BBEWEB SPAEEOW 457 



the first were observed, near Williams Butte, on May 6, although they 

 may have arrived there somewhat earlier. Southeast of the Mono Lake 

 region the migration begins in late March or early April. 



On September 18, 1917, Mr. Joseph Mailliard (1918, p. 17) identified 

 one of these birds among some Western Chipping Sparrows on the floor 

 of the Yosemite Valley. 



Throughout the summer months Brewer Sparrows are to be seen every- 

 where in the sagebrush country perhaps more commonly than any other 

 bird species. In early autumn the number of birds about Mono Lake 

 seems to be augmented, either by the arrival of migrants from the north 

 or by a post-aestival movement toward the Sierras from the drier flats 

 and valleys to the east. Whatever the cause of increase in local population, 

 our censuses at that season record 10 to 36 of these birds an hour in 

 sage-covered areas. The Brewers were still abundant when we quitted 

 the Mono Lake country on September 23, 1915. The wintering grounds 

 of these birds are on the deserts of the Southwest and so their migration, 

 whatever the date of departure from the Mono region, is not a very exten- 

 sive one. 



A nest of the Brewer Sparrow was found only about 10 inches above 

 the ground in a sagebush near the mouth of Rush Creek on June 3, 1916. 

 It held two blue eggs, far advanced in incubation ; the sitting bird flushed 

 as the observer grazed the side of the bush in passing. On June 30, 

 1916, adults were seen carrying food to young in the nest. The young, 

 with the streaked breasts of the juvenal plumage, do not appear abroad 

 in numbers until slightly later, that is in July; by the middle of August 

 many of them have already completed the fall molt which brings them 

 into a plumage almost exactly like that of the adults. 



Brewer Sparrows occasionally work up into the high eastern portions 

 of the Sierra Nevada in much the same way that many other kinds of 

 birds which nest at the west base of the mountains move up to Yosemite 

 Valley or beyond in late summer. But with the Brewer the movement is 

 not so general and when the birds do thus appear out of their normal 

 range they seek out, and keep close to, their accustomed shelter plant. 

 On August 25, and again on September 5, 1915, flocks of a dozen or more 

 of these sparrows were seen in some stunted sagebrush on a sun-heated 

 gravelly bench between Echo and Sunrise creeks, not far from Merced 

 Lake. 



