89 



VELOCITY OF THE MIGEATION FLIGHT. 



ERE, GATKE'S remarks in previous chapters on the 

 uninterrupted character and great elevation of the 

 so-called normal migratory flight of birds will 

 have prepared his readers for high estimates as to 

 the speed at which their journeys are accomplished. 

 These high estimates, indeed, are quite a necessary 

 sequence : for he also informs us that these un- 

 broken flights are performed by birds with their stomachs entirely 

 devoid of food. It is doubtful, though however much one might 

 be inclined to agree with the former theories if anything he has 

 previously written will have prepared his readers for the astonish- 

 ing results as detailed in the following paragraphs. 



Exception will be taken by many to his opening words on 

 p. 63, where he remarks : " 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 darkness 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 unknown 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 approxi- 

 mate relation to the wonderful velocity of flight attained by 

 them during their migration." 



It will be gathered from the above statements that in Herr 

 Gatke's opinion, the whole nature of a bird, including its powers 

 of flight and vision, become entirely changed, or at any rate 

 greatly augmented, during the periods of migration. In the light 

 of this contention his allusion to the marvellous speed of indi- 



