Animal Life in the Yosemite
NPS Arrowhead logo


TOLMIE WARBLER. Oporornis tolmiei (Townsend)

Field characters.—About two-thirds bulk of Junco. Head, neck, and breast gray, darkest in adult males; eyelids white; belly and under parts yellow; upper surface, wings, and tail, plain dull green. (See pl. 9h). Voice: Song of male three to five clear separated notes followed by one or several shorter ones close together and sometimes trilled: syr-pit', syr-pit', syr-pit', syr-sip sip sip sip; call note of both sexes a rather loud tchip.

Occurrence.—Common summer visitant to Transition and lower Canadian zones on west slope of Sierra Nevada. Recorded from Smith Creek (six miles east of Coulterville), Yosemite Valley, and Chinquapin eastward to Washburn Lake. Also common migrant along west side of mountains, as at Snelling and Pleasant Valley, and along east base, at Walker Lake and Mono Lake Post Office. Keeps to low shrubbery, usually over damp ground, foraging 4 feet or less from ground; nests in same sort of surroundings. Solitary, or in pairs.

The Tolmie Warbler, often called Macgillivray Warbler, is a denizen of brush at middle altitudes, living close to the ground in thickets of cherry, thimble-berry, ceanothus, brakes, and other similar plants. It does not commonly inhabit the dry chaparral. On the other hand, it is not so closely dependent upon proximity to streams as is the Pileolated Warbler, although it is at times found amid the same surroundings as the latter. The Tolmie is one of the largest of our warblers and its markings render identification by sight easy; yet it is so given to keeping within the dense shrubbery that it is likely to be more often heard than seen.

The male has the whole head, throat, and breast continuously dark gray, forming a cowl similar to, but not so dark as, that on the Sierra Junco. The body otherwise is clear yellow beneath (with dark flanks) and dull green above. (See pl. 9h). The female and young are colored similarly save that the gray on throat and breast is paler, sometimes grayish white. No other of our warblers is similarly marked. The Calaveras Warbler which has gray on the head, has the throat and breast yellow like the rest of the under surface.

The Tolmie Warbler arrives on the west slope of the mountains in May. It was already present at Hazel Green on May 14, 1919, and in Yosemite Valley on May 16, the same year. Some, however, migrate northward still later in the month, for the species was recorded, in 1915, at Pleasant Valley on May 23 and 30, and at Snelling on May 28. East of the mountains, where the Tolmie is thought to be solely transient in mode of occurrence, none was seen in 1916 until May 21, but immediately thereafter they came with a rush and were of almost daily record until May 31. After the nesting season the species is much less in evidence. Our last records in 1915 on the west slope are for August 28, when individuals were seen near Merced Lake and others at Washburn Lake, and for September 10 and 13, when single birds in migration were noted at Walker Lake. In 1920 Mr. C. W. Michael (MS) observed the species in Yosemite Valley on September 28.

The Tolmie Warbler population is not distributed so uniformly as that of certain other species, so it is more difficult to form a general estimate of the numbers. In the snowbush and huckleberry oak on the high plateau above the Valley between Indian Cañon and North Dome, 6 or 7 were noted in a 3-1/2-hour census, on June 24, 1915. Four or five singing males were recorded along the short trail between Camp Curry and Happy Isles on May 17, 1919. These counts were made in favorable territory; elsewhere the species is much less frequently encountered.

Most of the activities of the Tolmie Warbler are carried on within the cover of the brush. Yet in the late spring and early summer months the males not infrequently fly up into adjoining trees and sing from perches well above the ground. At Hazel Green, on May 14, 1919, a bird was observed fully 50 feet above the ground on one of the lower branches of a large incense cedar. The tree stood directly over a seepage slope covered with creek dogwood, which had evidently been chosen as headquarters for the summer. This bird sang ten times in two minutes, changing position usually after singing twice on one perch. The song was rendered by the observer sizik, sizik, sizik, lipik, lipik, little change being detected in successive songs. In the first three 'words' the 'z' sounds were strong, whereas the last two were more liquid. In singing, the bird would throw its head back, and put much bodily effort into the process of utterance. Soon the bird dropped close to the ground and sang from within the shrubbery, changing his position frequently. The sharp tsip of the female was heard at this time. After a few songs the male flew up to a perch 30 feet above the ground, sang twice, and then went below again, this time into a tangle of small young incense cedars.

Other individuals studied and timed while they sang gave their songs at intervals of 10 to 14 seconds. Song production is not continuous, however, for at times a bird will be silent for a minute or more. Some males seem to keep entirely within the shelter of the brush, where they alternately sing and forage.

The 'z' sounds heard from the bird at Hazel Green are entirely lacking in other songs studied. Two of these clearer utterances we wrote as follows: syr-pit', syr-pit', syr-pit', syr-sip-sip-sip-sip (J. G.), and another cheek-a, cheek-a, cheek-a, cheek-a, chee-e-e-e (T. I. S.). The first syllables are loud, clear, and set off from one another, while the shorter ones (sip) are given rapidly, faster than a person can pronounce them, and sometimes are run almost into a trill.

