984 U.S. NATIONAL MUSEUM BULLETIN 237 pakt 2 



as if to give his flight song, he instead gives the "tzee-tzee" call for 

 as long as it takes him to float to his perch. When the pair desists 

 briefly from the chasing routine, the male may assume a display 

 posture. He elevates and fans his tail, holds his head down, his 

 wings outward, then flutters his wings and tail. The female may 

 perch low in the same bush during the display. (The male and 

 female are distinguished only by identifying the male as he sings, 

 then keeping him steadily in view as he goes about his activities.) 



The following behavior of a courting pair was somewhat unusual: 

 A male sang steadily in one small area for 30 minutes. He sang both 

 perched and in flight. Suddenly a second bird flew up from the 

 ground, sat on top of a mesquite, hung its head, held its tail erect, 

 fluttered its wings rapidly, all the while uttering "tzee-tzee-tzee-tzee." 

 The singing bird was at the peak of his flight, and sailed downward 

 to light about 3 feet from the displaying bird. They immediately 

 took off together, flying about 2 feet apart, to a height at least twice 

 as high as the singing bird had been flying. They floated down, 

 landed in the grass some distance away, and were lost to view. 

 Neither sang nor called during this flight. 



In many hours of watching the behavior of Cassin's sparrows, the 

 authors observed copulation only once. The female was not dis- 

 playing or caUing, but was perched on top of a mesquite bush near 

 where the male was singing. The male flew to her from a perch, 

 not from his song flight. Probably the birds usually copulate while 

 on the ground where they are hidden from view in the grass. 



Nesting — The nest is situated on the ground at the foot of a small 

 shrubby plant or low bush; in a bunch of grass; among grass growing 

 in a brush heap. Or it may be in a low bush, seldom over 12 inches 

 from the ground. Often the nest is in the midst of a tangled patch 

 of the slender branching cactus Opuntia leptocaulis, where the nest 

 may be either on the ground or within the branches of the cactus. 

 Descriptions in the literature of nests of this species are about equally 

 divided between nests on the ground and nests above ground. 



L. J. Hersey and K. R. Rockwell (1907) found a nest near Barr, 

 Colo., in a Gutierrezia, or small rabbit-brush. "The nest was built 

 among the closely interwoven stems and branches of the plant, the 

 bottom of the nest resting on the groimd but not sunken into it." 

 Henry NehrHng (1896) wrote of this species in Texas, "The nests 

 which I had an opportunity to examine, were all placed on the ground, 

 near a tuft of grass or on the side of a low spiny cactus. A typical 

 nest found May 3, 1882, was built under the overhanging leaves of 

 the Yucca Jilamentosa in a mesquit prairie." George Finlay Simmons 

 (1925) writes of the nest sites he found near Austin, Texas: "On 

 ground among roots at foot of small, slender-stemmed rat-tail or 



