out or narrowing according to the character of the country over 
which it is passing. Dispersion over a wide area is the surest 
method of finding the way for in this manner a larger area of land¬ 
marks is visible to the migrating flocks. According to the best 
vantage point of vision, temporary leaders are continually created 
whom the others may follow. It is well known that when the 
leader in a harrow of wild geese becomes disabled the others arc, 
for a time at least, thrown into confusion, showing that they were 
keeping to the path by following a leader. While certain species 
fly in comparatively close array, as cowbirds for example, others 
may be straggling far behind the pioneers so that all the members 
of any one species may occupy over a month in passing a given 
point. Thus it is possible for any individual bird to have com¬ 
panions constantly to guide it on its way when it might be unable 
to proceed independently. It is not necessary, however, to assume 
that the same birds are always the leaders in the flight or that the 
leaders themselves depend upon landmarks which they can see. 
It seems reasonable to believe that sound serves to keep the indi¬ 
viduals of migrating hosts in communication with each other when 
sight fails for it is comomnly observed that bird-calls during mi¬ 
gration are much more frequent upon foggy than upon clear 
nights. 
In the case of carrier pigeons the successful individuals are 
those who have been trained over the course, that is, those who 
have learned the way either by seeing landmarks for themselves 
or by following a trained companion. There is no mysterious sixth 
sense of direction, no crossing of imaginary magnetic lines, no in¬ 
tricate automatic registry of distance and direction by means of the 
semi-circular canals. It is simply a case of a home-loving animal 
away from home putting its wits and senses and experiences to¬ 
gether to get back to its home and in this case these known re¬ 
sources are sufficient for the task. Why may not this also be the 
true explanation of the manner in which birds find their way on 
those greater pilgrimages which we call migration? The murres 
flying in the fog, the migrants striking out from Cuba for invisi¬ 
ble Florida or across the Gulf of Mexico toward an unseen shore, 
are all either traveling a course they have learned by experience 
or following within sight or call of others who know where to go. 
It does not seem any more impossible that a bird should learn to 
travel a familiar distance without landmarks than that a blind man 
is able to walk in a familiar path. What causes the migration move¬ 
ment is another problem entirely but, once given the incentive for 
this wonderful exodus, it seems reasonable to believe that the 
manner in which it is carried out, the way in which the path is fol- 
