Territory in Bird Life Part 2

Guillemots and Razorbills return at intervals to the breeding stations early in the season, and these visits are repeated with growing frequency until the birds are finally established. I have witnessed these periodic returns during March in the south of England, and during April in the north-west of Ireland, and I am informed that in the latter district such visits may occur as early as February. Gatke, who had ample opportunity of observing the birds in Heligoland, puts their return at an even earlier date. "They visit their breeding places," he says, "in flocks of thousands at the New Year, often even as early as December, as though they wanted to make sure of their former haunts being well preserved and ready for their reception." Such visits, however, are irregular in occurrence; the birds arrive, and, after spending a short time upon the ledges, disappear. And since there is not the same evidence in their coming and going of that method which we observe in the periodical returns of the Bunting or the Finch, it may be thought that needless importance is being attached to an episode in their lives which is quite intelligible in terms of a feeble response determined by a dawning organic change. While it may be quite intelligible in such terms it is not thereby explained; for every response must have as its antecedent an inherited connection in the nervous system determined on biological grounds. Besides, these early periodic returns conform in general to the type of behaviour displayed by other species, the males of which return to their breeding grounds many weeks before the real business of reproduction begins. Are we then justified in regarding them as accidents of the developing situation?

Are we not rather bound to admit that they have some definite biological end to serve?

[Ill.u.s.tration: Compet.i.tion for territory is seldom more severe than amongst cliff-breeding sea birds, and the efforts of individual Razorbills to secure positions on the crowded ledges lead to desperate struggles.

Emery Walker ph.sc.]

These examples show that the males of many species reverse their mode of life at the commencement of the breeding season and proceed to isolate themselves, each one in a definitely delimited area.

There are three ways in which we may attempt to interpret this particular mode of male behaviour. We may regard it as an accidental circ.u.mstance, nowise influencing the course of subsequent procedure; or, appealing to the law of habit formation, we may regard it as an individual acquirement; or again, we may invest it with a deeper significance and seek its origin in some specific congenital disposition determined on purely biological grounds.

Which of these three shall we choose? The first by itself requires but little consideration; for though it might explain the initial visit, it cannot account for the persistency with which the plot of ground is afterwards resorted to. Supposing, however, that we combine the first and the second; supposing, that is to say, we a.s.sume, for the purpose of argument, that the initial visit is fortuitous, and that constancy is supplied by habit formation--would that be a satisfactory interpretation? It is a simple one, inasmuch as it only requires that a male shall alight by chance in a particular place for a few mornings in succession in order that the process may be set in motion. Now an essential condition of habit formation is recurrent repet.i.tion; given this repet.i.tion and, it is true, any mode of activity is liable to become firmly established. But how can we explain the repet.i.tion? Even if we are justified in a.s.suming that the initial visit is purely an accidental occurrence, we cannot presume too far upon the laws of chance and a.s.sume that the repet.i.tion, at first, is also fortuitous.

So that we come back to the congenital basis, the last of our three propositions. And it will, I think, be admitted that the facts give us some grounds for believing that the securing of the territory has its root in the inherited const.i.tution of the bird. In comparing the behaviour of the migratory male with that of the resident, attention was drawn to the manner in which the occupation of a territory was effected: the former bird, it may be remembered, established itself without delay, whereas the latter did so only by degrees, and the difference was attributed to the incidence of migration which required a closer correspondence between organic process and external environment. But the significance for us just now lies in the fact that the definiteness, which accompanies the initial behaviour of the migratory male in relation to the territory, cannot have been acquired by repet.i.tion; for this reason, that when the male occupies its s.p.a.ce of ground at the end of its long and arduous journey, it does so without preparation or experiment, even without hesitation, as if aware that it was making good the first step in the process of reproduction. No doubt, if it happened to be an individual that had already experienced the enjoyment of reproduction, it might be aware of the immediate results to be achieved and act accordingly. But among the hosts of migrants that one observes, there must be many males which have not previously mated; and yet, upon arrival, they all behave in a similarly definite manner--so that experience cannot well be the primary factor in the situation. If, then, the essential condition of habit formation is absent and experience is eliminated, there is nothing left but racial preparation to fall back upon.

Nevertheless, it is true that many resident males seem to pa.s.s through a period of indecision before they establish themselves permanently in their respective territories; they come and go, their visits grow more and more prolonged, and only after the lapse of some considerable time does the process of establishment attain that degree of completeness which is represented in the initial behaviour of the migratory male.

Their whole procedure seems therefore to bear the stamp of individual acquirement; and, if it stood alone, we might be content to construe it thus, but the example of the migratory male necessitates our looking elsewhere for the real meaning of the indecision.

