ERAS Sea

PARLE NRE EEE ESSER EN SEEN

Z
Z
a
Zi
g,
A

ZA
A,
Ad
a
Zi

SOMMNAAANN

SAARI

SSIS SAS

SSO NESSES AIFAsa Sasso

SS 70 _]nn oda WW 0° 0 ”rKxvvvnrvr an. rtQHRNnnt.
ANAS NNAWAANAS IVAN NA DANAA NAA AAAAAAARANAAN NANA ANNAN ANE RA AR ES AN ANNAN NERA E RRR NAR CERN OE SO SQV AS SSANAANANS

NAAM

SAMARAS CAAA

MOO SSN

WC
\N

\\

SS

SSS

SScons

St See
\

WN

\N

SSS eae
LOO
‘

DRAKA ANN

apeehs 3
LEHR :
ADORNS

Everything contains an undiscovered principle, because we are in the
habit of only using our eyes with the recollection of what others have
thought of the thing we are examining. —FLAUBERT.

—_—

698.4
an THE MIGRATION
meer tSH: BIRDS

Their Post-Glacial Emigrations as Traced by
the Application of a Hew Law of Dispersal

BEING

DHCONTRIBUTION TO THE STUDY\LOF MIGRATION,
GEOGRAPHICAL DISTRIBUTION, AND
INSULAR FAUNAS

By CHARE ES? DLXON

AUTHOR OF ‘‘THE MIGRATION OF BIRDS,” ETC., ETC., E

WITH SIX MAPS

LONDON: CHAPMAN AND HALL, Lb.
1895

{Ad rights reserved]

RIcHARD CLay & Sons, LiMiTED,
Lonpon & BunGay.

lsd Sle ial sea Oa a

THE présent volume is the result of much additional
thought and hard work generally upon the subject of
Avian Emigration and Migration. It is a subject that
has a peculiar fascination for me, doubtless because it
offers all the charm of novelty, and is as yet a practically
unworked field of research. No branch of Ornithology
can possibly be more interesting than that which treats
of the Dispersal—either by Emigration or Migration—
of Birds over the globe.

To many naturalists this dispersal may appear
entirely fortuitous, or very largely due to such abnormal
influences as Glacial Epochs. I honestly confess that
for many years I was imbued with very similar ideas—
what all men accepted as true must assuredly have been
truth. But after a long and careful study of the phe-
nomenon of Emigration (or Range Extension) I began
to doubt some of the most generally accepted views
respecting the Geographical Distribution of Species.
Difficulty after difficulty arose, convincing me more and
more that the solution of the problem must be sought
in other directions. After much hard work at the

vi PREFACE

distribution of Birds generally, I have been enabled to
propound what I believe to be a Law of Dispersal.
The present volume is the development and applica-
tion of that Law. I may here remark that this Law
has been gradually developed from a vast number
of accumulated facts, and is not a result of any pre-
conceived theory.

I have selected British Birds for this application,
chiefly because our knowledge of their distribution, and
of the past physical changes in the areas they inhabit,
is not only extensive but fairly reliable. We are often
told that there is nothing new to be said about British
Birds. I offer the present volume as an answer to that
hackneyed remark, and desire specially to call attention
to our lack of information on many important subjects
connected with British ornithology, indicated here and
there in the following pages, as a possible field of very
fruitful research.

I am aware that much in the present volume is
opposed to the general views held by naturalists, and
even to those expressed by myself in former works.
For such portion of my work, a patient perusal and an
impartial judgment are asked. I am quite prepared to
meet with some amount of hostility from specialists
whose views are not in harmony with this new Law of
Dispersal. I have no fear for the results so far as Birds
are concerned ; and I await with profound interest, and
yet with every confidence, the results of its application to
other branches of biology, to which only specialists are
competent to apply it. Onits important bearing on the
Distribution of Floras I have already dwelt at some
length in my closing chapter.

Piel iA Cre vii

For the sake of convenience the work has been
divided into two parts; the first treating of physical
and climatic changes, and their effects on Birds and
species generally ; the ancient Emigration of birds to
the British Area, and its modern progress; lastly of
Island Avifaunas and their bearing on the entire subject.
The second part deals with the Migration of Birds with-
in the British Area; the Routes those birds follow ;
the conditions of their Flight ; the spring and autumn
aspects of the phenomenon; and lastly, with the very
curious and interesting subjects of Local Movement
or Internal Migration, and Irruptic Movement.

I earnestly hope that the present work may assist in
solving some of the many intricate problems connected
with the present and past Geographical Dispersal of
Life, and the Migration of Birds ; for then its purpose
will be amply attained, and the labour involved in its
construction ever recalled with pleasure.

CHARLES DIXON.

CONTENTS

PART I.—DISPERSAL:

A StuDY OF THE PHENOMENON OF AVIAN EMIGRATION
TO THE BRITISH ARCHIPELAGO AND ADJOINING AREAS.

CHAPTER I:

PAST GEOGRAPHICAL MUTATIONS AND CLIMATIC CHANGES.
PAGE
British Fossil Birds—Definition of the present Work—The ee
British Area—West European Submarine Plateau—The
British Seas—Ancient Land Areas between Greenland and
Europe — Effects of Submergence—The Great Submer-
gence of the British Islands—Evidence against it—Physical
Changes during the last Glacial Period—Geography of
Western Europe during late Pliocene, Pleistocene, and
early Post-Glacial Time—Commingling of Pliocene and
Pleistocene Species—Glaciation correlated with Elevation
and Subsidence—Changes in the Earth’s Centre of Gravity
—Coast-Line of British Area at the Close of the Glacial
Epoch—Geographical and Climatal Conditions—The 5o0-
Fathom Contour — The 4o-Fathom Contour — The 2o0-
Fathom Contour—The 15-Fathom Contour—Commingling
of Southern and Temperate Species—Absence of Large
Southern Mammals from European Post-Glacial Deposits
—The Flora and Fauna of Greenland and Iceland—Post-
Glacial Changes of Climate—Effects of Physical and
Climatic Change on Birds... is se Be NE eile

x CONTENTS

CHAPTER If.

RANGE BASES OR REFUGE AREAS.
PAGE

Results of Climatic Change during Post-Tertiary Time—Con-
dition of Europe during the Ice Age—Condition of the
Mediterranean Area—North-West Africa during Pliocene
and Post-Tertiary Time—The Saharan Region—Influence
of the Sahara on the Distribution of Species— North-East
Africa—Commingling of Palearctic and Ethiopian Types
—Homogeneity of the Fauna and Flora of Europe and
North-West Africa— Pleistocene Land Connections between
Africa and Europe—Effects of Glacial Epoch on the Euro-
Asian Mammalia of the Miocene and Pliocene Eras—Com-
mingling of Paleearctic and Ethiopian Types in the Sahara
—Erroneous Views of Naturalists—The Canary Islands—
The Cape Verd Islands and the Azores—Range Base or
Refuge Area I.—Flora and Fauna—Range Base or Refuge
Area II.—Its Climate—Range Base or Refuge Area III.—-
Its Uses and Climate—Change of Climate in East Africa—
Variations in Climate of Range Bases or Refuge Areas—
Effects of Changed Climate on Avian Life—The Law of
Dispersal—The Southern Exodus during Pleistocene Time
a Myth—* Arctic ” Animals—The Cape Flora _... eS)

CHAPTER hie

THE GLACIAL RANGE CONTRACTION AND POST-GLACIAL
EMIGRATION OF BRITISH BIRDS.

A New Law of Dispersal—The Third Cold Period of the Glacial
Epoch—Probable Avifauna of Refuge Area I. during this
Period—Effects of Cold Period on the Charadriidze—lInter-
polar Migration and Emigration—Avian Characteristics of
Refuge Area I.—Avifauna of Refuge Area II.—Resident

sritish Species—Southern Representative Forms—Species
Resident in British Isles and in Refuge Area II.—British
Species that Resort to Refuge Area II. in Winter—Winter
Visitors to the British Isles that also Winter in Refuge
Area II.—Summer Visitors to the British Isles—Winter
Quarters of these in Refuge Area I].—Ancient Sahara Sea
a Bar to Emigration fromthe South—Birds ranging further
South in East Africathan in West Africa— Winter Quarters
of British Summer Migrants in Refuge Area I1].—-Circuit-

CONTENTS x
PAGE
ous Routes of Migrants to West Africa—British Summer
Migrants from the South-East—British or West European
Species that have Emigrated from South-Eastern Areas—
Their Absence from Iberia—Their Allied Forms and Re-
presentative Species—Influence of Competing Species—
Reasons for their Absence from British Area—Abnormal
Migrants to British Area—West European Species nor-
mally Absent from British Area— Reasons for such Absence
—Past Emigrations of Storks and Red-crested Pochard—
Emigrations of Blue-headed Wagtail and Allies—Situation
of British Area now unfavourable to Emigration—Instances
showing Impassable Nature of a Sea Barrier—Avian Emi-
gration to Greenland—Nearctic Emigration—Post-Glacial
Emigration of Birds in West Europe—Emigration to Ice-
land and Greenland across the British Area—Table of
Emigrants one me Bee ae ae one Son 2)

CHAPTER. IV.

THE GLACIAL RANGE CONTRACTION AND POST-GLACIAL
EMIGRATION OF BRITISH BIRDS (condznued).

Anomalous Facts—Analysis of the Facts suggested by pre-
ceding Table—Table demonstrating the two Dominant
Lines of Post-Glacial Emigration in the extreme West of
Europe—Analysis of Table—Variations in the Northern
Limits of Species—Ancient Line of Emigration from the
British Area Eastwards into Continental Europe—The
North Sea Plains—Their Gradual Submergence and _ its
Effect on Birds—Table of East and North-East Emigrants
—Analysis of Table—Influence of Temperature on Birds—
Effects on Birds of Isolation of British Area from Con-
tinental Land—Professor Geikie on Emigration to the
British Area—Emigration to Ireland — Impossibility of
Southern Emigration to this Area from Scotland—Migra-
tion of Birds in the Valley of the Petchora—Emigration
of Birds within the British Archipelago—Resident Species
—Table of Resident Species—Analysis of Table—Absence
of Birds from Ireland—Summer Migrants—Table of
Summer Migrants—Analysis of Table—Table of Autumn
Migrants to and Coasting Migrants over the British Islands
—Analysis of Table—Table showing the Proportional Dis-
tribution of Species over the British Area—Deductions

xl CONTENTS

from the Facts—Table of Endemic British Species and
Races—ésumé of Present and Preceding Chapters—Im-
portance of New Law of Dispersal—Exterminating Effects
of Glacial Epoch—Effects of Cold Winters—The Dartford
Warbler—Importance of Southern Range Bases ...

CHAPTER Vi
RECENT EMIGRATION.

Increase, the Ruling Impulse of Life—The Ice Age and Emi-
eration—Emigration still in Progress—Effects of Civiliza-
tion on the Emigration of Birds—Present Emigration in
the British Area—Emigration of the Missel Thrush—
Effects of Severe Winter on that Bird—Emigration of
Song Thrush and Blackbird—Of the Redstart—Of the
Robin, the Nightingale, the Whitethroat, the Willow Wren,
and the Wood Wren—Absence of Wood Wren from Nor-
way—Probable Winter Quarters of Individuals Breeding in
Sweden—Emigration of Marsh and Sedge Warblers—Of
the Goldcrest—Migration Waves of Goldcrests—Emigra-
tion of Hedge Accentor, Nuthatch, and Tree Pipit—Of
the Greenfinch—F luctuating Breeding Range of this Species
in the British Area—Emigration of Sparrows—Emigration
of Tree Sparrow to the Faroes—Emigration of Chaffinch
and Bullfinch—Of the Starling, the Jay, the Magpie, and
the Rook—Of the Tawny Owl, he Ring Dove, and the Stock
Dove—Of the Great Crested Grebe and Woodcock—Table
of Species whose Emigrations are still in Progress—Analysis
of Table—Northward Tendency of Emigration—Emigration
attended by Migration—Extinction of British Species—
Effects of Law of Dispersal ...

CHAPTER Wik.
ISLAND AVIFAUNAS,

The West Palearctic Islands—Continental Islands—Birds of
Borneo, Formosa, the Philippines, ete.—Ancient Conti-
nental Islands—Birds of the Canaries, Madagascar, Azores,
Bermuda, etc.—Reasons for the Unequal Dispersion of
Species—Islands and Migration—The British Islands—
Endemic British Species — The Red Grouse—Endemic
British Races or Representative Forms—The St. Kilda

vAGE

. 168

CONTENTS xiii

PAGE
Wren—Races of Titmice—Poorness of British Avifauna in
Endemic Species—The Channel Islands and Heligoland—
West Mediterranean Islands—The Canary Islands—En-
demic Birds of—Number of Eggs laid by Birds in Canary
Islands—Madeira and the Azores—Japan and the Bonin
Isles—Various Tropical Islands—Endemic Avifaunas of—
Bearing of Migration on Insular Avifaunas—Conclusions
drawn from Facts—Bearing of Glacial Conditions on Island

Avifaunas a, te Sais pe oe ae neo ey)

PART II—MIGRATION:

A Stupy OF THE PHENOMENON OF AVIAN SEASON-FLIGHT
ACROSS THE BRITISH ARCHIPELAGO.

CHAP MER V TT:
ROUTES OF MIGRATION,

Difficulty of tracing Routes to British Islands—Definition of
a Migration Route—The Gradual Effects of a Changing
Climate on Birds—Impulses to Emigration and Migration
—The Turnstone and the Rose-coloured Pastor—Ancient
Breeding Ranges — Inter-polar and _ Inter-hemisphere
Species—Breeding Grounds and Winter Quarters coales-
cing — Routes followed by Summer Migrants to British
Area—Routes into the South of England—Species follow-
ing them—Routes into Ireland—How followed by Birds
—Absence of Routes into Scotland wzé Ireland — Past
Physical Changes indicated by Present Routes of Migra-
tion—Persistency shown by Birds in following Migration
Routes—Across the English and St. George Channels
and the North Sea—Palmén’s “ Fly Lines ”—The North Sea
Routes— Origin of—Effects of Submergence on the Emigra-
tion and Migration of Birds—West to East Migration—
Water Areas a Check to Emigration—Routes followed by
Winter Visitors to and Coasting Migrants over the British
Islands—The Routes of Migration that are most followed—
Inland Continuation of Migration Routes—Difficulty of
Tracing—Correlation of Routes with Breeding Grounds ... 209

XiV

CONTENTS

CHAPTER »VIilIl.

CONDITIONS OF FLIGHT.

Routes of Migration, how followed by Birds—Paley’s Defi-

nition of Instinct—Impulse of Migration—Restlessness of
Captive Birds—Certain Routes followed by Certain Indi-
viduals—How a Route of Migration has been Learnt—
Mysterious “Sense of Direction” a Myth—Altitude of
Migration Flight — Advantages of a Lofty Course—The
Order of Migration—A few Old Birds migrate as Early as
the Young—The Daily Time of Migration—Amount of
Sociability amongst Birds on Passage— The Perils of
Migration

CHAPTER IX.

THE SPRING ASPECTS OF MIGRATION IN THE BRITISH
AREA.

Commencement of Spring Migration in the British Islands—

Departure of Eastern Migrants—Departure of North-
Eastern Migrants—Abnormal Lines of Migration from the
British Area—Birds migrating too Early—Arrival of First
Spring Migrants from the South—Departure of Winter
Visitors to the British Islands—Coasting Migration in
Spring—Migration of various Northern Birds—Arrival of
Summer Migrants in the British Islands—The Growing
Intensity of Spring Migration— Months of Passage of
various Species—Gradual Advance northwards of Migrants
—Duration of Spring Migration— Vertical Migration in
Spring—The various Species performing it — Order of
Migration—Table indicating the Spring Migration of Birds
across the British Islands Say ice ae oe ied

CHAPTER Xx.

