11 



tiae species, with its loud clear call-uote, should be overlooked 

 under such circumstances is simply incredible. 



It will be seen at once that our acquiescence in the statement, 

 that we are undeniably entitled to assume that these Asiatic 

 species pass through central Europe in numbers proportionate to 

 the larger area of the latter in comparison with the area of 

 Heligoland, will depend in the first place on our acceptance of 

 the theory that their western flight is performed in a broad 

 column corresponding to the latitudinal extension of their 

 l)reeding grounds ; as their normal migrations are admittedly 

 north to south, and in the absence of confirmatory evidence, the 

 application of such a theory to these particular species seems to 

 he quite unwarranted. 



In perusing the contents of Herr Gatke's work, one is being 

 continually struck with the high estimates he places on the 

 numbers comprising the migratory flocks of birds passing the 

 island. 



Curiously enough it will be found, in the first place, that the 

 species which migrate from east to west in autumn are said 

 to amount to many hundreds (p. 33), and also that as many, 

 if not more, preserve a line of flight from north to south. As 

 the whole avi-fauna of Heligoland only amounts to some 400 

 species, one is rather puzzled how to account for these large 

 figures . 



It will be readily admitted that to arrive at an accurate 

 result in calculating the numbers of rapidly moving objects is 

 very difficult. It is equally difficult to arrive at a proper esti- 

 mate of the value we are to place on the author's computations. 

 In particular instances the reader can hardly fail to be struck 

 by evidence of the grossest, though no doubt unintentional, 

 exaggeration. This must perhaps be attributed to the artistic 

 element in Herr Gatke's nature. As an instance of this ex- 

 aggeration, the case of the Hooded Crow may be pointed out. 

 On page 64 he writes of this species migrating "in millions, 

 nay, billions" — an impossible estimate in any case, but still 

 more incredible if we bear in mind his theory of a " broad 

 migration column," and if we are also to assume that this state- 

 ment refers to the neighbourhood of Heligoland alone. It is 



