CALIFORNIA BUSH-TIT. Psaltriparus minimus californicus Ridgway

Field characters.—Size small, about one-third that of Junco; tail longer than body. Coloration plain gray, palest beneath; top of head inconspicuously brownish. No contrasted marks anywhere. Habits somewhat like those of chickadee. Voice: A low pst, pst, inflected variously under different conditions.

Occurrence.—Common resident of Upper Sonoran Zone on west slope of Sierra Nevada where recorded in nesting season from near Lagrange and at Pleasant Valley eastward to Smith Creek, six miles east of Coulterville, and to El Portal. Strays to higher altitudes in summer and fall months, as in Yosemite Valley, near Glacier Point, and on slope north of Mirror Lake. Recorded once east of mountains, at Williams Butte, September 22, 1915. Forages chiefly in foliage of oaks, sometimes in tops of the larger brush plants. In flocks of ten to twenty-five or so, except at nesting time when in pairs.

The California Bush-tit is a common inhabitant of the oak belt in the western foothills of the Sierra Nevada. It is one of the smallest birds found there, and is indeed one of the smallest birds in the Yosemite section, not much larger than a hummingbird. The California Bush-tit's coloration is of the plainest sort, dull gray with no contrasted markings anywhere. The top of its head is brownish, this being one of the features which separate the present species from the Lead-colored Bush-tit found on the east side of the Sierras; but this brown cap can be seen only at close range and when looked for especially. Certain individual bush-tits have the iris of the eye white though in the majority of the birds it is dark-colored. This is a peculiarity which does not seem to be correlated with age, sex, or season.

The bush-tit is characteristically a flocking species and for the greater part of the year the birds go in bands which number from ten to twenty-five or more individuals. The separation into pairs for nesting occupies the period from about late March through May. As soon as the young are fledged the family goes about as a unit, soon joining one or more other families to form the regulation flock.

The flock formation of bush-tits is not so coherent as that of blackbirds or sandpipers; each individual exercises a considerable measure of independence, especially in changing its location. A foraging flock is usually spread out through two or more trees and moves along slowly, the birds stringing along one after another, all going in the same direction from tree to tree, but no two moving at exactly the same instant. Those in the rear fly ahead and in turn are passed by their companions. While engaged in ordinary foraging the members of a flock keep up a series of faint notes which doubtless help to keep the band together. At times an individual will become absorbed in foraging in one particular place and be left behind his companions. The belated one then utters a series of notes quite insistent in tone, and as soon as he gets a response indicating the new location of the flock he hurries on in direct course to join the others once more.

In general behavior bush-tits remind one of chickadees. Individual birds when hunting food will assume any position, even that of hanging inverted from small branch or leaf. Their foraging is done very largely in the foliage of the live oaks, the leaves being scrutinized from all sides. The birds pay little or no attention to the larger twigs and branches, and they seldom fly out beyond the leafage as kinglets and Audubon Warblers are accustomed to do.

Mention of kinglets suggests making comparison between these two groups of birds, inasmuch as both are of small size, both feed among foliage, and they are to be found together in the foothill country during the winter season, though they summer in quite different zones. The bush-tit has a short thickish bill, the wing is relatively short, and the tail is decidedly longer than the body. The bird seldom flutters its wings and the members of a flock string along after one another in parallel courses. The kinglets, on the other hand, have proportionately, longer and more slender bills, and the wing is longer while the tail is as short as the body; they often twist about, end for end, and they do a great deal of fluttering of the wings. Only the Golden-crown, of the kinglets, is a flocking species, and its flock behavior is not at all like that of bush-tits. In point of color the Bush-tit is predominantly gray, whereas the kinglets are chiefly greenish-colored as to body plumage and each of the kinglets at least in the male sex, has special bright markings on the head.

The bush-tit is unlike its near relatives, the chickadee and titmouse, for it builds its own nest while both these other birds rear their broods within holes. The bush-tit's nest is an elongated pensile affair, 8 to 11 inches in length and 3 or 4 inches in greatest outside diameter. Entrance is gained through a hole on one side near the top, and the space within is tubular, flared somewhat toward the bottom. The whole cavity bears a suggestive resemblance to the interior of a woodpecker's nest hole, the sort of place so prized by chickadees at nesting time! The bush-tit's nest is composed of soft materials such as moss, lichens, spider web, and willow down, all of which is closely felted together. The structure is usually placed in an oak tree, at a height of 10 or 12 feet above the ground, and so attached that it hangs in or just beneath the crown of the season's new leaves. When engaged in building, and indeed at any stage in the nesting program, the members of a pair stay close about the nest site and make no effort to keep the location a secret. Their home is safe from the usual types of nest robbers.

We did not visit the foothill country early enough in spring to observe the beginning of nesting, but data gained later in the season indicate that building is commenced early in April. A new nest was seen at El Portal on May 2, 1916. At Pleasant Valley, in 1915, numerous pairs were noted on May 23 and 24, and young out of the nest were seen on May 28. Along Smith Creek a family group of adults and young was seen on June 2, 1915. The broods are fairly large, 6 perhaps being an average; thus a group of 8 would constitute but one family.

After the broods leave the nest, the families range about locally and some groups undertake a more extensive wandering which may lead them well up into the mountains. In 1915 the movement had carried at least one flock to Yosemite Valley by July 27. A flock of 12 was seen on that date making rapid time eastward through the golden oaks along the base of the north wall. On July 30 a flock of 8 was noted near the Tenaya trail where it leads down near Mirror Lake, and on various dates in August and September flocks of bush-tits were seen or heard in trees and brush bordering the several trails which ascend the Valley walls. By late fall the birds have returned to the foothills, our latest record for the species above its foothill range being for October 11, 1914, when some were heard on the Tenaya trail at about the 5700-foot level.

In 1920 bush-tits were observed by Mr. C. W. Michael (MS) in the Valley on various dates through the fall months, from August 29 even to as late as December 27. On the latter date "the largest flock yet seen" (17 birds at least) was encountered.

This species was discovered once east of the Sierras. A flock of bush-tits was encountered near Williams Butte on September 22, 1915, and the one individual shot proved to be a California Bush-tit; whether the remainder comprised this species or the Lead-colored Bush-tit was not learned. The former is not known to occur regularly on the east slope of the mountains in this latitude and this may be an extreme case of up-mountain, or rather, cross-mountain wandering from the west slope.