. Animal life in the Yosemite; an account of the mammals, birds, reptiles, and amphibians in a cross-section of the Sierra Nevada. Zoology. ROBIN 607. is accomplished by the birds as early as food conditions permit, irrespective of weather. Only 5 were seen at Pleasant Valley in a 3i/^-hour census on February 27, 1916; yet the population had not moved much higher into the mountains since none was noted in Yosemite Valley the following day. By the end of April (1916), however, robins had appeared in usual num- bers in Yosemite Valley. East of the mountains, the robin population is doubtless alt
. Animal life in the Yosemite; an account of the mammals, birds, reptiles, and amphibians in a cross-section of the Sierra Nevada. Zoology. ROBIN 607. is accomplished by the birds as early as food conditions permit, irrespective of weather. Only 5 were seen at Pleasant Valley in a 3i/^-hour census on February 27, 1916; yet the population had not moved much higher into the mountains since none was noted in Yosemite Valley the following day. By the end of April (1916), however, robins had appeared in usual num- bers in Yosemite Valley. East of the mountains, the robin population is doubtless altogether absent during the winter months. In late spring and throughout the summer the robins go about in pairs when one or the other bird is not in attendance at the nest. After the young are grown, family parties are to be seen for a while. As soon as the young are capable of getting their living independently they gather into flocks. Meanwhile the adults go off by themselves and remain sequestered until completion of their annual molt. Then, in late September, the robins, without regard to sex or age, gather into mixed flocks and, for the most part, spend the winter in such gather- ings. These flocks include anywhere from 4 or 6 up to half a hundred individuals. We observed flocks of 10 to 20 in many places in the mountains during September and October, 1915. The flock formation is always loose, and individuals leave and rejoin it at will. For a species like the Western Robin, which subsists largely on crops which fluctuate greatly from year to year as well as from place to place, the flocking habit must be of decided advantage as an aid in locating an adequate supply of food. The two sexes are very much alike in the robin. Male birds are slightly the larger, their breasts are on the average darker colored, and their bills in summer are nearly clear yellow. Some females are as dark colored on the breast as the lighter males, but their bills are always more or less tinged with
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Keywords: ., bookauthorgr, bookcentury1900, bookdecade1920, booksubjectzoology
