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 sex. 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
constitution 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 space 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 anticipatory
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 sexual 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 passed 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.
[Illustration: 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 succumbed.
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 assumed
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 attitudes 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 circumstance, but under all circumstances. 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 principal 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 assailants 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.
[Illustration: 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 grass; 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 pass 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 sexes. 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 sex 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 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.
[Illustration: 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.
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.
Formerly I deemed the spring rivalry to be the result of accidental
encounters, and I believed that an issue to a struggle was only reached
when one of the combatants succumbed or disappeared from the locality, a
view which neither recognised method nor admitted control. Recent
experience has shown, however, that I was wrong, and that there is a
very definite control over and above that which is supplied by the
physical capabilities of the birds.
Let us take some common species, the Willow-Warbler being our first
example; and, having found three adjoining territories occupied by
unpaired males, let us study the conflicts at each stage in the sexual
life of the three individuals, observing them before females have
arrived upon the scene, again when one or two of the three males have
secured mates, and yet again when all three have paired. Now we shall
find that the conditions which lead up to and which terminate the
conflicts are remarkably alike at each of these periods. A male
intrudes, and the intrusion evokes an immediate display of irritation on
the part of the owner of the territory, who, rapidly uttering its song
and jerking its wings, begins hostilities. Flying towards the intruder,
it attacks viciously, and there follows much fluttering of wings and
snapping or clicking of bills. At one moment the birds are in the
tree-tops, at another in the air, and sometimes even on the ground, and
fighting thus they gradually approach and pass beyond the limits of the
territory. Whereupon a change comes over the scene; the male whose
territory was intruded upon and who all along had displayed such
animosity, betrays no further interest in the conflict--it ceases to
attack, searches around for food, or sings, and slowly makes its way
back towards the centre of the territory.
Scenes of this kind are of almost daily occurrence wherever a species is
so common, or the environment to which it is adapted so limited in
extent, that males are obliged to occupy adjacent ground. The Moor-Hen
abounds on all suitable sheets of water, and it is a bird that can be
conveniently studied because, as a rule, there is nothing, except the
rushes that fringe the pool, to hinder us from obtaining a panoramic
view of the whole proceedings, and moreover the area occupied by each
individual is comparatively small. Towards the middle of February,
symptoms of sexual organic change make themselves apparent, and the pool
is then no longer the resort of a peaceable community; quarrels become
frequent, and as different portions of the surface of the water are
gradually appropriated, so the fighting becomes more incessant and more
severe. Each individual has its own particular territory, embracing a
piece of open water as well as a part of the rush-covered fringe, within
which it moves and lives. But in the early part of the season, when the
territories are still in process of being established, and definiteness
has still to be acquired, trespassing is of frequent occurrence, and the
conflicts are often conspicuous for their severity.
Now these conflicts are not confined to unpaired individuals, nor to one
sex, nor to one member of a pair--every individual that has settled upon
the pool for the purpose of breeding will at one time or another be
involved in a struggle with its neighbour. If then we single out certain
pairs and day by day observe their actions and their attitude towards
intruders, we shall notice that, instead of their routine of existence
consisting, as a casual acquaintance with the pool and its inmates might
lead us to believe, of an endless series of meaningless disputes, the
behaviour of each individual is directed towards a similar goal--the
increasing of the security of its possession; and further, if we pay
particular attention to the circumstances which lead up to the quarrels
and the circumstances under which such quarrels come to an end, we shall
find, when we have accumulated a sufficient body of observations, that
the disputes always originate in trespass, and that hostilities always
cease when the trespasser returns again to its own territory. By careful
observation it is possible to make oneself acquainted with the
boundaries--I know not what other term to use--which separate this
territory from that; and it is the conduct of the birds on or near these
boundaries to which attention must be drawn. A bird may be feeding
quietly in one corner of its territory when an intruder enters. Becoming
aware of what is happening it ceases to search for food, and approaching
the intruder, at first swimming slowly but gradually increasing its
pace, it finally rises and attacks with wings and beak, and drives its
rival back again beyond the boundary. Thereupon its attitude undergoes a
remarkable change; ceasing to attack, but remaining standing for a few
moments as if still keeping guard, it betrays no further interest in the
bird with which a few seconds previously it was fighting furiously. On
one occasion I watched a trespasser settle upon a conspicuous clump of
rushes situated near the boundary. The owner, who was at the moment some
distance away, approached in the usual manner, and, having driven off
the trespasser, returned immediately to the clump, where it remained
erect and motionless.
