At the end of summer the old birds disappear from their usual haunts to moult; and during this perhaps painful, and certainly dangerous, period, they remain secluded and unseen in the thickest foliage. When they reappear in new and brighter dress, restored to health and vigour, a fresh trial awaits them. The young they have hatched and fed and protected have now attained to maturity, and are in possession of their home. For it is the case that every pair of robins has a pretty well-defined area of ground which they regard as their own, jealously excluding from it other individuals of their own species. The young are forthwith driven out, often not without much fighting, which may last for many days, and in which the old bird is sometimes the loser. But in most cases the old robin reconquers his territory, and the young male, or males, if not killed, go otherwhere. And here we come upon an obscure point in the history of this familiar species; for what becomes of the young dispossessed birds is not yet known. It has been conjectured that they migrate, and that not many return from their wanderings beyond the sea. And it is not impossible to believe that the migratory instinct may exist in the young of a species, although obsolete at a later period of life. Nightingale. Daulias luscinia. [Illustration: FIG. 26.--NIGHTINGALE. ⅓ natural size.] Upper plumage uniform brown tinged with chestnut; tail rufous; under parts greyish white; flanks pale ash. Length, six inches and a quarter. * * * * *