204 BRITISH SEA BIRDS. 
houses and light-vessels. Vast numbers of birds 
kill themselves every spring and autumn by 
striking against these gleaming beacons of the 
coast. From this great mortality, however, 
naturalists have learnt much concerning the annual 
movements of birds; for the records kept by 
our light men, extending, as they do, over a 
number of years, of these fatalities and periodical 
visits of migrants, are most instructive and sugges- 
tive. Some of the scenes witnessed at these light- 
houses and vessels, during the seasons of migratiou 
—especially in autumn—are intensely interesting. 
These beacons are most fatal during cloudy 
weather ; few birds strike on clear and cloudless 
nights. Odd birds are continually striking against 
the lanterns. Now and then, however, there come 
nights when birds swarm like bees round the lamps, 
and kill themselves in thousands by-striking against 
the glass, sometimes with such force as to shatter it 
to fragments. The illustration at the head of the 
present chapter also shows another peril of migra- 
tion. Many nets are placed on the shores of the 
Wash, and great numbers of birds are, or used to 
be, caught during the autumn months. Information, 
however, has recently reached me that the birds 
are learning, by many years’ experience, to avoid 
these snares, flying over instead of through them, 
and that nothing like the numbers are caught 
nowadays. Fifteen years ago thousands of birds 
must have been taken in these nets. 
