428 THE BIRDS OF HELIGOLAND 



231. Swift [MAUERSEGLEH]. 

 CYPSELUS APUS, Illiger [Linnseus]. 



Heligolandish : Tohrn-Swoalk = Tower Swallow. 



Mauer-Segler. Naumann, vi. 123. 



Swift, Dresser, iv. 583. 



Martinet de muraille. Temminck, Manuel, i. 634, iii. 303. 



This bird is of quite common occurrence here during both 

 migration periods of the year ; on warm and fine May days these 

 birds congregate in great numbers until noon, without one's being 

 able to see either single birds or companies of them arriving ; they 

 chase about high up in the air with much noise, and disappear 

 during the early hours of the afternoon as unperceived as they 

 came, their number diminishing by degrees. It happens, however, 

 also, that large compact flocks pass later in the day also, high over 

 the island from west to east, without halting in their flight or 

 deviating from the direct line of their passage. In general they 

 occur equally numerously in spring and autumn, though in both 

 cases their number is entirely dependent on the weather ; during 

 west winds and rain one may be sure of not meeting with one 

 of these birds. The Swift is distributed over the whole of Europe 

 and Asia, but appears to be less numerously represented in the 

 latter than in the former of these continents. 



232. Alpine Swift [ALPENSEGLEB]. 

 CYPSELUS MELBA, Illiger [Linnaeus]. 



Alpen-Segler. Naumann, vi. 115. 



Alpine Sivift. Dresser,- iv. 603. 



Martinet a venire blanc. Temminck, Manuel, i. 433, iii. 403. 



During all the time I have been collecting, this bird has only 

 been killed here once viz. on the 7th of May 1871. However, 

 according to the reports of reliable authorities, it has been seen on 

 two other occasions without it having been possible to obtain 

 possession of either of the examples in question. Apart from its 

 larger size, this species is further distinguished in a striking manner 

 from the preceding, especially when on the wing, by its underside 

 being almost entirely white ; whereas in C. apus only the throat is 

 light-coloured. 



In England the Alpine Swift is a much more frequent visitor. 

 Harting gives some twenty instances of its occurrence up to the year 

 1871. This bird, however, occurs very numerously distributed as a 



