Territory in Bird Life

by Henry Eliot Howard

The battles between pairs of the same species are by no means uncommon. Observe, for example, the central pair of three pairs of Reed-Buntings occupying adjoining territories, and keep a daily record of the routine of activity practised by both sexes during the early hours of the morning; then, at the close of the season, summarise all the fighting under different headings, and it will be found that the number of occasions upon which the central pair attacked, or was attacked by, neighbouring pairs will form a considerable portion of the whole.

Or watch the Moor-Hen, and for the purpose choose some sheet of water large enough to accommodate three or more pairs, and so situated that the birds can always be kept in view. Early in February the pool will be haunted by numbers of individuals of both sexes, all swimming about together, and, if the pool is surrounded by arable land, wandering over that land subject to no territorial restrictions, apparently free to seek food where they will. But as time goes by, their number gradually decreases until a few pairs only remain, and these will occupy definite areas. If careful watch is then kept and the relations of the pairs closely studied, there will be no difficulty in observing the particular kind of warfare to which I am alluding, and it will be noticed that the encounters are of a particularly violent description. Thus two pairs approach one another, and, when they meet, throw themselves upon their backs, each bird striking at its adversary with its feet or seizing hold of it with its beak; and though, in the commotion that ensues, it is almost impossible to determine what exactly is happening, there is reason to believe that the sexes attack one another indiscriminately.

A struggle between two pairs of Pied Wagtails is worth mentioning. It impressed itself upon my memory because of the unusual vigour with which it was conducted. The battle lasted for fifteen minutes or more, and the four birds, collecting together, pursued and attacked one another—at one moment in the air, at another upon the roof of a house where they would alight and flutter about on the slates, uttering their call-note without ceasing—until finally they disappeared from view, still, however, continuing the struggle.

Such is the nature of the warfare which prevails between neighbouring pairs, and which can be observed in the life of many other species—the Chaffinch, Stonechat, Blackbird, Partridge, Jay, to mention but a few.

The conflicts between males that are definitely paired are of such common occurrence that it is scarcely necessary to mention specific instances. But the occasions on which a male attacks either sex of a neighbouring pair indiscriminately, or on which a pair combine to attack a female, are less frequent.

Now if it be true that males fight for no other purpose than to gain possession of a mate, what meaning are we to attach to the battles between the pairs, or what explanation are we to give of the fact that paired males are so frequently hostile? Those who hold this view will probably argue thus: "The presence of the female is the condition under which the pugnacious instinct of the male is rendered susceptible to appropriate stimulation, and the stimulus is supplied by a rival male; we admit that all the fighting which occurs after pairing has taken place has nothing to do strictly speaking with gaining a mate, but, inasmuch as the fact of possession is always liable to be challenged—and no male can differentiate between a paired and an unpaired intruder—we contend that it would add to the security of possession if the pugnacious instinct remained susceptible to stimulation so long as there were any possibility of challenge from an unpaired male; and we think that the waste of energy involved in the struggles between paired birds, and which we grant is purposeless, would be more than balanced by the added security." This is a possible explanation and requires consideration. It cannot account for all the diverse ways in which the sexes are mixed up in the fighting—it cannot, for instance, explain the fact that an unpaired male will attack either sex of an adjoining pair indiscriminately—but nevertheless it appears at first sight to be a reasonable explanation of some of them. We must remember, however, that fighting continues throughout the whole period of reproduction. Even after the discharge of the sexual function has ceased, and the female is engaged in incubation or in tending her young, the male is still intolerant of intruders; and it is difficult to believe that, at so late a stage in the process, a female could be any attraction sexually to an unpaired male. But apart from any theoretical objection, there remains the fact—namely that there is no evidence that a male, after having once paired, is liable to be robbed of its mate. And in support of this fact I have only to state that I have met with no single instance of failure to obtain and hold a mate when once a territory had been secured. Bearing in mind then that both sexes participate in the fighting, and that individuals of the opposite sex frequently attack one another; that all such conflicts are characterised by persistent effort, and that they are not limited to just the particular period when the sexual instinct is dominant but continue throughout the breeding season; bearing in mind that in at least one form of this promiscuous warfare the influence of the female can be definitely excluded, and that, in the remaining forms, the evidence which is required to link them up with the biological end of securing mates is lacking—can it be denied that the complexity of the strife makes against the view that the possession of a female is the proximate end for which the males are fighting?

We started with the most simple aspect of the whole problem, the fighting of two males in the presence of one female—the aspect upon which attention has usually been fixed. And if it remained at that, if observation failed to disclose any further development in the situation, then there would be no need to probe the matter deeper, there would be no reason to doubt the assertion that the quarrel had direct reference to the female. But assuredly no one can ponder over the diversity of battle and still believe that the possession of a mate furnishes an adequate solution of the mystery. Clearly such an hypothesis cannot cover all the known facts; there are conflicts between separate pairs, and there are conflicts between males when females are known to be absent and when their mates are even engaged in the work of incubation—these cannot be due to an impulse in a member of one sex to gain or keep possession of one of the other sex. So that taking all these facts into consideration, we are justified, I think, in hesitating to accept this view, and must look elsewhere for the real condition under which the pugnacious nature of the male is rendered susceptible to appropriate stimulation.

What then is the meaning of all this warfare? The process of reproduction is a complex one, built up of a number of different parts forming one inter-related whole; it is not merely a question of "battle," or of "territory," or of "song," or of "emotional manifestation," but of all these together. The fighting is thus one link in a chain of events whose end is the attainment of reproduction; it is a relationship in an inter-related process, and to speak of it as being even directly related to the territory is scarcely sufficient, for it is intimately associated with the disposition which is manifested in the isolation of the male from its companions, and forms therewith an imperium in imperio from which our concept of breeding territory is taken. But let me say at once that it is no easy matter to prove this, for since so many modes of behaviour, which can be interpreted as lending support to this view, are likewise interpretable on the view that the presence of a female is a necessary condition of the fighting, it is difficult to find just the sort of evidence that is required. Nevertheless, after hearing the whole of the evidence and at the same time keeping in mind the conclusion which we have already reached, I venture to think that the close relationship between the warfare on the one hand and the territory on the other will be fully admitted.