Let me first of all give some instances of the persistence with which a male remains in one spot, and this despite the fact that it has no mate.

A Reed-Bunting occupied a central territory in a strip of marshy ground inhabited annually by four or five males of this species. Throughout April, May, and until the 19th June, it clung to its small plot of ground, tolerated no intrusion, and sang incessantly.

Two Whitethroats arrived at much the same time--the 30th April approximately--and occupied the corner of a small plantation; the one obtained a mate the day following its arrival, the other remained unpaired for a fortnight.

A Reed-Warbler established itself amongst some willows and alders adjoining a reed-bed and made its headquarters in a small willow bush.

Not more than fifteen yards away, on the edge of the main portion of the reeds, another male was established and was paired on the 22nd May. Each morning the single male behaved in much the same way, singing continuously whilst perched upon the bush. And so the days pa.s.sed by until it seemed improbable that it would ever secure a mate, but one appeared on the 20th June, and a nest was built forthwith.

Now it is difficult to believe that a chance visit, even though repeated for a few mornings in succession, could have accounted for the Reed-Bunting remaining so persistently in the marsh, or the Whitethroat in one corner of the osier bed, or the Reed-Warbler in that one particular willow. Not only so, but if a habit of such evident strength can be acquired so readily, we have a right to ask why it should only be acquired in the spring--why not at every season? Considerations such as these lead to the belief that there must be some congenital basis to account for such persistent endeavour; the more so since it is difficult not to be impressed with the conative aspect of the male's behaviour. To a stranger, unacquainted with its previous history, the bird might appear to be leading a life of hesitation, whereas, if carefully watched, its whole att.i.tude will be found to betray symptoms of a striving towards some end; and the frequent departure and return, which might be pointed to as the material from which a definite mode of procedure would be likely to emerge, is in reality behaviour of a determinate sort.

My interpretation, then, of the apparent indecision in the behaviour of the resident male is this. During the winter most species live in societies, together they seek their food and together they retire in the evening to the accustomed roosting places; and the a.s.sociation of different individuals confers mutual benefits upon the a.s.sociates. The movements of these societies are dominated by the question of food; all else is subservient, and the supply of the necessary sustenance may, under certain conditions, become a difficulty which can only be met by energy and resource. After the long night the sensation of hunger is strong, and the birds, on awakening, fly to the accustomed feeding grounds, returning again in the evening to the selected spot, and by frequent repet.i.tion a routine becomes established. Thus the behaviour of each individual is determined not only by the powerful gregarious impulse but also by the habits formed in connection therewith during many weeks in succession. Now with the rise of the appropriate organic state, the disposition to seek the breeding ground and there to establish itself becomes dominant in the male. But the process is a gradual one. There is no need, as happens amongst the migrants, for the period of organic change to conform rigidly to the growth of any particular condition in the environment, and hence for a time the bird oscillates between two modes of behaviour--between that one organised by frequent repet.i.tion and that one determined by the functioning of this new disposition.

To look at the matter broadly, it is scarcely likely that so definite a mode of behaviour would recur with such regularity, generation after generation, in the individuals belonging to so many widely divergent forms, if it had no root in the inborn const.i.tution of the bird. But the law of habit formation has its part to play also. By itself it is inadequate; yet it probably does a.s.sist very materially in adding still greater definition, and it probably is responsible in a large measure for determining the limits of the territory according to the conditions of existence of the species--thus the Falcon seeks its prey over wide tracts of land, and, by hunting over certain ground repeatedly, establishes a routine, which broadly fixes the area occupied; the Woodp.e.c.k.e.r cannot find food upon every tree, and every forest does not contain the necessary trees, and therefore the bird regulates its flight according to the position of the trees; and the Warbler, finding food close at hand, does not need to travel far, and the area it occupies is consequently small.

So that the most likely solution of the problem will be found in a combination of our second and third propositions; that is to say, in an initial responsive behaviour provided for in the inherited const.i.tution of the nervous system, and in a definiteness acquired by repet.i.tion and determined by relationships in the external environment.

CHAPTER III

THE DISPOSITION TO DEFEND THE TERRITORY

In the previous chapter I endeavoured to show that each male establishes a territory at the commencement of the breeding season, and there isolates itself from members of its own s.e.x. And further I gave my reasons for believing that this particular mode of behaviour is determined by the inherited nature of the bird, and that we are justified in speaking of it as "a disposition to secure a territory"

because we can perceive its prospective value. But the act of establishment is only one step towards "securing." By itself it can achieve nothing; for any number of different individuals might fix upon the same situation, and if there were nothing in the inherited const.i.tution of the bird to prevent this happening, where would be the security, or how could any benefit accrue to the species?

