prevails between neighbouring pairs, and which can be observed in the life of many other species—the Chaffinch, Stonechat, Blackbird, Partridge, Jay, to mention but a few.
The conflicts between males that are definitely paired are of such common occurrence that it is scarcely necessary to mention specific instances. But the occasions on which a male attacks either sex of a neighbouring pair indiscriminately, or on which a pair combine to attack a female, are less frequent.
Now if it be true that males fight for no other purpose than to gain possession of a mate, what meaning are we to attach to the battles between the pairs, or what explanation are we to give of the fact that paired males are so frequently hostile? Those who hold this view will probably argue thus: "The presence of the female is the condition under which the pugnacious instinct of the male is rendered susceptible to appropriate stimulation, and the stimulus is supplied by a rival male; we admit that all the fighting which occurs after pairing has taken place has nothing to do strictly speaking with gaining a mate, but, inasmuch as the fact of possession is always liable to be challenged—and no male can differentiate between a paired and an unpaired intruder—we contend that it would add to the security of possession if the pugnacious instinct remained susceptible to stimulation so long as there were any possibility of challenge from an unpaired male; and we think that the waste of energy involved in
