Page:The British Warblers A History with Problems of Their Lives - 5 of 9.djvu/45

 were no commingling of the colours as a result of amphimixis and that, consequently, a dull-coloured female could not directly influence the colour of the male offspring, yet this would not affect the issue, for vitality must react upon the colour and influence the growth of the secondary sexual characters. Evidence of this can be seen in our domestic animal's, and to some extent even in ourselves. A dog in a low condition of health loses the brilliancy of the colouring in its coat, and, as is well known, the colouring of the human hair is affected by ill-health. But if a law of battle obtains amongst the females, we need no further explanation as to how the standard of efficiency has been maintained through numberless generations.

We have discussed the meaning of a territory to the individual, and have come to the conclusion that it is the attainment of reproduction; but inasmuch as this same result could be gained equally as well without all the complications introduced by a territory, it is evident that by this means some larger purpose is being fulfilled. That a breeding territory is of immense importance we can infer from the fact that we find the individuals of such widely separated species as the Falcons, Warblers, and the Moorhen struggling for possession. For my part I believe that the question of food supply has been one of the determining factors, although there are two observable facts which are somewhat opposed to this view. Firstly, that the members of any one of those species referred to, while objecting so strongly to a member of their own species breeding in their territory, frequently ignore the presence of one of another species, no matter how closely allied it may be, and no matter whether it would require a similar food; and, secondly, that there are a number of species that breed in communities. But upon further consideration these difficulties will be found to disappear to a great extent. It is true that in Nature we can find more than one species, requiring similar food, inhabiting the same small area of ground. But supposing the law of territory were temporarily suspended,