310 THE STRUCTURE AND LIFE OF BIRDS cap. 
danger to each other before the females. The Ruffs, 
who, unhappily, no longer breed in England, supply the 
best instance of this. They have regular places at 
which they assemble, known to fowlers by the grass 
being trampled down. Here day after day they con- 
gregate and go through their fantastic performance. 
Fighting pure and simple unaccompanied by antics 
iscommon. Humming-birds are said to fight des- 
perately. The males of the Common Waterhen have 
great battles, standing nearly upright in the water, 
and fighting with their feet. Robins are great fighters. 
The males of gallinaceous birds are often very pug- 
nacious and in their spurs they have a formidable 
weapon. The courage and ferocity of the Gamecock is 
proverbial. As a rule it is among polygamous species 
that we find the combats most desperate and the 
antics most elaborate. 
Theories to explain these Phenomena. 
Darwin was first in the field with a definite 
theory, to which he gave the name of Sexual Selection. 
The cock-birds fought and the hen-birds were the 
-prizes. There is no doubt that this theory rests on a 
foundation of fact. Selection by battle goes on in 
many classes of animals, notably among deer and 
cattle. But an explanation of the brilliant plumage 
was more difficult to find. The theory which we owe 
to him is very ingenious and plausible, but the evidence 
on which it rests is insufficient. The female bird, he 
maintained, selected the handsomest male bird, or the 
best singer, or the one that performed the most strik- 
