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field. There was no difference in the ability of these storks to find their way home compared with " control " birds with iron bars of the same size, but not magnetized, affixed in the same position. So the homing ability remains a mystery. If we could explain it we should be getting near to the solution of the mystery of migration itself, for in spite of all the work so far carried out, we still have to confess that we are " worlds away " from understanding this most mysterious and most exciting of bird problems. All we can say is that birds seem to possess a sense of geographical position which enables them to orientate themselves towards a desired spot, and that they probably fly blind along this route until they pick up landmarks and visual cues which tell them where they are. There remain one or two points to discuss before we can finally see our bird settled in the favoured family spot somewhere in England. In the first place, the observant bird-watcher who chronicles the time of arrival of the migrant species each spring will quickly notice that it is the male birds that arrive first. We shall see later that from the point of view of the establishment of a " territory " in which to breed, such an arrangement has definite survival value. As far as migrant birds are concerned we do not know definitely whether the cock birds keep separate from the hens and young of the year, in their winter quarters. Most of the migrant birds which visit this country in winter from Scandinavia are of species in which the cock and hen birds are not much different in plumage, such as redwing, fieldfare, starling and so on, so we cannot draw many conclusions from the flocks we see about the fields in winter. They may be all cocks, all hens, or a mixture of both. But we know that in the case of the chaffinch, the flocks are often composed mainly of cock or hen birds, and the question of the composition of winter flocks both here and in other " reception " areas for summer migrants is one which needs investigation. In its winter quarters therefore our bird may have been in a flock composed of males of the same species. When they left their quarters to come north on the spring journey, how did the birds come? Did they come along a well-defined route all together in a flock, all stopping at the same feeding places, and roosting together in the same wood |