A feature which marks all the fighting, and which we cannot afford to
disregard, is the conative aspect of the behaviour of the owner of the
territory. The bird attacks with apparent deliberation _as if_ it were
striving to attain some definite end. I recollect an incident which was
interesting from this point of view. A pair of Reed-Buntings were
disturbed by a Weasel which had approached their nest containing young.
Both birds betrayed symptoms of excitement; as the Weasel threaded its
way amongst the rushes, so they fluttered from clump to clump or clung
to the stems, uttering a note which is peculiar to times of distress,
and followed it thus until finally it disappeared in a hedge. The
rapidly uttered note and the excitement of the birds caused some
commotion, and the male from an adjoining territory approached the
scene. Now one would have expected that the presence of this bird, and
possibly its aid in driving away a common enemy, would have been
welcomed; one would have thought that all else would have been
subservient to the common danger, and that so real a menace to the
offspring would have evoked an impulse in the parent powerful enough to
dominate the situation and subordinate all the activities of the bird to
the attainment of its end. But what happened? Three times during this
incident, the male, whose young were in danger, abandoned the pursuit of
the Weasel and pursued the intruder. It was not merely that he objected
to the presence of this neighbouring male in a passive way, nor even
that he had a momentary skirmish with it, but that he determinedly drove
the intruder beyond the boundary and only then returned to harass the
Weasel.
Thus it seems clear that the proximate end to which the fighting is
directed is not necessarily the defeat of the intruder, but its removal
from a certain position. And inasmuch as this result will be obtained
whether the retreat is brought about by fear of an opponent or by
physical exhaustion, it is manifest that too much significance need not
be attached to the amount of injury inflicted. It is necessary to bear
this in mind, because it is held by some, who have carefully observed
the actions of various species, that overmuch importance is attached to
the conflicts, that in a large number of instances they are mere
"bickerings" and lead to nothing, and that they are now only "formal,"
which means, I suppose, that they are vestigial--fragments of warfare
that determined the survival of the species in bygone ages. But if the
conclusion at which we have just arrived be correct, if we can recognise
a single aim passing through the whole of the warfare--and that one the
removal of an intruder from a certain position, then we need no longer
concern ourselves as to the degree of severity of the battles--we see it
all in true perspective. Neither exhaustion nor physical inability are
the sole factors which determine the nature and extent of the fighting;
there is a more important factor still--position. According, that is to
say, to the position which a bird occupies whilst fighting is in
progress, so its pugnacious nature gains or loses susceptibility, and it
is this gain or loss of susceptibility which I refer to when I speak of
the fighting as being controlled.
What we have then to consider is the relation of "susceptibility" to
"position." We can explain the relationship in two ways. We can say that
the part of the nature of the male which leads to the occupation of a
territory, and is partly hereditary and partly acquired, is stronger
than the part which leads the bird to fight, and which is conditioned by
the presence of a female, and that consequently when the male passes the
boundary, the impulse to return asserts itself and the conflict ceases;
or we can say that the occupation of a territory is the condition under
which the pugnacious instinct is rendered susceptible to stimulation,
that the stimulus is supplied by the intruder, and that when the male
passes outside the accustomed area its instinct is no longer so
susceptible and it therefore retires from the conflict.
[Illustration: Long-tailed Tit Males fighting for possession of
territory. The feathers have been torn from the crown of the defeated
and dying rival.
Emery Walker ph.sc.]
