13 



of a rigidly maintained westerly flight, we take as our standpoint 

 the latitude of Heligoland as constituting the only true east, 

 then all points north of this latitude must be considered as only 

 approximating to the east in lessening degree, until at last true 

 north of the island is reached in Scandinavia. The same 

 remarks, of course, apply to the south. It follows, therefore, 

 that birds breeding in the north of Europe, and which may 

 happen to pass Heligoland on autumnal migration, must travel 

 in a direction more or less partaking of a direct southerly 

 character, even should they at the actual time of passage be 

 observed to be travelling due west. According to Herr Gatke, 

 however, the southward turn is only adopted towards the end 

 of a long westerly flight. 



If we adopt, however, the definition of the east in its narrowest 

 sense as we might not unreasonably do in the light of the 

 author's remarks on the rigidly-conducted line of flight it follows 

 necessarily that any species migrating from the east, and adhering 

 to this course until it reached the longitude of Heligoland, will 

 only be observed at the latter locality if the latitude of its nest- 

 ing station corresponds with that of the island. "All on setting 

 out from their nesting stations take up a direct westerly course, 

 which they pursue to its final goal," he writes (p. 33). This is 

 an important point in considering the undeviating character of 

 the flight, as described by Herr Gatke, and in face of the enor- 

 mous numbers of birds annually recorded as passing his observa- 

 tion. For are we not told to use his own words that at Heli- 

 goland migration takes place in " extraordinary and unexampled 

 grandeur" (p. 4). If we accept the theory of a broad migratory 

 column, advancing due west from regions in the far east, we 

 should naturally expect to find, in like manner, birds passing 

 other points to north and south of the island in equal abundance. 



These remarks especially refer to a well known species, viz., 

 the Hooded Crow. The migration front of this species has on 

 one occasion, according to the author, been known to cover a 

 longitude of thirty-six miles in the immediate neighbourhood of 

 the island, and possibly further still. But this distance is insig- 

 nificant in comparison with the latitudinal extent of the breeding 

 range. Eoughly speaking, the latter includes Scandinavia and the 



