which could least conveniently move their station, have supplies given them of a milky secretion for this purpose. Birds have nothing of this nature, and make no provision for their young; but they of all creatures, except fishes, can seek what may be required in distant stations with most facility. A sufficiency of food for the adult parent may be found in every climate, yet the aliment necessary for its offspring may not. Countries and even counties produce insects that differ, if not in species, at least in numbers; and many young birds we cannot succeed in rearing, or do it very partially, by reason of our ignorance of the requisite food. Every one, who has made the attempt, well knows the various expedients he has resorted to, of boiled meats, bruised seeds, hard eggs, boiled rice, and twenty other substances, that nature never presents, in order to find a diet that will nourish them; but Mr. Montague’s failure in being able to raise the young of the cirl bunting,[46] until he discovered that they required grasshoppers, is a sufficient instance of the manifest necessity there is for a peculiar food in one period of the life of birds; and renders it probable that, to obtain a certain aliment, this willow wren, and others of the insect and fruit-feeding birds, direct their flight to distant regions, and is the principal cause of their migrations. It is some stimulus like this, which urges that little creature, the golden-crested wren (motacilla regulus), that usually only flits from tree to tree, and never attempts upon common occasions a longer flight, to traverse the vast distance from the Orkneys to the Shetland Isles over stormy seas that admit no possible rest during its long passage of above fifty miles! There it breeds its young; but this one object accomplished, it leaves those isles, dares again this tedious flight, and seeks a milder clime. With us it never migrates, lives much in our fir groves during the winter, and breeds in our shrubberies in summer. Peculiar necessities, such as these, may incite the migration of many birds; but that certain species, which lead solitary lives, or associate only in very small parties, should at stated periods congregate from all parts to one spot, and there hold council on a removal, in which the very sexes occasionally separate, is one of the most extraordinary procedures that we meet with among animals.