Of these explanations, the first is not altogether satisfactory. It
requires the presence of a female and, as we have seen, a female is by
no means always present. Then it attributes to the one side of the
inherited nature an influence which is not borne out by the facts, for
in the ordinary routine of existence, without the incentive of battle,
every individual is liable to wander occasionally beyond its boundary
and to intrude temporarily upon its neighbours; and this it could
scarcely do, providing its nature to remain within the territory were
powerful enough to dominate its movements and curtail its activities
even during the excitement of an encounter. But there is nothing
inherently improbable in the alternative hypothesis, nor anything that
is at all inconsistent with the behaviour as observed; on the contrary,
if it is admitted, the facts become connected together and exhibit a
meaning which they otherwise would not have possessed.
So much for the controlling influence of "position," which alone seems
to me sufficient ground for believing that the fighting has reference to
the territory. But it is not the whole of the evidence.
Now if it were possible to demonstrate by actual observation that those
males which had not established territories were not pugnacious, we
should have something in the nature of proof of the correctness of this
view. Demonstrative evidence of this kind is, however, unattainable. Yet
we can come very near to obtaining it by reason of a peculiar feature
which marks the process of acquiring territory--the neutral ground. The
Lapwing will serve as an illustration. In the previous chapter I
referred to the small flocks that appeared in the accustomed water
meadow early in February, and I described how they settled day after day
in that meadow, but only in a limited part of it, where they passed
their time in rest, in preening their feathers, or in running this way
and that lazily searching for food; and how, at length, the flock
dwindled by reason of individuals breaking away in order to secure
positions on the remaining part of the meadow. Here the neutral ground
is adjacent to the territories, and, while still occupied by the flock,
is resorted to by the males that had deserted that flock in order to
establish those territories.
Suppose now that we have the whole meadow in view from some point of
vantage. In front of us are the territories, in the distance the neutral
ground; and in each territory there is a solitary male, while on the
neutral ground a number of individuals of both sexes are assembled, and
move about freely one amongst another. So that the scene presented to
view is somewhat as follows: a flat meadow, at one end of which, and at
fairly regular intervals, a few solitary individuals are dotted about,
each one keeping at a distance from its neighbours; while at the other
end a number of individuals are collected together in a comparatively
small space, apparently deriving some satisfaction from their close
association. That surely is a very remarkable contrast. But let us
continue our investigation, first fixing our attention upon the solitary
individuals; one is standing preening its feathers, another is squatting
upon the ground, a third runs a few yards in this direction then a few
yards in that, stimulated apparently by the sight of food, and so on.
Moreover, each one keeps strictly to a well-defined area and makes no
attempt to associate with its fellows. One of the males, however, whilst
roaming backwards and forwards approaches the limit of its territory,
and this brings the neighbouring bird, whose boundary is threatened,
rapidly to the spot. In an upright position both stand face to face, and
the battle then begins; with their wings they attempt to beat one
another about the body, with their beaks they aim blows at the head, and
in the mêlée wings and legs seem to be inextricably mixed; whilst at
intervals, driven backwards by the force of the collision, they are
compelled to separate, only, however, to return to the charge--and the
sound of beating wings and the feathers that float in the air are tokens
of earnestness. Such scenes are of frequent occurrence; but the
conflicts vary in intensity, and the circumstances under which they
occur vary too, and females come and go without leaving any clue as to
their ultimate intentions.
Turning now to the flock one is impressed with the friendship that seems
to exist between the various members. There are, it is true, occasional
displays of pugnacity which never seem to develop into anything very
serious; for instance, one bird will fly at another, and a momentary
scuffle is followed by a short pursuit but nothing more--nothing, that
is to say, in the least comparable with the battle previously described.
Of what is the flock composed? Of members of both sexes. There is no
difficulty in assuring oneself that this is so. But is it entirely
composed of individuals in whom development has not reached a stage
adequate for the functioning of the primary dispositions? No, not
entirely; for it will be observed that its number is a fluctuating one,
that birds come and go, and, if a close watch is kept upon the different
individuals as they leave, it will be noticed that some at least are
inmates of the territories at the opposite end of the meadow--the
solitary members whose behaviour we were recently watching. This fact is
an important one. We were impressed, it may be remembered, with the
contrast between the general behaviour of the birds at the opposite
ends of the meadow. But now it appears as if the contrast were not
between this individual and that, but between the behaviour of the same
one under different circumstances. The male, that is to say, which,
while in its territory, tolerates the approach of no other male, flies
to the flock and is there welcomed by the very individuals with whom a
short time previously it had been engaged in serious conflict.
