PLAIN TITMOUSE. Baeolophus inornatus inornatus (Gambel)

Field characters.—Size somewhat less than that of Junco or Linnet. Coloration everywhere plain, grayish brown above, pale gray beneath; no contrasted markings of any sort. Head with a tapered crest, which is habitually kept erect. Manners, flight and notes resembling those of Chickadees. Voice: Commonest spring call a sharp whistled peet'-o, given several (3-5) times in quick succession; also various other notes not readily transcribed. Ordinary call-note wheezy, chickadee-like.

Occurrence.—Common resident of Upper Sonoran Zone on west slope of Sierra Nevada. Recorded from near Lagrange (at 400 feet altitude), and from Pleasant Valley, eastward to Smith Creek (six miles east of Coulterville), to El Portal, and to Feliciana Mountain (4000 feet). Reported once in Yosemite Valley (C. W. Michael, MS). Lives chiefly in foliage of oak trees. In pairs, except when broods are in care of parents.

The word 'plain' in the name of the Plain Titmouse refers to the exceedingly somber garb of the bird. Even its crest, which is a character so prominent as to serve as a good field identification mark, is uniform grayish brown. But the lively notes and vivacious behavior of the bird, in such decided contrast to its scheme of coloration, easily lead one to guess the rather close relationship of the titmouse to the chickadee. Once within the range of the species the traveler cannot long remain ignorant of the presence of titmouses (the correct plural), for one or more pairs of the birds are likely to be in hearing if not in sight at any locality in the foothill oak belt.

Little or no difficulty need be experienced in identifying this species. The features mentioned in the preceding paragraph are usually sufficient to make the bird known. Its notes, until one has learned their many variations, are less dependable for this purpose than the crest and coloration. The Plain Titmouse is much larger than the bush-tit. As compared with the wren-tit the plain tit is of more chunky build. Moreover, its tail, which is not longer than its body, is seldom or never cocked up at an angle with the back.

The Plain Titmouse is an example of a species that is strictly resident within one zone, winter as well as summer. Individuals of several of the foothill birds such as the bush-tit and wren-tit move up-slope with the close of the nesting season. We have only one record of the Plain Titmouse leaving the Upper Sonoran Zone: A pair was noted near the mouth of Indian Cañon in Yosemite Valley on November 21 and 30, 1920, by Mr. C. W. Michael (MS). The oak foliage about which the species lives so much of the time evidently provides adequate forage not only for the adults at all seasons but for the broods of five or six young which appear at the end of spring. Even at El Portal where two different zones are accessible on the opposing sides of the cañon the titmouses keep to the warmer, north, sun-facing slope where there are live oaks, blue oaks, and digger pines; and although they forage in the golden oaks on that side of the valley they do not cross to the denser stands of golden oaks which grow on the shaded south slope only a fraction of a mile distant. Up the Merced Cañon the range of the Plain Titmouse, like that of the Brown Towhee, ends abruptly where the Transition Zones commences, at about 3300 feet altitude.

At Pleasant Valley 9 of these birds were recorded in a census of 3-1/2 hours on February 27, 1916. On May 24, 1915, about 30 were noted during 5 hours spent in the same general territory. In the latter number were 2 broods; if these be assumed to have numbered 5 each, the average for adults would be 4 an hour, more than were recorded during the winter census mentioned. But titmouses are more in evidence in spring; their voices are heard more frequently then, and this probably accounts for the differences in the two censuses. Six or more, all adults, were seen during an hour and a half spent on the hills near Lagrange on May 7, 1919. During most of the year the birds live in pairs, but in summer when the annual broods have been reared, family parties of 6 or 7 may be found rather commonly.

The Plain Titmouse nests in holes in trees. Old woodpecker holes are used when available, but many, perhaps a majority, of nests are placed in naturally rotted-out cavities. The height above the ground varies according to circumstances. One nest found near Blacks Creek on May 12, 1919, was only 33 inches (830 mm.) from the ground, measured from the entrance, and the nest surface was 6 inches (150 mm.) below that. Another studied in detail near Lagrange on May 8, 1919, was 10-1/2 feet (3170 mm.) from the ground. Both were in blue oaks.

This second nest was in the same tree with, and only 17 inches (440 mm.) from, that of a Western Bluebird; and there was a Swainson Hawk's nest in another oak 12 yards distant. The titmouse's was in a natural cavity of rather large size. The bottom held a mass of fine dry grasses, perhaps 4 inches in depth, and on top of this was a heavy felted lining of cow hair and rabbit fur. The top of this mat was 5-1/2 inches (138 mm.) below the margin of the entrance. There were in the nest 5 half-grown birds and one infertile egg. The young had acquired many of their feathers, though these were still mostly in the feather-sheaths. The finely comminuted remains of such sheaths as had been shed had sifted into the matted hair lining. These young birds would probably have left the nest within a very few days. The other nest mentioned contained three small young.

For purposes of record and study we wished to collect the entire family of this second nest. The young birds were obtained and two adult titmouses which frequented the vicinity and kept voicing disapproval of our actions were shot. Upon dissection the latter proved to be both males! One was undoubtedly the father of the brood but the other was an "innocent bystander" who fell victim because he had joined in the demonstration. The adults weighed 15.4 and 15.6 grams, respectively, while two of the young birds weighed 14.3 and 14.8 grams. The young at the time of leaving the nest are thus nearly the weight of the parents.

While as a general rule Plain Titmouses keep to the oak trees, the species sometimes invades the digger pines and occasionally drops down to the brush when foraging. An extreme departure from this habit was noted at the Campbell ranch north of Pleasant Valley, where two of these birds were caught in traps set in a field for the capture of kangaroo rats, the nearest trees being fully 50 yards off.

Near Coulterville a Plain Titmouse was watched as it went down to bathe one morning in May. The bird descended by short stages to a pool near a small oak, and after arriving at the margin it spent several seconds in looking about cautiously before venturing to flutter its wings in the water. It did not get drenched; few birds do. Of all the birds we have seen bathing in the wild, none get so wet as not to be able to fly readily.