Читать книгу Life Histories of North American Jays, Crows, and Titmice - Arthur Cleveland Bent - Страница 34
HABITS
ОглавлениеThis is the “crested blue jay” of the Sierra Nevadas and the inner coast mountain ranges of northern California. Ridgway (1904) gave it the common name of Sierra Nevada jay, which seems a more appropriate designation than blue-fronted, as the blue stripes on the forehead are not conspicuously more prominent than in some of the other races of the species. He describes it as “much lighter colored, and average size decidedly less” than in C. s. carbonacea, which, in turn, he calls “paler throughout and averaging slightly smaller” than C. s. stelleri.
The chosen summer haunts of the blue-fronted jay are in the coniferous forests of the Transition and Canadian Zones of mountain ranges, mainly in California. In the Lassen Peak region, according to Grinnell, Dixon, and Linsdale (1930), these jays “in summer were found in and about clumps of closely growing small coniferous trees, often as forming dense thickets of undergrowth in old forest that is thinning out, or at edges of forests. Kinds of trees that formed such suitable clumps and which were frequented by the jays were white fir, red fir, yellow pine, and hemlock. At the western frontier, the occasional pairs seen were usually in tracts of small yellow pines. The birds were seen most often at heights of close to four meters above the ground.”
The range of this jay in the mountains extends upward to about 8,000 or 9,000 feet, or to the lower limit of the Hudsonian Zone, where Clark’s nutcracker is found. It finds the lower limit of its range where the coniferous mountain forest gives way to the foothill oaks and chaparral; here it mingles to some extent with the California jay, but sticks mainly to the pines.
Professor Beal (1910) says: “It sometimes ventures to the edges of the valleys and occasionally visits orchards for a taste of fruit, of which it is very fond, but in general it keeps to the hills and wilder parts of the canyons. It is fond of coniferous trees and is likely to be found wherever these abound. Where ranches have been established far up the canyons among the hills, this jay visits the ranch buildings.”
Nesting.—J. Stuart Rowley writes to me: “I have located many nests of this bird in the Sierra Nevadas, from Tulare County in central California to San Bernardino County in southern California. The most frequently used nest site seems to be a young conifer, with the nest placed about 10 feet up near the main trunk and supported by horizontal branches. The incubating females are rather close sitters and make quite a fuss when flushed from the nests.”
W. E. Griffee sends me the following note: “While cruising timber in the lower Sierras, about 20 to 30 miles east of Placerville, Eldorado County, Calif., I found several nests of this subspecies. All were high on dry hillsides in rather dense reproduction of ponderosa and sugar pines and incense cedar, at elevations of 8 to 12 feet from the ground. Nests were, of course, easy to see and readily accessible, but to find them, had I not been climbing over the timbered hills as a part of my work, would have required a tremendous amount of walking.”
J. G. Suthard tells me that he found a nest containing four fresh eggs on April 21, 1940, in the San Bernardino Mountains. “The nest was situated 8 feet up in a willow along a mountain stream at 9,000 feet elevation. It was shielded from view by a cluster of branches growing up from the slanting trunk of the willow. There were plenty of pine and fir trees in the vicinity, but the jays seemed to prefer the willows, which are possibly less frequented by squirrels. At the time, there were numerous patches of snow along the stream, and a few hundred yards higher the whole range was completely blanketed in white. The willows were still dormant. As will be noted from the photograph (pl. 12), the nest is lined with pine needles, which are those of the Jeffrey pine (Pinus jeffreyi).”
Rollo H. Beck wrote to Major Bendire (1895): “I have found about a dozen of their nests, placed in oaks, buckeye, laurel, and holly bushes, at various distances ranging from 7 to 40 feet from the ground.” Some unusual, or unexpected, nesting sites have been recorded. Col. N. S. Goss (1885) found quite a number of the nests near Julian, Calif., “and in all cases but one in holes and trough-like cavities in trees and stubs, ranging from four to fifty feet from the ground, generally ten to twenty feet up. The nest found outside was built upon a large horizontal limb of an oak close beside a gnarl, the sprout-like limbs of which thickly covered the nest overhead, and almost hid it from view below. * * * The nests are quite bulky, made loosely of sticks, stems of weeds, and lined with fibrous rootlets and grasses, and as they are all built at or near the opening, the tell-tale sticks project and make the findings of their nests an easy matter.”
Walter E. Bryant (1888), on information received from A. M. Ingersoll, writes:
A strange departure from the usual habits of jays was noticed in Placer County, Cal., where they had persisted in building within the snow-sheds in spite of the noise and smoke of passing trains. The destruction of their nests by the men employed on the water train, which makes two trips a week through the sheds during the summer, sprinkling the woodwork and tearing down the nests of jays and robins with a hook attached to a pole, seemed not to discourage them. So accustomed do the jays become to the passing of trains, that they will often remain on their nests undisturbed. In one season more than two hundred nests of jays and robins were destroyed, so the train men say, between Cisco and Summit, a distance of thirteen miles.