But if the conditions are reversed and the flock happens to settle in an
occupied territory, the attitude of the owner towards the flock is very
different. In the year 1916 an incident of this kind occurred in the
meadow to which reference has already been made. The weather had been
exceptionally severe--very cold easterly and north-easterly winds,
frost, and frequent falls of snow had affected the behaviour of the
Lapwings, and seemed to have checked the normal development of their
sexual routine. The males would attempt to establish themselves, and
then, when the temperature fell and the ground was covered with snow,
would collect again in flocks and follow their winter routine. It was on
the 9th March, during one of the spells of milder weather, that the
flock on the neutral ground was disturbed and settled mainly in the
territory marked No. 3 on the 1916 plan, but partly on that marked No.
2. The owners thereupon began to attack the different members of the
invading flock. Fixing attention upon a particular bird whilst ignoring
the remainder, the No. 3 male drove it away, and then after a pause
drove another away, and so on until by degrees all the invaders were
banished, and the No. 2 male did likewise. The interest of this incident
lies, however, in the behaviour of the different individuals of which
the flock was composed; when attacked they made no real show of
resistance, but accepted the situation and left. The will to fight was
clearly lacking, yet their presence was a source of annoyance to the
owners of the territories. A short time previously a female had
accompanied one of the males and was at that time somewhere in the
vicinity, but beyond this there was no evidence to show that either of
them were paired, and even if the presence of the female were the reason
of the pugnacity of the one, it could not well account for that of the
other.
The neutral ground does not always happen to be so close at hand as in
the case of the meadow referred to. Sometimes the birds will resort to a
particular field, attracted probably by a plentiful supply of food, and
here they collect and behave as they do during the winter, running this
way and that as the fancy takes them, meeting together by accident at
one moment, parting at another, according to the direction in which they
happen to wander. Of animosity there is little sign; the season might be
the middle of winter instead of the middle of March for all the
indication there is of sexual development, and yet one knows that they
will behave differently when they leave this ground, as presently they
will, and return to their territories in the surrounding neighbourhood,
and that there each one will fight if necessary to preserve its acre
from intrusion.
It would seem, then, from this that the fighting must bear some relation
to the particular area of ground in which it occurs; and unless it can
be shown that there is some other factor in the external environment of
the male, that is the direction in which we must look for the condition
under which the instinct is rendered susceptible. One's thoughts turn,
of course, to the female, but she too passes backwards and forwards
between the territories and the neutral ground, and if her presence were
really a _conditio sine qua non_ of the strife, one would like to know
why, when she leaves those territories and joins the flock and the males
do likewise, similar conflicts should not prevail there also.
Other species have their neutral ground, but the environment seldom
affords such facilities for observation as does that of the Lapwing.
Even though the Moor-Hens, who are so conspicuously intolerant upon the
pool, _do_ feed together amicably upon the meadows adjoining; and the
Chaffinch that is so pugnacious in the morning, _does_ seek out the
flock later in the day; yet their conditions of existence prevent our
obtaining a panoramic view of the whole proceeding, and we have to study
each scene separately before discovering that the relationship between
intolerance and the territory on the one hand, and friendship and the
neutral ground on the other, is just as strong a feature as it is in the
behaviour of the Lapwing.
I shall now give a brief account of the conduct of a male Reed-Bunting
which by persistent effort established itself late in the season, and I
shall do so because its behaviour tends to confirm much that has been
said in the preceding pages.
