SIERRA JUNCO. Junco oreganus thurberi Anthony²⁸

Field characters.—A small sparrow (total length about 6 inches, tail about 2-1/2 inches long). Head, neck, and breast covered by solid black (most intense in males, grayish toned in females and immatures), sharply set off from white on under surface of body. Bill whitish-appearing. Back and wings dark brown, unmarked; tail black centrally, two outer feathers on each side pure white. Juvenile birds lack the black 'cowl' and have the whole head and body, both above and below, streaked. When on ground, hops about rapidly in zigzag course; if flushed, rises quickly, spreading tail so that white margin shows conspicuously; usually takes refuge within nearby trees or large bushes. Voice: Song of male a quavering trill, metallic in quality, rapid in utterance, eetle, eetle, eetle, eetle . . . . continued for from one to three seconds, weakening in intensity toward the end; repeated at irregular intervals. Call of both sexes a low seep or sharper tsick; one of these notes often given several times in quick succession as birds of a family or flock rise from ground.

Occurrence.—Abundant summer visitant throughout the Transition, Canadian, and Hudsonian zones on both sides of Sierra Nevada. Recorded in summer from 3 miles east of Coulterville and from Bullion Mountain eastward across the mountains to Parker Creek (at 7500 feet) and Warren Mountain. As a rule the range of this bird is limited altitudinally at timber line; the highest elevation at which we saw it was 11,000 feet on Parsons Peak, September 6, 1915. In winter descends to below the level of heavy snow, occupying the whole of foothill and lowland country; a few may remain as high as Yosemite Valley. Found in numbers in winter at El Portal and 6 miles east of Coulterville and from there westward to Lagrange and Snelling. In summer lives in and about openings in forest or along open stream banks; in winter ranges widely, but not onto open prairie. In pairs at nesting time, but in flocks of varying size during other parts of year.

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²⁸In addition to the prevalent Sierra Junco there is present in winter in small numbers another subspecies of the 'Oregon' Junco, the Shufeldt Junco, Junco oreganus shufeldti Coale, which summers in northwestern North America interiorly. This race has the wing and tail somewhat longer, the sides more dusky (less pink tinged), and the back of a duller brown than has the Sierra Junco. Specimens are at hand from Dudley (on Smith Creek), six miles east of Coulterville, taken December 25, 1918, and January 27, 1919.

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The Sierra Junco or Snowbird has proved, by actual census, to be the most abundant species of bird in the Yosemite section. During the summer season it is common throughout the forested portions of the mountains embracing the Transition, Canadian, and Hudsonian zones, on both slopes, while in winter it is abundant in the Upper Sonoran foothills of the west slope, and occurs in some numbers in the Transition and Lower Sonoran zones as well. Because it is thus a species of wide occurrence, and in addition possesses a distinctive type of coloration, we have chosen it for our standard of comparison in discussing the other small birds of the region.

The whole forepart of the Sierra Junco's body is covered by a solid dark cowl, jet black in the adult males, but grayish toned in female and immature birds. This black ends below abruptly against the white of the belly. The back and wings lack contrasted markings of any sort, but when the bird takes to flight the tail is seen to be broadly margined with white. The young in the juvenal plumage, which they acquire in the nest and wear until the first fall molt, are streaked over the whole body, and they lack any indication of the black cowl, but their white outer tail feathers are just as conspicuous as those of the parent birds. The middle of the back and sides of the body are reddish brown in the adult Sierra Junco, a feature which helps to separate this species from the near-related Shufeldt and Slate-colored juncos. No other bird is likely to be confused with the junco. The Spurred Towhee has a black cowl similar to that of the junco, but the former is a much larger bird, has white spots on the black wings and tail, and stays almost exclusively within heavy brush, instead of foraging out on open ground.

The Sierra Junco, in summer, is found throughout the main forest belt of the Sierra Nevada. It eschews dense growths of timber, preferring to live in clear areas beneath the larger trees or between tracts of timber, but always where there is convenient cover close by, to be sought if danger threatens. The bird gains the greater portion of its forage on open ground and nests there, but it uses the trees and large bushes as song perches and as safety refuges. In winter a lesser degree of restriction in habitation is evident, for then the juncos invade all sorts of vegetational environments save open prairie where no cover of any sort is available.

