282 THE BIKDS OF HELIGOLAND 



quarters further south, while those which breed in higli northern 

 latitudes do not extend their winter stations beyond northern 

 Africa. 



Now, the breeding areas of species nesting farther south become 

 habitable a whole month sooner than those of species nesting in the 

 far North ; accordingly, the former start sooner for their breeding 

 homes, than the latter do for theirs. Hence the remarkable fact 

 results, that the birds which have started from four to six weeks 

 earlier from their winter quarters in the far south Hy past and 

 beyond those which at that time are still wintering in north Afi-ica, 

 without however the latter being thereby induced to commence 

 their spring migration. They, in fact, quietly remain until their 

 homes in the raw North have become fit to receive them. There 

 still remains, however, the question — What is it that announces to 

 the one set of birds that the time for commencing its migratory 

 journey has approached, and to the other that it has still ample 

 time for resting in its winter abode ? 



The west-to-east range of the breeding area of this species 

 extends from Portugal to the Jenesei. 



106. — Chiffchaff [VVeidenlaubvogel]. 



SYLVIA RUFA, Bechstein.i 



Heligolandish : Liitj swart-futted Fliegenbitter = Xii'H?c Block-footed Wren. 



Sylvia ruf a. Naumann, i. 58 1. 



Cloiffchaff. Dresser, ii. 485. 



Bee-fin viloce. Temminck, Manuel, i. 225, iii. 154. 



This bird also visits Heligoland in abundance, if not quite so 

 numerously as the preceding Sjoecies. In spring it arrives sooner, 

 and in autumn remains later, than any other Warbler, and it seems 

 not at all to be afraid of rough weather. Its migration commences 

 as early as the end of March, and in autumn lasts as late as 

 November ; indeed, in 1S79, one of these birds was seen on the 

 shore among the boats, during the first days of December, engaged 

 in the pursuit of aquatic flies which were disporting themselves in 

 the noon-day sun. 



In this species, as in the preceding, the young, more intensely 

 yellow-coloured birds of the year initiate the autumn migration. 



The nesting stations of this species extend through Europe from 

 Portugal to the Ural, and in Scandinavia to the latitude of 05° N. 



' Phylloscojms mfus (Bechst.). 



