19 



Migration of Birds. 



By F. W. Frohawk, M.B.O.U., F.^.S.—Read October 2th. 1919, 



The phenomena of Bird Migration constitutes the greatest mystery 

 pertaining to the whole animal kingdom, an enigma which attracted 

 the attention of the ancients, yet to a great extent the mysterious 

 sense by which birds find their way hither and thither from one land 

 to another, over vast stretches of ocean, is a problem which modern 

 scientists are as incapable of explaining as were the earliest writers. 



The old superstitions and beliefs rogarding the disappearance of 

 several birds in the autumn, such as the swallow, cuckoo, and 

 nightingale, that it was due to hibernation were mere myths. It is 

 not such a great while ago that such ideas pi'evailed, when it was 

 thought swallows retired to the bottoms of ponds or hid in crevices 

 of rocks to pass the winter months in a state of torpor, and cuckoos 

 turned into hawks. It was also at a remote time believed that the 

 larger birds conveyed the smaller kinds from one country to another, 

 but there is no more truth in such notions than there is in the idea 

 that Bernicle geese were hatched from barnacles, the Cirriped {Lepas 

 anatifera). From the careful observations and study given to 

 migration during recent years, much knowledge has been acquired 

 on some points, especially on the routes taken and the destinations 

 of certain species. 



The migratory birds may be classed in three groups : — 



1. Birds which arrive on our shores in the spring and remain to 

 breed, and depart again in the autumn to their winter resorts further 

 south. 



2. Those which arrive here in the autumn, having bred in the 

 northern regions, and spend their winter with us. 



8. Birds-of-Passage are those which breed in the arctic, and winter 

 far south ; are only met with in this country for a short time in the 

 spring, and again in the autumn on their long journeys north 

 and south. 



The chief cause of migration is undoubtedly that of food supply. 

 Therefore, considering the difficulty which all animals are subjected 

 to at times in finding sufficient sustenance, it is not so surprising 

 that birds, possessing such perfect powers of locomotion, should 

 avail themselves of the facilities afforded them for securing food 

 where it can be more easily obtained ; but whether this is the 

 principal cause of the northern migration which takes place in the 

 spring appears doubtful ; possibly the amount of food would fall 

 short in supplying both parents and young of such a vast assemblage 

 of birds if all remained in the southern hemisphere. 



