CASSIN'S SPARROW 983 



Spring and courtship. — Although a few Cassiu's sparrows roinain 

 in southern and western Texas throughout the winter, they are not 

 conspicuous until the last two weeks of March when they begin 

 singing. It is assumed there is a movement of migrating birds into 

 the area at this time, though possibly the birds may be present several 

 weeks before they begin singing. The first songs are very soft, and 

 are usually given from an inconspicuous perch. As the season pro- 

 gi'esses, the males sing loudly from the highest perch available. 



Territorial defense is carried on by song duels between males. If 

 only one male is in the area, he usually sings from the top of a bush. 

 As soon as another male arrives, the first male begins singing in 

 flight and the second male replies. On one occasion, as male "A" 

 was singing, male "B" began singing about 1,500 feet away. "A" 

 rose into the air to the height at which he usually sang, then flew 

 steadily in the direction of "B." As he flew, he twice rose slightly 

 in his flight and sang. When he was about 50 feet away from "B," 

 he lit on the top of the tallest bush, where he sang three times. "B" 

 flew up twice, singing, but did not approach "A." "A" then flew 

 back until he was again in his own territory. 



On another occasion, two males were singing only twenty feet 

 apart. Each was singing in flight — first one, then the other, flying 

 up. Then, as male "X" was floating down to his perch, male "Y" 

 flew rapidly toward him, calling tzee, tzee, tzee, tzee. When "Y" 

 was about five feet away, "X" retreated to a more distant perch and 

 "Y" turned abruptly back to his own perch. Behavior like that of 

 "A" and "B" is more common, while active defense of territory 

 such as that shown by "Y" is rare. To date no actual physical contact 

 betw^een two males has been observed. 



Several authors have commented on "colonies" of Cassin's sparrows, 

 including Mrs. Bailey (1928) and J. Van Tyne and G. M. Sutton 

 (1937). It is true that this species concentrates in favorable areas. 

 But on the south plains of western Texas, cassinii is plentiful every- 

 where in uncultivated areas and gives no impression of coloniaHsm. 

 The extent of territory one male defends varies considerabW. In 

 a census of a 50-acre tract north of Midland, Texas, three pairs were 

 found to have territories whoUy within the tract, and four additional 

 pairs had territory partly within the area. Another 20-acre tract 

 contained only one pair, and both members of the pair ranged over 

 most of the territory. 



During courtship pairs of Cassin's sparrows spend much time 

 flying about their territories, just above the tops of the bushes. 

 Both the male and female give rapid "tzee-tzee-tzee" calls as they 

 chase each other around. Occasionally after a male has flown up 



