42 



when arrived at the Baltic they suddenly become incapable of 

 continuing their journey except by following the comparatively 

 small span of coast to Holstein?" To this one might fairly 

 retort Are we to assume that, because birds in passing Heligo- 

 land are either seen or heard to be travelling in an east-to-west 

 direction, that this is the course of flight maintained throughout 

 the whole duration of their journey ? 



We turn now to the consideration of Herr Gatke's remarks 

 on those species which he tells us travel to and from their breed- 

 ing-grounds in a direct north-to-south, or the reverse, line of 

 flight. There will not be the difficulty in accepting his conclu- 

 sions as to the general direction of this flight as in the previous 

 case, but exception must be taken to the assertion that it is per- 

 formed in the rigid and undeviating manner as described; and 

 also to the theory that it is conducted in a broad front, in a 

 similar mode to the east-to-west flight. 



In considering Herr Gatke's arguments, his admission that 

 not a single bird is seen to arrive at or depart from the island in 

 either a north or south direction must not be forgotten. Yet 

 he tells us that this north- to-south line of flight is " peculiar to 

 a large number of species, more especially such as have their 

 breeding-quarters in high northern latitudes, and, in respect to 

 the individuals taking part in it, fully equals the great east-to- 

 west migration, while, as regards the distance traversed, it in 

 many cases even surpasses the latter movement." We are, 

 therefore, driven to the conclusion that it is the consideration 

 of the breeding-ranges of the species which are said to comprise 

 this movement rather than the result of actual observations on 

 which he bases his theory. One is rather puzzled to know what 

 species are comprised in this flight, as, on pp. 25 and 30, several 

 having their breeding-grounds in the high north are included in 

 the list of those said to be derived from the far east ; others such 

 as " the Bluethroat, Wagtails and Warblers we are told 

 appear on and depart from the island in a manner precluding 

 the possibility of our being able to realise by our senses the 

 direction of either their arrival or departure." 



Amongst the species specially singled out in illustration of 

 this north-to-south flight is a very well-known one, viz., the 



