IV. VELOCITY OF THE MIGRATION 

 FLIGHT 



The velocity of the migration flight forms another highh'- 

 interesting division in the consideration of the migration pheno- 

 menon generally. Just as the latter is in essence something quite 

 sui generis in the life of the birds, so the separate phases under 

 which it manifests itself bear no comparison Avhatever with the 

 ordinary functions of their daily life. Thus, many birds are able to 

 follow the different pursuits of their life only by daylight, and 

 become the most helpless of creatures as soon as darlmess has set 

 in. With the advent of the migratory period, however, their whole 

 nature is changed to such a degree that after sunset they will soar 

 to heights hitherto entirelj' imknown to them, and on pitch-dark 

 nights are able to fly towards the goal of their wanderings with 

 unfailing certainty. Similarly, the speed at which their ordinary 

 daily locomotions in the air are performed has not even an 

 approximate relation to the wonderful velocity of flight attained 

 by them during their migrations. 



The subject of the speed of the migration flight of birds has for 

 a long time engaged the attention of naturalists and observers, but 

 no results consistent with the facts have as yet been established. A 

 Falcon belonging to Henry ii., which escaped from Fontainebleau 

 and was recaptured twenty-four hours later at Malta, is still cited as 

 a wonderful instance of the rapidity of bird-flight. ' Nine [German] 

 geographical miles in an hour!'^ people exclaim Avith astonishment 

 (Dr. Weissmann, The Migration of Birds, p. 36). If more thought 

 had been devoted to the matter, it would have been found that the 

 speed of flight must in the above case have been at least double 

 that of the first estimate ; for it is certain that the bird did not fly 

 unintermittently during the whole of the twenty-four hours, but 

 that it rested during the night, and in all probability managed to 

 secure booty on the way, which, after a full meal, it would digest 



^ Equal to thirty-six English geographical miles. 



