A History of North American Birds, Land Birds. Volume 3. Robert Ridgway
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Название: A History of North American Birds, Land Birds. Volume 3

Автор: Robert Ridgway

Издательство: Public Domain

Жанр: Биология

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СКАЧАТЬ species, or even race, of Burrowing Owl in North America. This is represented in the Smithsonian collection by over fifty specimens, including examples from all parts of its range. Upon a close inspection of all the specimens in this extensive series, I was very much surprised to find so little variation; indeed, all the specimens are so much alike that a detailed description of the colors of one would answer for almost any individual. The shade of color varies mainly according to the age of the feathers, those newly acquired having a darkness of tint and a softness of texture not seen in those more worn (as in midsummer dress), which have a bleached or faded appearance. I fail entirely to detect the different styles of plumage which Mr. Cassin has described, and his diagnoses of two supposed species will not at all hold good when applied to specimens from either of the two regions which they were considered to characterize.

      Examining critically the large series at my command, I find that the principal discrepancy among individuals is the amount of feathering on the tarsus; this extending to the toes was supposed to characterize the A. cunicularia of North America the habitat of which was considered as restricted in North America to the west of the Rocky Mountains (see Cassin, Birds of North America, as cited above); the nearly naked tarsus was believed to be characteristic of the A. hypogæa, as restricted, and the habitat assigned to this was “from the Mississippi River to the Rocky Mountains.” Now, dividing the series under examination into two sets, according to this feature, we have, first, cunicularia from the following localities: from the Rio Grande, all specimens but one; Tongue River, Montana; and Petaluma, Santa Clara, and San Francisco, California. Next, hypogæa represents the following localities, besides places within the range ascribed to it: Utah; Lower California, including Cape St. Lucas, all specimens; San Diego, California, several specimens; Santa Barbara, San Francisco, Sacramento, and Fort Tejon, California; and Tamaulipas, Mexico.

      Though we have but one species or form in North America, the South American bird is different: this is the true cunicularia of Molina, and though not specifically distinct from our bird, is nevertheless an easily recognized geographical race. It is larger, the wing measuring from 7.00 to 7.50, instead of 6.40 to 7.00; the brown of the plumage is appreciably darker than that of most specimens of hypogæa, but less extended; on the outer web of the primaries the white spots are larger,—sometimes confluent along the edge,—and on their inner webs the white largely prevails, the dusky bars appearing only towards the ends; the outer tail-feather is almost wholly white, instead of having brown bars, broader than the white ones. Of the var. cunicularia there are eight specimens in the collection (chiefly from Paraguay, Buenos Ayres, and Chile), while numerous others, in various collections, have been examined besides. All the American forms of this subgenus seem clearly referrible to one species, as being at the most but geographical races.

      Habits. The Burrowing Owl of North America inhabits the country between the Pacific coast and the Mississippi River, especially in the lower plains in Nebraska and in Kansas, as well as in particular districts in Utah, Arkansas, New Mexico, the Indian Territory, Texas, Arizona, California, and Mexico. They are usually very abundant, congregating together in large communities, and differing from most members of their family by living and breeding in burrows in the ground. Their habits are peculiar and interesting.

      Speotyto hypogæa.

      Thomas Say, during Colonel Long’s expedition to the Rocky Mountains, was the first of American naturalists to meet with this bird. He encountered it in our trans-Mississippian Territories, where he described it as residing exclusively in the villages of the prairie-dog, whose excavations are so commodious as to make it unnecessary for the bird to dig for itself, which it is able to do when occasion requires. These villages are very numerous, and variable in their extent, sometimes covering only a few acres, and at others spreading over the surface of the country for miles together. They are composed of slightly elevated mounds, having the form of a truncated cone, about two feet in width at base, and seldom rising as high as eighteen inches above the surface. The entrance is at the top or on the side. From the entrance the passage descends vertically one or two feet, and thence it continues obliquely downward until it terminates in the snug apartment where these animals enjoy their winter’s sleep, and where they and the Owls are common, but unfriendly, occupants.

      Mr. Dresser noticed this bird at all seasons, in the prairie country of Texas. They were rather common near the Rio Leon and Medina, and in one place he found they had taken possession of some deserted rat-holes. He obtained several specimens near San Antonio and at Eagle Pass. In the latter place he found them quite common on the sand plains near the town. The stomachs of those he shot were found to contain coleopterous insects and field-mice.

      Dr. Newberry states that he found this species in Northern California, in several places between San Francisco and Fort Reading, and again at the Klamath Basin, though less frequently at the northward than in the Sacramento Valley. There they occupied the burrows made by the Beechey’s and the Douglass’s Spermophile. He usually saw them standing at the entrance to these burrows, often permitting him to approach within gun-shot, and before taking to flight twisting their heads about and bowing with many ludicrous gestures, apparently in order to aid their imperfect sight, and to get a better view of the intruder. When shot at or otherwise alarmed, they fly with an irregular jerking motion, dropping down much like a Woodcock.

      Dr. Suckley obtained a specimen near Fort Benton, on the Upper Missouri, in Dakotah, and Dr. Cooper procured others thirty-five miles west of Fort Kearney, in Nebraska, in August. He saw them in great numbers on the plains of Nebraska, and did not observe any difference in habits between them and the birds of California.

      This species was found in Texas, near Fort Davis, and also at El Paso, by Mr. J. H. Clark. It was taken in Tamaulipas, Mexico, by Lieutenant Couch. Mr. Clark remarks that they were seen by him only in the prairie-dog towns, and were found in conjunction with the rattlesnake, and accuses them of feeding upon the young of the prairie-dog; but this ungrateful requital of the hospitality given them in the burrows of this marmot is discredited by Dr. Kennerly and others, who regard the apparent harmony in which the two dwell together as altogether incompatible with this habit.

      This species is also found on our Pacific coast, west of the Rocky Mountains, as far north as British Columbia. Mr. Lord met with it along the entire course of the boundary-line. It was not by any means plentiful, but pairs of them were occasionally seen. While in camp at the Dalles he dug out several squirrel-holes. In one he found two eggs of this species, the female bird, a racer-snake, and a female ground-squirrel (Spermophilus douglassi). The Owl he found to be strictly of diurnal habits, feeding principally on crickets, grasshoppers, large beetles, and larvæ. He thinks it never captures small animals or birds, and regards it as a peaceful and harmless bird.

      Dr. Kennerly met with this species near Los Angeles, California. At any hour of the day they might be seen seated upon the mounds erected around the holes of the marmot, or else with head protruding from its orifice, disappearing immediately when approached. When molested, they commence bowing and chattering in a somewhat ludicrous manner at the intruder, or fly swiftly away, keeping near the earth and alighting suddenly in the vicinity of a burrow to renew these amusing motions. He found it very abundant in the valley of the San Gabriel River, where it associated with the large ground-squirrel of that region.

      Dr. Heermann, who found them common on the extensive open prairies, speaks of its sight as very clear by day, and adds that it will not allow the hunter on foot to approach within shooting distance; but that, if approached on a horse or a mule, it may be easily shot. The nests he found were formed of a few straws carelessly thrown together at the bottom of its tortuous burrow, which is from six to eight feet in length. The eggs were usually four in number, and are described as nearly spherical, and as pure white.

      Dr. Townsend states that this Owl resorts to the forsaken burrows of marmots and badgers, but never lives on terms of intimacy with either. The nest he describes as of fine grass, and placed at the extremity of the hole. The eggs are uniformly four in number, pale white, and about the СКАЧАТЬ