Water-pipit. Whitewinged black-tern. Roughlegged-buzzard.
Firecrest. Sabine's gull. Honey-buzzard.
Norwegian-bluethroat. Grey-phalarope. Spoonbill.
Yellowbrowed-warbler. Great-snipe. Glossy-ibis.
1 Really a winter visitor from its southern breeding haunts south of the Equator, its winter being our summer.
1 Has bred in Britain.
592 BRITISH GENERAL MIGRATORY MOVEMENTS
IX. IRREGULAR VISITORS
Irregular visitors do not occur on our shores at any particular season, for their movements
are influenced by various factors. Some of these movements are recurrent at long intervals,
and partake of the nature of irruptions or invasions. The sporadic invasion of our islands, and
indeed of the whole of Western Europe, by hordes of Pallas's sandgrouse is probably the most
extraordinary of these irruptions; excessive fecundity of the species in its eastern breeding
area appears to occasion this attempt to colonise a wider field an attempt which invariably
ends in failure. The extraordinary visitation in certain years of crossbills, waxwings, even
bramblings and siskins, as well as marked occurrence in numbers of the rudcly-shelduck, are
also suggestive of sporadic invasion.
Amongst these irregular visitors must be classed a large number of birds which have
occurred on one or more occasions, but which do not arrive with sufficient regularity to be
included in the list of birds of passage. Mr. Eagle Clarke lists 53 from Continental Europe,
17 from Asia, 2 from Africa, 29 from North America, 9 from the Arctic regions, and
10 from Southern Oceans.
These numbers may be increased or decreased according to the judgment of any
ornithologist, for there are many birds which were treated as casuals a few years ago, but are
now known to be regular visitors. The barred-warbler is a good example. Prior to 1879 it
was unknown in Britain. Twenty years later Saunders enumerated twelve occurrences, and by
the beginning of 1912 the number had risen to thirty-two. Since the publication of the Hand-
List, the preface of which is dated April 1912, no fewer than twenty have been observed. Is it
to be considered as a lost or accidental wanderer any longer? Has it not been overlooked
in the past ?
The remarkable work accomplished by Mr. Eagle Clarke and his assistants at Fair Island,
the Flannans, St. Kilda, and elsewhere, and by the Misses Rintoul and Baxter at the Isle of
May, has added many unexpected recurrences of these " vagrants," and it is no idle guess to
state that far more must have passed unnoticed. In 1899 Saunders said that the blueheaded-
wagtail " can hardly be considered as more than an irregular visitor on migration " ; now it is
classed with regular summer visitors and birds of passage. Blyth's reed-warbler and the
Scandinavian chiffchaff were included in the Hand-List (April 1912) on the strength of single
occurrences at Fair Island and the Isle of Wight. Fair Island has since produced four or five
of the former, one has occurred at Holy Island and one in Holderness, while Mr. Eagle Clarke
says of the chiffchaff that " it appears to be a regular migrant " at Fair Island, and several have
occurred on the Isle of May.
The more systematically that ornithologists work, the more of these so-called " vagrants "
or " gypsy-migrants " will have to be included as regular birds of passage. This remark applies
most to those which reach us from Continental Europe and North Asia, for it is reasonable to
recognise the birds whose normal range extends no farther than South or even Central Europe
and Africa as lost wanderers when they appear in Britain. The subalpine warblers which
travelled from Southern Europe to St. Kilda and Fair Island are instances of birds wandering,
hopelessly lost, farther and farther from their base, and an even more striking instance is that
of the masked-shrike, which, on leaving winter quarters in Africa for its Asiatic summer home,
found its way to the Kentish shore.
Mr. Eagle Clarke says of the American visitors, that those " which find their way to our
shores unaided are birds which have a high northern summer range, and they doubtless reach
us after having travelled by way of Greenland, Iceland, and the Faeroes, not by an impossible
passage across the open Atlantic. In this way their voyages are not more wonderful than those
annually performed by the wheatear, redwing, whimbrel, and others along similar lines of
BRITISH GENERAL MIGRATORY MOVEMENTS 593
flight." Whether it is wise to say " impossible " in the face of evidence which we possess of the
journeys of the American golden-plover and other waders, is open to question ; l but with regard
to the majority of the American visitors it is evident that they made an error at the start, and
probably joined some band of south-eastward bound regular migrants instead of travelling with
their own kind in a south-westerly or southerly direction. Wind may drift birds from their
normal pathway at any point on their passage, and this fact probably accounts for the frequent
occurrence of ordinary east-coast birds of passage on our western seaboard and in Ireland. It
is, however, a fact that the west-coast passage has received less attention than that on the east.
