64 THE MIGRATION OF BIRDS 



Clarke, so long ago as 1896, showed it to be un- 

 supported by British evidence. 



Dr Allen, reviewing Dr H. E. Walter's " Theories 

 of Bird Migration" (3), cites the following experi- 

 ments as strong arguments in favour of orientation. 

 Dr J. B. Watson took fifteen sooty and noddy 

 terns from Bird Key, Tortugas, and liberated them 

 at intervals after they had been marked. The 

 shortest distance was 20 miles from the Key, the 

 farthest, Cape Hatteras, 850 miles ; thirteen re- 

 turned to the Key. Neither sooty nor noddy terns 

 range, as a rule, north of the Florida Keys, so that 

 it is unlikely that any of the birds had been over 

 the route before. They could have gained no 

 experience, or hereditary knowledge, and as they 

 were released during the breeding season, there 

 would be no marked movement southward which 

 they might follow, nor would they at that time be 

 impelled by any desire to migrate. The change of 

 direction from the Florida Keys, westward, to the 

 Tortugas, occasioned by the water course which 

 feeding habits would force them to follow, " removes 

 the direction of the wind as a guiding agency, whilst 

 the absence of landmarks over the greater portion 

 of the journey makes it improbable that sight was 

 of service in finding the way/' 



