62 THE STORY OF THE BIRDS. 
That the spur is a weapon of rivalry is shown by 
its larger development upon the wings of the males 
(though some females have it) and by the fact that 
where it exhibits itself only as a knob it tends to sub- 
side (in some plovers) after the fighting season is over. 
Its development thus by use may also be implied from 
the fact that while in some species of a family it is a 
well-developed spur, in others it is only a mere cal- 
losity on the wing’s bend, as seen in the swans and 
others. In the spur-winged goose it is strongly 
marked, but in our ordinary geese there is only the 
habit of striking a very effective blow with the “ butt 
of the wing,” as any one may observe in a goose fight. 
The writer has a very vivid remembrance of a time 
when, having the experience of about five summers 
only, he undertook to be too familiar with some fluffy 
goslings, and received upon his forehead a very prac- 
tical demonstration that an old gander had knuckles 
on his wings. 
Nearly all the low birds appear to have had ances- 
tors with this style of weapons. Among the fowl 
forms some of the brush-turkey tribe have rudimen- 
tary spurs upon the wings; there is a spur-winged 
pigeon; many plover forms show them variously, 
and at the junction of these and the rail forms is the 
jacana, similarly armed. At the bottom of the goose- 
duck group is the screamer, with double wing spurs, 
tying this group backward, while triangularly between 
the birds of prey, the herons, and cranes, and doubt- 
less older than all, is the spur-winged secretary bird. 
Dr. F. A. Lucas notes that when wing spurs are 