Early in March three male Reed-Buntings occupied a small water meadow
overgrown with the common rush, and by the third week all of them were
paired. On the 30th March two of the males were unusually pugnacious,
and on the following day fighting continued and at times was very
severe. Now I knew that the occupants of the ground in which the
fighting was taking place were paired, and not doubting that the
combatants were the owners of two territories marked for convenience
sake Nos. 1 and 2, I was at a loss to understand the meaning of so
determined and persistent a struggle. My attention, however, was
presently drawn to a third bird, which also joined in the conflict and
made the whole situation still more perplexing. This bird, as it soon
became clear, was none other than the owner of No. 2 territory, and the
one that I had previously regarded as such was a new arrival. On the
following day, the 1st April, fighting continued, and in my record for
that day there is a note to the effect that "No. 2 female seems to be of
no interest to No. 5 male (the new arrival); its purpose seems to be to
drive away intruders." On the 2nd April and subsequent days, this bird
attacked every other male that approached, and not only maintained its
position but ultimately succeeded in securing a mate. Here then we have
two territories occupied by two males, both of which had obtained a
mate. The relation of these two birds was normal, a month's routine had
defined their boundaries, and conflicts were less frequent than
formerly. But upon this comparatively peaceful scene a strange male
intrudes. Observe the manner of the intrusion. The stranger does not
wander about first in this direction and then in that, but acts _as if_
it had some definite end in view, and establishing itself in a small
alder bush which it uses as a base or headquarters, it gradually extends
its dominion, gains the mastery over the surrounding ground, part of
which belonged to No. 1 male and part to No. 2, and finally drives a
wedge, so to speak, between the two territories.
How is its behaviour to be explained, and why did its presence cause
such commotion? No one could have watched the gradual unfolding of this
incident day by day and not have been impressed by the persistent
endeavour with which this male maintained its position in one small part
of the meadow. This is the first and most important consideration. Then
there is the attitude, also significant, which it adopted towards the
females; for I take it that, apart from the question of territory, the
explanation of its intrusion must be sought in the necessity for
securing a mate--that it was attracted by the presence of the females,
and that the proximate end of its behaviour was the possession of one of
them. But if there is one thing that emerges from the facts more clearly
than another it is that the course of its behaviour was in no way
influenced by the presence or absence of either of the females. My
reasons for saying so are the following: in the first place, it made no
attempt to pursue or to thrust its attention upon either one or the
other of them; secondly, it even went so far as to attack and drive them
away when they approached too closely; and in the third place, when an
unpaired female did at length appear, it adopted a different attitude
and forthwith paired. And bearing in mind that these two females had
already been with their respective mates for some considerable time, and
that there was reason to believe that coition had actually taken place,
is it likely that any counter-attraction would have proved successful in
tempting either of them away from its mate, or probable, if they were
the sole attraction, that the intruding male would have been so
persistent in remaining? How very much simpler it is to fit the pieces
together, if for the time being we ignore the female and fix our
attention upon the territory. Each item of behaviour then falls into its
proper place, and the fighting which seemed so perplexing and
meaningless becomes a factor of prime importance. First of all the male
arrives; then it establishes itself in a small alder bush and advertises
its presence by song; next, by persistent effort in attacking the
neighbouring males, it frees a piece of ground from their dominion; and
finally, in proper sequence, a female arrives, pairing takes place, and
reproduction is secured.
[Illustration: A battle between two pairs of Jays
Emery Walker ph.sc.]
How then does the whole matter stand? If it were males only that engaged
in serious conflict, and if they fought only in the presence of a
female, the problem would resolve itself into one simply of obtaining
mates. But the warfare extends in a variety of directions, it is not
confined to one sex, nor to unpaired individuals, nor need the opponents
necessarily be of the same sex; it involves both sexes alike singly or
combined. Now the view that the biological end of battle is, in its
primary aspect, related to the female, cannot, as we have seen, apply to
the conflicts between different pairs, and only by much stretching of
the imagination can it be held responsible for the hostility that males
frequently display towards females or _vice versa_. It is valid only for
a certain form of warfare. But that form represents, you will say, a
large proportion of the whole, which is true; and so long as we ignore
the remainder, we might rest content in the belief that we had solved
the major part of the problem. But can we ignore the remainder? Can we
say that the conflicts between paired males, for example, are simply
offshoots of the pugnacious disposition, and have no part to play in the
process of reproduction? They recur with marked persistency season after
season and generation after generation; they are to be found in species
widely remote; they are frequent in occurrence; and no one who had
observed them and noted the vigour with which they are conducted, could,
I think, conclude that they were meaningless--and be satisfied. They
must somehow be explained. So that if anyone thinks fit to maintain that
possession of a mate is an adequate explanation of part of the
hostilities, it is clearly impossible to regard all the fighting as a
manifestation of one principle directed towards a common biological end.
