182 THE STORY OF THE BIRDS. 
While over water or great stretches of land where 
they do not care to alight the route of birds may be 
rather direct between points far apart, unless, as is 
often the case, they are deflected by winds; but 
where there are coast lines tending in the right direc- 
tion they are apt to be roughly followed, and inland 
great streams and wooded borders are followed. This 
last is likely because of the opportunities of rest, food, 
and shelter or proper haunt that they may offer. Even 
at sea birds are apt to lay their journeys by islands, 
and these islands will lie for ages in their routes. Or- 
dinary land birds are recorded as resting sometimes 
by simply floating for a while upon the water in mid- 
ocean. 
The island of Heligoland, in the North Sea (or 
German Ocean), has for generations been the resting 
place for migrants to and from northern Europe. It 
is said that the bird routes now over the Mediterra- 
nean Sea are over shallow places that were once isth- 
muses. bird routes even through the air are apt to 
be very permanent when once established, and these 
over the Mediterranean were probably set up by fol- 
lowing the land beneath when it was visible, and are 
followed now by the heritance of habit. Columbus 
was influenced in his voyage by following one of these 
bird “ aérial lanes,’ and was led on to the West Indies 
instead of Florida. These bird flights are said to be 
there to-day at the same season of the year. 
But by far the most interesting question about the 
migration of birds is, What guides them? There is 
quite a tendency among modern students to assert 
