Page:Territory in Bird Life by Henry Eliot Howard (London, John Murray edition).djvu/307

Rh which a bird displays in other species varies not only at different seasons but even from hour to hour. I have used the word "nature" as equivalent to "interest," and I have spoken of the bird's nature changing or altering according to the circumstances in which it was placed. But its nature is its inborn constitution, and its constitution cannot change from day to day, still less from hour to hour. So that, in a sense, and having regard to strict scientific accuracy, it is misleading in this particular connotation to say that the bird's nature changes.

What then does happen? The instinct of pugnacity must form just as much a part of the hereditary make-up of the migrant, when on migration, as when finally it reaches its destination; still more must it form part of the constitution of the Bunting when it leaves its headquarters temporarily and joins the flock. And, if it is there, the question arises as to why it does not respond. Now every instinct requires for its response a stimulus of an appropriate kind, and, therefore, a reasonable view to take would be that the necessary stimulus was lacking. But this is a view which we cannot uphold, because on all these occasions an opposing male was present-and, so far as it is possible to judge by observation, that is the stimulus which in the main evokes a hostile response. We must therefore look elsewhere than in its direction for a reason which will adequately explain the behaviour.

Though it be true that every instinct