But wherever we extend our researches, we find that the facts give
precision to the view that the occupation of a territory is the
condition under which the pugnacious instinct is rendered susceptible to
stimulation. The Lapwing, when in its territory, displays hostility
towards other males of its own species, but when upon neutral ground,
treats them with indifference; the Chiffchaff pursues its rival up to
the boundary and is then apparently satisfied that its object has been
achieved; the cock Chaffinch in March permits no other male to intrude
upon its acre or so of ground during the early hours of the morning, but
for the rest of the day it joins the flock and is sociable; the
Herring-Gull resents the approach of strangers so long as it occupies
its few square feet of cliff, but welcomes companions whilst it is
following the plough--all of which points to a relation between the
territory and the fighting. And this view has at least one merit--it
accounts for all the fighting no matter what degree of severity may be
reached or in what way the sexes may be involved. The complexity of the
strife presents no obstacle; for if the biological end of the fighting
is to render the territory, which has already been established, secure
from intrusion, each sex will have its allotted part to play at the
allotted time: thus the battles between the males before females appear
on the scene will decide the initial question of ownership; those
between the females will give an advantage to the more virile members
and insure an even distribution of mates for the successful males; the
constant struggles between paired males will roughly maintain the
boundaries and prevent such encroachment as might hamper the supply of
food for the young; and the co-operation of male and female in defence
of the territory will be an additional safeguard. Each form of battle
will contribute some share towards the main biological function of
reproduction.
Hitherto we have dealt principally with the male. We have referred, it
is true, to the fact that the female co-operates with her mate in order
to drive away intruders, but beyond this, we have made no attempt to
trace what part, if any, she plays in the whole scheme. We must do so
now.
The various steps by which the territory is not only established but
made secure from invasion, imply an inherited nature nicely balanced in
many directions--first of all the male must be so attuned as to be ready
to search for a territory at the right moment; then it must be capable
of selecting a suitable environment; and, having established itself, it
must be prepared to defend its area from a rival, and to resist
encroachment by its neighbours--and if it failed in any one of these
respects, it would run the risk of failure in the attainment of
reproduction. Each individual has therefore to pass, so to speak,
through a number of sieves--the meshes of which are none too
wide--before it can have a reasonable prospect of success. This being
so, we ask, in the first place, whether the female, too, may not have an
eliminating test to pass; and in the second place, whether she may not
also assist in furthering the biological end of securing the territory.
Now the answer to the first of these questions will be found to be in
the affirmative. Just as, in the securing of a territory, the ultimate
appeal is to the physical strength of the male, so, in the course of her
search for a mate, the female may be called upon to challenge, or may be
challenged by a rival, and the issue is decided by force. My attention
was first drawn to this fact by a struggle between two female
Whitethroats, which I have described elsewhere. The scene of its
occurrence was the corner of a small osier bed occupied by one male, and
the females that took part in it had only recently arrived, but the
male, an unpaired bird, had been in possession of its territory for some
days. The sequel to this struggle, which was protracted and severe, was
the disappearance of both females, the male being left without a mate
for a further ten days.
[Illustration: Emery Walker ph.sc.
The female Chaffinch shares in the defence of the territory and attacks
other females.]
Numerous instances have since come under my notice. Hen Chaffinches
become so absorbed that they fall to the ground and there continue the
struggle. Seizing hold of one another by the feathers of the head, they
roll from side to side, and then, without relaxing their grip, lie
exhausted--the quickened heart-beat, altered respiration, tightly
compressed feathers and partially expanded wings betraying the intensity
of the conflict.
As the breeding season approaches, hen Blackbirds grow more pugnacious.
