There is yet another puzzling feature in regard to the armature of the wings, and one which may yet help to a better understanding of the puzzles presented by spurs. A Jacana, one of the Plovers, has the radius broadened or flattened out from its middle onwards to form a flat plate or blade, but the use thereof is unknown. It may possibly serve as a weapon of offence, enabling the bird to beat its rivals with its wings, but from the nature of the structure, and of the effect such a use of the forearm would have upon the hand, it seems doubtful whether it serves any aggressive function. If used at all in fighting it is probably during fights in mid-air, when, after the fashion pursued by the Spur-winged Plover, and even in the case of our own Lapwing, a blow is struck by the uppermost bird at its rival, and often with fatal effect. It is significant to remark, by the way, that in the Lapwing a tubercle answers to the spur of Hoplopterus just as the tubercles of the French Partridge (_Caccabis_) answer to the spur of the Jungle-fowl or Pheasant: but the flattened radius of the wing of the _Metopidius jacana_ has no parallel. With birds, as with men, there must always remain the ability to appeal to force when some important end cannot otherwise be gained. The species which adopts the crazy tactics of the Quaker is doomed to extinction, sooner or later. The foregoing instances display force, as we may say, aggressively. But even the peacefully disposed birds can fight when aroused. Reference has already been made to dancing in this chapter; but so far no very striking instances thereof as a form of sexual display have been cited. The subject has been deferred because this peculiar type of activity is not always directly associated with the _furor amantium_.