55 



but in the spring many, on the other hand, will only be just 

 starting on their journeys, and consequently not so urgently in 

 need of food and rest. Even the author's own theory that at 

 the latter period birds " perform their journey from their winter 

 quarters to their breeding-grounds, if possible in one uninter- 

 rupted flight" (p. 44), would lead us to expect fewer callers on 

 the island at this season than in the autumn. 



With regard to the return of Siberian species, whose presence 

 on Heligoland is said to be due to the peculiar influence of certain 

 meteorological conditions prevailing at the time of migration, it 

 can only be suggested that as they have been led so much astray 

 by these causes, it is very doubtful, if they are ever capable of 

 finding their way back again to their proper breeding-grounds. 

 Most probably those which survive the dangers of winter join 

 parties of other species journeying to the north of Europe, where 

 the chances are very much against their ever finding a mate. 



In conclusion, the migration of several species whose breeding- 

 grounds are in the far north, such as the Knot, Sanderling, Curlew 

 and Pectoral Sandpiper, &c., may be pointed out as evidence quite 

 at variance with the theory that their flights are conducted in a 

 broad front. In a small area like that of the British Isles, where 

 the distance of the central portions from the sea is so insignificant, 

 all these species are of the rarest occurrence inland ; whilst on the 

 coast-lines, more particularly the eastern, several of them are 

 very abundant. The same is the case in other parts of the world, 

 and it is only in the great river valleys, such as that of the Volga, 

 that they are met with in any regularity. The Knot, however, 

 though very abundant on the Atlantic coasts of America, is 

 almost unknown inland, even in a great river valley Uke that of 

 the Mississippi. All these facts are quite contrary to what might 

 be expected were migration performed according to the theories 

 of Herr Gatke. 