THE AUTUMN ASPECTS OF MIGRATION IN THE BRITISH
AREA.

Migration more Apparent in Autumn than in Spring—Diffi-

culties of Observing the Phenomenon—Commencement of
Autumn Migration in the British Islands—Arrival of Birds
from the North and North-East—The Species that are the

PAGE

to

aS
ray

CONTENTS XV

PAGE
Earliest to Arrive—Growing Intensity of the Movement—
The Hardier Species are Latest to Appear—Autumn Migra-
tion of Fieldfare and Redwing—The Earliest Departures
from the British Area—Early Migrants Abnormal—The
Growing Intensity of Southern Migration as Autumn ad-
vances—Duration of Migration Periods—The Migration
into the British Area from the East—General Aspects of
the Phenomenon—Abnormal Lines of Migration in Autumn
—Cross Migration in Autumn — Reversal of Route by
Migratory Birds—Erroneous Interpretation of the Facts—
The True Explanation—Duration of Autumn Migration—
Vertical Migration in Autumn—Order of Migration—Table
indicating the Autumn Migration of Birds across the

British Islands ... ae es ae sas ans set, 200)

CHAPTER <l:

INTERNAL MIGRATIONS AND LOCAL MOVEMENTS IN THE
BRITISH ARCHIPELAGO.

Meagreness of Data bearing on this Question—Local Move-
ments in Spring and Summer—Internal Migration always
takes place within Normal Areas of Dispersal—Birds do
not wander from their Areas—Comparative Movements of
the Snow Bunting, the Northern Bullfinch, and the Crested
Titmouse—Emigration only undertaken during the Season
of Reproduction—Local Movement amenable to Law—
Effects of Severe Winters on Birds—Results of such Move-
ments ineffectual in extending Area—Redwings and Severe
Weather—The Want of Carefully-kept Records—Local
Movements at Lighthouses—Irruptic Movements—Their
Futility as Colonizing Agents...

iS)
NI
2)

CHAP TER Xi:
SUMMARY AND CONCLUSION.

The Present Volume illustrates the Development and Appli-
cation of a New Law of Dispersal—Past Geographical and
Climatic Changes—The Glacial Epoch and its Bearing on
the New Law of Dispersal—Effects of the Glacial Epoch
on Species—Range Bases—Application of the Law of Dis-
persal to the Range Contraction and Emigration of British
Birds—The Migration of British Birds—Routes of Migra-

XVI

CONTENTS
PAGE
tion—Conditions of Flight—The Spring and Autumn As-
pects of Migration in the British Archipelago—lInternal
Migrations and Local Movements in the British Area—
Irruptic Movements—The New Law of Dispersal— Its
Bearing onthe Arctic-Element in South Temperate Floras
—Inter-polar Floras—Impossibility of Emigration of Plants
from North to South—Presence of Southern Genera in
Europe—The Andes as a Route for the Southern Migra-
tion of Plants—The Floras of Mountains in the Torrid
Zone during Pre-Glacial Ages—“ Arctic” Floras could
never have been Developed in the Polar Regions—Dis-
persal of Plants North and South from Equatorial Range
Bases—Effects of Glacial Epoch on Northern Floras—
Absence of many Species from Equatorial Range Bases—
The “ Retreat” of Plants a Myth—Conditions of Successful
Dispersal—The Flora of the Mountains of Asia—Inter-
Hemisphere Species—Species in Polar and Temperate
Zones—The Distribution of Plants in Africa—The Tem-
perate Flora of South Africa—Northern Emigration from
Antarctic Centres obviously Erroneous—The Bearing of

this New Law of Dispersal on the Absence of Southern

Ni

IIT.
IV.

Vil.

Types from the Northern Hemisphere—The Dominant
Southern Flora—Its Dispersal from Range Bases south of
the Equator—The Problem of Migration and Geographical
Dispersal hitherto attacked at the Wrong End—Exter-
minating Influence of Glacial Epochs—Powers of Organ-
isms to extend their Areas of Dispersal—This Dispersal
not Fortuitous but governed by Law As ik “aes

List Or TENE S:

Map showing the 100-Fathom and 50-Fathom

Contours of the British Area... a6 ... Lo facepage §
Map showing the 4o-Fathom, 20-Fathom, and

15-Fathom Contours of the British Area aoe os op 21
Map showing Range Base or Refuge Area I. a i 47
Map showing Range Base or Refuge Area II. ... a 5 71

Map showing Range Base or Refuge Area ITI. ...
Chart showing the Principal Migration Routes
into the British Area... 3 a ick 209

9? 29 =

» 95

THE

MIGKATION OF BRITISH BIRDS

PARTY L—DISPERSAL

A STUDY OF THE PHENOMENON OF AVIAN EMIGRATION
TO THE BRITISH ARCHIPELAGO AND ADJOINING AREAS

pe h 1 —_ DISPERSAL,

CHAPTER I.

PAST GEOGRAPHICAL MUTATIONS AND CLIMATIC
CHANGES.

British Fossil Birds—Definition of the Present Work—The British
Area—West European Submarine Plateau—The British Seas
—Ancient Land Areas between Greenland and Europe—Effects
of Submergence—The great Submergence of the British Islands
—Evidence against it—Physical Changes during third Glacial
Period—Geography of Western Europe during late Pliocene,
Pleistocene, and early Post-Glacial Time—Commingling of
Pliocene and Pleistocene Species—Glaciation correlated with
Elevation and Subsidence—Changes in the Earth’s Centre of
Gravity—Coast-line of British Area at the close of the Glacial
Epoch — Geographical and Climatal Conditions — The 50-
Fathom Contour—The 4o-Fathom Contour—The 20-Fathom
Contour—The 15-Fathom Contour—Commingling of Southern
and Temperate Species—Absence of large Southern Mammals
from European Post-Glacial Deposits—The Flora and Fauna
of Greenland and Iceland—Post-Glacial Changes of Climate
—Effects of Physical and Climatal Change on Birds.

OWING to the excessive rarity of fossil bird-remains, we
possess but the scantiest paleontological evidence of
that avifauna which occupied the British area even during
Pleistocene and late Pliocene time, but judging from the
fragments hitherto discovered it presented very similar
aspects to that existing now in our islands, With

4 THE MIGRATION OF BRITISH BIRDS

regard to Miocene and Eocene time it is still more
difficult, from the present state of our knowledge, to
derive even a general idea of its aspects. Of this, how-
ever, we may rest assured, that it possessed many
dominant features which have long been entirely obli-
terated from existing types. Amongst these vanished
birds we may recall the giant Gastornzs klaassent; the
Accipitrine Lzthornzs vulturznus ; the imposing Argillor-
nts and Odontopteryx—allied to the Gannets and the
Cormorants ; Halcyornzs and Proherodius, representing
our modern Gulls and Herons; the Flamingo-like
FHlelornis, and the Ibis-like /dzdopszs. We need not,
however, speculate on the avifauna of so remote a past ;
it has little or nothing to do with the past emigrations
of existing species, or of the phenomenon of Migration
across what is now the British Archipelago, the philo-
sophy of those grand avian movements being amply
demonstrated by the forms inhabiting that area during
present time.

For the purposes of the present volume it will not be
necessary to go back, geologically, to a very distant past.
On the ancient origin of Avian Season Flight I have
already dwelt at some length in the A77gration of Birds.
The present work is more a study of the Post-Glacial
Emigrations of our avifauna and of Migration as under-
taken by birds in our own day, going on unceasingly
around us from year to year, than a history of the phe-
nomenon of Migration in remoter ages. Nevertheless we
shall find in our investigation of the interesting subject
that it will be advisable not only to go back at least to
late Pliocene and to Pleistocene or Quaternary time,
but to include the avifaunas of many areas more or less

PAST GEOGRAPHICAL MUTATIONS 5

contingent to our own, in order to arrive at a reasonable
and probably correct interpretation of the facts now
presented. It is absolutely impossible to understand
the present migration and geographical distribution of
British birds, unless we take into consideration the past
emigrations of these species, or their common ancestral
forms ; for undoubtedly those ancient emigrations pre-
sent the only means now available by which we can
explain a very large number of apparently anomalous
facts. It is equally impossible to understand them
without taking into consideration the various geo-
graphical mutations and climatic changes which have
taken place in this area during late Tertiary and Post-
Tertiary time. It becomes necessary therefore to glance
briefly at the probable state of Europe, not so much
during the height of the Glacial Epoch, but more
especially during the closing periods of that awful era
and in the earlier stages of Post-Glacial time.

The area which now forms the British Islands consists
of the elevated portions of a vast submarine plateau,
receding from the coasts of continental Europe, and for
the most part covered by a shallow sea varying from
fifteen to a hundred fathoms in depth. This plateau
extends from Denmark, some distance beyond the south
coast of Norway, the Shetlands, the west coast of
Ireland, and southwards along the French coasts of the
Bay of Biscay. Beyond this limit westwards the sea
rapidly deepens in a series of terraces from 500 and
1000 to 2000 fathoms. The greater part of this water
area, including most of the North Sea, ranges from
15 to 50 fathoms, but deeper trenches occur along
the centre of the bed of St. Georges Channel and the

6 THE MIGRATION OF BRITISH BIRDS

Irish Sea, in the North Channel between Ireland and
Scotland, and between the Inner and Outer Hebrides ;
these hollows range from 100 to 150 fathoms in depth,
and may be well described as a series of submarine
lakes and ancient river channels. Another narrow deep
channel, which was apparently an ancient fjord or lake,
extends round the southern coast of Norway, and is for
the most part some 500 fathoms in depth. To the
north-west of the Orkneys a narrow ridge, under 500
fathoms from the surface, extends to the bank of less
than 300 fathoms reaching to Greenland, and on which
the Faroes and Iceland are situated. It is probable
that this north-western and comparatively shallow sub-
marine bank was formerly a more continuous land area,
if not, as some authorities suggest, an actual isthmus,
connecting Greenland with continental Europe even
during early Post-Glacial time. It is interesting to
remark the vast effect such an isthmus would produce
upon the climate of Northern Europe by shutting out
the warm waters of the Gulf Stream, which would
unquestionably reduce the climate of Scandinavia to the
same state as that now prevailing in Greenland, and
clothe many of the Scottish mountains in canopies of
perpetual snow. The submergence of this land connec-
tion has been the chief means of rendering the climate
of North-western Europe so comparatively mild, by
admitting warm currents to circle round the coasts and
exert their beneficial influence on fauna and flora alike
to a most remarkable extent. The effect on the Migra-
tion of birds alone of such a physical change has been
far-reaching and profound, as may be readily perceived.

The accompanying map will better illustrate the

PAST GEOGKAPHICAL MOTATIONS 7

probable appearance of Western Europe during at any
rate the closing period of Pleistocene and early Post-
Glacial time. That a large portion of the British Islands
has been submerged to a depth of about 1400 feet
during the Glacial Epoch has long been the almost
universal opinion of geologists; the chief, if not only
evidence of this great submergence being the occurrence
in a few localities of glacial gravels and drifts containing
marine shells. Strong evidence against this “great
submergence,” however, is to be found in the fact that
the shells in these drifts differ considerably in habit,
some belonging to sandy, others to muddy bottoms,
some only known to exist below tidal water, others
confined to the shore, consequently they could not well
have lived together in the places where their for the
most part fragmentary remains are now found. Again,
no evidence of this submergence is to be met with on
the English lowlands, which, if it had really occurred,
would have formed the bottom of a sea no less than
1200 feet in depth, and must have left traces of old
beaches or marine remains characteristic of such a vast
depression. As Dr. Wallace recently remarked (/ort-
nightly Review, Nov. 1893, p. 633): “In consequence of
these various difficulties it was suggested by the late Mr.
Belt that the great Irish Sea ice-sheet had carried up a
portion of the sea-bottom embedded in its substance,
perhaps containing deposits of shells of various periods,
and thus explaining the intermixture of species as well
as their fragmentary condition. The fact that boulders
and pebbles from Scotland, Ailsa Craig, and Cumber-
land have been found in the Moel Tryfaen beds almost
amounts to a proof that they were so uplifted ; and a

§ THE MIGRATION OF BRITISH BIRDS

recent search has shown that in the other localities where
marine shells have been found in drift at great elevations
similar foreign rocks occur, rendering it almost certain
that the same ice-sheets which have distributed foreign
erratics so widely over our country, and which in doing
so must have passed over the sea-bottom, have in a few
cases carried with them a portion of that sea-bottom and
deposited it with the erratics in the places where both
are now found.” If the drift be taken as evidence of
submergence, then, as Mr. P. F. Kendal pointedly
remarks (Man and the Glaceal Period, p. 178): “A sub-
sidence of the Yorkshire Wolds took place on the east,
but not in the centre or west; that the Pennine Chain
was submerged on the western side to a depth of 1400
feet, and on the east to not more than 300 feet, even on
opposite sides of the same individual hill; that all the
lowlands between, say, Bacup and the Welsh border,
were submerged, and that the hills near Frondeg par-
took of this movement, but only on their eastern sides ;
that the centre of Wales was exempt, but the summit
of Moel Tryfaen forms an isolated spot submerged, while
the surrounding country escaped. These absurdities
might be indefinitely multiplied, and they must follow
unless it be admitted that the phenomena are the results
of glacial ice, and that the ice can move uphill.” That
the latter circumstance is a fact I need scarcely say has
been proved by irrefutable evidence. It is also very
dntcresting and suggestive to remark how the supporters
of the “great submergence” hypothesis assert that the
subsidence dwindled down to zero in the southern por-
tions of England, say to a line drawn between Bristol
and London, curving northward as far as Warwick,

PAST GEOGRAPHICAL MUTATIONS 9

which, it may be remarked, is the ascertained limit of
glaciation, the area below that boundary, embracing all
the English shires south of the Bristol Channel, and
the valley of the Thames, having for the most part
endured from the early Pliocene Period. It is also
significant that no drift containing marine shells has
been found at high levels in Scotland.

Whatever changes may have taken place elsewhere
in British Europe during the Glacial Epoch, it seems
pretty certain that the land which now lies buried under
portions of the Bay of Biscay down to the borders of
the French Landes, beneath the English Channel, the
Bristol Channel, St. Georges Channel, and to the south
of Ireland, endured through most if not all of that
period, and formed the bridge by means of which our
area was invaded by the large mammalia and other
forms of animal and vegetable life during the successive
mild inter-glacial periods. We shall yet see the even
greater importance of this southern land mass. It is,
however, suggested that during the third glacial period
the sea advanced up the English Channel—the high
temperature of its waters probably checking the
southern advance of the ice-sheets beyond the valley
of the Thames, Whether the depression extended up
the Bristol Channel or the Irish Sea area need not con-
cern us, for we have evidence to suggest that that
region was entirely glaciated or snow-clad. It is pre-
sumed that during this era the Selsey beds and the
various raised beaches which occur from Cornwall to
Brighton on the English coast, and from Brittany to
St. Valery sur Somme on the French coast were formed.
During this glacial period the North Sea is said once

10 THE MIGRATION OF BRITISH BIRDS

more to have made its appearance, and a portion of its
southern coast-line extended far within the present limits
of Northern France and Belgium. It is during this era
that the range of the Greenland whale and the walrus
is reputed to have extended as far south as the coast of
Lincolnshire. This state of things probably endured
long enough for the waters of the two seas to meet
across the narrow isthmus which joined England to
France, but was followed by terrestrial upheaval or
marine depression, and as the glacial period passed
away the Channel and the North Sea once more became
dry land.

