Henry Eliot Howard

“ Now it can be observed that the hostility is not limited merely to occasional acts of intolerance, but that there is organised warfare lasting, it may be, for many days in succession, and that the actions of the birds bear the stamp of a persistent striving towards some end. On one occasion the Willow-Warbler may be the aggressor, on another the Chiffchaff, and at times it is difficult to say which of the two is responsible for the quarrel. ”

“ Hence it is clear that the nature of a bird when on migration is not quite the same as it is when its destination is reached; that the positions occupied from time to time during the journey carry no meaning, or, rather, are not brought into relation with its life in quite the same way as is the position which it finally occupies; and further, it is clear that the interest it displays in other species undergoes a somewhat remarkable transformation when at length its destination is reached. ”

“ We have now considered the various ways in which the territory is useful in furthering the life of the individual. We have seen that, in some cases, there is competition for stations where the egg or eggs can be deposited and incubated in safety; that, in others, there is competition for stations capable of furnishing an adequate supply of food for the young; and that the establishment of "territories" not only renders the attainment of reproduction for the individual secure, but serves so to regulate the distribution of pairs that the maximum number can be accommodated in the minimum area. ”

“ Many a Warbler allocates to itself a space of ground more than sufficient to supply it with all that it needs; so, too, does the Finch, or the Pipit, or the Falcon—if we take no account of kindred species. Thus there is reason to believe that, by limiting the number of individuals in a given locality, this apparently wasteful expanse of territory is serviceable in that it provides against the pressure of the bird population upon the available means of support becoming too great. ”

“ And of all the facts we have reviewed, this is perhaps the most important in relation to our present subject, for it demonstrates that the change from sociability to hostility is not merely an incident of the sexual season, not merely an indirect result of the functioning of the general disposition which leads to the establishment of a territory, but that it is intimately associated with the whole process, and that the particular part of the bird's nature which is concerned is so nicely balanced that it will respond under one condition and one only. ”

“ On the other hand, the Sedge-Warbler is most aggressive towards other kindred species, and when a male happens to occupy the same ground as a Reed-Warbler, there are frequent battles between them and incessant commotion; they fly at one another and meet in the air with an audible clicking of bills, or pursue one another amongst the reeds, each one uttering its characteristic scolding note. ”

“ We saw that many different species require similar conditions of existence, that ancient breeding haunts disappear and that new ones come into being, and that in the ordinary course of events such species must often assemble in the same area for the purpose of reproduction. So that even though a male might be successful in protecting its ground from intruders of its own kind, yet it might still fail to rear offspring, just because it happened to choose a position in which other kindred forms had gathered. ”

“ But the fact that a bird has established a territory is riot in itself sufficient to render its hostile nature susceptible; it must be actually in occupation if a response is to be elicited. We reach this conclusion step by step: the behaviour of the migrant, that lacks the "will to fight" when on migration but is pugnacious when it has secured a territory, shows it; the behaviour of the resident, which temporarily joins the flock and is there sociable, shows it; and it is shown also by the determination with which both opponents fight when the question of ownership of a station is in dispute. ”

“ Yet a Whinchat, when it has established itself, is most pugnacious; it not only attacks every bird of a similar size that approaches its position, but its behaviour under such circumstances bears the impress of unusual determination; and if we were to take a male and place it in the position of the Stonechat, we should find that its nature would change, that the presence of the Stonechat would evoke a hostile response, and, conversely, that the instinct of the Stonechat would not be susceptible to stimulation. ”

“ First of all we took the case of a migrant, and, comparing its behaviour, as it journeyed, with that when finally it reached its destination, we found that the bird which was notoriously pugnacious when in occupation of a territory betrayed no interest in other species as it travelled to the accustomed breeding ground. ”

“ We must now consider some others in which each of the opponents acts as a stimulus to the pugnacious instinct of the other. It is here, of course, that we find the most violently contested battles, and it is here, too, that the purpose of the fighting seems clear. The persecution which the Green Woodpecker suffers from the Starling is well known. The purpose of the Starling's behaviour is clear, namely the possession of the hole occupied by the Woodpecker. Bird for bird, the Woodpecker is more than the equal of the Starling, but persistent endeavour ultimately wins the day. ”

“ So frequent, indeed, are acts of intolerance, and so readily awakened into activity is the pugnacious nature of the bird, that the fighting will almost bear comparison in volume with that which occurs between individuals of the same species. Between the Thrush and the Blackbird there are incessant quarrels early in the year, and the initiative seems to pass from one to the other according to the circumstances in which they are placed. If the territory of a Thrush is invaded the Thrush is the aggressor, and, conversely, if that of the Blackbird is threatened, the Blackbird becomes the aggressor ”

“ At one moment a Lapwing may be attacked, at another a Thrush or a Starling, harmless strangers that have approached the pool to drink; even a Water-Rail, as it threads its way through the rushes, may fail to escape detection; and, which is still more curious, a covey of Partridges will evoke response if they approach the pool too closely. Here is a curious instance of apparent waste of energy. A pair of Magpies built their nest in an ilex tree. ”