The question as to whether a bird is out of its course or on its ordinary route depends
largely upon how far the existence of direct migration pathways is admitted, or how wide or
narrow these pathways are believed to be. In some autumns certain species are more abun-
dant on passage on the east coast than in others ; this applies to regular visitors like the grey-
crow, shore-lark, and brambling, as well as to rarer " vagrants." Either the numbers of these
birds are subject to great fluctuations or they only travel by this route in some seasons.
Others of the same species are known to voyage along the eastern borders of the North Sea,
and it is probable that the numbers which take one passage or the other are regulated by the
direction and force of the wind at the time of departure, deviating the stream to one coast or
the other. The arguments that the direction of the wind has no influence at all upon the birds,
but that force alone acts as a stimulant or deterrent, are not convincing. The route in this
case is the whole of the North Sea, but most of the travellers move along one or other side-
track, where they may obtain food and rest, rather than brave the dangers of the central
Lastly, there are a number of petrels, shearwaters, and other pelagic birds, nesting in some
cases in the South Atlantic or even Pacific, which have wandered into the North Atlantic and
been recorded for Britain. These birds have hardly found their way to our shores, they have
lost their way until they found themselves stranded here ; their casual wanderings have little
association with true migration. With a few it is different ; the great and sooty -shearwaters,
for example, are regular northward migrants in the autumn ; they wander in search of food
from their southern breeding haunts in exactly the opposite direction to the Arctic-tern, which
from its arctic and northern home, which has a southern limit in our islands, travels during our
winter so far as the Antarctic. The explanation is very simple ; these two shearwaters, and
some others which come more rarely, are birds of the southern hemisphere.
The following list by no means includes all the birds which are upon the British List; it
is divided into two, the first portion including those species which have occurred so frequently
that even if we admit them as " vagrant," their wanderings suggest regularity of movement
towards the British area. The second portion includes a number of species which have been
observed on a few occasions only, and whose journey to our islands was probably caused by
influences affecting individuals rather than species. Many of these extraordinary occurrences
are probably due to the errors of youth, which almost invariably means subsequent death for
Serin. Whitewinged-lark. Rock-thrush. Blyth's reedwarbler.
Pine-grosbeak. Short-toed-lark. Whitespotted-blue- Aquatic-warbler. 2
Blackheaded-bunting. Crested-lark. throat. Melodious-warbler.
Meadow- bunting. Redthroated-pipit. 2 Alpine-accentor. Rosecoloured-starling.
Rustic-bunting. WaUcreeper. Great-reedwarbler. Alpine-swift.
1 See Coward, The Migration of Birdi, 1912, pp. 119-121.
2 These, and probably others, may be classed as regular birds of passage.
594 BRITISH GENERAL MIGRATORY MOVEMENTS
ing (two forms).
White's thrush .
Savi's warbler. 2
Bartram's sandpiper. Little-crake.
Pectoral-sandpiper. Baillon's crake.
Bonaparte's sandpiper. Goshawk.
Broadbilled- sandpiper. Lesser-kestrel.
S ardinian- warbler.
Rednecked-nigh tj ar.
Hawk-owl (two forms),
Little dusky - shear-
X. MOVEMENTS DUE TO SEVERE WEATHER
During winter any sharp spell of frost or heavy fall of snow will occasion extra migration
of ground-feeding and indeed most birds both resident and winter visitors. The volume of a
movement depends upon the severity of the climatic variation which occasions it. The birds
1 These, and probably others, may be classed as regular birds of passage.
2 Formerly a summer visitor.
BRITISH GENERAL MIGRATORY MOVEMENTS 595
which are largely influenced thrushes, finches, larks, lapwings, and golden-plovers may pass
westward towards the warmer peninsulas of Lleyn or Cornwall, or they may continue westward
to the mild Irish shores. In the same way exceptionally severe weather in northern or north-
western Europe will cause a late emigration to our eastern coasts, which frequently takes the
form of winter " rushes," which, however, are less extensive in area and numbers than the
rushes in autumn.
Normal migration, whether in autumn or spring, is even-flowing and steady, and in conse-
quence not easy to observe. When the travellers are not hurried by adverse weather or by the
sudden falls in temperature after a warm but stormy spell, which had held them up at some
point of departure, they steadily move towards our shores, along them, or through the country
in small parties, and stop to feed wherever food is plentiful. On the east coast in autumn we
may look out seawards over a birdless waste of water. A few specks to the east, or more
frequently to the north-east, catch the eye, and if we watch these specks we see them growing
larger and more distinct. As they approach nearer we distinguish them as birds, then note
their particular species some day-migrants, lapwings, skylarks, or grey-crows perhaps. They
reach the shore, pass steadily overhead, and alight on some field, often where others of their
species have already gathered to feed. Under ordinary conditions they show no sign of fatigue,
but now and then a tired straggler is met with, which has hardly power to fly when approached.
