284 STUDIES IN BIRD-MIGRATION 



As I anticipated, I found the Eddystone to be 

 favourably situated for observing emigration, and, 

 though it is probably only one among many points at 

 which the Channel is crossed by birds en route for their 

 southern winter retreats, yet its geographical position 

 must be regarded as somewhat exceptional, for, in addition 

 to many species which have sought the south coast of 

 Cornwall from inland localities on emigration bent, 

 hosts of migrants which have traversed the west coast 

 of Britain from the north doubtless cross the Channel 

 in its immediate proximity. The waters of the Channel 

 in the longitude of the Eddystone — i.e., between the 

 easternmost part of the south coast of Cornwall and 

 the westernmost part of Brittany — are 115 miles in 

 width. 



The amount of success which it was possible to 

 achieve during my visit was dependent to an extra- 

 ordinary degree upon the weather. This was especially 

 the case as regards night movements ; for it must be 

 borne in mind that conditions which are eminently 

 favourable for migration may be, and indeed in most 

 cases are, quite unfavourable for its observation. 

 Successful night observation I found to be entirely 

 dependent upon certain meteorological conditions which, 

 while favourable for emigration, also rendered the 

 lantern attractive to the migrants — a combination which, 

 though not very uncommon, is yet one of comparative 

 infrequency, and this results in the great majority of 

 movements being unobserved. The lantern of a light- 

 station, I discovered, is simply a decoy. It is one that 

 I found would only "work" under peculiar conditions, 

 which are dependent upon the amount of moisture 

 (rain, haze, cloud) present in the atmosphere. When 



