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districts intermediate, between the north-east and east of the 

 latitude of Heligoland. If so, shall we be justified in calling 

 a flight, which under these circumstances would trend more 

 or less from N.E. to S.W. ; a rigidly preserved westerly flight ? 



In suggesting a "concentration on to some common fly-line," 

 it must not be inferred that this implies any special intention on 

 the part of the flocks to meet together with this purpose in view, 

 but to point more to a fortuitous circumstance, brought about 

 possibly by the configuration of the country — as the Hooded 

 Crow is a low flyer. 



It is easy to see how this concentration may occur. If we 

 glance at the map of Europe we shall find that the land reaches 

 its highest northern latitude in Eussia, at the extreme north- 

 eastern boundary of the continent, and that as we travel west- 

 wards from thence, the coast line, as far as the shores of the 

 White Sea, gradually falls away towards the south-west. If we 

 grant for the moment that the Hooded Crows breeding in the 

 regions above the arctic circle migrate due west from their 

 nesting stations and rigidly preserve this direction of flight, they 

 will sooner or later reach the shores of the Arctic Ocean. Now 

 we have no reasons for thinking that at any point in the far 

 north, they leave the land to migrate across the sea to the Kola 

 peninsula. If, however, this actually takes place, then a con- 

 tinuance of their journey would take them to the west coast of 

 Norway, where they must either turn south or cross the North 

 Sea, and their further flight, in this case, would tend either to 

 miss Heligoland altogether, or, at the most, to cross the island 

 in a north to south direction. ' It seems, however, far more 

 reasonable to suppose, that such migratory flocks which breed in 

 the far north— still assuming that they take up a direct westerly 

 course — would, on reaching the sea, follow the coast line to the 

 delta of the Dwina, where other flights, from lower latitudes, 

 would coalesce with them, and thus continue their further 

 journeys in company. A similar concentration may very well 

 take place at many points along the eastern shores of the Baltic ; 

 whether individuals in the first instance migrate due west or south- 

 west ; and we can thus see how the immense hosts observed at 

 Heligoland may be marshalled together. The flocks comprising a 

 2 



