Page:EB1911 - Volume 12.djvu/662

Rh continents of Europe and Asia, as well as North America from the Aleutian Islands to Newfoundland. The red grouse indeed is rarely or never found away from the heather on which chiefly it subsists; while the willow-grouse in many parts of the Old World seems to prefer the shrubby growth of berry-bearing plants (Vaccinium and others) that, often thickly interspersed with willows and birches, clothes the higher levels or the lower mountain-slopes, and it flourishes in the New World where heather scarcely exists, and a “heath” in its strict sense is unknown. It is true that the willow-grouse always becomes white in winter, which the red grouse never does; but in summer there is a considerable resemblance between the two species, the cock willow-grouse having his head, neck and breast of nearly the same rich chestnut-brown as his British representative, and, though his back be lighter in colour, as is also the whole plumage of his mate, than is found in the red grouse, in other respects the two species are precisely alike. No distinction can be discovered in their voice, their eggs, their build, nor in their anatomical details, so far as these have been investigated and compared. A very interesting subject for discussion would be whether Lagopus scoticus or L. albus has varied most from the common stock of both. Looking to the fact that the former is the only species of the genus which does not assume white clothing in winter, an evolutionist might at first deem the variation greatest in its case; but then it must be borne in mind that the species of Lagopus which turn white differ in that respect from all other groups of the family Tetraonidae. Furthermore every species of Lagopus (even L. leucurus, the whitest of all) has its first set of remiges coloured brown. These are dropped when the bird is about half-grown, and in all the species but L. scoticus white remiges are then produced. If therefore the successive phases assumed by any animal in the course of its progress to maturity indicate the phases through which the species has passed, there may have been a time when all the species of Lagopus wore a brown livery even when adult, and the white dress donned in winter has been imposed upon the wearers by causes that can be easily suggested. The white plumage of the birds of this group protects them from danger during the snows of a protracted winter. But the red grouse, instead of perpetuating directly the more ancient properties of an original Lagopus that underwent no great seasonal change of plumage, may derive its ancestry from the widely-ranging willow-grouse, which in an epoch comparatively recent (in the geological sense) may have stocked Britain, and left descendants that, under conditions in which the assumption of a white garb would be almost fatal to the preservation of the species, have reverted (though doubtless with some modifications) to a comparative immutability essentially the same as that of the primal Lagopus. Moreover, the red grouse, restricted as is its range, varies in colour not inconsiderably according to locality.

Though the red grouse does not, after the manner of other members of the genus Lagopus, become white in winter, Scotland possesses a species of the genus which does. This is the ptarmigan, L. mutus or L. alpinus, which differs far more in structure, station and habits from the red grouse than that does from the willow-grouse, and in Scotland is far less abundant, haunting only the highest and most barren mountains. It is said to have formerly inhabited both Wales and England, but there is no evidence of its appearance in Ireland. On the continent of Europe it is found most numerously in Norway, but at an elevation far above the growth of trees, and it occurs on the Pyrenees and on the Alps. It also inhabits northern Russia. In North America, Greenland and Iceland it is represented by a very nearly allied form—so much so indeed that it is only at certain seasons that the slight difference between them can be detected. This form is the L. rupestris of authors, and it would appear to be found also in Siberia (Ibis, 1879, p. 148). Spitzbergen is inhabited by a large form which has received recognition as L. hemileucurus, and the northern end of the chain of the Rocky Mountains is tenanted by a very distinct species, the smallest and perhaps the most beautiful of the genus, L. leucurus, which has all the feathers of the tail white.

The bird, however, to which the name of grouse in all strictness belongs is probably the Tetrao tetrix of Linnaeus—the blackcock and greyhen, as the sexes are respectively called. It is distributed over most of the heath-country of England, except in East Anglia, where attempts to introduce it have been only partially successful. It also occurs in North Wales and very