These, like all jays, are very secretive in their nesting activities and use the greatest stealth in approaching the nest while building it or when it contains eggs or young. But Grinnell and Storer (1924) were able, under favorable circumstances, to observe a pair building their nest. They say:
One of the jays was seen to fly into a black oak, obtain a twig, and carry it off, upward, through the adjacent trees to the nest site, at the top of a yellow pine, fully 40 feet above the ground. Then the other member of the pair came, broke off a twig, dropped it, evidently by accident, and sought another. * * * Pieces dry enough to break off readily, and a little longer than the jay’s body, were chosen, and twisted off by a wrench with the bill. The twig would be worked along between the mandibles until held across the middle and then the jay would ascend by the usual vertical hopping and short flights to the nest. Following the taking of black oak twigs the two jays, together, flew across the river which flowed close by the nest tree, and there, descending quickly to the ground, sought material in an azalea thicket at the edge of the water. Each took a quantity of twigs and grass and apparently also some mud, and flew again to the nest tree. Again they took twigs from the black oak.
They say of a nest examined in the Yosemite region;
It was solid in construction, with a large external basal framework of dead and more or less weathered twigs of irregular shape and small diameter (2 millimeters or less). Many of these were black oak twigs while others were of a very furry herbaceous plant. All of the material of this outer framework, as was attested by the clean, fresh-appearing ends of the pieces, had been freshly broken off by the jays. This suggests that, save for the small amount of herbaceous material, all the outer constituents were gathered above the ground. The outside framework measured about 300 millimeters (12 inches) in one direction and 400 millimeters (16 inches) in the other.
The inner cup of this nest was composed of dry needles of the yellow pine, held together by enough mud to give the structure a firm resistant feel. The mud, however, did not extend to the inner surface. The interior of the cup consisted solely of pine needles, which crossed and recrossed so as to make a porous interior lining. This cup was 100 millimeters (4 inches) in diameter at the rim and 68 millimeters (2⅝ inches) deep at the center.
Eggs.—The blue-fronted jay lays three to five eggs, usually three or four; Mr. Rowley, who has examined a number of nests, tells me that sets of four are found as frequently as three but that he has found only one set of five. The eggs are usually indistinguishable from eggs of Steller’s jay, but Rollo H. Beck (1895) describes some variations, as follows: “In a series of these eggs now before me there is considerable variation in shape and markings. One set closely resembles those of the California Thrasher, another is marked exactly like the eggs of the Yellow-billed Magpie, and others the eggs of the California Jay. Some have but few spots, principally about the larger ends, while others have the ground color nearly obscured, so thickly are they spotted. The usual ground color is light-blue, which is spotted with various shades of brown and not infrequently with lavender and purple.”
The measurements of 52 eggs in the United States National Museum average 30.22 by 22.61 millimeters; the eggs showing the four extremes measure 34.0 by 24.0, 27.6 by 23.2, and 29.5 by 21.2 millimeters.
Young.—Bendire (1895) says that “an egg is deposited daily, and incubation lasts about sixteen days. The male assists in these duties, and usually but one brood is raised in a season.” Grinnell and Storer (1924) say: “During the nesting season the jays are to be seen in devoted pairs, and after the broods leave the nest the full-grown young and their parents remain for a time in family parties. With the coming of fall, the parental and filial instincts wane, these family parties break up, and the individuals scatter out rather uniformly through the forest.”
Food.—Prof. F. E. L. Beal (1910), in his study of the food of this jay, examined 93 stomachs and found that the animal food amounted to 28 percent and vegetable matter to 72 percent. The animal food consists largely of insects; beetles, a little more than 8 percent; Hymenoptera, about 11 percent, the largest item of animal food; grasshoppers and crickets, about 3.5 percent; caterpillars and moths, a little more than 2 percent; other insects were found only in insignificant amounts. Of the Hymenoptera, he says: “They were found in 30 stomachs altogether, and 2 were entirely filled with them. Ants were found in only 2 stomachs. Three honey bees were identified, one in each of three stomachs. One was a worker, another a drone, and the third indeterminate. None of the smaller parasitic Hymenoptera were identified. The greater part of this item of food consisted of wasps and wild bees, which would indicate that this bird is an energetic and expert insect catcher.” Miscellaneous creatures identified were spiders, sowbugs, raphidians, hair and skin of a mammal, “two bits of bone, probably of a frog,” and eggshells were found in 13 stomachs. “Only 6 of these egg-eating records occurred in June, the nesting month. All the rest were in September or later and were probably old shells picked up in abandoned nests or about ranch buildings or camp grounds.”
