PACIFIC BLACK-HEADED GROSBEAK Zamelodia melanocephala capitalis Baird

Field characters.—Between Junco and Robin in size; tail shorter than body; bill large and blunt. Adult male in summer: Upper surface largely black; end of tail and middle of wing with large spots of white; collar around hind neck, rump, and under surface of body, light reddish brown. Female and immature: Head with a light stripe over each eye and another over crown; rest of upper surface dull brown, streaked with blackish; under surface brownish white. Yearling males often wear a plumage inter mediate between that of adult male and of female. Voice: Song of male elaborate—a rapidly timed series of full warbling notes with both ascending and descending inflection; call note, uttered by both sexes, a sharp spick.

Occurrence.—Abundant summer visitant at lower altitudes on both sides of Sierra Nevada (chiefly in Upper Sonoran and Transition zones). Recorded from Snelling and near Lagrange eastward to Hazel Green, floor of Yosemite Valley, and near Chinquapin; also at Mono Lake Post Office and near Williams Butte. Forages largely in crown foliage of deciduous trees, sometimes in shrubs, occasionally on ground. Non-flocking.

There is probably no species of bird better known to summer visitors to the Yosemite Valley than the black-headed grosbeak. This is the bird which is wont to fly down from the trees surrounding a camp and pilfer viands, especially butter, from the dinner table. Indeed so well has this trait been developed among the grosbeaks in Yosemite that they have been nicknamed "butter birds." The species is likely to bring itself to the attention of visitors in other ways as well, for it is of large size for a finch and the male possesses bright and contrasted coloration and a loud and pleasing song.

The black-headed grosbeak arrives on the west slope of the Yosemite section during April. The species was common in Yosemite Valley on April 29, 1916; and in early May, 1919, it was well established in the western foothill country. East of the mountains its migrations are somewhat later. The first seen there in 1916 was observed on May 14. During the summer season the birds are much in evidence and can scarcely be missed by anyone who enters their domain. They quiet down in July, and thenceforth are much less noticeable. Mr. Joseph Mailliard (1918, p. 19) states that in 1917 none was seen in Yosemite Valley after September 20. This accords with our own findings in 1915; in that year the birds departed from the Valley prior to September 24.

These grosbeaks are abundant in both the Upper Sonoran and Transition zones. At Pleasant Valley on May 23, 1915, 20 were recorded during a 4-hour census, and two days later 12 were noted in 2 hours. In Yosemite Valley at the same season 8 to 12 birds were observed during each of several 4-hour trips on the floor of the Valley. At Snelling the population was smaller, and along the shores of Mono Lake the numbers were likewise small, only 3 being seen in 3 hours at the latter locality on May 31, 1916. In general, the preference of the species is for rather open foliaged, broad-leaved trees, such as blue oaks, black oaks, and willows. The birds are most likely to be found in scattered growths rather than in thick woods, and generally they are not very far from water.

The adult male black-headed grosbeak is a strikingly colored bird. At first glance one gets an impression of black, white, and brown in highly mixed pattern. Upon closer examination this coloring is seen to consist of black on the head, back, wings, and tail, a large white patch on middle of spread wing, and white thumb marks at the ends of the outer tail feathers. There are also numerous scattered white spots elsewhere on the wings. The rump, the collar around the back of the neck, and the under surface of the body are colored brown, of a bright tone but not so red as the breast of the robin. The female grosbeak is quite different. Dull brown everywhere replaces the black, the amount of white is much smaller and the head and back are coarsely streaked. There is a conspicuous light stripe over each eye and another over the crown. The big bill, in either sex, can easily be made out at ordinary field distance, and in making identifications, its presence helps to rule out other birds of roughly similar appearance.

Some spring breeding males exhibit a plumage intermediate between those just described for the adult male and female. In these "peculiar" birds some or all of the flight feathers in the wings and tail are old, faded, and worn, much more so than in males which are in the black plumage. This condition of the flight feathers shows that the birds which wear them are from broods of the previous season and therefore are just under a year in age. The small percentage of these differently plumaged birds suggests that they represent cases of incomplete molt. Reports of 'singing females' are probably explained by the fact that these so-called singing females are males in this more or less immature condition of plumage.