Individuals that early in the year have frequented the same spot daily
and have even shown every sign of friendship, become openly hostile. For
two years in succession I had an opportunity of observing females under
such conditions, and of studying the gradual change in their
relationship. Each morning at break of day and for some hours afterwards
they could be seen in the same place, one following the other as they
searched for food first in this direction and then in that, as if they
derived some special pleasure from the fact of their companionship. Then
a change began to manifest itself. Indications of animosity became
apparent; one would run towards the other in a threatening attitude and,
in a half-hearted manner, peck at it; and gradually the hostility grew,
until the tentative pecking developed into a scuffle and the scuffle
into a conflict.
Much fighting also occurs between the females of the Reed-Bunting, and
likewise between those of the Moor-Hen, and because these two species
are not only common but inhabit respectively open stretches of marshy
ground or large sheets of water, the fighting can be readily observed.
Why do the females fight before they are definitely paired? To obtain
mates? This certainly seems to be the obvious explanation because any
question of securing territory can be excluded; yet if it be true that
their sex is numerically inferior, it is difficult to understand the
necessity for such strenuous competition. But what is the condition
under which the pugnacious instinct of the female is rendered
susceptible to stimulation? It cannot be merely the presence of a male
ready to breed, for then there would be endless commotion amongst the
flocks of Chaffinches or of Lapwings which in March are composed of both
sexes, including even males that have secured territories. There must be
some other circumstance; and, judging by experience, it is to be found
in the territory--a male, that is to say, in occupation of one, is the
condition under which the inherited nature of the female is allowed free
play. We must bear in mind, however, that the competition between the
males is very severe, that large numbers probably fail to pass even this
preliminary test, and that only a proportion are in a position to offer
to the female the condition under which her process can successfully run
its course; so that the presumption is--though it is incapable of
demonstration--that there is a competition for such males each recurring
season, and that, on the average, the weaker females fail to procreate
their kind.
But apart from any direct assistance she may give in driving away
intruders, does she in any way help to further the biological end of
reproduction? This is a difficult question to answer, and the suggestion
I have to make can only apply in those cases in which the territory is
occupied throughout the breeding season. Much of the fighting between
the males occurs in her presence, and it must be admitted--though it is
difficult to speak with any degree of certainty--that such fighting,
taken as a whole, bears the stamp of exceptional determination. Let us
then grant that the excitement of a male does, under these
circumstances, reach a higher level of intensity, and let us see how
this will add to the security of the territory. The fact that the male
has established itself and obtained a mate is not alone sufficient to
accomplish the end for which the territory has been evolved. During the
period between the initial discharge of the sexual function and the time
when incubation draws to a close, much may happen to prejudice the
future of the offspring; there is always the possibility of invasion by
an individual whose development is backward or which has been
unsuccessful in making good the first step, and, as we saw in the case
of the Reed-Bunting, a portion of the ground won may be lost; there is
always the danger of gradual encroachment by neighbouring owners; and
there is even a possibility that a pair may be so persistently harassed
by more virile neighbours as to forsake the locality permanently. If
then a male is to attain a full measure of success it must be capable
of keeping its boundaries intact up to the time when the young are able
to fend for themselves, and consequently it is important that its
intolerant nature should remain susceptible to stimulation throughout
the greater part of the season.
Does the presence of a female serve to promote this end? Now we know
very little of the influence exerted by one sex upon the other.
Professor Lloyd Morgan has suggested that the male raises the emotional
tone of the female, a suggestion which seems to me in accordance with
the facts. There is reason to believe, however, that the converse is
also true--namely that the excitement of the male reaches a higher level
of intensity when a female is present. Granting then that his emotional
tone is raised, how will this affect the question? So great is the
difference of opinion as to the part that the emotions play in
furthering the life of the individual that one hesitates to accept any
particular one. But it seems to be generally admitted that emotion adds
to the efficacy of behaviour, and this is the view of Professor Lloyd
Morgan. "Whatever may be the exact psychological nature of the emotions,
it may be regarded," he says, "as certain that they introduce into the
conscious situation elements which contribute not a little to the energy
of behaviour. They are important conditions to vigorous and sustained
conation." Therefore, if it be true that the female raises the emotional
tone of the male, the result will be an increased flow of energy into
all the specific modes of behaviour connected with reproduction, amongst
which those directly concerned in the securing and defence of the
territory will receive their share; so that instead of a progressive
weakening of just those elements in the situation which make for
success, the level of their efficiency will be maintained as a result of
such reinforcement. But the female becomes intolerant of her own sex
when she has discovered a male ready to breed, and, later, assists her
mate in resisting intrusion; and by raising her emotional tone, he may
be the means of furthering more strenuous behaviour on her part. Each
member of the pair would in this way contribute towards the energy of
behaviour of its mate, and hence add indirectly to the security of the
territory.
