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mostly restricted, in grayish, bush-like patches, from the margin of the sage-plains to an elevation of from seven thousand to eight thousand feet.
A more contentedly fruitful and unaspiring conifer could not be conceived. All the species we have been sketching make departures more or less distant from the typical spire form, but none goes so far as this. Without any apparent exigency of climate or soil, it remains near the ground, throwing out crooked, divergent branches like an orchard apple-tree, and seldom pushes a single shoot higher than fifteen or twenty feet above the ground.
The average thickness of the trunk is, perhaps, about ten or twelve inches. The leaves are mostly undivided, like round awls, instead of being separated, like those of other pines, into twos and threes and fives. The cones are green while growing, and usually cover all the surface of the tree, forming quite a marked feature as seen against the bluish-gray foliage. They are quite small, only about two inches in length, and give no promise of edible nuts. But when we come to open them, we find that about half the entire bulk of the cone is made up of sweet, nutritious seeds, the kernels of which are nearly as large as those of hazel-nuts.
This is undoubtedly the most important food-tree on the Sierra, and furnishes the Mono, Carson, and Walker River Indians with more and better nuts than all the other species taken together. It is the Indians' own tree, and many a white man have they killed for cutting it down.
In its development Nature seems to have aimed at the formation of as great a fruitbearing surface as possible. Being so low and accessible, the cones are readily beaten
NOTE. There are four or five other conifers in
the Sierra: Pinus muricata, which comes in from the coast range around the head of the Sacramento Valley, Taxus brevifolia, Torreya Californica, and Cupressus Lawsoniana, none of which forms any telling portion of the general forest to ordinary observThe cupressus is a beautiful tree, seventy-five or eighty feet high, growing along the banks of cool streams on the upper Sacramento, toward Mount Shasta. Only a few trees have as yet reached the Sierra. Taxus brevifolia is a bush or small tree, with dark-green foliage, found in shady dells in the northern Sierra, at a height of from two thousand to three thousand five hundred feet.
Torreya Californica, or California nutmeg-tree, is found in gulches and along cool streams on the western flank of the range throughout the lower portion of the main forest-belt, attaining its fullest
development at an elevation of about four thousand feet. It is a small, glossy, dark-green tree, the largest about thirty or forty feet high, and from six to eighteen inches in diameter, with rather slender, feathery branches, spreading and radiating near the top. More frequently, however, it is small and ragged and of no determinate form. The fruit is not at all cone-like, but, on the contrary, resembles a greengage plum-smooth, oval, about an inch and a half long, green and fleshy, containing one seed like an acorn, the shell of which is hard, and the albumen so colored and folded that a cross-section resembles that of the common nutmeg, whence the popular name.
The wood is fine grained and of a beautiful creamy yellow color like box, sweet scented when dry, though the green bark and leaves, when bruised, emit a very disagreeable odor.
Picea nobilis, Loudon, is only a variety of amabilis with long projecting bracts. Intermediate forms, with the bracts scarce at all exserted, blend inseparably with the so-called nobilis, the bracts of which project half an inch or more.
THE vast half-sphere of plain and sky
Come, mighty shade, till earth might be
Till I lie drowned beneath a sea
Till I might think that o'er my eyes,
The earth, caressed with showers of gold. Close-shut, the earth forever lies.
And yet, not so, sweet night,
Not so I long for thee,
Not so come thou to me.
So longs my soul for thee, Oh, so, I pray, sweet night, So come thou unto me.
THE MIGRATION OF BIRDS.
ALTHOUGH there are few more familiar phenomena than the periodical migration of birds, none is usually considered so thoroughly enveloped in mystery. Even recent writers on the subject have not hesitated to affirm that it may be looked upon as the "mystery of mysteries" of the animal world. Yet our knowledge respecting many points of the problem is nearly complete. Where the birds, which in summer inhabit the temperate and colder latitudes, go in winter, is no longer a matter of conjecture; their wanderings have been quite fully traced, and their winter homes are known, in the majority of cases, with considerable exactness. At a not very remote time, it was a general belief that swallows, rails, and some other birds passed the cold season in a state of torpidity, concealed in hollow trees or in the mud at the bottom of ponds and rivers. As late as the beginning of the present century this belief found supporters among naturalists of high standing, and even within the present decade instances of the discovery of hibernating swallows have been detailed by intelligent observers so circumstantially that cautious writers on the subject are loath to aver that such a thing is, on physiological grounds, wholly impossible, especially in view of the fact that not a few mammals, which live in cold countries, pass the winter in a lethargic state. While the possibility of hibernation among birds is not, even now, universally denied, the supposed evidence is practically ignored, since our knowledge of their movements precludes the necessity of any theory of hibernation to account for their disappearance from northern latitudes during the cold season.
