44 



and travels in a broad migration front which corresponds to 

 the longitudinal range of its nesting area, and of which Heligo- 

 land forms the most western limit. Even a slight westerly 

 deviation from their southerly course of such species (indivi- 

 duals?) as breed in the west of Norway could not fail to convey 

 large numbers of these birds to the east coast of England, 

 and their all but total absence there furnishes, therefore, an 

 undoubted proof of the persistence with which the southerly 

 course of migration in this instance is adhered to." It has 

 already been pointed out that the Bluethroat is not of so 

 casual an occurrence in England as Herr Gatke supposes, and 

 if we bear in mind that the winter quarters of this species in 

 North-eastern Africa are limited almost to Egypt, it becomes 

 evident that the individuals lireeding in the westernmost parts 

 of their range would, on their return journey, if they took a 

 direct route, fly from north-west to south-east. The pretty 

 regular appearance of examples in England is, therefore, still 

 more worthy of note. One would naturally expect the species 

 to occur fairly numerously in central Europe on the return 

 journey, owing to the proportion of young birds which would 

 then be travelling, and also on account of tlie more leisurely 

 manner in which the latter flight is conducted. But, judging 

 from the evidence placed before us, it appears to be rather local, 

 even in this large area. 



The difficulty of accepting the theory of a migration conducted 

 in a broad front is perhaps more apparent in the case of the 

 Northern Bluethroat than in any other species to which Herr 

 Gatke refers. Writing on the spring flight lie remarks (p. 265) : 

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

 May and April, it appears here [i.e., Heligoland] , 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." 

 He also tells us (p. 44) that on May 26th, 1880, the species 

 occurred on the island in thousands. In certain preceding 

 passages Herr Gatke lays special emphasis on the fact that the 

 Northern Bluethroat has only been obtained during its spring 



