Every detail of this movement of birds has a problem
; and the details are numberless because the different species have entirely different ways. The most eccentric—and immoral—bird in our _British list is the cuckoo ; and therefore, perhaps, it should not be taken as a type. But the most illuminating symptoms of the migratory impulse that I know concern the cuckoo. Consider the ways of our cuckoos. There seems to be no doubt at all that the old birds (which have a highly specialized diet) hurry off south and east while their young are " cadging " on foster parents. Young birds are indeed to be seen in England to-day, though some old birds left in July. This means, of course, that the young birds must find their own way by a route and to a destination of which there is no previous experience. The detail of all details-- that I should most wish to know is Whether these young birds go to the same place or by the same route as the old. If the standard books be taken as a test extremely little is known of the destination of the cuckoo ; but Mr. Witherby. (I believe) had one ring returned from Italy.
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