BREWER SPARROW. Spizella breweri Cassin

Field characters.—Size, proportions, and coloration close to those of Chipping Sparrow. No reddish brown on crown or distinct light line over eye. (See pl. 8e). Top of head, like back, brownish gray streaked with black; lower surface plain ashy white. Voice: Song of male more varied and more musical than that of Chipping Sparrow, remindful of some themes in song of tame canary; call note, a weak tseet.

Occurrence.—Common summer visitant along east side of Sierra Nevada, in vicinity of Mono Lake. Recorded from Silver and Walker lakes eastward. Occurs, also, in spring migration, along west base of Sierra Nevada, as at Lagrange (May 6, 1919) and Smith Creek, east of Coulterville (March 23, 1916). Noted in Yosemite Valley, September 18, 1917 (Mailliard, 1918, p. 17). A few appear at higher altitudes in early fall, as near Merced Lake (August 25 and September 5, 1915). Habitually in sagebrush. In pairs while nesting; in loose flocks at other times.

The Brewer Sparrow is a common and characteristic summer visitant in the great inland sea of sagebrush which covers the floor of the Great Basin. It is a near relative of the Western Chipping Sparrow, but wears still duller colors, having none of the bright markings on its head which characterize the latter bird. (See pl. 8e). The general tone of its whole coloration is subdued to a pale tint of gray which closely matches the gray color of the brush in which it lives.

The time at which the Brewer Sparrow arrives in the Yosemite region has not been ascertained closely. Birds which were undoubtedly migrants were observed at Smith Creek, 6 miles east of Coulterville, on March 23, 1916, and near Lagrange, on May 6, 1919. About Mono Lake, in 1916, 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 everywhere 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 extensive 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.