It will perhaps be most convenient to deal first with
the geographical mutations which our area has under-
gone during the last phase of Pliocene time, and from
the close of the Glacial Epoch down to the period when
the British Islands were finally severed from continental
land, so that we may better understand the various
points at issue, and be able to refer with clearness to
such changes whenever the exigencies of our investiga-
tions render such a course advisable or necessary. We
have already seen (see Map, p. 5) that a vast submarine
plateau or bank covered by a shallow sea extends far
into the Atlantic, some 50 miles beyond the British area
to the north and west, and some 150 or 200 miles to
the south off Finisterre, whence it is contracted down
the shores of the Bay of Biscay to Biarritz. Upon this
submarine plain many important physical changes have
occurred since the close of the Pliocene Period. We
possess sufficient evidence to suggest that in those
remote ages the North Sea was much more contracted,
and the land mass of our area was very much more

PAST GEOGRAPHICAL MUTATIONS II

extensive than it is during present time. From the
Shetlands to the Bay of Biscay, following the Ico-
fathom line, was apparently dry land, our eastern coast-
line conforming much to the general direction which it
does now, extending, however, some 70 miles further
out to sea than in our time, to as far south as the
Wash, where, however, the sea encroached upon what
is now land in North-east Norfolk and East Suffolk
and Essex to a little north of the Thames. The con-
tinental coast was equally extended, the shores of the
Netherlands approaching our own to within some 70
miles at the narrowest part. During this late Pliocene
Period, therefore, a great portion of the southern part
of the North Sea was a wide alluvial plain, studded
with lakes and intersected by sluggish streams, very
similar in character to the Broad district of to-day,
bounded on the west by higher forest-clothed ground,
and traversed by a continuation of the Rhine with the
Thames as a tributary stream. Of the fauna and flora
of these remote days, according to Professor J. Geikie
(Prehistoric Europe, pp. 261, 334), the remains include
“those of elephant, hippopotamus, horse, cave-bear, urus,
Irish deer, and many other Cervide. The fauna is
remarkable as showing commingling of Pliocene and
Pleistocene species. Thus we have among the former
a bear (Ursus arvernensis), a rhinoceros (2. etruscus),
and a deer (Cervus polignacus) which have not yet been
met with in any deposits of more recent age. Again,
several of the forms which appear in the ‘forest bed ’
are common Pliocene species that seem to have van-
ished from the European fauna in early Pleistocene
times. Among these are I/achairodus, and others which

12 THE MIGRATION OF BRITISH BIRDS

occur in the older Pleistocene deposits, but have not
been dug up in beds pertaining to the latest stage of
the Pleistocene Period. Nevertheless, the characteristic
Pleistocene fauna is well represented in the ‘forest
bed’ of Norfolk by such animals as cave-bear, wolf,
fox, wild-boar, urus, mammoth, Irish deer, roe, stag,
beaver, and mole. The fauna of the ‘forest bed’ is
thus intermediate between that of the Pliocene on the
one hand, and the Pleistocene on the other, and is more
closely allied to the latter than the former.’ Professor
Geikie continues: “Underneath the oldest known
boulder clay—that of Cromer in Norfolk—occur certain
fluvio-marine deposits, the plant remains in which be-
speak the kind of climate that characterized England
at the commencement of the first glacial epoch. That
flora embraced Scots fir, spruce fir, yew, alder, oak,
birch, white and yellow water-lilies, bog-bean, common
sloe, etc.—indicating a climate perhaps a little colder,
but not essentially differing from that of Norfolk at
present. But as the plants are traced upwards through
the strata they were found by Mr. Nathorst to become
more and more stunted and meagre, until in a bed
immediately underlying the boulder clay he came upon
the Arctic willow (Sa/zx polaris) and a moss (Hypnum
turgescens) now confined in temperate latitudes to the
highest alps.”

We possess but little reliable information respecting
the physical history of the British area during the
Glacial Epoch, and great difference of opinion prevails
among authorities thereon. Fortunately such history
does not very intimately concern the subject of our
investigations, which in its entirety is amply accounted

PAST GEOGRAPHICAL MUTATIONS 13

for by glaciation alone, or embraced by Post-Glacial
time. Of one thing we may be pretty certain, that
when the penultimate inter-glacial period had attained
its meridian the climatal conditions (“more humid, and
much more equable”) of our area, and the fauna and
flora inhabiting it, resembled very closely those which
characterized later Pliocene time. It seems probable,
however, that the shallow North Sea of late Pliocene
ages had vanished, perhaps partly due to upheaval,
especially in the north, or marine depression, but more
likely, to a very great extent, silted up by the vast
quantities of detritus carried by the Scandinavian and
Scottish ice-sheets that several times swept its bed.
For, as Mr. Jukes-Brown remarks (Zhe Buzlding of the
British Isles, p. 426): “a recent boring at Utrecht has
proved that the surface of the Pliocene deposits is more
than 500 feet below that part of Holland, and as the
Pliocene sea probably deepened northward, it is there-
fore hardly too much to assume that the same surface
lies some 100 fathoms below the present bed of the
North Sea between Norway and Britain, and conse-
quently that the upheaval necessary to convert this sea
into land after the Glacial Period was 100 fathoms less
than would have been required to effect the same result
in later Pliocene time.’ With the coming on of the
third glacial period, the “great submergence” of the
British Islands is presumed to have occurred; but, as
we have already seen, this great subsidence could never
have taken place—and Professor Geikie himself admits
that there is no evidence of any such universal depres-
sion in Scandinavia, unless all trace has been removed
by succeeding glacial action, which does not seem

14 THE MIGRATION OF BRITISH BIRDS

probable. It is suggested, however, that during this
epoch the North Sea appeared once more, and that
the Atlantic invaded the English Channel. The low
grounds of Prussia are said also to have been sub-
merged about this time.

There can be no doubt that periods of glaciation
have always been accompanied by great variation in
the relative level of sea and land, but whether so much
of this has been caused by elevation or subsidence of
vast areas of land, as many geologists so positively
assert, seems to the present writer somewhat doubtful.
I am disposed to agree with the late Dr. Croll, who has
conclusively shown, almost to the extent of absolute
demonstration, that oscillations of sea-level may be
produced by an alteration of the earth’s centre of
gravity, caused by the greater amount of ice at one
pole than the other, the ocean conforming to such
alteration, and appearing to rise in one hemisphere
and to fall in the other. Thus the sea-level might rise
in a given area without any terrestrial movement what-
ever. Dr. Croll points out that the great ice masses
which were characteristic of the last Glacial Epoch would
cause a rise in the sea-level by altering the earth’s
centre of gravity, and he suggests (according to Pro-
fessor Geikie) “that some of our recent raised beaches
may indicate periods when the ice of north polar regions
attained a considerable augmentation, while, at the same
time, the ice of the Antipodes suffered a corresponding
diminution.’ The enormous ice-sheets which once
covered so much of the Northern Hemisphere may
therefore have caused sufficient change in the earth’s
centre of gravity to produce an oscillation in the sea-

PAST GEOGRAPHICAL MUTATIONS 15

level of several hundreds of feet irrespective of any
land movement whatever.

To whatever cause, however, we may ascribe it, the
British area at the close of the Glacial Epoch appeared
to have stood at least 300 feet higher than it does at
the present time, or the sea was depressed to that
extent. The coast-line of the British area at that period
would, generally speaking, correspond at least with the
contour of 50 fathoms, but the land surface may possibly
have been even more extensive. Indeed such eminent
authorities as Lyell, Godwin-Austen, and Professor
Geikie fix the coast-line of this period at the 100-fathom
contour, which would go far to suggest that the land
area of this portion of Western Europe was as extensive
at the close of the Glacial Epoch as during the later
stages of that era. As Professor Geikie remarks: “In
short there was a return of those geographical conditions
which we have every reason to believe characterized
certain Inter-glacial epochs.” It seems much more
reasonable to suppose, however, that these geographical
conditions had endured to a very great extent, as we
have already seen that the great submergence hypo-
thesis cannot be supported by any reliable evidence.
Whatever was the exact contour, we may be pretty
certain that the coast-line of West Europe during early
Post-Glacial time was outside our islands. Terrestrial
conditions during this period were remarkably favour-
able for the emigration to our area of the fauna and
flora which had not been exterminated by the preceding
glacial period, or such portion of them as had survived
its rigours, or were able to return, We picture the
North Sea as a broad undulating plain once more,

16 THE MIGRATION OF BRITISH BIRDS

traversed by the Rhine with all our eastern rivers from
the Thames northward as its tributaries; we picture
the Irish Sea as another plain, more rugged, perhaps,
in character, perhaps with a long central lake and an
ex-current river, draining parts of Ireland, England, and
Scotland. We picture the Bristol Channel as a verdant
valley with precipitous sides, watered by a Severn flow-
ing on to join the main river of the Irish Sea valley.
Further, yet again, we must picture the English Channel
as another broad plain watered by the Somme and the
Seine, then one river, with tributary streams from the
south of England, flowing south-west to fall into the
Atlantic, whose coast-line then extended many miles to
the west of Ouessant Island.

We appear to possess no evidence of the time that
these geographical conditions endured. Sufficient time
must have elapsed, however, for the climate to become
so modified as to allow of the growth of a luxuriant
flora and of the emigration of vast numbers of birds and
animals from more southern regions to which their range
had been contracted by extermination by the preceding
elacial period. Submergence seems, however, to have
been in progress, due either to terrestrial action or
marine disturbance, and Ireland became separated from
England before more than twenty-two of the forty
species of British Mammalia, and four of the thirteen
species of Reptilia and Amphibia had succeeded in
establishing themselves in that area. So far as birds
are any evidence the land must soon comparatively
have been invaded by the sea, until the contour of 4o
fathoms was reached. This would bring Ireland almost
to its present contour and isolate it from England and

PAST GEOGRAPHICAL MUTATIONS 17

from the Continent by a wide sea in the south, which
was probably then the dominant line of Emigration of
all species moving north with the changing climate.
The 40-fathom contour, however, would leave Ireland
joined to Scotland by a narrow isthmus—of no conse-
quence as regards southern Emigration, as I hope to
show in a future chapter—and submerge about half of
the North Sea plain beneath the waves. The sea at this
contour would encroach considerably upon the English
Channel area, but still offer little obstacle to the northern
or western Emigration of species by that route; whilst
sufficient land would be left between Denmark and
England to allow of Emigration and Migration on a
vast scale, as the sequel will show. Proof of the rich
mammalian fauna dwelling at this time in Western
Europe is suggested by the great quantities of its remains
which have been dredged from the bottom of the North
Sea, especially from the Dogger Bank, from which
latter locality bones, teeth, and antlers have been ob-
tained, relics of the reindeer, Irish elk, stag, woolly
rhinoceros, mammoth, hyzna, bear, wolf, etc., some of
which must have roamed that ancient plain during
prehistoric ages.

But the sea still continued to encroach upon the land,
terrestrial submergence or marine upheaval steadily pro-
gressed. The North Sea crept southwards or spread
east and west, and the Atlantic meantime encroached
more and more up the English Channel, the Bristol
Channel, and the Irish Sea, until the contour of 20
fathoms was reached, and the Dogger and other banks
in the North Sea became islands, on some of which

many large animals appear to have been imprisoned by
C

x S

18 THE MIGRATION OF BRITISH BIRDS

the surrounding sea, and eventually exterminated in the
final disappearance of this area beneath the waves.
How long the contour remained at some 20 fathoms we
have no means of ascertaining, but the final severance of
the British Isles from continental land occurred at no
very remote geological period, when the waters of the
English Channel and the German Ocean encroached
upon the narrow isthmus between France and England
and finally met at the Straits of Dover. At first the
newly-formed Strait was exceedingly narrow, perhaps
less than a mile. For some time after the final sever-
ance of Great Britain from continental Europe nearly
all the coast-line of England, part of Ireland, and part
of Western Europe remained apparently at the 15-fathom
contour, as is suggested by the phenomenon of submerged
forests. At the 15-fathom contour the coast-line of the
east of England from the Humber to the north of
Norfolk would extend many miles further out to sea
than is now the case; elsewhere it would only reach a
few miles beyond existing limits, with the exception of
a considerable distance outside the present coasts of
Norfolk, Suffolk, and Essex. The coasts of the Nether-
lands and Belgium also probably extended further out
to sea during this period. The significance of these
facts will be made apparent in a later chapter.

Such, broadly speaking, are the principal physical
changes which the British area has undergone from the
close of the Pliocene epoch down to prehistoric time.
In order to render the subject more complete and to
enable the reader better to grasp these mighty changes
in their natural sequence, I append a brief résumé of
the events recorded, associating with them the various

PAST GEOGRAPHICAL MUTATIONS 19

physical and climatal changes occurring contempo-
raneously in other parts of Europe, together with the
probable effects of such changes on the co-existent
faunas and floras. For this latter information especially
I am chiefly indebted to the profound researches of
Professor Geikie, one of the highest authorities on the
subject.

We may begin our cursory sketch with the gradual
passing away of the second glacial period—with the
retreat of the ice-sheets from North-western Europe and
the melting of the glaciers in the valleys of the Alps
and other mountain chains of Central and Southern
Europe. We remark the northern advance of plants
and animals, their invasion of alpine regions, and their
replacement by more temperate species from still
more southern areas, emigrating northwards with the
amelioration of climate. Dense forests gradually spread
northwards and up the mountain sides, under the de-
velopment of favourable climatic conditions; and a
mixed and luxuriant flora slowly covered the long-
desolated land. Once more the mammals emigrated
northwards, many passing from Africa to Europe by
land connections between Italy and Tunis, and Spain
and Barbary; southern and temperate forms com-
mingling and ranging from the shores of the Mediter-
ranean up to the north of England, and even into
Scotland; large carnivores frequenting the forests and
bears the caves. “If laurels, fig-trees, and judas-trees
grew side by side in Northern France with the sycamore
and the ash, and in low-lying countries on the borders
of the Mediterranean with pines, oaks, beeches, pop-
lars, and elms, so also,” writes Professor Geikie, “were

20 THE MIGRATION OF BRITISH BIRDS

elephants, rhinoceroses, and hippopotamuses, horses,
oxen and deer, hares and rabbits, wolves, foxes, lions,
and hyzenas joint occupants of the same. regions.” The
geographical conditions at this period were such that
the coast-line of North-western Europe extended beyond
the British Islands, reaching what we have seen was
probably the 100-fathom contour, and in the Mediter-
ranean region the land was distributed differently from
what is now the case.

Once more a change of climate and of physical con-
ditions are initiated by the coming on of another—the
third—glacial period, and another great extermination
of the fauna and flora is commenced. As the cold
increased the southern forms vanished from northern
areas, and as the rigours of the climate became more
intensified, temperate and boreal forms became less
northerly in their distribution, until ultimately the dwarf
birch, the Polar willow, and Arctic mosses, saxifrages, and
lichens inhabited the lowlands of Central and Southern
Europe; the mammoth and the glutton, the reindeer,
the marmot, and the musk sheep dwelt only upon the
northern shores of the Mediterranean. During this era
the sea is presumed to have invaded the plains of the
English Channel and the German Ocean, whilst it is
suggested that the low grounds of Prussia were sub-
merged. The British area, with the exception of England
from Yorkshire southwards, was for the most part
covered with snow-fields and ice, and the surrounding
seas were filled with glaciers; many of the mountain
regions of Central Europe were glaciated; and even
as far south as Gibraltar and Malta heavy snows
and severe frosts prevailed. Again the severity of

CHAFMAN & HALL, LIMITED.

