NOCTURNAL MIGRATION 6;^ 



north to breed, and had subsequently returned to 

 spend the winter in one particular area of thicket, 

 brush-pile, and open glade in southern Georgia. 

 Such precision of movement impresses one as truly 

 remarkable. 



The regularity with which birds move, appear, 

 and disappear during migration has naturally oc- 

 casioned much comment, and has resulted in various 

 theories that attempt to explain it. Thus a peculiar 

 magnetic sense whereby birds are attracted by the 

 magnetic pole; a special nasal sense that enables 

 identification of air-currents and other phenomena; 

 the direction of regular winds; the angle or direction 

 of the sun, and of light rays; a reflex attraction, 

 masked by one author under the caption of tropism; 

 memory of routes once traversed; telepathy; direct 

 perception of the point toward which the journey is 

 directed; and hereditary memory of the route to be 

 traversed, all have been put forward as hypotheses 

 to explain the facility with which birds reach distant 

 points. All have had their champions, and with all 

 this divergence of opinion, it must be admitted that 

 the matter is as yet far from definitely settled. 



Mr. A. H. Clark ^ has presented a clear statement 

 of what he considers to be the method of pathfinding 

 employed by the golden plover in its journey south 

 to South America. This he attributes to a course 



» Juk, 1905, pp. 134-140. 



