ROUTES 45 



sideration. The observations at lightships and 

 lighthouses are mostly made when untoward circum- 

 stances bring the birds within range of vision, and 

 on dark and foggy nights cause them to strike the 

 light in great numbers. What is their normal course 

 when no great migration wave or ' rush ' is ob- 

 served ? Are the few passing stragglers noted all 

 that go by this route in fair weather ? The same 

 uncertainty must be applied to the observation of 

 passing birds in inland localities. The immense 

 numbers which do pass is shown by the observation 

 of large movements, when as occasionally happens 

 some check to normal migration leads an army of 

 birds to a dangerously low altitude, or when high 

 winds hold up a portion of the host on our coasts ; 

 but even these multitudes must be small compared 

 with the millions of birds which annually pass from 

 zone to zone unseen. The few or many birds we 



\j 



meet with, either on the coast or inland, resting on 

 passage, may represent a lost or wandering party of 

 stragglers or weaklings from a vast army which has 

 passed over ; they may or may not be on the route 

 or course normally followed by the majority. The 

 cartography of bird migration is a study in itself. 



Mr Abel Chapman, describing his experiences in 

 the Mediterranean, says " For forty hours we were 

 passing across (or beneath) the lines of an army of 

 migrants say 500 miles in width ; yet not a sign 