Of the vegetable food, “fruit amounts to 22 percent and was found in 55 stomachs. Prunes were identified in 2 stomachs, cherries in 2, grapes in 2, Rubus fruits in 15, strawberries in 1, elderberries in 15, bay laurel fruit in 1, unknown wild fruit in 2, and fruit pulp, not fully identified but thought to be of cultivated varieties, in 16 stomachs. Thus 38 stomachs held fruit supposed to be cultivated. This number contains all containing Rubus fruits, which probably were not all cultivated—perhaps none of them were. * * *
“Grain amounts to 5 percent, and was found in 15 stomachs, distributed as follows: Wheat in 7, oats in 9, and barley in 1. * * * The chief food of this jay, however, is acorns, though occasionally it eats other nuts or large seeds. Mast amounts to 42.5 percent of the yearly diet, and was found in 38 stomachs. * * * In October and November it amounted to 76 percent, in December to 90, and in January to 99 percent.”
He considers the economic status of this jay as of minor importance:
In destroying beetles and Hymenoptera it performs some service, but it destroys only a few. Of the order of Hemiptera, which contains most of the worst pests of the orchardist and farmer, it eats scarcely any. The Orthoptera, which are almost all harmful insects, are eaten only sparingly, and the same applies to the rest of the insect food. The destruction of birds’ eggs is the worst count against the jay. But none were found, except in June, until September, when it was too late in the season for fresh eggs to be obtainable. In June 17 birds were taken, and 6 of them, or 35 per cent of the whole, apparently had robbed birds’ nests. Now, it is evident that if 35 per cent of all the Steller jays in California each rob one bird’s nest every day during the month of June the aggregate loss is very great.
So far as its vegetable food is concerned, this bird does little damage. It is too shy to visit the more cultivated districts, and probably will never take enough fruit or grain to become of economic importance.
In his paper on Modoc County birds, Joseph Mailliard (1927) writes:
In September, 1924, this jay was so numerous in Eagleville as to be a pest in the many small apple orchards of the settlement. These orchards are small, for home supply only, and the inroads made by the jays upon the apple crop assumed serious proportions. With the crop limited as it was by the drought of that year, the owners of such orchards as were bearing fruit waged incessant warfare upon the jays, both of this species and of the following one. Hundreds were shot, but those that were left soon became expert in dodging their pursuers and the slaughter lessened.
In fall and winter, while wandering about in the foothills and valleys, these jays become quite omnivorous, picking up any scraps of food, bread, crackers, meat, or anything edible, that they can find around the camps or ranches; what they cannot eat on the spot they carry off and hide; they have even been known to steal a piece of soap. They probably store some acorns and other nuts for future use and are suspected of robbing the stores of the California woodpecker.
Behavior.—There seems to be nothing in the behavior of the blue-fronted jay that differs materially from that of other races of the species, to which the reader is referred.
Voice.—Its vocal performances are apparently similar also to those of other races, though some different descriptions of its various calls have appeared in print. Ralph Hoffman (1927) says that “besides the ringing tchek, a little lower in pitch than the cry of the California Jay and generally given in flight, the Crested Jay utters from its perch a loud kweesch, kweesch, kweesch. It has besides a deeper chu-chu-chu and a note resembling a squeaking wheelbarrow, kée-lu, kée-lu. * * * Occasionally from the cover of dense foliage, it utters a formless succession of liquid, pleasing notes quite unlike its usual discordant notes, or a purring or rolling note.”
Grinnell and Storer (1924) give slightly different renderings of what are apparently the same as the above notes, and add that “when two jays of a pair are hunting close together a low crackling or growling ker’r’r’r’r’ is uttered.”
Field Marks.—Any of the jays of the stelleri group may be easily recognized by the long, brownish-black crest, so conspicuous at all times and giving the bird an entirely different outline from that of the flat-headed jays of the genus Aphelocoma. The dark brownish-black head, neck, upper breast, and upper back, contrasting with the blue of the lower back and abdomen, are also distinctive; and the blue of the wings and tail is conspicuous in flight.
Winter.—In winter these jays desert to a large extent their summer haunts in the mountain forests and wander about in the foothills and valleys, visiting camps and ranches in search of food. John G. Tyler (1913) says that “during the winter of 1900-01 large numbers of these jays invaded the valley, being found literally by hundreds everywhere eastward from Fresno, where they frequented the trees bordering the vineyards, roadsides and ditches. Their large size and gay plumages rendered them very noticeable, and no doubt not a few of their number were missing when the blue-coated host returned to its Sierran home. The species has not been observed in the valley since that time.”
