64 THE STORY OF THE BIRDS. 
their feeding habits, they are apt to be conscious of 
their use, as is seen in petrels and vultures ejecting 
the offensive contents of their stomachs as a means of 
offense and defense. 
In some mammals it is quite evident that their 
weapons have been changed in shape at the demands 
of ornamentation, but there is nothing of this among 
the birds. Thus horns of deer have been unneces- 
sarily branched even till there is danger to both con- 
testants in fighting. This has no reference to victory. 
Those of sheep, antelopes, and goats have been beauti- 
fully corrugated, curled into spirals, or curved into 
lyre shapes till they are almost useless in their origi- 
nal purpose, and are now only butting implements at 
their bases. But, unless we except the occasional 
lengthening of beak during the charming season, there 
is nothing of this kind in the birds. Ornament seems 
to have seized on other parts. 
There is evidence among the mammals that one 
style of weapon has given place to another, as where 
ruminants, acquiring horns, have lost their weapon- 
like canine (“ eye” and “stomach”’) teeth. Some deer 
that have no horns still shoot out tusks like a wild 
boar. 
So it is not improbable that weapons, once ac- 
quired, have been gradually lost in birds, as other 
methods of winning wives have been developed. 
The spur comes no further up in the scale than the 
pigeons and hawk forms. Color and display are per- 
haps younger than special weapons, and it is certain 
that song is a more recent form of overcoming a rival 