In withdrawing from its companions in the spring, the male is breaking with the past, and this action marks a definite change in its routine of existence. But the change does not end in attempted isolation; it is carried farther and extends to the innermost life and affects what, humanly speaking, we should term its emotional nature, so that the bird becomes openly hostile towards other males with whom previously it had lived on amicable terms.

The seasonal organic condition is responsible for the functioning of the disposition which results in this intolerance, just as it is for the functioning of the disposition which leads to the establishment of the territory; and the effect of these two dispositions is that a s.p.a.ce of ground is not only occupied but made secure from intrusion. The process is a simple one. There is no reason to believe, there is no necessity to believe, that any part of the procedure is conditioned by antic.i.p.atory meaning; the behaviour is "instinctive" in Professor Lloyd Morgan's definition of the word, since it is of a "specific congenital type, dependent upon purely biological conditions, nowise guided by conscious experience though affording data for the life of consciousness."

That the males of many animals are apt to become quarrelsome during the mating period is notorious. Darwin collected a number of facts, many of which related to birds, showing the nature and extent of the strife when the s.e.xual instinct dominated the situation. And pondering over these facts, he deduced therefrom a "law of battle," which, he believed, bore a direct relation to the possession of a female. And it must be admitted that he had excellent ground for his conclusion in the fact not only that the conflicts occur mainly during the pairing season, but that the female is often a spectator and seems even to pair with the victor.

I accepted it, therefore, as the most reasonable interpretation of the facts. But, as time pa.s.sed by, incidents of a conflicting character led me to think that after all there might be another solution of the problem. And when it was no longer possible to doubt that there was a widespread tendency to establish territories, it at once became manifest that the battles might have an important part to play in the whole scheme. But how was this to be proved? What sort of evidence could show whether the proximate end for which the males were fighting had reference to the female or to the territory? Clearly nothing but a complete record of the whole series of events leading up to reproduction could supply the necessary data upon which a decision might rest. In the present chapter I shall give, in the first place, the reasons which lead me to think that the origin of the fighting cannot be traced to the female; afterwards, the evidence which seems to show that it must be sought in the territory; and finally, I shall make a suggestion as to the part the female may play in the whole scheme.

[Ill.u.s.tration: Male Blackbirds fighting for the possession of territory.

The bare skin on the crown of the defeated bird shows the nature of the injuries from which it succ.u.mbed.

Emery Walker ph.sc.]

The facts upon which the "law of battle" was founded were ample to establish the truth of its main doctrine. But the evidence upon which the interpretation of the battles was based was somewhat superficial. It was based mainly upon the general observation that one or more females could frequently be observed to accompany the combatants; and if this were the sole condition under which the fighting occurred, one must admit that this view would have much to recommend it. But it is not merely a question of males disputing in the presence of a female; for males fight when no female is present, pair attacks pair, or a male may even attack a female--in fact there is a complexity of strife which is bewildering.

In attributing the rivalry to the presence of the female, it is a.s.sumed that males are in a preponderance, and that consequently two or more are always ready to compete for a mate. Her presence is presumably the condition under which his pugnacious nature is rendered susceptible to its appropriate stimulus, the stimulus being, of course, supplied by the opponent. There would be nothing against this interpretation if it were in accord with the facts; but it can, I think, be shown that the males are just as pugnacious and the conflicts just as severe even when the question of securing a mate is definitely excluded; and I shall now give the evidence which has led me to this conclusion.

In the previous chapter we had occasion to refer to the difference in the times of arrival of the male and female migrants, and we came to the conclusion, it may be remembered, that this was a fact of some importance, because it gave us a clue to the meaning of much that was otherwise obscure in their behaviour. But it is also of importance in connection with the particular aspect of the problem which we now have in view, for if it can be shown that males, when they first reach their breeding grounds, are even then intolerant of one another's presence, if their actions and att.i.tudes betray similar symptoms of quasi-conation, if disputes are rife and the struggles of a kind to preclude all doubt as to their reality, then it is manifest that in such cases their intolerance cannot be due to the presence of the female.

