Natural History 431 



migration takes place at night, and that wide stretches of open sea 

 are habitually crossed. Furthermore, the young of the year in 

 many species migrate southwards before the parents in the case 

 of the Cuckoo, long after their parents and must thus find their 

 way without any memories to guide them. Anything which lies 

 in the experience of the race, as distinct from that of the indi- 

 vidual, must in these cases be handed on by inheritance purely and 

 not by tuition and imitation. 



Our knowledge of the routes that birds follow in their migra- 

 tory flights is still very scanty. Hooded Crows caught and marked 

 as birds of passage at the south-eastern corner of the Baltic have 

 been shown to come from Southern Finland and the Petrograd 

 district of Russia, and to follow the coasts southwards and west- 

 wards as far as the north-eastern corner of France. Black-headed 

 Gulls ringed at the same place, but as nestlings, have been re- 

 ported from right round the coasts to the Bay of Biscay, from 

 along the courses of the Rhine and the Rhone, and as far as the 

 Balearic Isles, and from along the courses of the Vistula and the 

 Danube and across to Northern Africa. 



In its migratory flight the whole life of a bird is raised to a 

 higher pitch. It is estimated that many birds attain a speed of 

 fifty miles an hour, and a carrier-pigeon has been known to keep 

 up the rate of fifty-five miles an hour for four successive hours. 

 It is unlikely that this is often surpassed by migratory birds on 

 long-distance flights. 



"Homing" 



The question "How do birds find their way?" is not one which 

 can be answered at present. More must first be learnt of the 

 nature of the routes which are in fact followed by migrants, of 

 the relationship of particular summer quarters to particular 

 winter quarters, and as to whether winter quarters are as clearly 

 defined and as accurately sought out as summer quarters are 

 known to be. It is probable, however, that the question may be 