Many migrants come in during the night or early morning, and it is in the early hours that we
may note the changes in the avian population of any particular district caused by the nocturnal
immigrants. During the daytime the passage of coasting birds may be noticed. Swallows and
martins skim along the shore, snapping up insects here and there, but seldom changing their
general southward direction for more than a short diversion to right or left ; lesser blackbacked-
gulls stream past over the sea in parties varying in number, or ducks and waders in more or
less ordered flocks swing by over the waves. It is only possible to judge that these birds i % e
migrating from their constant arrival from the north and movement towards the south.
When, however, numbers of birds have accumulated at a point of departure, owing to
meteorological conditions unfavourable for oversea travel, and some favourable change releases
them, there is a hurried departure. It is then that the passage or arrival of hastening migrants
is most easily observed ; it is then that migration becomes forced and abnormal ; it is then that
the perils of the frail travellers are increased, and many join the great army of the unfit, fall
out of the race, and perish. 1
1 I am indebted to Mr. J. L. Bonhote and Rev. F. C. R. Jourdain for suggeiting a few alterations, especially
in the classification of the migrants. [T. A. c.]
STUDY OF BIRD BEHAVIOUR
WITH A BIRD-WATCHER'S GUIDE 1
[F. B. KIRKMAN]
IN order to study birds in the wild state successfully, it is obviously not enough to go forth
with a binocular and watch them. One has to watch with a seeing eye. To do this it is
necessary to know what to look for ; there must be in one's mind definite questions to answer.
To go forth in search of facts needed to answer definite important questions, be the questions
great like those which occupied the mind of Darwin, or be they small, is an essential condition
of success in natural history.
The fundamental questions that face the student of the behaviour of birds are the same as
those which face the student of animal behaviour in general. A brief statement of the nature
and scope of this latter study must .here suffice to indicate what these questions are.
The word " behaviour," as commonly understood in this context, comprises all the bodily
activities of the animal considered as a unit e.g. its gestures, ways of feeding, of protecting
itself, of playing. 2 The word " animal " includes, of course, man. It is important, further,
to note that animal behaviour is not necessarily associated with consciousness or mental
process. It is conceivable that the lowest forms of animal life are without consciousness.
There are three kinds of animal behaviour commonly distinguished instinctive,
intelligent, and rational. Instinctive behaviour is inherited or congenital. A familiar example
is supplied by the ejection of its fellow-nestlings by the young cuckoo, which is able to perform
this feat without previous experience ; it has no means of learning how to do it. The complex
nervous-muscular co-ordination involved is entirely inherited.
Every animal, including man, comes into the world with a certain stock of instinctive ways
of behaving. This ready-made behaviour is, except in the case perhaps of the lowest forms of
life, capable of modification by experience. A chick just out of the egg will peck instinctively
at any small object within reach, whether it be eatable or not. Now if its instinctive behaviour
were incapable of modification, it would continue throughout its life to peck at a number
of useless objects only to have to drop them. This is not what happens. The chick learns to
recognise uneatable objects and to leave them untouched, thus saving itself much unprofitable
exertion. It learns by experience. Its behaviour, in so far as thus learnt or acquired, is termed
intelligent to distinguish it from instinctive behaviour, which is not learnt but inborn. Those
intelligent acts which become " mechanised " by repetition are termed " habits."
The distinction between intelligent and rational behaviour is more difficult to define. It
lies chiefly in the capacity or incapacity to form a mental image sufficiently free to enter into
1 My thanks are due to Professor Lloyd Morgan for very valuable comments on the matter of this chapter.
2 Excludes, therefore, in the restricted sense here used, the activities of the animal's bodily parts considered as
units (cell unit, organ unit).
STUDY OF BIRD BEHAVIOUR 597
new combinations, to form part, that is, of a reasoning process. An example will show what
is meant. A dog sees its master standing with a stick in his hand and calling in a loud and
angry voice ; it thereupon puts its tail between its legs and grovels or runs. Obviously the dog
is unable to form a verbal inference ; it cannot reason, " My master is angry, has a stick ; is,
therefore, going to beat me," for it has no word-imagery. But can it form a mental picture of
the stick playing on its back as last term in the process : master angry, stick ? If it can form
such an image, it is, according to the definition, capable of rational behaviour. If it cannot, if
it has learnt by painful experience merely to attach a meaning to certain proceedings on the
part of its master, to associate them with unpleasant consequences, to recognise them as ominous
without, however, being able to recall mentally the act of flagellation, then it is incapable
of rational behaviour ; it lacks the power of mental imagery without which no higher
mental life is possible. Its behaviour, in so far as not instinctive, is intelligent, and depends
always upon an object actually perceived, that is present to one or more of the organs of sense.
