Various birds have spurs on their wings. But the Egyptian goose (_Chenalopex ægyptiacus_) has only “bare obtuse knobs,” and these probably shew us the first steps by which true spurs have been developed in other allied birds. In the spur-winged goose, _Plectropterus gambensis_, the males have much larger spurs than the females; and they use them, as I am informed by Mr. Bartlett, in fighting together, so that, in this case, the wing-spurs serve as sexual weapons; but according to Livingstone, they are chiefly used in the defence of the young. The Palamedea (fig. 38) is armed with a pair of spurs on each wing; and these are such formidable weapons that a single blow has driven a dog howling away. But it does not appear that the spurs in this case, or in that of some of the spur-winged rails, are larger in the male than in the female.[74] In certain plovers, however, the wing-spurs must be considered as a sexual character. Thus in the male of our common peewit (_Vanellus cristatus_) the tubercle on the shoulder of the wing becomes more prominent during the breeding-season, and the males are known to fight together. In some species of Lobivanellus a similar tubercle becomes developed during the breeding-season “into a short horny spur.” In the Australian _L. lobatus_ both sexes have spurs, but these are much larger in the males than in the females. In an allied bird, the _Hoplopterus armatus_, the spurs do not increase in size during the breeding-season; but these birds have been seen in Egypt to fight together, in the same manner as our peewits, by turning suddenly in the air and striking sideways at each other, sometimes with a fatal result. Thus also they drive away other enemies.[75]