308 STUDIES IN BIRD-AIIG RATION 



form, and yet the wings of the males varied from 5.38 

 in. to 5 in. (4 being over 5.25 in.), and those of the 

 females from 5.15 in. to 4.85 in. (13 being over 5 in.). 

 Some, probably most, of this remarkable variation 

 was due to age, or individualism, none to race. This 

 influence of age was well illustrated in the Blackbirds 

 obtained ; the wings of the young males measured from 

 .30 to .40 in. less than the adult. To be of any real use, 

 beyond, of course, the important one of identification, 

 all wings should be accompanied by the age and sex of 

 the specimen from which they were taken, and it is im- 

 portant, where possible, to obtain a number of examples 

 from the same movement. Until these essential data 

 are forthcoming, it is impossible to realise the true 

 significance of wing-measurements, and it is worse than 

 useless to draw deductions from them. 



As regards the characters which may distinguish the 

 various Continental representatives of many of our 

 commonest species, much yet remains to be learned, 

 though, thanks to Dr Hartert, considerable progress in 

 this branch of ornithological knowledge has been made 

 during recent years. But the age of certain birds in 

 the late autumn is not an easy matter to determine, for 

 the histories of their plumages at that season do not 

 appear to be sufficiently well known to help us to 

 reliable conclusions on this point. 



On the question of the young and old birds travel- 

 ling together or apart on their migrations, or of what 

 species follow the one practice or the other, my obser- 

 vations at the Eddystone throw some light. Swallows, 

 both adults and juveniles, were observed passing in 

 company during the daytime ; and young and old of the 

 Mistle-Thrush, Redwing, Blackbird, Wheatear, Stone- 



