THE BIRDS OF HELIGOLAND 265 



so many other cases, this little island has proved itself to be a true 

 ornithological observatory. Its meridian represents the extreme 

 western limit of the migratory flight of this Bluethroat between its 

 breeding stations and its winter quarters, and it is in only isolated 

 instances that this limit is ever exceeded. 



During its spring passage from central and northern Africa to 

 the north of Scandinavia, this bird has, according to Giglioli, been 

 met with in Italy only in very isolated instances, in the proportion 

 of one to a hundred of S. leucocyana. The same is stated respecting 

 Austria (Backofen von Echt). In the whole of Germany, too, it is 

 during the spring months of rarest occurrence. Naumann says, 

 ' Only single individuals are, in rare instances, met with on the 

 banks of rivers in Thuringia, near Dresden, Vienna, and other 

 places.' Dr. Hey has met with this species near Leipzig only in 

 autumn, never in spring, and knows of only one instance of its 

 capture, by a friend of his, during the latter season. Mr. W. 

 Schliiter of Halle states that during his long experience he has 

 never met with nor received this bird during its spring migration, 

 and has obtained but few specimens during autumn. 



Respecting northern Germany, Sylvia suecica has, according 

 to recent statements, not only been met with in isolated instances, 

 but, surprising as it may appear, has actually remained to breed 

 near Waren in Mecklenburg, and near Em den in Friesland. These 

 statements, the validity of which cannot fairly be doubted, do not, 

 however, in any way affect the above conclusions as to the mar- 

 vellous rate of flight of this bird during its spring migration, for 

 the latter two localities are situated only two-thirds of a degree 

 to the south of Heligoland, equal to a flight of about thirteen 

 minutes. 



In Heligoland, on the other hand, this bird is, during the same 

 migration period, of quite common and generally known occurrence. 

 In the absence of cold and dry northerly winds at the end of May 

 and April, it appears here as a daily visitor, and if, in addition, 

 the weather be warm and fine, with a light south-east wind, it 

 frequently occurs in such large numbers that, on days of this kind, 

 Oelrich Aeuckens and myself have succeeded in obtaining as many 

 as from thirty to fifty male individuals. In fact, I remember one 

 occasion, in May 1845 or 1846, when there were some sixty of the 

 most beautiful male birds of this species, all picked specimens, 

 lying on a large flat dish in my cellar ; and I might easily have 

 doubled that number had I accepted all that were offered me on 

 the same day. Aeuckens obtained nearly as many, all these birds 

 having been caught by boys in nets, inasmuch as grown-up shooters 

 here do not trouble to catch them. 