Here, however, I must refer to a view which is held by some psychologists, namely, that amongst the higher animals, even on the occasion of the first performance of an instinctive act, there is some vague awareness of the proximate end to be attained. Discussing the nature of instincts, Dr M'Dougall[3] says, "Nor does our definition insist, as some do, that the instinctive action is performed without awareness of the end towards which it tends, for this, too, is not essential; it may be, and in the case of the lower animals no doubt often is, so performed, as also by the very young child, but in the case of the higher animals some prevision of the immediate end, however vague, probably accompanies an instinctive action that has often been repeated." A similar view seems to be held by Dr Stout.[4] "As I have already shown," he says, "animals in their instinctive actions do actually behave from the outset as if they were continuously interested in the development of what is for them one and the same situation or course of events; they actually behave as if they were continuously attentive, looking forward beyond the immediately present experience in preparation for what is to come. They apparently watch, wait, search, are on the alert. They also behave exactly as if they appreciated a difference between relative success and failure, trying again when a certain perceptible result is not attained and varying their procedure in so far as it has been unsuccessful. All these characters are found in the first nest-building of birds as well as in the second; they are found also in courses of conduct which occur only once in the lifetime of the animal." Both these writers would, I imagine, contend that, even when a female is absent, the idea of the female, as the end in view throughout, is present; and they would argue that the fact of her absence during the fighting in no way disposes of the belief that she is the condition under which the pugnacious instinct of the male is rendered susceptible to stimulation. What reason is there to think that this interpretation is applicable to the case under consideration? When a female is present, we observe that the males are pugnacious, and, when she is absent, that they still continue to be hostile--that is to say, they behave _as if_ she were present. Now, as far as I can ascertain, the "_as if_" is the only ground there is for supposing that the female is represented in imaginal form--there is no evidence of the fact, if fact it be. On the contrary, the behaviour of the male affords some fairly conclusive evidence that no such image is the primary factor in exciting the instinctive reaction. For if it be the actual presence of the female, or, in the absence of such, a mental image, that renders the pugnacious nature of the male responsive; provided the usual stimulus were present, the instinct ought surely to respond, not only under one particular circ.u.mstance, but under all circ.u.mstances. Yet, as we shall presently see, a male is by no means consistently intolerant of other males. It may be sociable at one moment or pugnacious at another, but the pugnacity is always peculiar to a certain occasion--the occupation of a territory. What shall we say then--that a mental image is a situational item only when the territory is occupied? It may be so; it may be that the fact of occupation gives rise to the mental image which, in its turn, renders the fighting instinct explosive, which again renders the possession of the territory secure. That such an interpretation is possible we must all admit. But if it were true, though it would not affect the main consideration, namely, whether the fighting has reference to the possession of a particular female, or to the protection of the territory, it would make further discussion as to which of these is the condition of the fighting unprofitable, for each would have its part to play in the process, the territory remaining, however, the princ.i.p.al factor in the situation.

Now the difference in the times of arrival of the male and female migrant varies in different species from a few days to a fortnight or even more. It is most marked in those that return to their breeding grounds early in the season, and the greater the margin of difference the greater scope is there for observation. In my records for the past twelve years, there are frequent references to these initial male contests in the life of the Willow-Warbler and of the Chiffchaff; and in the district which I have in mind, these two species arrive early in the season, the males preceding the females by a week or even as much as a fortnight. Suppose, then, that two Chiffchaffs establish themselves in adjoining territories; or suppose that a male settles in a territory already occupied; what is the result? Well, scenes of hostility soon become apparent; as the birds approach one another they become more and more restive, their song ceases, they no longer search for food in the usual methodical manner, but instead their movements are hurried and their call-notes are uttered rapidly--all of which betrays a heightened emotional tone. Then the climax is reached, there is a momentary fluttering of tiny wings, a clicking of bills, and for the time being that may be all. But unless one or other of the combatants retires, this scene may be repeated many times in the course of a few hours, and repeated with varying degrees of severity. Yet the fighting, even in the most extreme form, when the birds locked together fall slowly to the ground, is seldom of an impressive kind, and one has to bear in mind the capabilities of the actors, remembering that the most severe struggle might readily be interpreted as a game if it were not for certain symptoms which reveal its inner nature.

The males of many other migrants can frequently be observed to fight when there was every reason to believe that females had still to arrive.

The Blackcap is notoriously pugnacious, but not more so than the Marsh-Warbler or the Whinchat. Here in Worcestershire, the _Arundo phragmites_ grows mainly on certain sheets of water which are comparatively few and far between, and the Reed-Warbler is consequently restricted to isolated and more or less confined areas. The males arrive early in May before the new growth of reeds has attained any considerable height, and each one has its own position in the reed-bed, sings there, and throughout the whole period of reproduction actively resists intrusion on the part of other males. I have kept watch upon a small area of reeds daily from the date of the first arrival; each individual was known to me, and as the growing reeds were only a few inches in height, a female could scarcely have escaped detection. Yet time and again disputes arose, and males pursued and pecked one another, striving to attain that isolation for which racial preparation had fitted them.

