196 SWALLOWS 



once on the wing they separate, each pursuing 



his own course in search of flies. 



Swallows when feeding have no system of 

 linked flight, nor perhaps at any time ; swifts, 

 however, when not actually catering, perform 

 wonderful combined evolutions at extraordi- 

 nary speed. At these times the birds scream 

 for the same reason that the travelling geese 

 " gabble." 



Though the swallows and martins are seen 

 to leave the telegraph wires simultaneously, 

 they come back independently and swing 

 themselves up one after another, or in twos 

 and threes, but when settled are again in 

 telepathic sympathy. 



One day the observer returns to find the 

 birds gone, and concludes they must have left 

 the night before. This is probably the case ; 

 for though it may have fallen to the lot of some 

 to have witnessed the final departure during 

 the daytime, it would be exceptional, which 

 points to the fact that the birds are in the 

 habit of travelling at night. 



What actually determines the psychological 

 moment of departure we cannot say, though 

 we may be sure that it is not a case of " making 

 up their minds " ; birds have no minds, in that 

 sense, to be made up, they cannot reason on 

 abstract matters. However, we can surmise 