PAST GEOGRAPHICAL MUTATIONS 21

the climate abated, the ice-sheets of the north dis-
appeared, the glaciers slowly shrank up the mountain
valleys, and once more a general faunal and floral
northern exodus commenced. The larger southern
mammals—elephants, rhinoceroses, and hippopotamuses,
hyenas, and the larger carnivores—however, never appear
to have invaded Europe again, for no relics of their
occurrence have yet been met with in the Post-Glacial
deposits of that region. This absence of the large
southern mammalia is very generally ascribed to the
submergence of the land connections across the Mediter-
ranean between Europe and Africa, but I think their
disappearance from the European fauna of Post-Glacial
times is due to other causes which will be discussed in a
later chapter. We must omit from this period the great
submergence of the British area, and in proceeding to
discuss Post-Glacial phenomena, merely remark that
with the passing away of this and the Baltic glacier
phase of the Ice Age a very general elevation of pre-
viously submerged land took place, the 100-fathom
contour being eventually re-established. This elevation
would restore the plains of the North Sea, and perhaps
connect Greenland with Europe by way of Iceland and
the Faroes, not necessarily by a continuous coast-line, but
by a considerable increase in the area of those islands.
Following this elevation we have the series of submerg-
ences through Post-Glacial time which eventually cul-
minated in the severance of the British area from
continental land. I may here take the opportunity of
remarking that the evidence furnished by the early
Post-Glacial Scandinavian fauna is against the presump-
tion of a direct land connection between Europe and

22 THE MIGRATION OF BRITISH BIRDS

Greenland by way of Iceland and the Faroes. Sucha
land mass would effectually shut out the Gulf Stream
from the shores of Norway, and render the climate of
that area too rigorous for the luxuriant flora which
paleontological evidence proves to have occupied the
land after the Ice Age passed away. I would suggest
a greater extension of land between Greenland and
Europe in the form of islands; and that a greater land
surface occupied this region during some portion of
Post-Glacial time (after the third glacial period) is con-
firmed in a remarkable way by the migratory birds that
follow this now submerged area, as we shall learn ina
later chapter. Professor Geikie’s views on the geography
of this region during absolute Post-Glacial time (his first
age of forests), in which he maps out Europe and Green-
land united by an isthmus, seem therefore untenable.
Evidence for the greater extension of land between
Greenland and Europe during early Post-Glacial time is
furnished by the flora, and toa less marked extent by
the fauna. So great an authority as Sir Joseph Hooker
has shown the Scandinavian or North-west European
character of the flora (through Iceland and the Faroes),
and the paucity of Arctic American elements. So far
as the mammals are an indication, we have the Arctic
fox (remains of which have recently been found in the
south of England) and the polar bear, found also in
Iceland.'. On the other hand, three other species are
exclusively North American, although the fossil remains
of one of them, Ovzbos (the musk sheep), occur in the
Post-Glacial gravels of Siberia, Germany, and France,

1 There is, however, always the strong probability of these ani-
mals reaching Iceland on floating ice.

PAST GEOGRAPHICAL MUTATIONS 23

and in the brick earths of England—a fact in itself sug-
gestive of a former land connection between Greenland,
and Europe. Of the others, J/yodes torquatus may have
been introduced by man, and Lepus glacialis on icebergs
None of the land birds, however, especially of South
Greenland, show very striking Palearctic affinities ; and
this to a great extent may be due to the present glacial
conditions of the country, north of 65° on the east coast,
combined with the wide water areas. The land birds
indicate a more remote connection of South Greenland
with Europe than with America, inasmuch as all the
terrestrial species recorded by Hagerup (zrds of Green-
land, 1891) as breeding in South Greenland are Nearctic
forms of Palzarctic species, Palzearctic species that have
invaded America from Eastern Asia, or species common
to both regions. Iccland, as might be expected, shows
more affinity with Europe in its avifauna, only one species
belonging otherwise exclusively to the Nearctic region,
viz. Clangula islandica. It also contains a Wren
( Troglodytes borealis) found elsewhere only in the Faroes,
and which is most nearly allied to the Norwegian 7. der-
gensis and the St. Kildan 7. Aertensts—a fact which
strongly indicates a purely Palearctic emigration. But
the most interesting avian proof of a more continuous
land area between Greenland and Europe is that fur-
nished by the Wheatear (Saxicola wxanthe). The Wheat-
ears breeding in Iceland and perhaps North Greenland
are distinctly larger than the typical European form, and
pass the British Islands regularly on passage during
April and May, when the individuals of this species that
spend the summer with us are already breeding. We
are thus able actually to prove that this route is followed,

24 THE MIGRATION OF BRITISH BIRDS

the size of the birds and the date of their passage pre-
venting any possibility of a wrong interpretation of the
facts. The Wheatears or Chats (Savzcola) are exclusively
an Old World group, confined to the Ethiopian and
South Palzarctic regions, with the single exception of the
Wheatear, so that there can be no doubt whatever as to
the line of emigration followed by that species, or as to
the more continuous land surface of its migration route
whilst that route was being established.

The climate from the close of the third glacial period
down to the dawn of historic time appears to have
suffered considerable changes—alternations in fact of less
and less strongly-marked genial and cold conditions,
culminating in the fourth (and less extensive) glacial

period, the epoch of the great Baltic glacier—as the
eccentricity of the earth’s orbit gradually diminished
and approached that limit which characterizes the pre-
sent era. There can be little doubt that the third
glacial period was succeeded by a warm and genial
climate, much more favourable to the growth of large
vegetation than now, especially in the north, as is proved
by the remains of forest trees in the peat-bogs of the
now sterile Hebrides, Orkneys, Shetlands, and Faroes.
Following this we appear to have a relapse to a colder
period (the epoch of the Baltic glacier) than marks
present time, followed by the submergence which was
eventually to isolate our area from continental land, and
also to separate Greenland from Europe by the wide
water-ways that now exist. Local glaciers and snow-
fields probably also appeared on the mountains of
England, Wales, and Ireland, as they certainly did on
those of Scotland. The climate during this period

PAST GEOGRAPHICAL MUTATIONS 25

was not only cold but extremely humid; vast forest
areas of oak, alder, and other deciduous trees were
destroyed, and the ground converted into marshes and
bogs, not only in the British Isles, but in Northern Ger-
many and throughout North-western Europe. Event-
ually this cold, humid period passed away, and a second
era of more favourable conditions supervened, during
which a vigorous growth of forests (chiefly pines and
birches) flourished. This era was marked by a gradual
retreat of the sea. The subsequent destruction of many
of these later forests and their burial in sphagnum peat
mark a relapse to another period of cold, humid con-
ditions, accompanied by a rise of sea-level and sub-
mergence of much forest-clad area in many maritime
districts. To this latter period most of the submarine
forests of the British coast-line are said to belong. With
the passing away of this cold, wet period we approach
the earliest ages of written history, the invasion of
Britain by the Romans, the climatal conditions and
arboreal surroundings which are characteristic of pre-
sent time. The effects of these gradual yet enormous
changes of climate upon the migration and distribution
of birds in our area will never be known. That these
changes must have influenced the fauna as well as the
flora is unquestionable, but unfortunately these are
details of our inquiry which will probably always remain
beyond the limits of human knowledge or conjecture.

Chea ir
RANGE BASE OR REFUGE AREAS.

Results of Climatic Change during Post-Tertiary Time—Condition
of Europe during the Ice Age—Condition of the Mediterranean
Area—North-west Africa during Pliocene and Post-Tertiary
Time—The Saharan Region—Influence of the Sahara on the
Distribution of Species—North-east Africa—Commingling of
Palearctic and Ethiopian Types—Homogeneity of the Fauna
and Flora of Europe and North-west Africa—Pleistocene Land
Connections between Africa and Europe—Effects of Glacial
Epoch on the Euro-Asian Mammalia of the Miocene and
Pliocene Eras—Commingling of Palaarctic and Ethiopian
Types in the Sahara—Erroneous Views of Naturalists—The
Canary Islands—The Cape Verd Islands and the Azores—
Range Base or Refuge Area I.—Flora and Fauna—Range
Base or Refuge Area II.—Its Climate—Range Base or Refuge
Area III.—Its Uses and Climate—Change of Climate in East
Africa—Variations in Climate of Range Base or Refuge Areas
—Effects of Changed Climate on Avian Life—The Law of
Dispersal—The Southern Exodus during Pleistocene Time a
Myth—* Arctic” Animals—The Cape Flora.

BEFORE proceeding further with our investigations re-
specting the dispersal of birds over the British area, it
is of the utmost importance to our inquiry that we
should endeavour to ascertain the character and amount
of that physical and climatic change which took place
contemporancously in areas adjacent to our own. We
have already seen that climatic variations during Post-
Tertiary time have been enormous and severe. The

RANGE BASE OR REFUGE AREAS a7,

inevitable result of such changes has been on the one
hand to contract the range of species far to the south
by extermination, on the other hand to encourage
northern emigration, both movements being on a scale
so enormous that we can only form a conception of
their magnitude by a close and careful study of their
results as manifested by the present distribution of
existing species. What became of the numerous forms
of animal and vegetable life dwelling in the areas
suffering such glacial visitation? whence did they go
during the devastation of their northern or alpine homes
by the invading ice-sheets, snow-fields, and glaciers?
Before we can hope to understand the philosophy of
their distribution at the present time it becomes abso-
lutely necessary for us to endeavour to trace out the
areas these species occupied during the era of their
extermination from glaciated areas, and from which
they again set out as colonists upon the gradual return
of more favourable climatal conditions.

Taking as our guide the present geographical dis-
tribution of the European fauna and flora we shall, I
think, experience little difficulty not only in tracing out
these areas of refuge, but in ascertaining to some extent
the physical changes which those areas have undergone
during late Pliocene and Post-Tertiary time. So far
as Europe is concerned, the evidence I have been able
to collect points to the existence of no less than three
fairly well defined range bases or refuge areas. Europe,
the western coast-line of which, following the contour of
100 fathoms, then extended outside the British area, at
the climax of the Ice Age was to a great extent covered
by one vast ice-sheet which descended to about lat. 50°

28 THE MIGRATION OF BRITISH BIRDS

off the south coast of Ireland, and to about lat. 514° or
52 across the south of England and Holland; thence
southwards more or less irregularly to lat. 50° as far east
as the northern Carpathians, whence it contracted north-
wards across Russia, here and there sending out furca-
tions or spurs to about lat. 61° near the Urals. South of
these limits were many local glaciers in Spain, in the
Pyrenees, the Alps, the Carpathians, and the Caucasus.
By far the most important of these vast ice-sheets were
those in the Alps. For not only did they coalesce in
the west with those on the mountains of Eastern France,
but in the north probably with the Great Ice-sheet itself,
through the glaciers on the mountains of Germany,
Austria, and Bohemia. There can be no doubt what-
ever that during the climax of the glacial periods Europe
was even more effectually divided into two portions by
this vast central glacial system and its attendant snow-
fields, than if a sea of equal breadth had stretched
between them. There is evidence of two distinct glacial
periods in the Black Forest, and, it is said, of three
such glaciations in the Alps, separated by inter-glacial
mild eras. During the maximum of glaciation or second
of these glacial periods Central Europe, as we have
already seen, was completely occupied by ice and snow-
fields, the grand JZer de glace extending through the
Black Forest into the valley of the Rhine and elsewhere,
and coalescing with the glaciers of the Alps. During
the third and the fourth glacial periods the northern
ice-sheets appear not to have extended so far south-
wards, and did not deploy upon the low grounds
beyond say lat. 52, or coalesce with those of the Alps;
so that the Wer de glace during the latter part of the

RANGE BASE OR REFUGE AREAS 29

Glacial Epoch was broken, although it is probable that
ice-sheets and snow-fields in Moravia and elsewhere
helped to isolate Eastern from Western Europe, between
the Alps and the Carpathians.

The condition of the Mediterranean and the distri-
bution of land in that area during the Glacial Epoch
are the next stage in our investigations. There is strong
evidence to suggest that the Mediterranean Sea has
endured throughout Pliocene and Post-Tertiary time ;
but, on the other hand, there is equally good ground for
believing that the relative distribution of land and water
in past ages has been very different from that which
characterizes this region during present time. At a
pericd no more remote than the penultimate inter-
glacial era, and when the west European coast-line
extended beyond the British Islands, it is suggested
that Southern Spain was united to Barbary (Alboran
Island probably then marking the western limit of the
Mediterranean Sea); the Balearic Islands formed part
of the Spanish mainland; Sardinia and Corsica were
united and formed an isthmus which joined continental
Europe in the Gulf of Genoa with North-west Africa ;
Italy, Sicily, and Malta were connected with each other
and with the opposite coast of Tunis ; the Adriatic and
the waters surrounding the Grecian Archipelago were to
a great extent dry land, extending southwards possibly
to beyond Crete and Cyprus. The Mediterranean would
then form three seas divided by the comparatively
narrow necks of land formed by the Italian and
Sardinian peninsulas being prolonged southwards into
isthmuses joining Europe and Africa. What is now the
northern portion of the latter continent was thus united

30 THE MIGRATION OF BRITISH BIRDS

to Europe by several important land masses which have
now sunk beneath the waves, leaving Europe completely
isolated from that region. We thus see that throughout
Post-Tertiary time the Mediterranean has always been
a very important barrier to the northern emigration
and to the southern range contraction from Europe
of vast numbers of plants and animals. This to my
mind shows very clearly that the narrow strip of
North Africa then attached to Europe was never
occupied very dominantly by animals and plants whose
European range was extensive northerly. It indi-
cates that North Africa was then a land difficult of
access in the only direction from which species could
enter and colonize it by our Law of Dispersal, namely
from the east or south-east. As we know, the great
Sahara Sea between Tunis and Egypt must have barred
all emigration to North Africa so long as it continued,
and when this barrier was removed, an extension of
range southwards for all northern forms would have
been necessary to colonize this area. Hence the total
absence of all boreal forms from North Africa.

