38 THE MIGRA TION OF BIRDS. 



But these migratory journeys of the birds are replete with 

 accidents due mainly to the elements. They are often 

 caught by cyclonic storms while en route and blown hundreds 

 and sometimes thousands of miles from their course, and 

 not unfrequently out to sea, where they perish by thousands 

 from exhaustion and drowning. Or they become confused 

 by fogs or thick weather, and for the time being are lost. 

 It is at such times that they flit about lightships and light- 

 houses, and are killed by flying against the bewildering 

 lantern, which proves to them a beacon of destruction in- 

 stead of a guide to safety. Not unfrequently they are de- 

 stroyed in spring by unseasonable storms, they having 

 been lured north by a warm wave, or a period of mild 

 weather, only to encounter greater inclemency than they are 

 able to withstand. Every few years, great loss of life from 

 this cause overtakes many of the later migrants, as the War- 

 blers, Swallows, Tanagers and Flycatchers. Instances are 

 on record where a species, as the Purple Martin in Massa- 

 chusetts many years ago, after having reached its breeding 

 station has been wiped out of existence over a considerable 

 region, causing a great scarcity of the species for years after- 

 ward over the area of destruction. In fact, in view of all 

 tlie varied accidents and disasters birds are liable to en- 

 counter during migration it is almost a matter of surprise 

 that the natural increase is sufficient to offset the annual loss. 