The black-headed grosbeak possesses a rich voluble song that forces itself upon the attention of everyone in the neighborhood. In fact at the height of the song season this is the noisiest of all the birds. The song resembles in some respects that of a robin, and novices sometimes confuse the two. The grosbeak's song is much fuller and more varied, contains many little trills, and is given in more rapid time. Now and then it bursts forth fortissimo and after several rounds of burbling, winds up with a number of 'squeals,' the last one attenuated and dying out slowly.

Early in the season the males are to be seen, now and then, in ecstatic song flights. These are most likely to occur just as the sun touches the tops of the trees in the early morning. Launching forth on a horizontal course, circling out from the summit of a tree, with wings and tail spread to fullest extent, every feather seemingly held tense, the bird utters an almost continuous "bold breathless, bubbling song," richer and fuller even than the usual utterance and almost torrential in its delivery.

Of lesser notes there is a sharp explosive call or alarm note, spink or spick, sometimes repeated at short intervals and given by both males and females. The males are in song upon their arrival in spring and continue to sing until some time in July (July 15, 1920, at Dudley). Thenceforth, until the departure of the species in September, only the sharp call is given and this but seldom. The young have a distinct call, a soft musical whistle. This note is to be heard coming from berry patches and fruit trees all through the summer. The adults at nesting time evince extreme concern for their broods, and if their precincts are raided give voice to squalls, loud and ear-piercing. The effect, as demonstrated in our own experience, is to absorb the invader's attention so that he fails to look farther for the eggs or young.

In late April and early May, soon after their arrival from the south, the grosbeaks engage actively in courting. Sometimes two or even three males will be singing and flying about in the vicinity of one female. Near Lagrange on May 6 to 8, 1919, there was much frenzied chasing of females by males and of rival males by one another. In some places it seemed as though there was a surplus of males. The same conditions existed near Coulterville on May 9 to 12; but by May 16 in Yosemite Valley, nesting was well under way. Here, a female was seen gathering building material on that date; on the 17th another bird had already completed her nest and laid five eggs. At Pleasant Valley, in 1915, a brood of bob-tailed young already out of the nest was seen on May 25; nesting in this instance must have been commenced close to the first of May. Two nests with small young were seen in Yosemite Valley on June 24, 1915. Another with the male brooding one small youngster was seen there as late as July 29 (1915). Hence nesting may commence about the first of May; it is well under way by the middle of that month; broods are emerging in numbers toward the end of June, while a few pairs whose nesting program has been delayed or interrupted are still busy with nestlings as late as the last week in July.

Nests of the black-headed grosbeak are placed in trees or large brushes, usually at a height of not more than 12 feet from the ground. We have record of several at approximately 8 feet, and others at 4, 6, 7, 15, 20, and 30 feet, respectively. Young black oaks, small incense cedars, mountain lilac, apple trees, and chokecherry bushes, all had been used in instances noted by us. A crotch, or a group of horizontal twigs, forms the usual support, and the nest is frequently located against the main vertical stem or trunk. The nest itself is an openly constructed affair, often little more than a platform slightly concave above, and is so thin in weave that the contents can be seen, at least in outline, from beneath. Sometimes the nests are firmer and more cup-shaped than this usual type, although they still exhibit the open-work style of construction. Small long plant stems, grasses, and crinkly rootlets are the important structural elements. One nest, rather deeper than the average, measured 5 inches across the outside and 2-1/2 inches in height, while the interior was 3-1/4 inches across at the rim and about 1-3/4 inches deep at the center.

A female was watched gathering nest material in Yosemite Valley on May 16, 1919. She hopped about in a mountain lilac bush, finally selected a small twig which, with a few pulls assisted by the cutting edges of her mandibles, she broke off. Then she worked the twig along in her bill until it was held across the middle. Still retaining the first twig, she gathered a second in the same manner, after which she made off in irregular course through the trees, en route to her nest.