From the physical characteristics of the Mediterranean
area during the Glacial Epoch we now pass on to the
opposite continent of Africa, and endeavour, with the
evidence furnished by the present geographical distribu-
tion of European birds, to trace out its physical con-
ditions during Pliocene and Post-Tertiary time. The
present distribution of species seems very forcibly to
suggest that Africa during those remote ages was
divided into two unequal portions ; or, rather, that the
whole of North Africa, above the Sahara, including the
Canaries, formed part of continental Europe. At that

RANGE BASE OK REFUGE AREAS 33

period the Sahara was either a great eastern inlet of the
Atlantic, a relic of that vast primeval ocean which we
know swept from the Atlantic to the Bay of Bengal
during the Eocene and Miocene ages; or a vast sterile
waste even more barren than at the present time, owing
to the more recent retreat of the sea. Whether the sea
actually invaded this area or not during Pleistocene
time is, however, of little consequence: the fact remains
that a vast barrier, either of sea or barren desert,
effectually prevented all northern progress in this
direction of plants and animals from Africa, and that
the southern range of all western and temperate
species never extended below this area. The vast
influence of the Sahara on the distribution of species
continues to be exerted down to the present time,
and the strictly Ethiopian fauna and flora have almost
entirely failed to establish any appreciable element
amongst the Palzarctic types that still continue to
occupy Africa north of that sterile barrier. In the
north-east of Africa, however, we find a very different
state of things, Ethiopian types ranging right up the
Nile valley to the shores of the Mediterranean. Owing
to the far easier conditions of dispersal we also find much
commingling of Palearctic (more correctly described,
however, as of Ethiopian origin) and Ethiopian types
in this area, the former penetrating the Ethiopian region
to its southernmost limits, and from which region they
originally emigrated northwards, and the latter encroach-
ing upon the Palearctic region to an appreciable extent.
The Ethiopian element persists throughout Egypt even
to the delta of the Nile; and the range of between thirty
and forty species of birds characteristic of that region

32 THE MIGRATION OF BRITISH BIRDS

extends to Palestine, amongst the most notable forms
being species of Cossypha and Dromolea. \We must not
view these forms as remnants left behind in the
north when the great and entirely legendary exodus
into Africa was in progress, but either as Inter-hemi-
sphere (conf. p. 60) species that have spread from an
Antarctic, or Southern Hemisphere, centre of dispersal
northwards across the entire Ethiopian region, or from
an equatorial base. In Palestine, it may be remarked,
we also find a commingling of types peculiar to the
Oriental and the Ethiopian regions in such genera as
Nectarinia and Pycnonotus. Such facts demonstrate very
clearly that where the land surface is continuous and
sufficiently fertile to support life,a commingling of types
peculiar to different faunal regions invariably occurs, but
in the Northern Hemisphere the invasion is never of a
purely Southern character, the encroaching species con-
forming entirely to the Law that forbids a Southern
extension of area (conf. p. 60), and also confirm the view
previously expressed that the Sahara, either as an inland
sea or a sterile desert, checked all such mixture of Pale-
arctic and Ethiopian types in the west of Africa, the
division between the two faunas, so far as we know in
that district, being a very abrupt one, whilst in the east
of Africa, where no such barrier exists, the faunas of
the two regions blend in a very suggestive manner. It
is a most remarkable fact that the fauna and flora of
Europe and North-west Africa have retained their
homogeneity although separated by one of the deepest,
widest, and most ancient seas in the world—phenomena
that suggest a long-enduring and:recent land connection,
which we know existed at no remote epoch, as the

RANGE BASE OR REFUGE AREAS 33

paleontological remains on certain islands and_ the
presence of submerged banks in their vicinity between
the now disunited continental areas, undoubtedly prove.
No such land connections ever appear to have
bridged the primeval Sahara sea, and consequently the
links between the typical African and European faunas
and floras are insignificant and exclusively of recent
appearance.

It now becomes necessary to revert fora time to the
land connections between Africa and Europe during the
Pleistocene Period. There can be little doubt that an
extension of land surface across the Mediterranean was
taken advantage of by birds, which seem always adverse
to extend their range beyond water areas. These land
passages across the Mediterranean have been chiefly
insisted upon by geologists to account for the presence
of the large mammalia in Europe during the Pleistocene
Period, and for the presence in the North-west African
flora of a decided European element: the Mollusca of
the Sahara have also, I believe, exclusively Palzarctic
facies. But, as I hope ultimately to prove, these land
‘connections between South Europe and North-west
Africa were incapable of preserving from extinction the
large pachyderms and carnivores so characteristic of Pleis-
tocene time. A glance at the map will show the reason
for this. The area to the south of the Mediterranean
from which these ancient land passages led—say be-
tween Spain and Italy respectively—must have been
very restricted, confined at most within as narrow limits
as at the present time, and bounded by sterile deserts or
wide seas marking the southern limits of all the West

European fauna and flora. Not only was the area an
D

34 THE MIGRATION OF BRITISH BIRDS

exceedingly limited one ; it was also singularly ill-adapted
to the requirements of such hordes of mighty beasts.
North-west Africa possesses no large rivers in which the
rhinoceros and the hippopotamus could find congenial
haunts; no vast forests and wild fertile areas suitable
for the elephant, the sabre-toothed tiger, and the mam-
moth. That many of these larger mammals inhabited
North-west Africa during the Pleistocene Period, when
the area was continuous with northern continental land,
we have abundant proof in the remains which have
been discovered in the caves of Algeria of Eguzaus, Bos,
Antilope, Hippopotamus, Rhinoceros, Ursus, Canus, and
Flyena ; but how few of these have left descendants,
and succeeded in preserving their species or their types
in that area when it became isolated ! |
It is generally presumed that these large mammals
retreated south in Africa to the haunts in which they
live now, and which were then occupied by many of the
same species, coming north again with the return of
milder climatal conditions. But there can be little
doubt that many of these animals dwelt in the vast
Euro-Asiatic continent which then included North-west
Africa, over which they were widely dispersed as a
dominant fauna, the range of at least some species ex-
tending northwards from tropical Africa, as that area was
united to the northern continent by the upheaval of part
of the bed (from Egypt and Abyssinia to the delta of
the Ganges) of that primeval ocean which then extended
from the Atlantic to the Bay of Bengal, this event
taking place in late Miocene or early Pliocene time. As
we have already seen, the western portion of that ancient
ocean perhaps endured across what is now the Sahara

RANGE BASE OR REFUGE AREAS 35

throughout the Glacial Epoch. As a proof of the exist-
ence of this Sahara sea at no very remote geological
era, I may remark that the remains of species of marine
shells, still existing in the Mediterranean, are found
scattered over the desert, both in the valleys and up to
elevations of 900 feet ; whilst at least one species of fish
has been found in the salt lakes of that region, south of
Algeria, which is also an inhabitant of the Gulf of
Guinea, nearly 2000 miles to the south! The large
quantities of salt so characteristic of the whole region,
as I can testify from experience, may also be safely re-
garded as direct proof of the recent existence of a vast
salt-water area.

I hope I have succeeded in making it tolerably plain
to the reader that the great exit from tropical and South
Africa for species increasing their northern range was in
the north-east, down the valley of the Nile; and it is by
this route, and this route alone, that we trace the ancient
range contraction of such species that had penetrated
far into the Palearctic region. Even this area is now,
as it undoubtedly was during Pleistocene time, not very
favourable to the emigration northwards of Ethiopian
mammals and plants. There can be little doubt that
the Glacial Epoch was the cause of the extermination
of all or nearly all the great, varied, and dominant
mammalian fauna that roamed in that vast Euro-Asiatic
continent during Miocene and Pliocene ages; and the
utter absence of the remains of the great pachyderms
and carnivores from Post-Glacial deposits in Europe
(with the one doubtful exception of the mammoth) must
not be ascribed to the submergence of the land passages
between North-west Africa and South Europe during

36 THE MIGRATION OF BRITISH BIRDS

the last glacial period, but as an eloquent and uncon-
trovertible testimony to their extermination through
adverse conditions of life, due not only to severities of
climate but to narrower areas of distribution. As Pro-
fessor Geikie himself remarks: “We have seen that a
number of characteristic Pleistocene animals had made
their appearance in England at the close of the Pliocene
Period, or shortly before the advent of the earliest
recognized glacial epoch of Pleistocene times. They
were associated with several Pliocene forms, such as
Hippopotamus amphibius, Elephas meridionalis, Machat-
vodus latidens, Rhinoceros etruscus, R. megarhinus, Ursus
arvernensis, Cervus dicranios, and C. polignacus. Of
these, one, the hippopotamus, is still living, while others
do not appear to have survived in North-western Europe
the first glacial epoch. The southern elephant and the
megarhine rhinoceros, however, struggled on into inter-
glacial times, when the former occupied the valley of the
Rhone, Central France, and Northern Italy, and the
latter ranged from Southern Europe into England. The
sabre-toothed tiger also would seem to have persisted
well on into the Pleistocene Period. Of the other
animals that come into view for the first time in the
pre-glacial deposits of Cromer, many appear and re-
appear in successive inter-glacial deposits ; but we note
as we advance toward the later stages of the Pleistocene
that some of them become rare, while others vanish
altogether. The recurrent glacial epochs seem to have
told severely upon many of the herbivorous animals.
The only two pachyderms that have survived are the
hippopotamus, already mentioned, and the African
elephant. During each successive glacial epoch those

RANGE BASE OR REFUGE AREAS 37

species which could only exist under a mild climate
would be forced to the extreme south of Europe,
where, confined within ever-narrowing limits, they would
gradually die out. Only the more robust types, such as
stag, megaceros, urus, bison, horse, mammoth, woolly
rhinoceros—species capable of enduring some severity
of cold—would live on. The carnivores, however, might
be expected to thrive wherever their food supply was
sufficiently abundant, they would prey alike on the
denizens of the southern regions and the occupants of
less temperate latitudes. Most of them, therefore, were
enabled to endure all the climatic vicissitudes of the
glacial period, and many are recognized as still living
species.” As will be seen, but one of these pachyderms
has managed to survive the Glacial Epoch, and that is
now an inhabitant of tropical Africa. To the present
writer there seems no reasonable doubt that this sur-
viving species, the hippopotamus, is the descendant of
individuals that entered Africa in late Miocene or early
Pliocene ages, when that region was invaded by so many
of the higher species of mammalia either from the east
or west, and that the Ethiopian portion of this species
never had any experience whatever of the Glacial Epoch.
The African elephant is said to be specifically distinct
from the European elephants of Pleistocene time (perhaps
northern and southern forms), but its remains, however,
have been found in North-west Africa, individuals which
were isolated there during the glacial climate of Europe
and exterminated by adverse conditions. Had con-
ditions been favourable for emigration to Africa of the
various large forms of Pliocene mammalia, there can be
no reasonable doubt that many species would have

38 THE MIGRATION OF ERITISH BIRDS

availed themselves of such a retreat to the tropics and
survived amongst such congenial surroundings down to
the present day, yet, so far as I can ascertain, there is
not a single trace throughout the Ethiopian region of
any such Pleistocene exodus, for the Law of Southern
Dispersal forbids it. The evidence also points to the
conclusion that the same Law forbade the retreat of
these Euro-Asiatic mammals into Africa by way of the
Nile. The presence in tropical Africa of the hippo-
potamus, the sole surviving form, undoubtedly proves
that the range of this.species during the Glacial Epoch
was Ethiopian. Precisely the same remarks apply to
birds. We have abundant evidence of the former exist-
ence in Europe during Tertiary time of many Oriental
and Ethiopian types, such as Collocalia, Trogon, Psittacus,
Necrornis, Limnatornis, Centropus, etc.,\—all species that
had spread northwards and eastwards from southern
or equatorial bases and become sedentary in the warm
equable climate of Euro-Asia until exterminated by the
advent of adverse conditions of life, primarily due to a
change of climate ; and that now continue to be solely
represented by types that have preserved their identity

1 Every species that did not BREED south of glacial limits must
have perished ; numbers of other species that were resident in
many parts of Euro-Asia must also have been exterminated by the
adverse change in the climate. Among these were such types as
are here instanced. If the advent of a glacial climate could
initiate a migratory southern movement or an extension of perma-
nent habitat in the same direction, then numbers of such types
would have survived and left traces of their southern exodus
behind them ; but adverse climatic conditions can never lead to
increase or extension of winter or non-breeding area, and extermina-
tion is the inevitable result, unless modification may in some cases
preserve them from utter obliteration.

RANGE BASE. OR: REFUGE AREAS 39

because they were never subjected to such vast exter-
minating conditions as have entirely removed every one
of these their northern descendants. If the range base
was beyond the limits of exterminating influences (either
connected by migration or continuous breeding area) the
species or the type survived ; if entirely within such fatal
limits, just as surely did such types or species vanish
for ever; for the Law of Dispersal (conf. p. 60) in the
_ Northern Hemisphere forbids all southern emigration
either to increase breeding area, or to escape adverse
climatic change, or unfavourable conditions of life. One
of the most graphic examples of the inability of a fauna
to escape from utter extermination is afforded at the
present time in New Zealand. ‘Let the reader peruse
Mr. W. H. Smith’s sad account of the extermination of
birds in that country (/ézs, 1893, pp. 509—521), and he
will be speedily convinced of the truth of the axiom
that species never “retreat” from unfavourable con-
ditions only by extermination. In the case of a wide-
ranging dominant species, only such portions of the
species are affected as are subject to the adverse con-
ditions; but if the species occupies a narrow area
nothing can save it from utter extermination if the
adverse conditions continue.

Of the rich and magnificent fauna of Euro-Asia what
an utterly insignificant remnant has been preserved to
us, how devastating has been the result of the Glacial
Epoch upon these, some of the highest as well as the
more archaic forms of life! The present distribution in
Africa of many of the larger carnivores (such as the
lion, panther, cheetah, jackal, and hyzena) may, however,
be slightly due to a Pleistocene range contraction from

40 THE MIGRATION OF BRITISH BIRDS

Europe during the last glacial period. After the range
of these animals had been contracted into Africa by
extermination down the land passages, if you will, which
existed between that continent and Europe, we can
readily understand how a portion of these species might
have been left isolated in North-west Africa after the
submergence of such passages, and consequently never
re-appeared by Post-Glacial Emigration in Europe with
the return of milder climatal conditions. Here, sub-
jected to comparatively easy conditions of life, for
abundance of food could be obtained, many of them
were doubtless able to subsist even to the borders of the
Southern Sea or arid desert; and as this area eventually
became studded with oases and scattered vegetation, the
descendants of the individuals of many of the same
species which entered Africa in Miocene or early Pliocene
ages gradually spread northwards or westwards, so that
the distribution of the species, once discontinuous, eventu-
ally became uninterrupted as at present. The Sahara
has unquestionably been peopled from the east and
south. Emigration commenced from both points as
soon as life could be supported there; from the east by
species in search of an extension of range, and from the
south by species similarly extending their areas of dis-
persal northwards in summer, or during the period of
reproduction, The presence in this area, however, of
endemic forms of these southern and eastern animals,
seems to suggest that the colonization of the old Eocene
sea-bed in the south was not very extensive, and took
place under more or less unfavourable conditions, Even
where mammalian and reptilian affinities are not with
European species they are with Asiatic forms and not

RANGE BASE OR REFUGE AREAS 4

with Ethiopian ones, another proof of the complete
isolation of the old African fauna. It is impossible to
say in what portion of the Saharan region the Palzarctic
and Ethiopian faunas intergrade, or whether they do so
at all to any appreciable extent, until we possess more
complete information respecting the animal] life of this
profoundly interesting area. Any one reading Mr.
Sharpe’s recent paper on the distribution of birds
(Natural Science, 1893, p. 105) would very naturally
infer that the Ethiopian element penetrates into Morocco.
That naturalist remarks: “It is a somewhat important
fact that a truly Sudanese form like AZelerax polyzonus
has been found in Mogador and Southern Morocco.” In
the first place it is an error to describe this bird—one
of the chanting Hawks—as strictly Sudanese, seeing
that it is distributed over the whole of Africa, except
the Desert, the north-coast countries, and Egypt. It is
erroneous and misleading thus to infer that the Sudanese
element extends to Mogador because this bird has
only accidentally strayed into Morocco, as I was
assured by the late Mr. Gurney, then our highest
authority on the Raptores. As well say with equal
propriety that the Nearctic avifauna coalesces with
the Palearctic avifauna in the British Islands because
an example say of the Yellow-billed Cuckoo or the
American Bittern has been captured in them! Dr.
Wallace, in the latest edition of his /s/and Life (pp. 396,
397), gives a long table of “Land birds common to
Great Britain and Japan,” and he is careful to inform us
in a footnote that “accidental stragglers are not reckoned
as British birds.’ Yet, incredulous as it may appear, he
actually includes such species as the Nutcracker, the

42 THE MIGRATION OF BRITISH BIRDS

Rustic Bunting, and the Eagle and Scops’ Owls! Dr.
Wallace states that this list “is very interesting when
we consider that these countries are separated by the
whole extent of the European and Asiatic continents,
or by almost exactly one-fourth of the circumference of
the globe.” Out of the fifty-three species enumerated
eleven have no right whatever to be classed as British
at all, but are abnormal or nomadic migrants from the
far East, from the South, or North; whilst in the other
instances the area of distribution between Britain and
Japan is continuous, or intermediate sub-specific forms,
due chiefly to climatic variation, constitute an unbroken
link between species common to both countries! Such
statements are terribly misleading to the student, shake
his confidence in work in which he is not sufficiently
expert or has not the requisite special knowledge to test
its accuracy, and illustrate very forcibly how absolutely
necessary it is that naturalists should thoroughly under-
stand not only the rudiments but the higher philosophy
of the Geographical Distribution of Life, before they
attempt to theorize upon it or endeavour to demonstrate
it. Me sutor ultra crepidam just as aptly applies to
scientists in general, and to Royal Institution lecturers
in particular, as to shoe-makers or any other craftsmen.