The reason why birds retire to warm countries at the approach of winter is, in most cases, evident, being, in at least very many instances, obviously due to the failure of food through the decline of temperature and other seasonal changes. How they are guided in their journey; what it is that impels their return in spring to their summer homes, and enables them to reach them with such precision, after the long absence of months, at localities thousands of miles distant-these are the "mysteries" that science still strives to solve.
As is well known, all birds are not in the same degree migratory, and before
attempting any explanation of the mys teries of migration, it may be well to consider briefly its phases and modes. In respect to our own birds, we note the appearance in spring of many species which remain only during the warmer season, disappearing again at the approach of autumn. In winter, we observe others which have come from more boreal regions to pass the inclement season, but which repair to their northern homes with the return of milder weather. Others still are seen for only a few weeks in spring and fall, they visiting high northern latitudes to rear their young, and finding a winter home amid the verdure of the tropics. Comparatively few species reside with us permanently, and even of these only a small proportion are truly sedentary, there being a periodical swaying of the whole mass northward and southward, unperceived by ordinary eyes, but easily detected by the ornithologist. In other words, while certain species may remain with us throughout the year, their winter representatives are not the birds which enliven our fields and forests in summer, but migrants from the north, which at this season replace the summer sojourners that have moved a short distance southward. While the species is really migratory, it appears to be sedentary, since the great wave of migration does not wholly sweep past us. Other birds, which may properly be termed resident, are, to some degree, roving in winter, their movements being influenced by the supply of food, and never extending far from the place of their birth. The few strictly sedentary species are the various kinds of grouse, which rarely leave their native copses, while the jays, crows, and woodpeckers afford examples of the resident, but more or less roving, class. Titmice, nut-hatches, creepers, and some kinds of sparrows illustrate those which, to the common observer, are sedentary, but which are in reality represented by different individuals in winter and summer. Of the migratory species, some wholly retire from the norther States in winter, which may still be found within a few hundred miles of the northern limit of their summer range; others are not found north of southern Georgia, Florida, and the Gulf States, while still others pass on to Mexico, the West Indies, Central America, and even northern South America.
We have thus, among our own birds, every degree of migration, from those which always inhabit the same places to those that are simply roving in winter, or move but a few hundred miles southward, or even pass the summer within or near the arctic regions, and the winter within the tropics. But the chain of gradation is even still more nearly complete, for several species, as the meadowlark, the purple grackle, the red-winged blackbird, and the towhee bunting, are partly migratory and partly sedentary, those which occupy the northern half or twothirds of the breeding range of the species moving southward in winter, while toward the southern limit of their respective habitats, the same individuals are permanently resident.
Considered in respect to their food, it is found that the strictly insectivorous species -as the swallows, swifts, and fly-catchersare, with few exceptions, the earliest to depart and the latest to arrive. Those which subsist chiefly upon insects, but partly upon soft, pulpy fruits, as the vireos, tanagers, and grosbeaks,—are almost as early in their departure and as late in their return as those which are exclusively insectivorous. The great mass of the warblers and thrushes tarry still later; while the hardier seedeating finches remain till the leaves have fallen and sharp frosts have seared the fields. The sandpipers, woodcock, and snipe linger till the oozy shores and marshes no longer yield them their accustomed food, the chill of autumn having driven their insect prey beyond their reach. The water-fowl and sea-birds abandon their summer haunts only when the touch of winter has locked in ice the inland lakes and rivers, or driven their finny prey to deeper waters. The non-migratory species-as some of the woodpeckers, the omnivorous crows and jays, and the grouse are those whose food is of such a nature that the change of season only remotely affects the supply. As would be naturally inferred, the distance traversed by the migratory kinds in passing from their summer to their winter homes is in direct relation to their habits in respect to food; those wholly, or almost wholly, insectivorous being not only the first to leave, but those which penetrate farthest south, only finding congenial surroundings in subtropical or inter-tropical regions. Temperature has, doubtless, less influence in inciting. migration than failure of food, although it is impossible that the early autumnal migrants could long withstand the chilling
blasts they would soon encounter, were the food supply unfailing. Only by a gradual change, acting through a long series of generations, could these lovers of summer skies become inured to frost and snow. That change of temperature is not the direct incentive to migration seems evident from a study of our hardier migrants, a few individuals of whom sometimes linger throughout the winter at sheltered localities, where food remains accessible, safely daring the severest cold.
