THE BIRDS OF HELIGOLAND 281 



plumage, with the upper breast and sides of the breast of a brilliant 

 pure silky white ; this pure white coloration renders the bird 

 at once distinguishable from all its relatives even at some distance. 

 Bonelli's Warbler breeds in the mountainous regions of southern 

 Europe, Asia Minor, and Palestine, its range extending on the north 

 as far as south Germany. Hence it seems difficult to explain how 

 the two examples in question could have got to Heligoland during 

 the autumn migration ; from their occurrence in October one would, 

 according to the general phenomena of migration, conclude that 

 their home was in the East. 



105. Willow Warbler [FITISLAUBVOGEL]. 

 SYLVIA TROCHILUS, Linn. 1 



Heligolandish : Liitj Fliegenbitter = /Sma?J Wren. 



Sylvia trochilus. Naumann, iii. 568. 



Willow Wren. Dresser, ii. 491. 



Bee-fin Pouillot. Temminck, Mannel, i. 224, iii. 152. 



This little bird, which breeds throughout the whole of Europe 

 up to the extreme North, also visits Heligoland in abundance 

 during both periods of migration, and is, in fact, the most 

 numerous of all the Warblers which visit the island. Its 

 principal times of migration are May and September, but on warm 

 spring days it may arrive even earlier. Similarly, fine warm 

 weather, with light south-easterly winds, may convey the bird to 

 Heligoland as early as August, fairly large numbers being met with 

 under these conditions in the potato-fields. 



The breeding zone of this bird has probably a wider latitudinal 

 range than that of any other European species, extending from north 

 Africa up to the extreme northern point the North Cape of 

 Scandinavia from 34 to 71 N. lat. The winter quarters of the 

 species are distributed over the whole of Africa down to its most 

 southern provinces. From what we know of the facts of migration, 

 we cannot assume that the millions of individuals, the breeding 

 homes of which are distributed through Europe from the North Cape 

 to the Mediterranean, pour into Africa in one vast chaotic horde, 

 their movements and the range of their migrations being the results 

 of mere accident; but that in this respect also a fixed order as to time 

 and space prevails, in accordance with which, species whose breed- 

 ing homes are in the extreme south likewise have their winter 



1 PhyUoscopus trochilu* (Linn.). 



