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8 doubt that the same principle governs the motions of young and old birds. Of hostility on the part of the parents I have seen but little, nor is it necessary; for the young, which are now distinguished by a different coloration, both of plumage and bill, making them look like another and quite mature species, delight to associate together, so that both the rocks and the water become the scene of tolerably large gatherings of them, at which hardly an old bird is present. As the parents of these assemblies are now free from the cares of domesticity, it seems as though the reason for such a segregation must be of a psychical nature, since one can hardly suppose that the dissimilarity of plumage has anything to do with it, seeing that young and old are as familiar with one another's appearance as with their own. It is the same thing, no doubt, with the gulls on this island, but as the whole interior, or rather the crown of it, is little else than their nesting-ground, it would be difficult for the younger generation to foregather, without the constraining presence of the elder one. The inconveniences of this may be imagined. Not a remark but would be overheard, not a side-glance but would be supervised and harshly interpreted, not a giggle that would pass unreproved. In these irritating circumstances, apparently—this, at least, is my theory of it—the young people have migrated en masse, a striking proof that, with birds no less than with ourselves,