So that although if you casually observe a flock of rooks in the daytime they seem to wander hither and thither just as fancy leads, or as they are driven by passers-by, in reality they have all their special haunts; they adhere to certain rules, and even act in concert, thousands upon thousands of them at once, as if in obedience to the word of command, and as if aware of the precise moment at which to move. They have their laws, from which there is no deviation: they are handed down unaltered from generation to generation. Tradition, indeed, seems to be their main guide, as it is with savage human tribes. They have their particular feeding grounds; and so you may notice that, comparing ten or a dozen fields, one or two will almost always be found to be frequented by rooks while the rest are vacant. Here, for instance, is a meadow close to a farmstead--what is usually called the home-field, from its proximity to a house--here day after day rooks alight and spend hours in it, as much at their ease as the nag or the lambs brought up by hand. Another field, at a distance, which to the human eye appears so much more suitable, being retired, quiet, and apparently quite as full of food, is deserted; they scarcely come near it. The home-field itself is not the attraction, because other home-fields are not so favoured. The tenacity with which rooks cling to localities is often illustrated near great cities where buildings have gradually closed in around their favourite haunts. Yet on the small waste spots covered with cinders and dustheaps, barren and unlovely, the rooks still alight; and you may see them, when driven up from such places, perching on the telegraph wires over the very steam of the locomotives as they puff into the station. I think that neither considerations of food, water, shelter, or convenience, are always the determining factors in the choice made by birds of the spots they frequent; for I have seen many cases in which all of these were evidently quite put on one side. Birds to ordinary observation seem so unfettered, to live so entirely without rhyme or reason, that it is difficult to convey the idea that the precise contrary is really the case.