In late May and during June it is a relatively easy matter to locate occupied nests of the black-headed grosbeak, for the male bird does much of its singing within a hundred feet of the nest and often even while actually on the nest. Several nests in Yosemite Valley were found by following up singing males. On one occasion, while one of us was walking along the road near the Royal Arches, a female flew across the road to a black oak in which the male had been perching. After giving a few calls she flew away. The male then flew directly over the observer, alighting in the same general vicinity whence the female had first come. After a minute he hopped farther onto what was then seen to be the nest. The bird sang a number of times, spicked between songs, and then worked himself down close over the eggs so that only his head and tail showed above the low rim of the nest. Another male bird, on a nest in a black oak at the roadside, was watched from a distance of but 15 feet. He sang snatches of song off and on for many minutes; each utterance was marked by an up-and-down twitching of the tall, which projected over the edge of the nest and could be easily seen beating time, as it were, to the rhythm of the singing.

Still another nest of the black-headed grosbeak was found in a coffee-berry bush on the north side of Yosemite Valley on the morning of June 19, 1915 (Mrs. Joseph Grinnell, MS). Some workmen had removed all adjacent shrubbery a few days previously, evidently leaving this bush only because of the nest. Originally the site had possessed a measure of seclusion, but now it was exposed to the view of all passers-by. Attention was quickly drawn to the nest by the male voicing his loud song as he brooded the four small young. The latter were clad in the white natal down which was about one-fourth of an inch in length and quite thick, though the yellowish pink skin showed through in places. At sundown the same day, when we passed, the female was seen to be brooding. Next morning at 8:30 the male was seen to feed each youngster in turn and then brood them. At 5:30 this second afternoon the female was again on the nest. On June 26 the eyes of the young were open. The nest was not watched further, but the young must have left soon afterward.

No nest of the black-headed grosbeak was watched continuously; but brief observations on a number of nests including others than those specifically mentioned above make possible the following summary. Courting and selection of mates is carried on after the birds arrive within their summer haunts. The female alone gathers nest material. After the eggs are laid both members of the pair engage in the function of incubation. When the eggs hatch the male does a good share of the food-gathering and brooding. The young (fig. 55b) remain in the nest at least 8 days, and likely somewhat longer. The male sings frequently while on the nest, both before and after the eggs hatch.

Four is the usual number of eggs laid although we saw sets of both 3 and 5 in which incubation had commenced. Several nests seen held 4 young but no unhatched eggs, indicating that all the eggs in these particular sets were fertile and had hatched successfully.

During their residence here the black-headed grosbeaks levy upon a wide variety of materials for food. At Snelling, on May 26, 1915, the birds were feasting on the wild blackberries which were then ripening in abundance. At Pleasant Valley at the same season, males were noted on the ground in search of insects. At Lagrange birds of both sexes were seen flying out from the trees to capture passing 'bugs.' In Yosemite Valley Mr. Joseph Mailliard records (1918, p. 14) that he saw family parties of these birds foraging in barnyard chaff at the "Kenneyville" stables; grains from the dried stalks of oats, wheat or barley were being picked out. At Mono Lake Post Office on May 21, 1916, two males were seen feeding upon the hearts of cherry blossoms. These birds were working rather rapidly and a blossom would drop every fifteen or twenty seconds.

Fig. 55. (a) Young Mariposa Fox Sparrow; Chinquapin, July 13, 1915. (b) Young Pacific Black-headed Grosbeak; Pleasant Valley, May 25, 1915.

The black-headed grosbeaks in Yosemite have become accustomed to the presence of people and also have learned to patronize habitually the bird-feeding tables, which many persons establish during the period of their sojourn in the Valley. The grosbeaks often dominate these places to the exclusion of other birds, even the robins; and among the grosbeaks themselves certain individuals seem to be more aggressive than others.