Page:The Zoologist, 3rd series, vol 1 (1877).djvu/237

Rh do not quite see why the bird, once in full migratory swing, should stop again till in the natural course of events it flies itself to death. Compared with the drifting seed, it is positively at a disadvantage, having no sea coast to bring it up: like that marvellous mechanical leg we read of somewhere, which when once wound up and started could not be stopped again, so the bird ought to keep going—aimlessly and purposely, perhaps—but still going.

It is a well-ascertained fact that the young of the year of many birds migrate before their parents, and in separate flocks; these have never travelled the route before, and how they find their way over these thousands of miles of sea and land seems a very puzzling problem. It is a curious fact that although the young come in separate flocks, we constantly find an old bird or two—usually old females—amongst them, so that the young may to some extent be in leading strings. As most birds, however, travel by night, and on very dark ones too, they cannot trust to guidance alone, and they are not able to make use of such landmarks as prominent capes and headlands. They come much as did the old sea rovers,—without chart or compass, "by rule of thumb,"—certain to hit the land somewhere, and when once the land is seen knowing all will be right. With the wonderful vision birds possess, and the great height at which they usually travel, they would be able, much more readily than we suppose, at early dawn to distinguish known features of land or sea coast (supposing them to have travelled the route before) at, to us, immense distances. Nor would their inherited instinct, I believe, fail under any circumstances, whether in young or old, to bring them to their goal.

As a familiar instance of this inherited instinct in birds we may cite the case of the Common Partridge. How is it, except by this, that Partridges, having had no actual experience for many generations of the real Kite or Buzzard, cower or rush at once to the nearest shelter when the paper kite's "shadow saileth across the open shaw"? Some years since, when the telegraph-wires were first carried across the Lincolnshire marshes. Partridges and Plover were constantly' picked up killed by flying against the wires; now, after the lapse of some years, this is rarely if ever the case, the generations of Partridges that witnessed this immolation of their comrades has long passed away, yet the present birds have learnt through this same hereditary instinct to avoid the danger.