island about 6o miles away. These birds- were seen repeatedly 
looming up in the fog behind the steamer then passing on ahead 
out of sight, flying as steadily and surely as if by compass al¬ 
though it was possible to see hardly more than a boat’s length 
ahead. Such cases strengthen the conviction of many that there 
must be present in birds an unknown sense which serves them in 
some such way as the compass serves the mariner. This view, 
however, is hardly better than the instinct theory since it gives the 
answer to the problem in unknown terms. 
The Landmark The landmark theory has rather more to rec- 
Theory ommend it. Exner came to the conclusion that 
carrier pigeons find their way home by seeing familiar landmarks 
and when such landmarks are not visible the birds explore until 
landmarks are found. This explains how his pigeons, whether 
whirled, galvanized or narcotized, were quite as well able to get 
home as those which had not undergone such interference with 
their sensory impressions upon the outward journey. Anyone who 
has observed swallows hawking for insects upon a summer after¬ 
noon or who has seen a hawk swoop down upon a field mouse 
from a dizzy height in the sky, must be convinced that the sight 
of birds is very acute. This is proven not only by their behavior 
but by anatomical evidence as well. The eye of the hawk is per¬ 
haps the most perfect optical instrument in nature. So far as the 
sense of sight goes it may be admitted that birds are well endowed 
to observe landmarks from a distance, while those birds that habit¬ 
ually migrate during the twilight, as nighthawks, bitterns, wood¬ 
cock and certain sandpipers, being accustomed to feed at this time 
of day, have no difficulty in seeing objects in semi-light. 
The objection must be raised to the landmark theory, however, 
that many birds do not follow river valleys, coast lines or moun¬ 
tain chains in the way they might be expected to do if they were 
guided by what appear to us to be the most obvious landmarks. 
Furthermore, migratory birds leave Cuba for Florida without 
hesitation upon cloudy nights when no landmarks are possibly vis¬ 
ible and the stretch across the Gulf of Mexico, which is also regu¬ 
larly traversed by birds, is so great that even if migrants rose to a 
height of five miles, which is beyond reason, they could scarcely see 
one third of the way across to the other shore on account of the 
curvature of the earth. Sight alone, then, although it is an impor¬ 
tant factor, cannot be the only resource of the migratory bird. 
The Follow-the- Still another theory with a large element of 
Leader Theory probability in it may be briefly described as fol¬ 
lows. Birds are social animals and fly in company with each other. 
The total migratory stream is a vast straggling army, spreading 
