202 Directive Coloration in Animals. 
The first observations which eventually proved the germ of this 
paper were made on the plains of Dakota. During the long, mon- 
otonous rides over that region, one pleasant circumstance was the 
sudden rise of various birds from the nearly naked ground and their 
as sudden disappearance on lighting. Ere long it was noticed that 
in the process of lighting there was, very commonly, a conspicuous 
flashing-out of white on wings or tail, or on both. This was noticed 
in several of the sparrows, the meadow-lark, the lark-bunting, the 
Carolina dove, and less prominently in the prairie-hen or grouse. 
i facts were noted also of the jack-rabbit and antelope. 
The question then arose, very naturally, Why is this prevalent char- 
acter? Of what advantage is it? For the smaller birds, the answer 
came readily. The plains are constantly scoured by hovering hawks 
—therefore, protective coloration is of prime importance. If, how- 
ever, they should become of a uniform gray color all over, they 
would be as completely and constantly hidden from their friends as 
from their foes. That would be quite disastrous, especially where 
the former are fewer than the latter. To prevent such a result, 
there is the following arrangement. When at rest, or about the 
ordinary occupation of feeding, the gray surface only is exposed ; 
the same is true also in some cases during flight; but in checking 
its velocity for lighting the tail is fully spread, exhibiting the con- 
spicuous colors fully, and marks the location of the leader, that the 
rest may govern themselves accordingly. To escape the hawk, 
should he happen to note the location, the sparrow resorts to doub- 
ling on its course and skulking. When the danger has passed, the 
flock, if they have followed the leader, are likely to be within call 
of one another, and if they have become too much scattered, this 
same automatic telegraphy must assist much in enabling the strag- 
glers to find their fellows. Some species, as the meadow-lark, have 
a habit of spreading the tail at almost every chirp. This would 
seem to work as rationally as the rallying-call of the bugle and the 
waving of a flag to call a troop together. Yet after all, in the bird 
it is doubtless mainly automatic, the effort of the ery producing the 
twitch of the tail, as truly as in the prairie-dog. 
But this conspicuous flash tells more than the place of alight- 
ing. It reveals the species at hand. These white patches form @ 
kind of natural heraldry among the denizens of the plains, by which 
each kind is recognized by friend and foe. Its vivid white secures 
