56 



ALTITUDE OF THE MIGEATION FLIGHT AND 

 METEOEOLOGICAL CONDITIONS WHICH IN- 

 FLUENCE MIGEATION. 



^:^]l HOUGH Herr Gatke has devoted separate chapters 

 in deahng with his observations on the altitude 

 of the migration flight, and the meteorological 

 conditions which influence migration ; to the 

 writer it seems a better plan to discuss both 

 features together, as they appear to him to be 

 so closely connected; and it is also stated in 

 many places by Herr Gatke that the height of the flight is 

 governed by the prevailing weather. 



His opening words in Chapter III. are very important, as they 

 define his views of the normal height and manner in which 

 migration is performed. He remarks : — " Observations extending 

 over many years have led me to the conclusion that, as long as 

 migration proceeds under its normal conditions, this elevation is, 

 in the case of by far the larger number, so great as to be com- 

 pletely beyond the powers of human observation ; while we must 

 regard as disturbances and irregularities of the migration move- 

 ment proper, due to meteorological influences, such portions of it 

 as are brought within our notice. Here I ought to remind the 

 reader that when I speak of migration proper I mean those 

 large extensive movements which, on the one hand, in autumn, 

 conduct our migrants from their breeding homes to, or very near 

 to, their winter quarters in one uninterrupted, and for the most 

 part, nocturnal flight ; and on the other hand, in spring, convey 

 them in the opposite direction from their winter quarters to 

 their breeding haunts — the uninterrupted continuity of the flight 

 being still more marked in this latter phase of the migratory 

 phenomenon." 



On page 53 he further remarks : "In the case of our small 



