58 
BY TEE WAYSIDE 
require a northward course and this 
would, we have no doubt, be determined 
also by the remembrance of and fondness 
for home. 
Perhaps the most urgent need of birds 
which spend the winter near the equator 
and the summer ip higher latitudes, 
which impels them to their long jour¬ 
neys, is to be found in the impossibility 
of rearing the young in low latitudes*. 
Something like this certainly occurs in 
our own species in various parts of the 
world. The English, for example, in In¬ 
dia, can hardly be said even yet to be 
acclimated there, for they find it nec¬ 
essary in order to raise the children to 
take them into the mountain districts 
for a considerable part of every year, be¬ 
tween the ages of six and sixteen. Now 
if anything like this were also necessary 
with any of the birds, all such, accept 
those who comply with these require¬ 
ments, would be exterminated, leaving 
only those with established migatory 
habits to continue into our time. 
Tf birds did not move from the lower 
into the higher latitudes with the ap¬ 
proach. of summer, a vast territory, ca¬ 
pable of sustaining bird life, would be 
unoccupied, and when we associate with 
this fact two others, namely, first, the 
young of a large majority of birds must 
be reared mainly upon insect food, and. 
second, the number of insects so consum¬ 
ed in a few weeks is very large indeed, 
we have an abundant reason why even 
those species which can successfully rear 
their young in the low latitudes often 
send some of their kind as far poleward 
as it is possible for bird life to exist. So 
intense has been the struggle for insect 
food among birds that we now find an 
extensive division of labor among them, 
and groups, like the woodpeckers and 
swallows, have become profoundly fitted 
ror their special modes of securing food. 
e must look upon this migratory 
habit of birds, then, as having been es¬ 
tablished by insensible steps, extending 
across centuries of time, and in obedi¬ 
ence to the laws of self-preservation 
which dominate animal life. 
In Europe, where the movements of 
birds have received a much more extend¬ 
ed and careful study than in this coun- 
try, it has been found that there the 
feathered throng appears to divide up 
into streams which follow well marked 
courses. Of these streams nine have 
been pointed out by Herr Palmen. Some 
of them lead from island to island and 
along coast lines, others along great wa¬ 
ter-courses, as up the Rhine valley and 
over into that of the Rhone. Others still 
lead from one inland sea or lake to an¬ 
other. Certain species appear to move 
habitually along one of these courses, 
while other species as persistently choose 
another, and this, too, even when the 
summer home of the two species may 
be in the same locality. Do birds then 
have certain landmarks which serve as 
guide-boards on thes’e long journeys? 
Rut some birds pass over extremely long 
intervals without even stopping. The 
bluethroat, which breeds on the moss of 
northern Norway and which spends the 
winter in Egypt and the Upper Nile 
country, is not found during the migra¬ 
tions between these two places of abode, 
and yet the distance from the southern 
shores of the Baltic to the northern 
coasts of Africa is more than 1,300 miles. 
Again, there are two cuckoos which 
spend the summer in New Zealand, one 
supposed to come from Australia and 
the other occurring widely distributed 
throughout Polynesia, and yet an island¬ 
less ocean of more than a thousand miles 
must be crossed twice each year by the 