It may be well to illustrate the foregoing remarks. Suppose that there
is a small piece of woodland barely sufficient to hold three pairs of
Willow-Warblers, and suppose that the male and female in the middle
territory did not respond to one another's influence quite as readily as
the adjoining males and females, what would be the result? The emotional
tone of the central pair would stand at a lower level of intensity; and,
since their congenital dispositions would lack the necessary
reinforcement, the birds would tend to become less and less punctilious
in keeping their boundaries intact, whereas the adjoining pairs, always
on the alert and meeting with little opposition, would encroach more and
more and gradually extend their dominion. And so, by the time the young
were hatched, the parents would be in occupation of an area too limited
in extent to insure the necessarily rapid supply of food, and would be
compelled to intrude upon the adjoining ground. But knowing how routine
becomes ingrained in the life of the individual, knowing that for weeks
this pair had submitted to their neighbours, can we believe that they
would be capable of asserting their authority and that the young would
be properly cared for? Or suppose that different pairs of Kittiwake
Gulls on the crowded ledges, or different pairs of Puffins in the
crowded burrows, varied in like manner, would they all have equal
chances of rearing their offspring? The struggle for reproduction is
nowhere more severe than amongst the cliff-breeding sea birds; it is not
for nothing that one sees Kittiwake Gulls, locked together, fall into
the water hundreds of feet below and struggle to the point of
exhaustion, or, as has been reported, to the point of death; it is not
for nothing that Puffins fight with such desperation. And surely success
will be attained by that pair whose emotional tone stands high and whose
impulse to fight is therefore strong, rather than to the ill-assorted
couple.
The argument, then, is briefly this. In the spring, a marked change
takes place in the character of the males of very many species; instead
of being gregarious they either avoid one another and become hostile,
or, if their conditions of existence require that they shall still live
together, they become irritable and pugnacious. This change is made
known to us by the battles of varying degrees of severity which are such
a feature of bird life in the spring; and since a female can commonly be
observed to accompany the combatants, the possession of a mate appears
at first sight to be the proximate end for which the males are
contending. But when the circumstances which lead up to the quarrels are
investigated closely, the problem becomes more difficult; for it is not
merely a question of males fighting in the presence of a female, as is
generally supposed to be the case, but on the contrary there is a
complexity of strife which is bewildering--males attack females or _vice
versa_; female fights with female; or a pair combine to drive away
another pair, or even a solitary individual no matter of which sex. This
complexity of strife makes against the view that the possession of a
mate is the reason of the fighting. But an even stronger objection is to
be found in the fact that males are hostile when no female is
present--and hence we must seek elsewhere for the true explanation.
Now if the behaviour of a male be closely observed, it will be found
that its pugnacious instinct gains or loses susceptibility according to
the position which it happens to occupy--when its ground is trespassed
upon, the impulse to fight is strong; but when it crosses the boundary
it seems to lose all interest in the intruder. Moreover, in some
species, the male rejoins the flock at intervals during the early part
of the season and for a time leads a double existence, passing backwards
and forwards between its territory and the neutral ground. Its behaviour
under these circumstances affords some valuable evidence, for the bird
displays little if any hostility when accompanying the flock, yet when
it returns to the ground over which it exercises dominion, no male can
approach without being attacked. The conclusion, therefore, seems to be
inevitable, namely that the actual occupation of a territory is the
condition under which the pugnacious nature of the male is rendered
susceptible to appropriate stimulation.