BRITISH WARBLERS
the Chaffinch, and, in the case of the latter species, the females struggle fiercely together, their battles being as desperate as those which occur between the males. I have seen two individuals struggling intermittently for nearly half an hour, and for the greater part of that time the fighting took place on or near to the ground. There was no doubt that the conflict was genuine; the rapid breathing, tightly drawn feathers, the rolling over and over on the ground, and the fluttering up in the air, showed this only too plainly. The male watched the contest from a branch above, and occasionally interfered by flying into the arena, but whether he attacked one bird only I was unable to ascertain; his efforts were of little avail in putting an end to the battle. This, then, is the sum-total of the evidence—insufficient, perhaps, to justify any definite conclusion; and there for the present we must leave it. But if there be any who think the evidence unreasonably scanty, supposing the struggles of the females to be a reality, I would ask them to consider this point—one to which I shall presently refer with regard to the males—that it is unnecessary for every individual to struggle for a territory, and this must be even more true of the females. It is not necessary, neither is it possible, for each female to have a rival for the territory in which she has settled. Probably it will only occasionally happen that two females meet in competition in any one particular locality, but if, when they do so meet, the stronger gains an advantage, that is all that will be required to maintain the strength of the species.
Our confidence in the truth of a theory must increase in proportion to the number of observations which receive an explanation under that theory, but not under any other. And there are two observations which become intelligible under the theory of breeding territory, but which, hitherto, have been inexplicable. The first of these, and the more important, is the fact of the males arriving at their breeding haunts before the females. It has long been recognised that amongst the migrants the first individuals to reach their destination in the
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