62 



On occasions like these the number of birds which alight 

 during the morning hours, is at that time considerably diminished, 

 and the few birds that do so, soon start afresh on their journey, 

 so that by the time that the wind has completely changed to the 

 west and rain has begun to fall, not another bird is to be seen. 

 To the writer this all points to the fact that birds, on becoming 

 aware of the approach of a storm from the quarter to which they 

 are travelling, as a rule fly to meet it, and also hasten their speed 

 in order to reach a desired goal before it breaks over them. 



In formulating his various theories, Herr Gatke appears to be 

 constantly under the impression that all birds which are passing 

 his observatory have already flown long distances without a 

 break before they come under notice. 



If the relative position of Heligoland to the adjacent masses of 

 land is studied, and the observations of other ornithologists are 

 borne in mind, the opposite conclusion can hardly fail to be arrived 

 at, the majority of birds having probably only executed a short 

 flight before their arrival at the island. This must be especially 

 the case during the autumnal migration. As Heligoland presents 

 such limited accommodation for rest and food, they are com- 

 pelled to fly further on, in the face of the approaching storm, to 

 seek the necessary food and shelter elsewhere. It is difficult to 

 imagine, however, if at the time of starting they were actually 

 aware of the storm they would have to encounter on their 

 journey, why they should set out at all. 



In the face of these considerations it seems more reasonable 

 to suppose that migrants flying towards a storm only become 

 aware of its approach about the same time as an ordinary 

 barometer at the surface of the earth would have indicated its 

 vicinity. The particular instance, so graphically described on 

 page 79, as occurring the third week of October, 1882, seems to 

 bear out this contention. Birds which had been migrating at 

 low elevations in large numbers for a fortnight previously, the 

 weather having been favourable, on becoming aware of the 

 approaching change, hurried forward at great speed to reach a 

 place of shelter before it burst upon them. Whilst the storm 

 raged no birds were seen at the island, but in the opinion of the 

 author, migration was not interrupted but continued in its normal 