It now becomes necessary to glance briefly at the
Canary Islands and the Cape Verds. The former group
is situated off the coast of West Africa between the 27th
and 29th parallels of latitude, and the nearest of the
islands are not much more than fifty miles from the
continent. They are separated from Africa by a channel
more than 830 fathoms in depth, are mountainous, and
are entirely volcanic. Dr. Wallace is of the opinion that

KANGE BASE OR REFUGE AREAS 43

they have never been connected with the adjoining
continent, and bases his belief chiefly on the absence
of all indigenous land mammalia and reptilia. I am,
however, inclined to believe that these islands have
experienced a continental period in remote ages, and
that they are but the isolated terminal portion of the
great Atlas range. The vast elevation of the ocean bed
required (some 5000 feet) to unite them now with conti-
nental Africa is not so much as Dr. Wallace himself
shows necessary to join the Philippines with continental
Asia (some 6000 feet), and but little more than what
must have occurred to connect certain land surfaces in
the eastern Mediterranean, of which we have direct
paleontological proof of union during Pleistecene time.
Further, it is a well-known fact that local marine de-
pressions of vast depths are by no means uncommon
features of regions subject to volcanic action. The
absence of terrestrial mammals and reptiles does not
appear such an insurmountable obstacle when we re-
member that the area during a past continental period
was a very isolated one, and that the adjoining parts
of Africa even during Pleistocene time were too arid,
desolate, and barren to support a very large mammalian
or reptilian fauna, and the probabilities are that it did
not contain any such animals at all in areas contingent
to the Canary group. I would suggest a submergence
(perhaps of a sudden, rather than of a gradual character)
some time during the Pleistocene Period, after such
desert-loving species as the Courser, Houbara Bustard,
and Sand Grouse (dominant desert forms) had gradually
spread westwards with the slow emigration of life over
the recently elevated Sahara. The avifauna of the

44 THE MIGRATION OF BRITISH BIRDS

islands is with one exception entirely of Palzearctic
derivation, and we have direct proof that they were
inhabited by Palzearctic species throughout Pleistocene
time, when the breeding range of birds was contracted
by extermination down to North-west Africa by the
devastating ice-sheets which descended upon northern
and temperate Europe. The only Ethiopian element
in the Canarian avifauna is the Black Oystercatcher
(Hematopus capensis). There can be no doubt that
this species is a very recent emigrant to the islands—
a bird gradually extending its range northwards along

the now continuous coast-line of Africa; for we have ~

strong evidence to suggest that when the breeding
range of birds of this genus was contracted south by
the Glacial Epoch it had no base down the African
coast-line beyond the Canaries, the ancient ocean de-
fining the range limits in that direction (see Map), but
had spread westwards across North Africa from an
Ethiopian or Asiatic base. The Black Oystercatchers
appear to have been differentiated in and dispersed
from a southern hemisphere base. To the present time
the Canary Islands are the winter resort of numbers
of European species; they contain many insular forms
or representative species of Temperate European or
North African forms, and a number of species range
from these islands eastwards across the whole of North
Africa—facts which seem to suggest a colonizing move-
ment during a remote period of continuous land surface,
rather than a fortuitous western emigration (of at least
50 miles across the sea), especially when we bear in
mind the reluctance of birds to cross a wide water area
in extending their range from centres of dispersal.

i

RANGE BASE OR REFUGE AREAS 45

The Cape Verd Islands are a much more debatable
area. They are probably oceanic islands of great
antiquity, separated from continental Africa and from
themselves by a sea some 7000 feet in depth. They are
also extremely isolated, lying between 300 and 400
miles from the coast of Senegambia. Unfortunately, we
possess few reliable particulars respecting the fauna of
these islands. There can be little doubt that they have
been entirely populated by fortuitous emigration from
the Palearctic and Ethiopian regions. There is certainly
a strongly-marked Palearctic element in the avifauna,
combined with several Ethiopian forms, some of the
species very clearly indicating the line of emigration
followed. The islands are situated off the African coast,
a little to the south of the Sahara, and probably in a
direct or nearly direct line with the ancient southern
shore of that sea which once covered the Desert. Some
of the birds appear to have emigrated along the southern
coasts of this ancient sea, or, in more recent times, along
the borders of the Desert from more southern areas in
Africa. It is true one or two species of birds are found
in the latter islands as well as in the Cape Verds, but
there is nothing to suggest a southern emigration ; whilst
on the other hand we have absolute proof of a north-
western emigration from the south. Thus the Blackcap
Warbler (Sylvia atricapilla) is only known to resort to
the Canaries in autumn, when large numbers visit the
islands and swell the resident population of this species.
Now, did the birds pass further south by this route they
would be seen in spring coming north again, but no
such migration has been remarked. This Warbler passes
the Nile valley and certainly goes as far south in East

46 THE MIGRATION OF BRITISH BIRDS

Africa as Abyssinia. There can be no reasonable doubt
that one of its fly-lines passes south of the Desert to
Senegambia in West Africa, where the bird is also found
in winter, and from which an extension of range com-
menced to the Cape Verds. Again, the Spectacled
Warbler (S. conspicillata) has probably reached the
islands by a similar route, seeing that it is a resident in
the Canaries, but winters far into the Desert. There are
also several typical desert species found upon the Cape
Verds, such as Certhzlauda desertorum and Ammomanes
cinctura, Palearctic or Oriental in affinities, and which
have reached the islands by fortuitous emigration from
those regions. As regards the Ethiopian elements we
have a Kingfisher (4/alceyon erythrorhyncha), very nearly
allied to the H. semzcewerulea of Arabia and North-east
Africa, further indicating an emigration along the
southern borders of the Sahara; whilst Acczpzter me-
lanoleucus and Pyrrhulauda nigriceps seem to suggest
an emigration to them from an equatorial base, seeing
that the former species is now found throughout Africa
south of the tropic of Cancer, and the latter is said
even to occur as far north as the Canaries. We shall
have occasion to allude to this migration route across
Africa from the north-east to the west in a future
chapter. I may here state that it is exceedingly im-
probable that Corvus corone and Milvus ictinus ever
normally visit the Cape Verds, although both have been
included in their avifauna.

The Cape Verds (and we may also say the Azores),
therefore, although decidedly Palzarctic in the facies of
their fauna (including the Coleoptera and certain genera
of land shells), can scarcely be regarded as part of any

not British Birds Plate I
———_—__—__

“Ancient Coastline.
Limite of Maxiveune Glaciation.
= Limits of Glaciation, 3rd Glacial Perisd.
| (9 Gtaciated ‘Areas

\
55

CHAPMAN & HALL, LIMITED.

RANGE BASE OR REFUGE AREAS 47

glacial refuge area or range base, but owe their present
forms of animal life purely to fortuitous emigration.
We do not yet possess sufficient knowledge of the
Cape Verd Islands to say whether any Palzarctic birds
regularly winter in them; if such be the case, I should
expect, judging from the evidence at present available,
that they were reached by a south-westerly migration
route from South-western Asia and North-eastern Africa,
rather than by a direct southerly route from Europe and
North-western Africa. The sea passage is much too
wide to expect any regular migration to this purely
oceanic area; although if the species remain constant
in that area the fact would seem to imply pretty
frequent visits, intercrossing preventing any tendency
to segregation due to isolation. It is probable that
island forms do exist in the Cape Verds, especially
when we know they are so prevalent in the Canaries,
a far less isolated area. I have dwelt at some length
upon the probable condition of North Africa during
the Pleistocene Period, because it is of great import-
ance to our inquiry, as we shall learn eventually when
we come to enter into details respecting the distribution
of British birds in that area.

As the preceding evidence suggests, the three great
RANGE BASES or Refuge Areas of British birds during
the Ice Age may be defined as follows:

RANGE BASE OR REFUGE AREA I.: This area in-
cluded all the now submerged land in the English
Channel to about W. long. 10°, and from thence south-
wards along the western coast of France to Biarritz.
The land of this area which still endures consists of
England, say south of the Thames and the Bristol Channel,

48 THE MIGRATION OF BRITISH BIRDS

Belgium, and Germany, about as far as E. long. 10,
together with that greater portion of France which re-
mained free from permanent glaciers and snow-fields.
Thanks to the researches of geologists and paleeonto-
logists we can form a pretty good general idea of the
state of this area during the Glacial Epoch. At the
climax of the Ice Age, and probably for ages after that
event, there can be little or no doubt whatever that
bird-life was utterly exterminated from all parts of
Western Europe, including the British Islands, say north
of lat. 52°. The present area may be described as the
head-quarters of those now high Arctic species that
in those remote days contrived to live and thrive
and perhaps become modified into “boreal” forms
amidst the rigours of the glacial ages, practically on
the margins of the snow-fields and ice-sheets. The flora
of this region was very similar to that which charac-
terizes Scandinavia and the high Alps at the present
time, perhaps the most characteristic Arctic plants of
Southern England then being equa!ly modified mosses,
lichens, saxifrages, and the dwarf birches, and willows
of various species, as were, for instance, ascertained
by the late Mr. Pengelly and Professor Heer, and again
by Mr. Nathorst, to occur in the clays of Devonshire.
The reindeer and the elk, the lemming, the glutton, the
Arctic fox and the pika—all now thoroughly Arctic
species—were dwellers in this area, as their remains
have so eloquently demonstrated, and with a range base
in that area which must have endured from Pre-Glacial
times, or a dispersal thereto from more eastern and
southern non-glaciated areas during the continuance of
glacial conditions elsewhere (conf. Map, p. 47).

RANGE BASE OR REFUGE AREAS 49

RANGE BASE OR REFUGE AREA II.: This area in-
cluded all the now submerged land in the Mediterranean
west of say E. long. 20°, and extended as far south as
the northern coast-line of that ancient sea which once
occupied the Sahara. It also included the peninsula of
which the Canary Islands and Madeira now form the
few lingering relics, and the additional Atlantic coast
area which would be obtained by making the contour
of 100 fathoms represent the possible coast-line of this
period. The land of this area which now endures con-
sists of the Spanish peninsula, Alboran Island, the
Balearic Islands, Corsica, Sardinia, Italy, Sicily, Malta,
a portion of Tripoli, the whole of Tunis, Algeria, and
Morocco, together with the Canary Islands. Thisarea is
by far the most important one, so far as British birds are
concerned. It formed the chief, nay probably the only
range base of nearly all the species that now breed in our
islands, as well as of most of the avian life that had been
exterminated by the glaciers and climatic changes in all
regions lying directly to the north of it. The climate of
this region in the southern portions was probably as genial
as now, even at the climax of the glacial era; whilst in
the northern portions, although at that period more rigor-
ous than now, it was sufficiently genial to admit of the
constant existence of temperate plants and animals
within its limits. The summers in the northern portions
of this area were probably always as favourable to bird-
life as now, nay even more so, if at times they were some-
what shorter ; whilst the winters of the southern portions
were always marked by those genial conditions which
are so imperative to the needs of such vast numbers of

species (conf. Map, p. 71).
E

50 THE MIGRATION OF BRITISH BIRDS

RANGE BASE OR REFUGE AREA III.: This area in-
cluded all the now submerged land in the Mediterranean
east of say E. long. 20°, and Europe south of about lat,
47°, and east of the Adriatic. At this period probably
the whole of what is now the A®gean Sea was dry land,
the coast-line extending along the western shores of
Greece and continuing unbroken or nearly so along
Crete to Cyprus, and thence down the coast of Syria,
which possibly extended seawards much further than
is now the case. South of the Caucasus, Georgia, Ar-
menia, Asia Minor, Syria, Northern and Western Arabia,
Persia, and Afghanistan, must be included as part of this
refuge area; as also must the entire continent of Africa
as it then existed, its northern coast-line reaching from
the Atlantic along the southern limits of the ancient
Saharan sea. The chief physical changes in this area have
been on the one hand the vast series of submergences
which have produced the Grecian Archipelago, and
isolated Crete and Cyprus ; and on the other hand, the
retreat of the ocean from the Sahara with the accom-
panying increase of the land surface of continental
Africa in the north. So far as concerns British species
this area is the least important of the three. We have
the most positive evidence to show that the range base
of purely West European birds did not extend to that
region during the Ice Age to any important extent. It
is, however, absolutely necessary for us to recognize such
an area, for it formed the range base of certain species
which, in ultimately extending their area to the British
Islands during Post-Glacial time, present some very
curious instances of dispersal, and forcibly illustrate the
eccentricities which sometimes characterize the migration

RANGE BASE Ok REFUGE AREAS 51

routes of birds. The northern portions of this area pro-
bably differed little, ifat all, in their climate from portions
of the preceding refuge area within the same parallels
of latitude; the climate of the southern portions we
may reasonably infer was not influenced to any great ex-
tent by the Glacial Epoch, although mountainous regions
have unquestionably suffered some local modification
in this respect. Proof of geologically recent change of
climate in East Africa was obtained by Mr. J. W.
Gregory in his expedition to Mount Kenya. Mounts
Kilima Njaro and Elgon, the mountains of Abyssinia
and the Cameroons, I believe I am correct in stating,
furnish additional proofs of local climatic change, due to
more intense glaciation in remote ages. There is also
much evidence to suggest that North-east Africa at no
geologically remote epoch was much more wooded
than is now the case—conditions that would favour the
western emigration of arboreal forms (conf. Map, p. 95).

Of course it must be clearly understood that the
climate of these refuge areas, most especially in the
first, underwent considerable variation during the course
of the Glacial Epoch, which, as we know, was made up
of a series of alternate mild and cold periods. Mild
climatal conditions were succeeded by eras when the
cold was more intense, and these in their turn gave way
to warmer ones; at one time the summers must have
been short and hot, the winters long and intensely cold ;
at another, longer and colder summers prevailed, and
the rigours of winter were less severe, or the seasons
were more blended; whilst yet again the pluvial con-
ditions of the warm season were much intensified during
certain epochs, Vast plain and valley floods were the

52 THE MIGRATION OF BRITISH BIRDS

summer characteristic of some of the glacial ages, and
enormous tracts of low-lying country were inundated, as
for instance in parts of Middle Europe and Southern
Russia, in the midst of which birds must then, as we
know they do now, have found a perfect paradise, teem-
ing with food. Similar floods, but on nothing like so
gigantic a scale, caused by the rapid melting of vast
quantities of snow and ice, continue to be one of the
most characteristic features of the continental Arctic
regions, especially in the river valleys, where the break-
up of the streams in the scarcely-perceptible northern
spring is the grandest natural phenomenon of each
recurring year. The melting of the snow from the
Alps, causing vast areas to be annually flooded, is
another present day instance. The higher latitudes of
course, then as now, were subject to the greatest cold.
The range of birds throughout the varying phases of the
Ice Age must therefore have expanded and contracted
north and south as the climate alternately favoured or
enforced one movement or the other—oscillated as it
were between northern and southern areas with each
mild or cold Glacial Period. It will. probably ever
remain a hopeless task to attempt to portray those
avian movements, or to indicate the probable species
that made them. Our only chance of success seems to
rest with the close of the glacial era; with the last cold
periods of the Ice Age which contracted (by extermin-
ation or restriction of northern breeding areas) avian
distribution southwards, and with its ultimate expansion
across those desolated northern areas, as the cold passed
away, and was succeeded by milder climatal conditions.
Broadly speaking, the last range contraction south and

RANGE BASE OR REFUGE AREAS 53

its expansion north are a facsimile of those phenomena
that preceded them.