The total junco population on the Sierra Nevada during the summer months is in excess of that of any other one species of bird. Three to five an hour will usually be seen at this season in any part of its range, save perhaps in Yosemite Valley. The Sierra Junco is outnumbered by the Western Chipping Sparrow on the floor of the Valley, but it is much better represented in the zones above, especially in the Canadian. The junco population is larger, relatively as well as absolutely, on the west slope of the Sierras than on the east slope. The winter distribution is less uniform. Then the birds are in flocks and their inclusion in a census depends upon the observer's meeting one of these companies, which may aggregate 15 to 50 birds.

Many juncos remain in the highlands through the crisp fall weather, and the birds are then present literally in droves in the red fir territory immediately above and surrounding the Yosemite Valley. But the first flurry of snow, forecasting the approach of winter, starts them down-slope rapidly and soon relatively few remain even as high as Yosemite Valley. Some depart for the lower altitudes by October; these are joined later by those which linger until they are literally forced out of the high mountains by the snow mantle which covers up their food supply there. The bulk of the population at this season is concentrated in the foothills, but some go down still farther to the west, into the San Joaquin Valley. It is during the fall and winter months that individuals of the Slate-colored and Shufeldt juncos are occasionally encountered in flocks of the Sierran birds. These have probably traveled all the way from summer localities in British Columbia and beyond.

In the fall of 1915 we remained in Yosemite Valley through the first real snowfall of the season which began on the evening of November 8 and continued into the following day. On the morning of the 9th juncos were in active migration down the Valley. They did not fly along continuously nor did they alight in the snow, but from the clear ground about the base of one thick-foliaged tree they dashed on a few rods to another similar shelter and hopped about there for a minute or so before moving farther. Each individual was moving independently, yet all in the flock were going in the same general direction. One bird would fly ahead, loiter a minute, and be passed by others previously left behind, and so on. At any one point there would be a rapid succession of juncos while the flock as a whole moved more slowly. It was quite evident that the birds from the plateau above the Valley were migrating down-slope and westward, as more juncos were seen on that morning passing one place on the north side of the Valley than had been seen all told in the preceding month on the whole floor of the Valley.

On December 26 and 28, 1914, when the early snows of that season had largely melted off on the north (sunny) side of the Valley, several companies of juncos were observed there, and it is possible that amelioration of conditions had led them to come in again from the westward. Some of the birds were around the buildings of the old Presidio, foraging far back within the open basements. Subsequently, a resident of the Valley reported that about 25 juncos had stayed around his house during the winter of 1915-16, as he thought, because of the food continually put out for them.

In general demeanor the junco is more active than many of the sparrows. On the ground it gets about with quick movements, turning first to one side and then the other, but not often hopping many paces before stopping to examine its surroundings. It does little scratching, and indeed neither its claws nor its bill are of the stout type found in birds such as the fox sparrows which dig out their food. The Sierra Junco, like the Western Chipping Sparrow, is a surface forager and gets its provender by moving about rapidly and scanning a relatively large area of ground. This is as true of the members of a winter flock as of individual birds in summer.

When frightened, a junco flies directly to cover, taking shelter usually within trees or large bushes. Its general procedure is to fly along a short distance above the ground, usually reaching the nearest foliage at the first flight; then, after a pause, and some hopping about from branch to branch, it descends again to the ground near by. If badly scared the bird will make off to a distance, though usually going from one tree to another rather than making a continuous, direct flight in the open.

While foraging on the ground a junco opens and shuts the tail slightly from time to time, so that the white margins show for an instant. Upon taking flight either from the ground or a tree the bird spreads its tail widely and then the white shows broadly and conspicuously. Some naturalists believe that the bird's flashing of these contrasting areas serves to apprize other members of the species of the particular individual's location and of the direction taken by it when it moves off; any threatening danger seen by one bird may thus be reported to other juncos in the vicinity which, in turn, seek safety. Accompanying the display of white when an alarmed junco flies up are the well-known call notes given in rhythm with the wing-beats and movements of the tail; and these notes are believed to be of similar purport. The sense of hearing is thus brought into service to supplement that of sight.

The song of the male junco is to be heard throughout the spring and early summer months; it usually ceases some time in July. It is a quavering trill, pleasing to the human ear, given rapidly and possessing a tinkling quality. The syllables are practically alike, eetle, eetle, eetle, eetle, on about the same key, but with the intensity lessening toward the end. In spring the male gives his song at practically any hour of the day, perhaps not so much at dawn and dusk as during the mid-day hours. Yet we have heard it as early at 5:15 A.M. (June 2), in Yosemite Valley, and sometimes the birds break out in song in the middle of the night. The sharp call note, seep or tsick, uttered by both sexes, is usually repeated several times as the birds rise from the ground, and if given while foraging there, its utterance is often accompanied by momentary flashing of the white outer tail feathers. A heavier note, of alarm, is also given, tsup.

