416 ANIMAL LIFE IN THE YO SEMITE 



pancy of the hig-her level continues until fall, as on October 9 (1915) 

 several were seen at Ten Lakes. In 1920 the species remained in Yosemite 

 Valley at least until October 9 (C. W. Michael, MS). Meanwhile those 

 of the species which have remained at the lower levels gradually assemble 

 in flocks. The approach of winter drives down those individuals which 

 have invaded the mountains and they join the bands in the lower valleys. 

 By December or January the flocks often number hundreds and not 

 infrequently thousands of individuals. At Snelling* about one thousand 

 of these birds were seen on the afternoon of January 2, 1915. They were 

 perching on the telephone wires and in the cottonwoods near the river. 

 On January 7, 1915, 1200 were recorded in a three and a half hour 

 census. "Great clouds" were the words used to describe their numbers 

 and the notebook entry states that in addition small flocks were continually 

 passing overhead. Below Lagrange a flock of fully 500 was seen on 

 December 22, 1915. 



East of the Sierras gatherings of the same sort are to be seen, although 

 they do not involve such large numbers. On September 13, 1915, fully 

 200 birds were seen in the vicinity of Silver Lake and in the adjacent 

 sagebrush. At nightfall the birds flew in and roosted in the trees near 

 the lake, and in the morning, between 6 and 7 o'clock, they left in small 

 bands, flying down the cailon of Rush Creek to start anew the daily hunt 

 for food. 



During the summer months insects form the principal item of food 

 for the Brewer Blackbird. The young birds seem to be fed largely if not 

 exclusively on this sort of diet. The up-mountain movement of the birds in 

 summer is probably induced by the abundance of insect food then to be 

 obtained in the alpine meadows. At Silver Lake many of the blackbirds 

 were catching grasshoppers among the sagebushes. At Mono Lake, on 

 June 30, 1916, about 50 Brewer Blackbirds were seen feeding on the "Mono 

 Lake fly," myriads of which were hatching out on that date. The birds 

 seemed to be seeking certain individual adult insects, or perhaps the larvae, 

 among the great mass of debris, chiefly pupa cases, which lay along the 

 lake shore. Below Lagrange on December 22, 1915, a large flock of these 

 birds was seen following a gang plow and feeding on worms and insects 

 turned up from beneath the surface of the ground. 



