What meaning does the song convey to a male that is unestablished? Does the bird recognise that it is forestalled; does it foresee and fear the possibility of a conflict, and conclude that the attempt to settle is not worth while 1 I do not imagine that it thinks about it at all. How then does the warning warn? We will endeavour to answer this question, but, in order to do so, we must review the stages by which a territory is secured.
We take as our starting point the internal organic changes which are known to occur. These changes are correlated with other changes, manifested by a conspicuous alteration in behaviour—to wit, the disappearance of sociability and its replacement by isolation. Having found a station which meets the requirements of its racial characteristics, the male establishes itself for a season, becomes vociferous, displays hostility towards others of its kind, and in due course is discovered by a female. The whole is thus an inter-related whole, a chain of activities which follow one another in ordered sequence. Now we have seen that it is neither pugnacious nor vociferous until the territory is actually occupied,; we have seen that the fact of occupation is the condition under which the instincts of pugnacity and of song are rendered susceptible to appropriate stimulation; we have discussed the nature of the stimulus in each case, and we wish to know the sort of meaning that the song conveys to an individual which is still in the preliminary stage of seeking a station. In