“ Many different species assemble together in winter and roam from place to place in search of food. But in spring their behaviour undergoes a remarkable transformation; they avoid one another and become quarrelsome, so much so that whereas the outstanding feature of the winter is sociability, that of the spring is hostility. With this general fact before us, we proceeded to investigate this change of behaviour still further. ”

“ Hence if the territory is adequately to serve its purpose, some control over the local distribution of species is of paramount importance. Nevertheless, if all the different forms that require similar conditions of existence were intolerant of one another in a like degree, the smaller bird would have no chance in competition with the larger. This, however, is not the case. Some, as we saw, arouse little or no animosity in others, in fact the more closely related the rivals, the more responsive their pugnacious nature seems to become. ”

“ But here we start on firmer ground, because the one factor which introduced an element of uncertainty—the female—can be definitely excluded; at least it seems so to me, for granting even that her presence is the condition under which the pugnacious nature of the male is rendered susceptible to stimulation, it is difficult to see why a male of a different species should supply that stimulus, or what biological purpose could be served by its doing so. ”

“ Many of these changes are slow and imperceptible, many can be observed in our own lifetime. The timber is felled and the undergrowth cleared in some wood, and the following spring we notice a change in the character of the bird population. Migrants which formerly found in it no suitable accommodation now begin to appear, and as the seasons pass by and the undergrowth affords more and more shelter for the nests and an increasing supply of insect life, so their numbers increase until the wood becomes an important breeding station, resonant with the song of many individuals. ”

“ Sometimes both members of the pair leave together in order to seek food, at other times they separate and the male may be in his territory whilst the female is with the flock. Apart from occasional manifestations of sexual emotion on the part of a male, there is nothing to disturb the harmony of the flock nor anything in the behaviour of the birds which would lead one to suspect that, when they return, their nature will change and that they will be no longer sociable ”

“ Success or failure probably depends more upon the cumulative effect of many combats entailing physical exhaustion, than upon the issue of any one particular battle; and whilst observation might quite well fail to distinguish any resultant change in the relative positions of the birds, or any harmful effect upon their constitutions, yet the area occupied by this one might be sufficiently curtailed to prejudice the welfare of the young, or the vitality of that one might be seriously impaired—and we should be none the wiser. ”

“ Hence, inasmuch as breeding stations are limited and competition for territory so severe, only those forms in which the fighting instinct responds freely to a wide range of stimuli will be in a position to maintain a footing upon the cliff.
In trying to estimate the importance of the hostility in its relation to the territory, we must bear in mind that competition varies in different seasons and in different localities. The surface of the land is constantly undergoing modification, partly owing to human and partly to physical agency—forests are cleared ”

“ But manifestly no matter how active a male may be in driving away members of its own sex and kind, it will neither make its position secure, nor insure a supply of food for its young, so long as any number of individuals of different kinds are allowed to establish themselves in the same space of ground. ”

“ When dealing with the attitude of a male towards others of its kind, we attached considerable significance to the fact that its pugnacious nature gained or lost susceptibility according to the position which it happened to occupy. We found, it will be remembered, that the same bird that was pugnacious in its own territory took no further interest in its opponent when the boundary was passed ”

“ Now the southern end of the Common is always inhabited by individuals belonging to one of these species, or to others of close affinity; so that wherever these travellers settle whilst passing across it, the chances are that they will find the ground occupied—and their behaviour under such circumstances is no less interesting than the behaviour of the bird upon whose ground they are trespassing. ”

“ Early in the season it establishes a territory, and because food is then scarce it is forced to seek it elsewhere than on the small plot of ground which it has acquired; and so it makes its way to some spot where the supply is abundant, and there, meeting with other species bent on a similar errand, forms with them a flock. Part of its time is then spent in the territory and part on the .feeding ground, and between these two points a highway is formed by the bird passing constantly to and fro. ”

“ Here, any increase in the size of the territory would inevitably lead to the extinction of the race, so that nothing stands between failure and success except the ability of the bird to defend its territory. If we study the bird population at one of the breeding stations on the coast, we find, generally speaking, that each kind of bird inhabits a particular portion of the cliff ”

“ Where the Raven finds shelter for its nest, there, too, the Peregrine has its eyrie—and so it happens that these two species are continually at war. Now the warfare occurs not only during the season of reproduction but continues throughout the greater part of the year, and can even be observed in the late summer or early autumn—the period when we should expect to find the instinct least susceptible to appropriate stimulation. ”

“ The behaviour of the Lapwing scarcely justifies such a conclusion, for all its actions denote a striving towards some end which we can describe, and it seems to gain satisfaction only when the ejection of the intruder has been accomplished.
Many of the Warblers display irritation when approached by other birds which we should scarcely expect would arouse their hostility. The Hedge-Sparrow, for example, is frequently regarded with suspicion, and it is by no means unusual to see it attacked by so small a bird as the Chiffchaff. ”

“ During autumn and winter, many birds of more or less close affinity assemble together in flocks, wherever the supply of food is abundant, and are then not only sociable, but, so there is reason to believe, are mutually helpful both in discovering the necessary means of subsistence which are often none too plentiful, and in affording protection from enemies, which, on the contrary, are often numerous. ”