It is not here implied that a rational being would necessarily take the trouble to form a mental
image under the above circumstances, or even a verbal inference, which is only another form
of mental imagery. But the capacity to form the mental image would be there, and it is the
necessary condition of any process of reasoning that involves an object not actually perceived.
Of the three kinds of behaviour, the instinctive is the most primitive. The life of the
lowest animals appears to be almost wholly, if not wholly, of this kind. But in the very
nature of things instinctive behaviour cannot suffice, for environment is not constant, and
hence the little round of instinctive acts that are adapted to a given environment become
useless or positively dangerous, when for some reason or other that environment changes, or the
creature moves into another. A stone-curlew, crouching instinctively on its native waste,
escapes detection owing to its concealing coloration. Turn the waste into green pasture, and the
bird's instinctive crouching causes its destruction. It is here that intelligence comes to the
rescue. If a species has sufficient innate plasticity to enable it to modify its instinctive
behaviour to suit new conditions, it survives ; if not, it perishes. And most have perished, if
our reading of the geological record is right.
Kational behaviour succeeds intelligent. But at what point in the scale of animal life?
Has any animal below man the power to form a mental image ? This is still an open question.
A great mass of experimental evidence bearing on the point has in recent times been collected,
chiefly by American workers, but no convincing result has been reached. 1 There can be little
doubt that the behaviour of animals below man is, apart from a doubtful element of ration-
ality, mostly a complex of instinctive and intelligent, and it is by no means easy in given
cases to be sure where the one begins and the other ends.
The chief questions that face the student of animal behaviour, and consequently of bird
behaviour, will be already apparent. Firstly, is this or that act instinctive, intelligent, or
rational ? For example, to what extent is the art of nest-building inherited, to what extent
acquired by experience ? Secondly, what is the origin of the three kinds of behaviour ?
Is rational behaviour evolved from intelligent, and this again from instinctive ? How did the
instinctive arise ? Is there, in short, continuity of development in animal behaviour, and what
is its origin? Finally, one might go further and ask, what is the relation between behaviour
and the associated conscious states, between nervous process and mental process, body and mind?
but this question of questions takes us outside the scope of our study.
Such are the fundamental questions, and to answer them many subsidiary questions must
be put. A list of some of those which have reference to the study of bird behaviour will be
found below. To answer a few of them might well occupy the leisure of a lifetime.
If to have in one's mind definite questions that call for answer, if knowing what to
1 For the evidence, see Washburn, The Animal Mind (The Macmillan Co., K.Y.), and works there cited.
VOL. IV. 4 G
598 STUDY OF BIRD BEHAVIOUR
look for is an essential condition of success in the study of natural history, or of any science,
it is not the only condition ; there are others that cannot be ignored, and which are almost
unconsciously fulfilled in the practice of every good naturalist. One is to record observa-
tions with a sole eye to accurate statement, uninfluenced by any prejudice in favour of
preconceived theory. Another is to verify. A common error is to argue without hesitation
from the individual to the species ; it abounds in the pages of the older naturalists, and is not
absent from those of the modern. A third condition of good work is to practise with a
religious devotion the precept of the immortal Cuttle : ' When found, make a note of.' And
add the date. In the study of wild birds and most other vertebrates there is, need I add,
peculiar need of two qualities : patience and the ability to keep still.
In drawing conclusions there are two dangers worth noting. The first is the tendency to
assume in other animals the mental powers of man. A safe familiar rule is to explain by the
simple and more primitive rather than by the higher and more complex. A good example of
the danger is to explain origin by utility. For instance, the utility of a bird's nest is that it
keeps the eggs close together, so that the whole clutch can conveniently be incubated. To
affirm, however, that the primitive bird learnt to build a nest in order to keep the eggs
together, is to assume that it was, in the first place, capable of remarking that eggs roll down
and not up an incline; and, in the second place, of bearing this fact in mind with a view to the
annual construction of its nest. It is difficult to see how it could bear it in mind without
forming at least a visual mental image. We have no right at present to assume that it can.
The utility of the nest, if it does not explain its origin, may well, however, explain its
persistence ; the nest survived, or was " selected," because of its fitness for its purpose. Let us
add that in this case the affirmation that utility explains the origin of the nest-building
instinct involves another unproved assumption, which is not infrequently implicit in the
conclusions of naturalists : it is that acquired modes of behaviour can be inherited. The bird