The courting of the junco is not so elaborate or varied a performance as that of some birds. The pursuit of females by males or of rival males by one another may occasionally be observed, but for the most part the birds are rather quiet. Occasionally males either on the ground or perched, when females are close by, will hold the tail spread for some seconds so that the white margin shows forth with extraordinary brilliance. The song seems to be the principal factor in courting. In order to study this subject satisfactorily, an observer would need to keep track of flocks just before they break up in the spring and then watch the behavior of the pairs during the whole course of the development of the mating instincts.

When the first rush of human travelers reaches the Yosemite region in May the juncos are preparing to nest, and by early June many pairs of the birds have their nesting well under way. Our earliest record of a completed nest with eggs was made on June 10 (1915) at Chinquapin. But earlier instances will doubtless be found upon further search; for we saw a bird carrying nest material on May 20 (1919). The peak of nesting activity is reached in June, during which month, in 1915, we found, without special search, over a dozen nests. The first young noted out of the nest in that year were observed in Yosemite Valley on June 21, soon after which new broods were common. But nesting does not cease at an early date. Either some pairs are delayed, through accident or other cause, or else they rear more than one brood. A nest found at Merced Lake on August 20, 1915, held two young not old enough to fly; and bob-tailed youngsters were seen near Washburn Lake on August 24 the same year.

The majority of the nests observed were located either at the margins of wet meadows, or along open creek banks. The birds seemingly prefer to be able to fly to and from the nest unimpeded by vegetation. The nest is a compactly woven cup, about three inches in outside diameter and the same in depth. It is almost invariably sunk in the ground so that the rim is flush with the surface. Sometimes it is placed at the side of a log or beneath a fallen branch, but as often it is on open ground amid the grasses, and one nest was seen in the center of a traveled road. As an exception to the general rule may be cited a nest placed on an overhead beam under the roof of a painted cottage porch in Yosemite Valley. This nest was bulkier than usual, and the materials composing it straggled down the side of the beam. It was evidently built in good faith because two eggs were laid ere a gust of wind cast it to the ground.

The average nest is composed largely of small plant or grass leaves and stems compactly woven together. The larger pieces are on the outside, and the size of the pieces of material gradually decreases as the center is approached. The inside lining is usually of horse hair, but occasionally shed hairs from some of the native mammals are used. Four is the usual number of eggs laid and no more than this complement were seen in any nest examined by us. Sometimes but three seemed to constitute the completed set.

During the summer the members of a pair of Sierra Juncos keep in close company, and if the vicinity of their nest is approached the two will often exhibit a high degree of concern. If the female is incubating she will usually leave in a flurry, with the tail widely spread (whereby the eye catches the white quickly), and then trail along the ground, giving an appearance of being injured in an effort to focus interest upon herself and draw attention from the nest. Soon the male, if not already at hand, will appear and the two will hop excitedly about either on the ground or among the low branches of an adjacent conifer, repeating their call notes with an intonation which suggests extreme anxiety.

After the broods are reared the adults continue to guard and care for their charges for some time; in some cases, at least, the family stays together through the fall molt. From this initial grouping it is but a step to the formation of the flocks in which the birds spend the winter. Flock formation persists until the birds seek their nesting grounds again the following spring.

From late April until July pairs are the rule. Then young begin to appear in numbers and family parties are of common observation. Such groups were seen at Merced Lake on August 23, and in Yosemite Valley even as late as September 24 (1915). Flock formation is under way about the latter date; one band of 20 was seen in Yosemite Valley on September 25, and several of 20 to 50 each in Tioga Pass, September 28, 1915. The flocks hold together through the winter months, sometimes becoming mixed with those of Chipping Sparrows in the valleys, but more often keeping by themselves. At Pleasant Valley on February 27 and 28, 1916, bands of 12 to 35 were seen; and a flock of 15 was observed in Yosemite Valley on February 29 the same year. By April 27, the time of our next visit, the lowlands were cleared of juncos, and the birds seen in Yosemite Valley on April 28, 1916, were not in flocks. On May 14, 1919, juncos at Hazel Green were paired and the males were trilling their songs.