station together, and that as spring approached the dominant 

 male showed an increasing intolerance towards juncos other than his 

 mate. Mrs. Sabine (1952) suggests that though she observed no 

 courtship gestures as such, probably her observations were incomplete 

 for she "has seen them in a different pair of the species and also has 

 seen elaborate displays in a migratory flock of J. hyemalis." 



Among spring flocks of foraging juncos, an individual bird may 

 detach itself, fly a more or less brief circle, and alight not far from 

 whence it started. More often than not another junco will give 

 chase, as it were, flying the same course. A person observing the 

 the flight is immediately aware of the flashing white outer tail feathers. 

 Whether or not this behavior should be interpreted as courtship 

 needs further study. 



Nesting. — I have never found nesting pairs at any great distance 

 from water. The water may be a small seep or a minute trickle 

 from a melting snow bank, but it is water. 



Junco nests are usually on the ground in a cup-shaped depression. 

 Typically they are made of grasses or fine stems and placed at the 

 base of a shrub or plant. Animal hairs are often incorporated into 

 the nest structure or used for lining. Chester Barlow (1901) writes 

 of nests in the California Sierras built on the ground in the sides of 



