132 Mr. W. Eagle Clarke — Bird-migration 



note that in six Wheatears, all females in identical plu- 

 mage, killed or captured on the early morning of September 

 25th, the range of wing varied from 3*62 to 3'88 inches. It 

 may also be noted that of twenty-two Skylarks obtained on 

 September 29th the wing-range was only from 3" 78 to 4'35 

 for young and old males and females, the average beiug 

 4*07 inches ; while of ten examples captured on the 17th- 

 1 8th October it varied from 3*93 to 4" 70 inches, the average 

 being 4*3 inches. 



The height at which birds fly when migrating is a subject 

 on which much has been written, and the fact that they 

 have been observed proceeding at considerable elevations 

 has been advanced as an explanation of the mystery as to 

 how birds find their way, especially when a considerable 

 extent of sea has to be crossed. That some birds do fly at 

 great heights, and that under certain conditions (which are 

 at present unknown to us) it may be an advantage to them 

 to do so, I will not for a moment deny, but I am convinced 

 that it is not a necessity as a means of finding their way. 



The birds observed crossing from E. to W. in the latitude 

 of the Kentish Knock would have a flight of at least 120 

 miles to perform between the Continental and the English 

 coasts. When observed at that lightship they bad over one- 

 fourth of their journey still before them, so that it was an 

 excellent station for witnessing this and the various conditions 

 under which the journey was performed. During all these 

 movements, great and small, the migrants of every species 

 flew close to the surface of the water under all conditions 

 of weather. On certain occasions, notably on the 1 1th 

 of October, the state of the atmosphere was such that it 

 must have been quite impossible for them to see more than 

 one, or at most two, hundred yards ahead; and yet under 

 these conditions, when it might possibly have been an 

 advantage to fly high, they sped onwards just skimming the 

 crests of the waves, and never departing from a true east to 

 west course. On fine clear days, with a light wind, these 

 flights were performed in a precisely similar manner. Such 