While there is an easily recognized cause for the movement of birds from a colder to a warmer climate, the reason for their return is less apparent. The summer of high latitudes doubtless affords them the most congenial environment during the nesting season, but how has this fact become so impressed upon their consciousness that they experience an irresistible desire to return after the lapse of a definite interval ? The return of birds to their accustomed breeding stations-their only true homeshas been attributed by some to that strong home-affection which so many birds give evidence of possessing in a high degree, as will be presently noticed in connection with another portion of the general subject of migration. Others believe it to be due mainly to those ever-recurring physiological changes which mark the annual cycle of bird-life; or, in other words, the "instinct” of procreation,-to something innate, and not to any external impressions directly resulting from seasonal changes of climate. However unsusceptible of demonstration these suppositions may appear, no other hypothesis seems adequate, while certain well-known facts, at least, favor them. In some species, for example, which require. several years to attain maturity, the young or immature birds do not complete the full migration, but pass the summer at points far to the southward of the usual southern limit of the breeding range, while in other cases they are the laggards which arrive much later than the fully mature birds. The usual answer given, not only to this question, but to the cognate ones of what impels birds in the right direction at the outset, and how they are guided in their long journeys, is the magic word "instinct," which, in most cases, is merely the confession of complete ignorance. If, however, we accept the term instinct in its modern sense, namely, as transmitted habit, or inherited intelligence, we gain at least one step in the solution of these questions.
As preliminary to any theoretical considerations, let us regard for a moment the bird fauna of North America in relation to the geographical distribution and probable place of origin of its principal types. Viewed in this relation, the species fall naturally into three classes,-namely: first, those which belong to genera which are nearly cosmopolitan; second, those belonging to genera which are restricted to the northern hemisphere, where, however, they have usually a wide distribution; third, those which represent distinctively American types. These latter may be supposed to have originated either within or near the present American tropics; or—and, perhaps, with greater probability—at more northerly points, prior to the inception of the extremes of climate that now so strongly characterize different portions of the continent. The metropolis of the groups to which these latter belong is, almost without exception, still within the tropics. Even that most numerous and distinctively characteristic group of North American birds, the family of the wood-warblers, and particularly the genus Dendroica, is still represented by resident species within tropical latitudes, to which several genera of the family are as yet exclusively confined. The brightly colored tanagers, the brilliant orioles, the fly-catchers, the humming-birds, and some of the more showily attired finches, are but waifs from the tropical home of the groups they respectively represent. Our grackles and cow-birds belong to genera the species of which are otherwise tropical, as are all their most intimate generic allies. Throughout the great equatorial belt, and for some distance on either side of it, the birds which there rear their young are, as a rule, nonmigratory, the migratory birds consisting mainly of winter exiles from higher latitudes. The characteristic or peculiar forms are, therefore, sedentary, while the migrants belong to families which are for the most part cosmopolitan.
With these facts in view, we have but to indulge in a few suppositions, so probable in their nature as to amount almost to certainties, to obtain an apparently rational clue to the origin of the instinct of migration. The change in climate at the close of tertiary times, which reduced the temperature of the higher latitudes from subtropical, or at least warm-temperate, to frigid conditions, must have resulted in the crowding of bird-life toward the equatorial regions, thereby intensifying the struggle for life to
such a degree that the overcrowding of the species would lead those best able to withstand climatic change to avail themselves of the milder interim of summer to enlarge the boundaries of their range, while the recurrence of winter would force a temporary removal to milder regions. Granting the hereditary nature of habit, now so generally conceded, we have at once the conditions for the development of a new instinct, at first, doubtless, feeble and uncertain in action, but strengthening by exercise and by the inevitable "weeding out" of those individuals in which it was undeveloped or weakest. With the increased diversity in the conditions of environment called into existence by the great climatic and other changes occurring at or near the close of the tertiary epoch, there was greater play for the modifying action of physical influences, resulting in the development of new specific types as well as the instinct of migration. A greater diversity of forms not only began now to characterize the North American fauna, but in many instances a separation, not only specific but occasionally generic, of homogeneous types that previously ranged over a large part of the northern hemisphere. Prior to this period, or when climate was everywhere more nearly equable, the necessity for migration can hardly be supposed to have existed, since nothing would apparently have been gained by change of locality. The invasion of the cold wave being from the northward, rendering uninhabitable the extreme northern portions of the continent, the pressure of bird-life southward would cut off and isolate species belonging to wide-ranging generic and family types, which, as slightly differentiated forms, still linger as components of the North American avi-fauna, transformed from sedentary to migratory species, in accordance with present climatic necessities.
