Cashmere, Central Asia or Europe. In the cold season they turn southwards again and diffuse themselves over every corner of India. Many reasons have been assigned for this strange " migratory instinct," as it is called, which affects so many species of birds. No philosopher, as far as I know, has bestowed as much thought upon this same instinct as it manifests itself in Viceroys and Governors, members of Council, wives and other species of the genus Homo. To me the matter appears to lie in a nutshell. When a place becomes too hot, or too cold, or too wet, the inhabitants feel a very natural inclination to leave it and go to some place which is more comfortable. And they do so. Not all; some humble creatures, muskrats, for example, and frogs and toads and husbands and some others, cannot get away. Others are kept back by a love of home, or a disinclination for change. But those that can go generally do go, and so it grows into a fashion. Among birds a fashion soon acquires a hereditary force and we call it an instinct. In the case of the Tree Warblers there is a simple and all-sufficient reason for this annual journey southwards, which is, that if they remained they would starve. Birds that live entirely on small, soft-bodied insects, cannot afford to spend the winter in a climate in which the lower forms of life almost cease during that season. But in the tropics there is no time of the year when spiders and little insects of many kinds may not be had. So to the tropics they go, as Jacob and his family went to Egypt. And in every green tree, at almost any hour of the day, you may see them hopping from twig to twig, flitting, clinging, looking