Our earliest record of nesting for the Tolmie Warbler is for May 22 (1919) when a completed but empty nest was seen in a thicket of chokecherries along Redwood Lane in Yosemite Valley. The rim of this was 12 inches above the ground. During the season of 1915, 3 nests of this species, all located on the floor of Yosemite Valley, came under more or less continued observation.

The first of these was found June 10 (Mrs. Joseph Grinnell, MS). It was 12 inches above the ground in a thimbleberry bush in a thicket near a stream. The structure was made of pine needles and grass blades and stems, and was lined with fine round grasses and black horsehair. On this date there was in it a single egg, about the size of that of a Western Chipping Sparrow, creamy white with brown splotches around the larger end. Two days later the nest held three eggs, showing that one had been deposited each day. The set was increased to four, presumably, on the day following, although the place was not visited again until June 17. On none of these visits was either of the parents seen. Identification of the nest was only made at a later date when one of the adults was surprised there. When seen on June 24 (pl. 51b) the eggs seemed nearly ready to hatch and this surmise was confirmed the following day, June 25, when four naked pinkish yellow nestlings were found entirely out of their shells. Assuming that the fourth egg was laid on June 13, and that the parent bird began incubation immediately thereafter, the period of incubation in this case was 13 days. On June 26 the young birds showed dark gray down which looked purple when the sunlight touched it. On June 28 the young in this nest had disappeared and since, when last seen, they were entirely too small to leave voluntarily, some prowling enemy must be held to account for their early disappearance.

Another nest, found on June 13, 1915, has been described by Miss Margaret W. Wythe (1916, pp. 123-127). It was discovered soon after the eggs were laid and was watched until the young had left. The nest rim was 9 inches above the ground, the outside diameter and height each 3-1/2 inches, the cavity 2-1/2 inches across and 1-1/2 inches deep. It was placed between four stems of chokecherry, and in construction was similar to the one previously described.

The female alone brooded, sitting very close some days, but being absent continuously for fully twenty minutes on the 18th. Two eggs hatched on June 23 and another by the following morning. The fourth proved infertile. The two young that hatched on the 23d grew appreciably in one day, and on the 24th were about 2 inches in length and the same in stretch of wings. The down was conspicuous on these two on the second day. The female brooded at intervals. An hour's observation at close range on June 27 disclosed the fact that the female came to the nest every 3 to 5 minutes, while the male visited the place but once during the period specified. The three young were now about of equal size and juvenal feathers had appeared on the head, back, and wings. The eyes of one bird were open on this date and those of another the day following.

On June 29 the three young were found asleep, all facing in the same direction. On the observer touching a branch no response was elicited, but her imitation of the adult Tolmie's tsip woke two of the young which thereupon threw open their mouths in expectation of food. The tail feathers were beginning to grow out on this date. On the seventh day, June 30, the behavior of the female warbler changed. Previously she had, when disturbed, hopped about within the shelter of the brush. On this date she dropped to the ground within 3 feet of the observer, slowly raised and lowered her wings, and called continually in an anxious manner. She showed increasing wariness in visiting the nest to feed the young, and the latter began to show signs of fear, and 'froze' when the nest was approached by anyone, or the overhanging branches touched. On this date the young first uttered hissing notes at the approach of the parent. July 1 most of the down had disappeared and on July 2 the feathering of the wings was nearing completion. On this, the tenth day after hatching, the young left the nest (Wythe, loc. cit.).

Still another nest was noted by us, on June 24, 1915, in a thicket of thimble-berry and coffee-berry bushes and brakes near the old Presidio. It was, at the rim, 28 inches above the ground and supported partly by a coffee-berry stem and partly by several shoots of thimble-berry, the whole area being shaded by a grove of yellow pines. The nest outside was about 4-1/2 inches in diameter and 3 inches high, while the cavity was 2 inches across and 1-1/2 inches deep. The materials used consisted of numerous broad strips of bark, round grass stems bent at sharp angles, a sub-lining of shredded grass stems, and an inner layer of horsehair. When first seen, on June 24, it was empty; by June 26 there were 2 eggs, on June 27, 3, and on June 28, 4; upon the last date the female was first found to be incubating closely. When the nest and eggs were collected, for purposes of record, on July 3, it was found, however, that the 4 eggs were in various stages of incubation, indicating the probability that brooding had actually commenced before the last egg was laid. When this nest was visited, on July 3, the female was on, but she slipped off shyly, and made off along the ground through the vegetation. After a time she was heard at a 50-foot radius uttering occasional chips. The male was singing 100 yards away, but later he too showed some anxiety and uttered notes similar to those of his mate.

On June 24, 1920, in Yosemite Valley, a bob-tailed young Tolmie Warbler was seen 10 feet above the ground in a cottonwood where it was being fed by the male parent.

Summarizing the findings with respect to these four nests, we note that building by some pairs is instituted in mid-May, although others (possibly because of accident to earlier nests) are to be found building at the end of June. Eggs are laid on successive days, incubation begins immediately upon the laying of the last egg or possibly before, and is completed in 13 days, the young hatch on the same day, or on two successive days, and leave the nest 8 or 9 days after hatching. The male seems to participate but little in caring for the brood.


Animal Life in the Yosemite
©1924, University of California Press
Museum of Vertebrate Zoology

grinnell/birds169.htm — 19-Jan-2006