Accepting the above brief outline of the origin of the instinct of migration as at least probable, we have still to consider how birds are guided in their long wanderings. Whatever the directing principle may be, it can hardly be considered as separable from the instinct of movement itself. The heredity of habit in animals, on which the above hypothesis so largely depends, and on which hangs much of the reasoning which follows, being so well supported by fact and observation, and so generally conceded by those who have given most attention to the subject, no argument will be
here attempted in support of so well-sustained an assumption. The phenomena of the "homing" of carrier-pigeons, and the return of lost animals to their homes under most perplexing circumstances, point to memory as a powerful agent in the problem. Memory must have been the chief guide during the early stages of the development of the migratory instinct, the inheritance of which, becoming stronger and stronger in succeeding generations, may well have resulted in what we now term the instinct of migration. That birds possess remarkable memory of direction and locality is indicated by the readiness with which they find their carefully concealed nesting-sites, be they in the reedy marsh, the level, grassy prairie, or the thick forest. Birds of prey are well known to return year after year to the same eyrie, after a roving life of many months, or, perchance, according to the habits of the species, after an extended winter migration. Colonies of herons resort from time immemorial to the same swamps, and even the same trees, to rear their young; terns, gulls, cormorants, and other water-fowl in like manner repair to the same stretch of sandy beach, or the same cliffs, and only abandon them for more secure retreats after a long period of ceaseless persecution from human foes. Many, it is believed most, other birds return year after year to the same tree or the same immediate locality to nest. While it may be urged that absolute proof of this is wanting, owing to the difficulty of positively recognizing individual birds, such recognition is at times possible, and has in many instances been made. Circumstantial evidence is, however, abundant, as all who have observed birds closely will testify. Expert field ornithologists have no doubts in the matter, and often profit by their experience in securing rare nests and eggs for their cabinets; knowing that the same pair of birds will in all probability return, if spared, to the same spot the following year, the collector notes the locality and returns with some degree of confidence at the proper time to secure the coveted spoils. This is true not only in the case of the larger species, but equally so for the smaller ones, and has been especially noted in those which are of rather rare occurrence, attention having been naturally most directed to these. In the case of hawks, not only has the same pair been observed to return to the same tree, the same cliff, or the same marsh, according to the habits of the species, for a long series of years, but
the intense solicitude they display for many weeks (in some cases, before the breeding season begins) when the precincts of their home are invaded, shows that their return is actuated by strong home affection. No one at all observant of bird-life can have failed to notice the manifestations of joy displayed by our familiar bluebird on its first arrival. in spring at the old nesting-tree or birdhouse which has been its home in former years, or how persistently it defends it from all intruders for weeks before the actual nesting-time arrives. Orioles and vireos appear to return often to the same tree, or even to affix their nest to the same branch, for successive years; the wren, the pewee, and the robin in like manner repeatedly occupy the same nesting-sites. Such observations show that birds are able to find their way not only to the general district of their former home but to its exact locality, with a facility that betokens great strength of memory and prompt recognition of landmarks, and that such return is actuated by a true home love.
In regard to the question how birds find their way, it is found that careful consideration of the manner in which their long migratory journeys are performed affords many suggestions toward its solution. With most species, the movement is a gradual one, occupying generally a considerable period, and is performed frequently by easy stages, the birds stopping for portions of each day for rest and food. In the case of those which pass over but a few hundred miles of territory, the same individuals often tarry for days together at various points along the way. In other instances, the passage is more rapid, varying in proportion to the distance separating the winter and summer homes of the species. The swallows, preeminent in power of wing and keenness of vision, migrate with the greatest rapidity; but, even with these, a considerable interval elapses between their appearance in spring in the Gulf States and in Canada or New England, and between their disappearance at different points in fall. Some species migrate singly, many others in small, scattered parties, and some in immense flocks. While some appear to move chiefly by day, others are believed to migrate almost exclusively by night, and still others, as is certainly known, indifferently either during the day or night. The arrival of some species is, consequently, first noted toward evening; others are seen in numbers in the early morning, where not a repre