THE BIRDS OF HELIGOLAND 429 



breeding species in the mountains of Spain, whence we may pro- 

 bably assume that these English examples are individuals which had 

 early lost their spouses at their nesting stations, and reassuming 

 their spring migration in its original direction, south-to-north, had 

 reached the south of England by way of the Bay of Biscay or the 

 Pyrenees, a view to which we have already given frequent and 

 detailed expression in connection with related phenomena. 



That, under similar conditions, residents in Switzerland do not 

 likewise more frequently get to Heligoland, is probably to be 

 ascribed to the situation of this island considerably further north 

 than the south of England ; so, also, the only known instance of 

 the occurrence of an Alpine Swift in Denmark dates back to the 

 year 1804. 



This bird is a resident breeding species from Portugal to India, 

 including North Africa and Palestine. Its northern range seems 

 rarely to extend beyond Switzerland. As the name of each species 

 indicates, the Alpine Swift prefers the rocks of high mountain- 

 chains for its nesting places, while the Common Swift 1 almost with- 

 out exception selects high walls for its dwelling. 



Swallow Hirundo. Almost all the species of these charming 

 birds which are resident in Europe are also very numerously repre- 

 sented in Heligoland ; the only species hitherto not observed in 

 Heligoland is Hirundo rupestris, whose breeding home ranges 

 within the same parallels of latitude from Spain to China, though, 

 according to Naumann, solitary individuals are found breeding as 

 far north as Switzerland and the Tyrol. On the other hand, another 

 southern or south-eastern form, H. rufula, has been met with here 

 on one occasion, while H. cahirica has occurred repeatedly. 



233. Swallow [RAUCHSCHWALBE]. 

 HIRUNDO RUSTICA, Linn. 



Heligolandish : Swoalk = Swallow. 

 Hirundo rustica. Naumann, vi. 49. 



Swallow. Dresser, iii. 477. 



Hironddle de cheminte. Temminck, Manuel, i. 427, iii. 297. 



Although this familiar bird has not yet built its nest on this 

 island, it occurs in very large numbers on its homeward passage 

 in spring, and on its journey to its winter quarters in autumn. 



1 German for Cypsehis apus is ' Mauersegler ' i.e. Wall-Swift. This explains 

 above reference. B. R. 



