52 



Herr Gatke seems to think that the appearance of certain 

 species on Heligoland, whose breeding grounds for the most part 

 lie in Asia, is due either to an innate tendency to wander, or to a 

 deliberate turn to the west on setting out on their migrations. 

 In other places, however, it must not be forgotten that he 

 attributes this westward wandering to meteorological influences 

 prevailing at the period of autumnal migration. If the former 

 supposition is correct, it is difficult to see how this tendency has 

 been inherited without producing a more general effect on the 

 particular species which are said to be subject to its influences. 

 It is significant that those which are supposed to be so affected 

 have, as Herr Gatke admits, for the most part only been detected 

 on the island in single instances ; but as the Yellow-breasted 

 Bunting and Yellow-headed Wagtail have occurred more fre- 

 quently, it is remarkable that he has not brought them forward 

 too in illustration of this tendency rather than treating them as 

 species, which prove how rarely a certain other group of birds 

 deviate from a rigidly performed north-to-south flight. The 

 probability of the fact, that because certain species have occurred 

 on Heligoland in small numbers, therefore they should in like 

 manner occur in much larger numbers in Central Europe, seems 

 to the writer to depend entirely on our acceptance of the theory 

 that birds migrate in a broad front. Whether this is so or not, ' 

 it seems very unlikely, however, that the small number which 

 are apparently induced to travel westward should adopt such a 

 form of migration. 



With regard to the progress of the spring migration from south 

 to north, Herr Gatke's remarks are very interesting, and form 

 a striking example of how the habits of birds differ in various- 

 localities. On page 41 he writes: "Here we nowhere meet 

 with any attempts at dividing the long migration flight into short 

 convenient stages such as is often the case after the first great 

 advance during the autunm migration ; nor do the birds at this 

 time anywhere exhibit a tendency for taking long spells of rest 

 in the course of their journey. Unrest and an impelling haste 

 are everywhere the prominent characters of the movement dur- 

 ing its whole progress." Observations conducted on Heligoland 

 no doubt bear out this statement, and we can hardly imagine 



