With the approach of the breeding season we witness that remarkable change which I have endeavoured to make clear in the previous chapters--the disintegration of the flock and the reinstatement of the individual. Instead of continuing with the flock, the individual now goes forth to seek the appropriate breeding ground; and having arrived there, is not only content to remain in isolation, but so behaves that isolation is insured. Intolerant of the approach of a stranger, intolerant even of the approach of the very members of the community whose companionship was previously welcomed, it not only fights to maintain the position it has selected, but fights indeed for the possession of ground already occupied, and, until reproduction is completed, asserts its individuality and exercises dominion over its territory. What, then, is the prospective value, biologically considered, of the changing interest that A displays in B, and to what will such changes lead? These are the questions to which we will now direct inquiry. The annual life-history of a bird is in broad outline conditioned by two powerful and at first sight opposing impulses--the one to live in society, the other to live solitary. But, manifestly, a bird cannot be governed by opposing impulses. It has but one character, within which, according to the season and the circumstances, different impulses predominate. But these impulses, no matter how different they may appear to be, have their respective parts to play in furthering the life of the individual. Hence they cannot oppose, though they may conflict, if the resultant behaviour contributes towards survival.