BRITISH WARBLERS
way, singing continuously while perched upon the sunny side of the bush which he had made his headquarters. If a single bird or one of another pair attempted to intrude upon his small domain, he fiercely attacked it, rapidly pursuing the trespasser some distance into the dense mass of reeds, and when a collision did occur the impact was considerable. If it was a pair that was intruding the attack was generally aimed at the male, but the female from the adjoining territory, while collecting food for her young, was also attacked. Thus the days passed by, sometimes peaceably, sometimes the reverse, until this jealous defence of his territory seemed to me to be a waste of energy and time, as it appeared to be improbable that a female would arrive at so late a date. In this, however. I was mistaken, for on June 20th a female appeared on the scene, and nesting operations were forthwith commenced. His behaviour now differed from what it had been previously; the headquarters were of secondary importance, and he now followed the female submissively. It is an interesting fact, and not a little curious, that on the day on which the female arrived—June 20th—the young of the adjoining pair finally left the nest. Why should this male for twenty-eight days have remained in the same small plot of ground? Why should he day after day have been found in the same bush and upon almost the identical branch pouring out his song? And above all, why should he have resented the approach of other members of his own species, and have attacked them so viciously? I have already mentioned this question of breeding territory in the life of other species. It is, I believe, a factor of no small importance in the animal kingdom, and as such demands further consideration.
Those who have paid attention to the habits of birds during the season in which the sexual organs are developing can hardly have failed to notice the battles which are of such frequent occurrence between the males of the same species. Darwin believed that the primary object of these struggles was the possession of a female, but for reasons
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