I may say in conclusion that so far as I have been able
to ascertain, many of the views expressed in the present
chapter are entirely new. I maintain that the immediate
Pre-Glacial dominant fauna (including Aves) and flora of
temperate Euro-Asia were never very closely associated
with Africa, or with Australia; probably nothing nearly
so much as were the immediate Pre-Glacial fauna and
flora of North America with those of South America.
Professor Geikie writes: “The European flora of to-day
differs so much more from that of Pliocene and Miocene
times, than the flora of North America does from the
plant life of those periods. In the latter continent there
existed a continuous passage to the south across which

plants and animals alike could make good their retreat.”

Now to my mind this very conclusively proves that the
line of Antarctic connection is most dominant along the
American continents, and that the floras were more
continuous than in the Old World. Unfortunately,
Professor Geikie (to whom this Law forbidding southern
dispersal or emigration was unknown) makes this con-
tinuous land mass a proof of Southern Emigration rather
than a contraction of range. The Law that forbids
southern dispersal in the Northern Hemisphere prevented
a southern emigration of all the purely Euro-Asian
species, and consequently the Glacial Epoch nearly exter-
minated that fauna and flora. Hence the abundance
of its paleontological remains bears eloquent testimony
to the helplessness of such animals to escape from their
glacial doom. A few relics only survive whose range
then extended right across that region from north to

54 LHE MIGRATION OF BRITIS® BIRDS,

south. No purely Polar type could have survived this
or any other glacial epoch—not even that one famous
Prz-Pliocene ancestor of the Charadriide. Species,
however, that were of South Palearctic, Ethiopian,
Oriental, Australian, Antarctic, South Nearctic, or
Neotropical origin survived the vast exterminating in-
fluences of the Ice Age, their northern range simply
contracting by extermination more or less upon the
southern base of those species, or what are now their
ancestral forms. Hence the reason why the early
Europern flora was a portion of that which now
exists only in the tropical and sub-tropical lands of
the Eastern Hemisphere. There could have been,
therefore, no southern exodus of all living things, as
scientists so unanimously assert there was; no trace
whatever of that southern emigration during Pleistocene
time exists, and the only species that succeeded in
maintaining themselves throughout that era were those
whose range was either cosmopolitan throughout the
lands whose northern portions were affected, or species
whose emigrations had extended from a far southern
base, and were then continuous with that base, either
by extension of uninterrupted breeding area, by sub-
species or representative races, or by migration from
and to a southern base, the winter range coalescing
with that of summer. One apparent difficulty is pre-
sented in the fact of high Arctic animals occurring

only in the south during glacial eras, which looks like —
a purely southern emigration. We have no absolute
proof that the southern bases were ever entirely deserted
by these what we now class as boreal forms, and I
would suggest that these species had endured in the

RANGE BASE OR REFUGE AREAS 55

south during milder intervals of climate, by portions
of them ascending to great altitudes on mountains as
migrants, which again descended to the lowlands as
residents as the climate again became glacial. Southern
mountains were in fact the grand preservers of the
species in the south during warm intervals of climate,
just as we find to be the case to-day. It is by this
means probably many types or species have succeeded
in maintaining their existence during the Glacial Epoch ;
many instances might be given of boreal birds breeding
at high elevations on southern mountain ranges, and
wintering on the lowlands, or migrating much further
south to an original base. The migratory tendencies
of all Arctic animals is significant. These animals
are Arctic in the sense of having become Arctic since
the Glacial Epoch passed away. There is no evidence
whatever to suggest that they were confined exclu-
sively to the Polar latitudes during Pre-Glacial time.
Arctic animals are species that have spread north
from southern bases during Post-Glacial time, not
species that have been driven from a previous Polar
haunt by glacial climates. They are species that have
slowly adapted themselves to Arctic conditions, as
their range has been extended north by Post-Glacial
emigration into Polar latitudes. Note the various
Arctic forms or representative races of more southern
species. Arctic climates would produce Arctic forms.
This by no means implies that Arctic species emigrated
south, but that a glacial epoch exterminated them,
and that the effect of a much lower latitudinal Arctic
climate prevailing during glacial epochs had its usual
effect on species, or such portion of species that came

56 THE MIGRATION OF BRITISH BIRDS

within its influence, and were able by modification to
withstand its rigours. Speaking generally, Arctic cli-
mates do not affect structure so much as dermal covering
and colour; so that fossilized remains of these reputed
boreal types are by no means a complete record of
their characteristics! It may therefore be safely pro-
phesied that all peculiar boreal forms now living exclu-
sively in the Arctic regions would perish in a glacial
epoch, if that glacial climate included the southern limits
of their present range. The reindeer would perish as
surely then as the Irish elk has utterly vanished in the
past. This Law of Dispersal also explains why none of
the Euro-Asian deer and bears have penetrated into
the Ethiopian region, why not a single emigrant
extended its range southwards across the land connec-
tion of Abyssinia and Arabia as Africa became united
to Euro-Asia ; although some of “the most prevalent
types of modern African zoology” migrated northwards

1 Many “arctic” animals may have become so specialized by
dwelling in areas subjected to the severe climates, directly south of
the ice-fields, during the continuance of glacial conditions, and
followed the ameliorating climate northwards, that being the best
suited to their conditions of existence, owing to their protracted
residence within its influence. The nearly uniform climatic influ-
ences which have prevailed over temperate and arctic lands for
sixty thousand years are quite sufficient to explain the modification
of the fauna and flora subject to those influences, without invoking
a purely legendary exodus from the north of boreal forms and their
ultimate return. As Dr. Wallace himself writes (/sland Life, new
edition, page 231) : “ We are sure that some species would become
modified in adaptation to the change of climate more readily than
others, and these modified species would therefore increase at the
expense of others not so readily modified ; and hence would arise
on the one hand extinction of species, and on the other the
production of new forms.”

7

RANGE BASE OR REFUGE AREAS 57

across that newly-formed land and entered Euro-Asia,
where, as we know, their remains abound in the Mio-
cene deposits of Greece and elsewhere. This Law of
Dispersal also renders it impossible for any “old South
Palearctic fauna” to have “poured into Africa,” and
to have “ finally overran the whole continent ” (Wallace,
Geographical Distribution of Animals, vol. i., p. 288)—a
temperate fauna entering a tropical area! We need no
“persistence through long epochs of barriers isolating
the greater part of Africa from the rest of the world,”
as Dr. Wallace insists, to account for the absence of
such groups as bears, moles, camels, deer, goats, sheep,
or such genera as Sos and Sus, a law forbidding the
southern emigration of such types is sufficient to ex-
plain the facts, without invoking more or less hypotheti-
cal geographical obstructions.

Many of these facts undoubtedly point to a much
greater land surface in the Southern Hemisphere as well
as to the former existence of a vast Antarctic land—
a South Polar continent or continents with extensive
land connections stretching far to the north. So long
as this Antarctic continent is ignored we shall never
arrive at a sound conclusion on the grand question of
geographical dispersal. The South Pole must have been
the centre of a great and dominant avifauna, of which
the Charadriide, the Anatidez, and the Procellariide (all
groups in which migratory habits are dominant) were
strongly-marked features. The great changes which
that vast region has undergone and which have utterly
exterminated (so far as we know) the avifauna dwell-
ing within it, has been the cause of a great northern
dispersal or range contraction southwards, especially of

58 THE MIGRATION OF BRITISH BIRDS

such families as those just mentioned. It is chiefly
amongst such species that the avifaunas of Euro-Asia
and North America show any similarity. The more
temperate and southern forms are utterly dissimilar, and
could never have occupied a common North Polar area.
I would also allude to that wonderful flora of the Cape
area in South Africa, as an example of a range base
which has preserved so many species from that vast
extermination consequent on the glaciation and sub-
mergence which is now characteristic of the Southern
Hemisphere. We have only to have a continuous land
connection and the withdrawal of glacial conditions as
we absolutely did have in the Northern Hemisphere to
start that flora on its southern progress, not as an
example of species driven north by adverse conditions
in South Polar areas returning to old habitats, but as an
instance of surviving relics saved from extermination
entirely because their base was beyond the limits of the
glacial invasion and its attendant submergence ; extend-
ing their area under a return of favourable conditions for
range expansion. Here we have no trace of emigration or
range expansion zorthwards ; although an emigration of
North Temperate forms southwards has been repeatedly
invoked by some of our greatest biologists. The whole
subject does not come within the scope of the present
work, but it is impossible to ignore these facts in dealing
with the emigrations and migrations of British birds.
The next chapter will attempt to give an outline of
this Glacial Range contraction and Post-Glacial emigra-
tion as they are unquestionably indicated by the present
distribution of British species and their allied forms.

(CoS ANG rag Cae a

THE GLACIAL RANGE CONTRACTION AND POST-GLACIAL
EMIGRATION OF BRITISH BIRDS.

A New Law of Dispersal—The Third Cold Period of the Glacial
Epoch—Probable Avifauna of Refuge Area I. during this
Period—Effects of Cold Period on the Charadriidae—Inter-
polar Migration and Emigration—Avian Characteristics of
Refuge Area I.—Avifauna of Refuge Area II.—Resident
British Species—Southern Representative Forms—Species
Resident in British Isles and in Refuge Area II.—British
Species that Resort to Refuge Area II. in Winter—Winter
Visitors to the British Isles that also Winter in Refuge Area
II.—Summer Visitors to the British Isles—Winter Quarters
of these in Refuge Area I].—Ancient Sahara Sea a Bar to
Emigration from the South—Lirds ranging further South in
East Africa than in West Africa—Winter Quarters of British
Summer Migrants in Refuge Area III.—Circuitous Routes of
Migrants to West Africa—British Summer Migrants from the
South-East—British or West European Species that have
Emigrated from South-Eastern Areas—Their Absence from
Iberia—Their Allied Forms and Representative Species—
Influence of Competing Species—Reasons for their Absence
from British Area—Abnormal Migrants to British Area—
West European Species normally Absent from British Area—
Reasons for such Absence—Past Emigrations of Storks and
Red-crested Pochard—Emigrations of Blue-headed Wagtail
and Allies—Situation of British Area now unfavourable to
Emigration—Instances showing Impassable Nature of a Sea
Barrier—Avian Emigration to Greenland—Nearctic Emigra-
tion—Post-Glacial Emigration of Birds in West Europe—
Emigration to Iceland and Greenland across the British Area
—Table of Emigrants.

BEFORE entering into the details of the subject of this
chapter, it may be advisable to promulgate the following

60 THE MIGRATION OF BRITISH BIRDS

Law, which the reader must repeatedly bear in mind in
dealing with the facts presented.

LAW OF DISPERSAL.—Northern Hemisphere species
never increase their Breeding Area Southwards—always
North, East, or West from a Range Base or Centre of
Dispersal, which contained the sole surviving portion of
the species during glacial ages. Inter-polar and Inter-
hemisphere species north of the Equator never extend
their breeding range Southwards if suitable areas are
open to the North; Inter-polar and Inter-hemisphere
species south of the Equator never extend their breed-
ing range Northwards if suitable areas are open to the
South. The tendency of Birds, if not of all living
organisms, is to spread in the direction of the Poles.
During present time a bird in the Northern Hemisphere
never increases its range in a Southern direction ; it
may do so North, North-east or North-west, East or
West; but that it never does so South is proved by
the fact that no Migration Route is known which trends
South in spring, or which trends JVorth in autumn.
During present time a species in the Southern Hemi-
sphere never increases its range in a Northern direction ;
it may do so South, South-east or South-west, East
or West, but that it never does so North is proved
by the fact that no Migration Route is known which
trends Worth in spring, or which trends South in
autumn. The route of Present Migration is always
an unerring guide to, and unfailing indication of, the
general line of Past Emigration.

From this Law we draw the following Corollaries :

COROLLARY I.—Migratory birds winter at the present
time in the Glacial Refuge Areas or Range Bases

LAE NGEACIAL RANGE “CONTRACTION, ETC. 61%

occupied by the species or its ancestral forms, or the
remnants of such that escaped extermination during the
Glacial Epoch, however near or remote such Range
Bases or Refuge Areas may be from their present
breeding grounds.

COROLLARY II.—The northern limit of a Northern
Hemisphere species in any area marks the limit of Emi-
gration from a more southern area, not necessarily south
of it. A bird’s Breeding Grounds are always at the limits
either of its Past Emigrations or Present Migrations.

COROLLARY III.—The Present Migration of a species
is a recapitulation of the Past Emigrations or Range
Expansion of that species.

COROLLARY IV.—Species never “retreat” from ad-
verse conditions. If overtaken by such they perish, or
such portion of the species that may be exposed to them.

COROLLARY V.—Extension of Range is only under-
taken to increase Breeding Area, and therefore during
most favourable climatic conditions.

COROLLARY VI.—Contraction of Range is only pro-
duced by Extermination amongst sedentary species, and
probably also by Extermination (through inability to
rear offspring) amongst migratory species that are
neither Inter-polar nor Inter-hemisphere.

In my opinion this Law will explain not only why no
typical Nearctic species encroach upon the Palearctic
Region across Behring Strait,! but also assist in solving

1 T am fully aware that there is a slight intermixture of Paleearctic
and Nearctic species in Alaska and North-eastern Siberia, especi-
ally amongst migratory birds. I have already alluded to this fact
in the Migration of Birds (p. 234); whilst Mr. Seebohm has

recently pointed out other instances (conf. /dzs, 1894, p. 293).
There is, however, not the slightest evidence to suggest that any

62 THE MIGRATION OF BRITISH BIRDS

many puzzling problems of Geographical Distribution
elsewhere, especially in the Oriental and Australian
Regions. Its bearing on Mammalia, etc., during the
Glacial Epoch has already been shown; whilst its
relation to the subject of the permanence of continents
is equally apparent. Migration primarily is the result
of a vast extermination of Birds from their ancient home
in the north (or south), caused by the adverse climatic
conditions resulting from a glacial epoch, and the
constant endeavour of what we must now regard as but
the relics of such exiled life to regain and re-people the
area that it once occupied during Pre-Glacial time.
Whether the climate of Europe was ever so mild and
genial during each or any successive warm inter-glacial
period, as it unquestionably was in Pliocene ages before
the advent of the Glacial Epoch, appears not to be
known with absolute certainty. There can, however,
be no doubt whatever that towards the close of the
Pleistocene Period an intensely cold climate succeeded
a warm and genial one. The coming on of this third
Cold Period marked the beginning of that last great

one of these species has extended its area either into Alaska or
into Siberia in a southerly direction or to a lower latitude than its.
point of entrance into each region respectively. The facts are in
strict accordance with our Law of Dispersal, and suggest a former
greater land extension between this portion of the two continents,
which we know once existed, and of which the Aleutian Islands
are the principal surviving relics. This intermixture of Asiatic
and American forms must have taken place before the two con-
tinents were separated by the sea. I may also say that we remark
no southern extension of these encroaching Palearctic species
into America during winter, or a similar extension of Nearctic
species into Asia at the same season. Each migratory species
returns to its base of extension in autumn in absolute compliance:
with the law of its dispersal.

