Читать книгу Life Histories of North American Jays, Crows, and Titmice - Arthur Cleveland Bent - Страница 48
ОглавлениеHABITS
In the Lower Austral and Arid Tropical Zones of the southern half of Lower California, south of latitude 28° or 29° N., we find this smaller and paler form of the California jay. Not only is it decidedly smaller than the more northern forms of the species, but also the blue portions of its plumage are a lighter and more clearly azure blue, the under parts are more purely white, and the bill and feet are relatively larger.
William Brewster (1902) writes: “This, the only Jay known to inhabit the Cape Region, is very common and generally distributed there, being found almost everywhere from the sea-coast to the tops of the highest mountains. About La Paz it nests in March, but the birds seen by Mr. Frazar on the Sierra de la Laguna in May and early June were in flocks and showed no signs of having bred that season or of being about to breed. They probably leave the mountains before the beginning of winter and seek more sheltered haunts in the valleys and foothills at lower elevations, for Mr. Frazar did not find a single individual on the Sierra de la Laguna during his second visit, in the latter part of November, 1887.”
Griffing Bancroft (1930) says of its haunts: “The habitat of these jays is arboreal associations other than those of the oases. The level country adjoining San Lucas Lagoon in places is heavily overgrown with mesquite and palo verde. The small cañons in the mountains support scattered trees. The large valleys are frequently dotted with them, especially where moisture is not too far beneath the surface. The riparian associations are almost uniformly accompanied by the taller growths. Within these limitations hypoleuca is common, for a jay.” He also writes to me that he found it “most abundant in the vast mangrove swamps of Magdalena Bay, but did not observe it elsewhere in the mangroves.”
Nesting.—Although eggs were collected by Xantus as early as 1860, Walter E. Bryant (1889) was the first to describe a nest, as follows: “A single nest of this new variety was found by myself a few miles southward from San Ignacio on April 12, 1889. The nest was built about three meters high in a green acacia near the trail. The female was sitting, and did not fly until preparations for climbing the tree had commenced. The nest was in quite an exposed situation amongst scant twigs on a horizontal branch. It is composed of small loosely laid dry twigs, and a shallow receptacle lined with fibre and horsehair.”
Mr. Bancroft (1930) says of the nesting “The breeding habits of the Xantus Jay, however, are unlike those of the other races of its family, partly through choice and partly from necessity. Nearly all the nests we found were in the arrow tree whose dense growth of leaves afforded a maximum of concealment. The nest is usually in the heart of the foliage, six to ten feet above the ground. It consists of a foundation of fine twigs which support a semispherical cup. The foundation may be scanty or it may be quite pretentious, according to the requirements of its location. The cup is thin and neatly woven. It is composed of fine rootlets, tree yucca fibres, or cow-hair. It may be of one material only or the three may be used together. It is stiff enough to maintain its shape; the foundation merely serves to hold it in place.”
Nesting dates seem to differ considerably in different parts of the peninsula, for J. Stuart Rowley (1935) says: “My notes show that on the last of April along the shore of Concepcion Bay on the Gulf, many nests of this jay were found, and without exception all contained newly hatched young. Then, after crossing the peninsula to the Llano de Yrais on the pacific slope, no nests were found occupied, but young were flying about in nearly full plumage (specimen of such juvenal collected there). When we reached Miraflores, in the Cape district, nesting activities were just beginning and from May 10 to 19, inclusive, at this locality eight sets of two eggs each and five sets of three eggs were taken. * * * To the northward, at San Ignacio, only one nest was found to hold even eggs, three fresh being taken on April 27; the majority of birds were apparently just building here.”
One of the sets, now in the Doe collection, was taken by Mr. Rowley from a nest placed in the center of cardon growth 6 feet up.
Eggs.—Two or three eggs seem to be the usual complement for Xantus’s jay, and oftener two than three constitute a full set. Mr. Rowley (1935) located over 50 occupied nests and never found more than three eggs or young in a nest, and he thinks three are “rather uncommon.”
Major Bendire (1895) says that the two eggs in the United States National Museum, taken by Xantus in 1860, “have a pale bluish-green ground color and are spotted over the entire surface with small markings of grayish brown, which are slightly heavier about the larger end of the egg. The eggs are ovate in shape and slightly glossy.”
Mr. Bancroft (1930) says that “laying begins in April, two eggs being the usual number. Reversing the customary order, as the season progresses the size of the clutch increases until, in June, we found three more often than two. That number represents the largest set of which we have knowledge. The eggs differ from those of any other subspecies of the California Jay in averaging a very much greener background and in being marked with decidedly finer spots.”
Mr. Doe tells me that the eggs referred to above are “very dark emerald green, obscurely spotted with gray brown.”
The measurements of 50 eggs average 27.2 by 20.2 millimeters; the eggs showing the four extremes measure 30.1 by 22.8, 23.4 by 17.8, and 26.8 by 13.5 millimeters.