38 THE MIGRATION 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 e7 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 umseasonable 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 
the 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. 