But on account of their violence, or their novelty, or because the absence of a female was beyond question, some battles stand out in one's memory more prominently than others. An instance of this was a struggle between two Whitethroats which happened in the latter part of April and lasted for three successive days. The scene of its occurrence was more or less the same on each occasion, and the area over which the birds wandered was comparatively small. The fighting was characterised by persistent effort and was of a most determined kind, and so engrossed did the a.s.sailants become that they even fluttered to the ground at my feet. No trace of a female was to be seen at any time during these three days, nor, during the pauses in the conflict, was the emotional behaviour of a kind which led me to suppose that a female was anywhere in the vicinity. And, if she had been near, she must have made her presence known, for the belief that she is a timid creature, skulking on such occasions in the undergrowth, is by no means borne out by experience.

Even more impressive was a battle between two male Cuckoos. It occurred high up in the air above the tops of some tall elm-trees which roughly marked the boundary line between their respective areas, and the actions of the birds were plainly visible. At the moment of actual collision the opponents were generally in a vertical position, and wings, feet, and beaks were made use of in turn; one could plainly see them strike at one another with their feet, and one could observe the open bill which generally denotes exhaustion, but may of course have been due to anger, or used as a means of producing terror. Yet no female appeared in the locality until six days after the occurrence of this struggle--and she certainly is not easily overlooked, for her note is unmistakable even when the behaviour of the male does not betray her arrival.

[Ill.u.s.tration: Male Cuckoos fighting before the arrival of a female

Emery Walker ph.sc.]

That the actual presence of the respective females exercised any influence on the course of these struggles is more than doubtful. Not only did one fail to detect them, but one's failure to do so was confirmed by the knowledge that they had not yet arrived in those particular localities. Hence the fact of the male preceding the female is a valuable aid to the interpretation of subsequent behaviour; and one appreciates it the more after having experienced the difficulty of deciding whether she is present during the conflicts between resident males, for no matter how carefully we may observe the conditions which lead up to, and which accompany, such conflicts, or how closely we may scrutinise the surrounding trees, undergrowth, or ground, there always remains the possibility that she may, after all, have been overlooked.

But this must not be taken to imply that in such cases direct observation alone can lead to no serviceable result, or that the evidence gained therefrom is worthless. Far from it. Failure to detect a female is so very common an occurrence that, even if we lacked the corroborative evidence supplied in the life of the migratory male, it would still be unreasonable to suppose that it were solely due to mistaken observation. We mark her absence during the conflicts between the respective males of many common species--the Finches, Buntings, and Thrushes that occupy their territories early in the season when the hedgerows and trees are still bare; but more frequently amongst those that inhabit open ground, because the movements of the birds are there more accessible to observation. For instance, half a dozen or more Lapwings can be kept in view at the same time, and as they stand at dawn in solitary state, keeping watch upon their respective territories, they are conspicuous objects on the short, frosted gra.s.s; no stranger can enter the arena without the observer being aware of it, no commotion can occur but one detects it, no movement however small need be missed. And so they fight, in a manner which leaves no doubt as to the reality of the struggle, when their prospective mates are absent not only from the particular territories in which the conflicts take place, but absent too from those adjoining.

If the fact that males fight before they are paired and in the absence of a female could be placed beyond all question, it would no longer be possible to regard her possession as the end for which they are contending, and consequently there would be no need to produce further evidence. But the examples which I have given refer, of course, to only a few migrants and a few residents--and moreover it must be admitted that a female _is_ often conspicuous during the battles--so that by themselves they must be regarded, and rightly so, as inconclusive. We must therefore pa.s.s on to consider evidence of a somewhat different character.

I spoke of the complexity of the strife. By this I mean that it is not merely a matter of disputes between adjoining males, but that it is a far more comprehensive business involving both s.e.xes. Thus female fights with female and pair with pair, or a male will attack a female, or, again, a pair will combine against a single male or a single female. And from all this complexity of strife we gain much valuable evidence in regard to the question immediately before us. For when one pair attacks another, or males that are definitely paired fight with one another, or an unpaired male attacks either s.e.x of a neighbouring pair indiscriminately, there is surely little ground for supposing that the possession of a mate is the reason of it all.

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 s.e.xes 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 s.e.xes, 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 s.e.xes 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.

[Ill.u.s.tration: Two pairs of Pied Wagtails fighting in defence of their territories.

Emery Walker ph.sc.]

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.