THE GLACIAL RANGE CONTRACTION, ETC. 63

extermination of birds in the Arctic and North Tem-
perate regions; the passing away of that ungenial
climate marked the commencement of their return—
the beginning of that vast movement northwards of
birds which even at the present day has not ceased,
as will be seen in a future chapter1 These vast
changes of climate, there is every reason to believe,
took place almost imperceptibly during the course
of ages. As the cold climate came on which was
eventually to culminate in the third glacial period, the
range of the temperate fauna and flora was gradually
contracted south by extermination, and that of the
“Arctic” fauna and flora slowly followed. Each re-
curring winter waxed colder and colder, possibly so
slowly that no single generation of species detected
the change or were perceptibly influenced by it, yet
eradually the temperate range of birds became less and

1 Before the Glacial Epoch finally passed away several severe
fluctuations of climate occurred, culminating in one more Glacial
Period (the fourth), designated by Professor Geikie as the epoch
of the Great Baltic Glacier. During this period Iceland, most of
North Scotland, and the highest mountains of England, Wales,
and Ireland, together with nearly the whole of Scandinavia and
Finland, the Alps, and parts of the Caucasus and the Pyrenees,
were glaciated. All living things within glacial influence must
have perished during this era, but the extermination was on
nothing near so vast a scale as that which characterized the
glacical periods preceding it. That this fourth glacial period was
a severe check to the emigration of species in certain directions
is unquestionable, and its influence in such range extension con-
tinues to be demonstrated by the distribution of birds in Western
Europe, as we shall eventually learn. The student must bear in
mind that the later and less intense periods of the Glacial Epoch
successively affected smaller and smaller areas of country—a fact
of little or no consequence so far as concerns our general argument,
but of importance in studying the present geographical distribution
of species.

64 LHE MIGRATION OF BRITISH BIRDS

less northerly; the Arctic area of distribution more
and more contracted, until the glaciers and the snow-
fields had killed or reduced the range of all living
things as low in West Europe as say the 53rd parallel
of latitude. England, say from Yorkshire southwards,
Northern France, Belgium, Holland, and parts of North-
western Germany, eventually became to all intents and
purposes the Arctic regions of Western Europe, with
a scanty resident avifauna, and a flora in which Arctic
willows and mosses, dwarf birches, lichens, and saxifrages
were perhaps the most characteristic features.

So far as birds are concerned, and to them, of course,
our inquiry is exclusively limited, I am compelled to
reject the hypothesis that any temperate species sur-
vived the Ice Age as residents in the south of England.
I do so because I cannot trace a single species fairly
classed as temperate whose winter range to-day in
Western Europe reaches no further south than the
British Area, or say the northern portion of Range Base
or Refuge Area I. It will be interesting to sketch, if
possible, the resident avifauna of this district during
those far-off ages, when the greater part of England
was reduced to an Arctic waste. Then, as now, the few
resident birds of the Arctic regions were all Nomadic
Migrants—those restless wanderers of the avian world,
with no regular seasons of passage, that linger in their
accustomed haunts so long as they can obtain food,
and that travel no further than to districts where their
wants can be supplied. What we now class as Nomadic
Migrants were species whose southern range base just
escaped the glacial invasion; they are species that
survived on the very margin of the ice-sheets and

THE GEACIAL RANGE CONTRACTION, ETC. 65

snow-fields, and were the first to move north with an
amelioration of climate. In the accompanying table I
have arranged those species which probably composed
the avifauna of this area during the third, and most
probably the second cold periods of the Glacial Epoch,
giving their normal southern winter limit in Western
Europe at the present time, together with the food
on which they habitually subsist, and which is of
precisely that character which would be obtainable
under the glacial conditions of the climate of that
remote period.

| PRESENT S. WINTER LIMIT

SPECIES. IN W. EUROPE. FOOD.
Linota flavirostris ... Normally France. Seeds and insects.

45 Jie Geeye pore France. Fite es S5
Plectrophenax nivalis a Se A BS
Hierofalco caudicans i Lemmings, etc., birds.

35 islandus British Islands. 55 ae an
I) gyrfalco 2”? 29 29 29 ”
Nyctea nyctea at Northern France. >. 33 AD
Lagopus albus Bon British Islands. Buds, leaves, seeds, in-
sects, and berries.
Anser brachyrhynchus | English Channel. Grass, shoots of herbage.
Bernicla leucopsis He ar Marine grass; crusta-
ceans.
3 brenta ... Normally English | Grass wrack and laver.
Channel.
Harelda glacialis ... English Channel. Mollusks, crustaceans,
and water plants.
Somateria mollissima ae 5 Mollusks, crustaceans,
eke:
an spectabilis 5p 3 Mollusks, crustaceans,
etc.
Ra stelleri ... $5 53 Mollusks, crustaceans,
| etc:
Pagophila eburnea... | English Channel. Marine animals; seal-
| droppings, etc.
Mergulus alle... 2 2 | Small crustaceans, etc.
Alca impennis si British Islands. Marine animals, fish.
Whaaenylles fe ee. English Channel. Crustaceans, fry, small
fish.
Colymbus glacialis Abnormal below Eng- | Fish.
lish Channel.
Fulmarus glacialis ... Bay of Biscay. Mollusks, cuttle-fish, etc.

Ie

66 THE MIGRATION OF BRITISH BIRDS

There seems little doubt that the species mentioned
in this table were able to live during these last cold
periods of the Glacial Epoch on our southern coasts—
then extending much further south towards the Bay of
Biscay—or in suitable inland districts as far north as
our first Refuge Area extended. Many of these species,
it will be seen, were aquatic birds, able apparently to
subsist anywhere near to open water; whilst the others
were hardy species living on Arctic berries, seeds, shoots,
and buds, and on their smaller and more helpless com-
panions, as well as on the various animals that we know
also survived the glacial invasion of the land. Trees
were entirely absent from the British or most northern
portion of this Refuge Area, or were too small and
stunted for the requirements of Woodpeckers (PICID.®)
and other arboreal species. Hence the non-migratory
habits of these birds. It may be remarked that every
one of the birds included in this table could have lived
in winter in such an area; if they could not they
would assuredly have vanished for ever, as we have
uncontrovertible evidence to show that the food on
which they are known now to subsist was then actually
obtainable.

As further confirmation that these birds formed the
avifauna of this area during the Ice Age, we may men-
tion that not a single species is represented in the south
by an allied race. Broadly speaking, then, not one of
these species dwelt south of our first Refuge Area, for
not one down to the present day normally wanders
south of that area, and not one is represented south of
it by a closely allied form which would indicate a
southern Range Base and contraction of range by ex-

THE GLACIAL RANGE CONTRACTION, ETC. 67

termination during the Glacial Epoch. Very different,
however, was the case of the Arctic birds that lived
on animal substances alone—the Plovers, Sandpipers,
and their allies. The range of these species at the
coming on of the Ice Age became more and more
southerly, and their migrations inter-polar, probably
because they could not find suitable winter quarters
or breeding grounds except in the Polar regions.
As I have already shown in the Jlzgration of Birds,
we have abundant proof of this Inter-polar Migra-
tion and Emigration, not only in the vast journeys
many of these birds still undertake, but in the many
allied forms left behind in the Southern Hemisphere
when the northern Glacial Epoch passed away and
the North Polar breeding grounds became available once
more. It is a most significant fact that every Chara-
driinze species goes further south to winter than our
first Refuge Area; that is to say, that although some
members of certain species may winter therein, other
members extend their flight to the south of it. Not a
single species of the Charadriidaz can be classed as a
Nomadic Migrant. Not a single migratory species (non-
Nomadic) throughout the Northern Hemisphere winters
exclusively within what are defined by uncontrovertible
evidence to be the limits of glaciation—eloquent testimony,
I take it, of the southern range bases during Pleistocene
time of all the surviving species that have now re-peopled
the once glaciated land areas. To my mind these facts
are convincing proofs that the high Polar latitudes were
deserted by bird-life ages before it was exterminated
from more temperate and southern latitudes ; in other

68 THE MIGRATION OF BRITISH BIRDS

words, that the various climatic fluctuations of the Ice
Age waxed and waned very slowly. It should be re-
marked that the range of some of the species tabulated
may be lower in the New World than in Europe, due
to more rigorous climatal conditions and to the much
greater southern extension of the glaciers in North
America.

It requires but little strain upon the imagination to
recall the avian characteristics of this Refuge Area I.
at the climax of the third cold period of the Ice Age.
England south of Yorkshire, the Bristol Channel, and
much of the land now lying submerged beneath the
English Channel and the North Sea, were probably
in the condition of an Arctic tundra, bounded by the
sea on the south in which huge icebergs floated, and
on the north by the vast glacier whose southernmost
slopes retreated or advanced a little way as summer or
winter came on. The resident land birds were few in
number. The Twite and the Mealy Redpole wandered
about the winter wastes subsisting on the seeds that
were obtainable amongst the snow ; the charming little
Snow Buntings gathered into flocks and led the nomad
life they still continue to lead, going no further south
than their very limited range base extended, hurrying
north again with the first dawn of spring. The Willow
Grouse, clad in its winter plumage of unsullied white,
managed to find enough food in the buds and seeds
and twigs, and in the frozen Arctic ground fruits which
it managed to obtain by burrowing into the snow. The
large Arctic Falcons and the Snowy Owl kept closely
to the tundras and the shores, preying upon the Finches

THE “GEACIAL RANGE CONTRACTION, ETC. 69

and the Grouse and the various species of water birds
that no glacial invasion appears to have succeeded in
utterly exterminating from this area. The Pink-footed
Goose, the Bernacle Goose, and the Brent Goose lingered
at their range base throughout the winter in this Refuge
Area ; the Harlequin Duck and the Long-tailed Duck,
together with the three species of Eider, if their present
distribution be any indication, apparently did the same.
The Ivory Gull survived amongst the icebergs and the
floes ; as also did the Great Auk, the Little Auk, and
the Black Guillemot ; whilst the White-billed Diver and
the Fulmar seemed to have ranged no further south
than the open water, which probably then existed all
the winter through along the southern coasts of this
Refuge Area, owing to the ameliorating influence of the
Gulf Stream.

Of the summer aspects of this region it is difficult to
speak with any degree of certainty. There can, how-
ever, be little doubt that as the climate moderated
numbers of species would come north into this area to
breed, although they had imperatively to retire south to
winter in Refuge Area II. The Charadriinz birds that
had been banished to the South Polar area would also
gradually return as breeding species, but they were
possibly among the latest to do so, waiting until at
least some portion of the higher latitudes of Europe
was free from ice, or the glaciers at the South Pole began
to contract their area. The phenomenon of Migration
in Western Europe as we see it to-day was undoubtedly
initiated with the passing away of the third glacial
period. Species after species became more and more

70 THE MIGRATION OF BRITISH BIRDS

southerly as the winters almost imperceptibly waxed
longer and colder, and exterminated all the northern
portion of the sedentary species; slowly the northern
breeding range of species after specics became more
and more contracted as the food supply decreased, or
the summer temperature lowered. And so matters
went on until only our three Refuge Areas contained
representatives of the species that had been extermin-
ated, or whose northern range had been contracted.
For the most part these three areas were probably
inhabited by a sedentary avifauna; but even at the
climax of this cold period I think there can be little
doubt that a certain percentage of the temperate species
in Refuge Area 1].—the hardiest—undertook a migra- |
tion from south to north with each recurring summer.
With a great number of these hardy species Migration
finally ended in Emigration, as the climate ultimately
became sufficiently genial for them to winter in safety.
There may also have been a considerable local migra-
tion within each respective area, north in spring, south
in autumn, gradually extended as the glacial conditions
passed away ; for to my mind it is difficult to believe
that birds did not respond in a migratory way from the
south to the changes of the seasons with their accom-
panying advantages or perils.

Post-Glacial Migration therefore must have originated
south of our area, and gradually extended north as the
range of species expanded in obedience to more genial
conditions, and in many cases have lapsed as the climate
moderated.

Now with regard to the birds that reached Refuge

RANGE BASE OR REFUGE AREA IL.
f 20 6

CHAPMAN & HALL, LIMITED.

BHEVCLACIAL RANGE (CONEKACTION, ELC. * 74

Area II. There can be no doubt whatever that during
the glaciation of the British Area, the range of a very
large number of the then indigenous species was con-
tracted down to the Iberian Peninsula, and what is now
North-west Africa and the Canaries, and that from this
area the survivors gradually emigrated northwards as
the ice retreated. We find absolute proof of this fact
in the traces of that ancient range contraction and
subsequent emigration which are still preserved to us
in the by no means small number of representative
species and races of British birds left behind, especi-
ally in the southern portions of this second Refuge
Area, when the movement north commenced. At the
present time our resident species may be computed
at about 115.1 It is a profoundly interesting and
significant fact that of these no less than twenty-one
species, or more than one-sixth of the whole, are repre-
sented in Iberia, North-west Africa, and the Canaries
by closely allied species (in some cases two or three
distinct representatives) or sub-specific forms whose
complete segregation may be retarded or prevented
by their interbreeding with the individuals of the typical
species which reach that area as winter migrants, not
necessarily from the British Islands, but from conti-
nental Europe. These species, with their representative
forms or species, are shown in the accompanying
table.

' Probably this is much in excess of the actual number, as many
species are largely increased in number by migratory arrivals from
northern or eastern areas, and our own breeding individuals may
draw south, seeing that many species supposed to be resident with
us are well-known winter migrants further south.

=

7

THE MIGRATION OF BRITISH BIRDS

BRITISH

Falco peregrinus
Buteo vulgaris

Asio brachyotus
Corvus corax
Pica caudata

RESIDENTS.

Garrulus glanda-

rius
Fringilla chloris

Fringilla ccelebs
Lanius excubitor!

Parus ater

Parus czeruleus
Acredula rosea

Regulus cristatus
Cinclus aquaticus

Erithacus rube-
cula =
Pratincola rubi-
cola

Anthus pratensis
Gecinus viridis

Picus major
Picus minor
Larus argentatus

'Fringilla chloris | Fringilla chloro-

i

|
|

i}
|

REPRESENTATIVE SPECIES OR RACES.

IBERIA.

Asio capensis

Pica caudata mau-
ritanica

aurantiiventris

Lanius meridion-
alis

Acredula irbii

Cinclus aquaticus
albicollis

Gecinus viridis
vaillantii

Gecinus sharpii

Larus argentatus
cachinnans

et |

N. W. AFRICA.

Falco barbarus |

|
Buteo desertorum |
|
| . .
Asio capensis
| Corvus tingitanus
Pica mauritanica

. onl
| Garrulus cervicalis)

ticus
Fringilla spodio-
gena
Lanius algeriensis|
|
| .
| Parus ledouci

|
Parus ultramari- |
nus |

/Cinclus minor

!
| |
|

|
|

Gecinus vaillantii |
|

| Picus numidicus

Picus ledouci
Larus argentatus |
cachinnans

CANARY ISLANDS.

Buteo desertorum

(?)

Corvus tingitanus

Fringilla tintillon

Lanius algeriensis

P. palmensis
P. ombriosus
Regulus tenerifize

\ and Grand
| Canary)
Pratincola daco-
tiae

Anthus bertheloti

Parus ultrama-
rinus
P. teneriffze

Erithacus super-
bus (Teneriffe

Some differences

Larus argentatus
cachinnans

one which does not pass to the south of the Pyrenees to winter. ;
2 Mr. Scott Elliot has recently recorded this species from an elevation of 10,000 feet,
near the Albert Edward Nyanza, Equatorial Africa (conf. Natzze, 1895, p. 271).

1 This species cannot fairly be classed as a resident now in the British Islands, but is

This list, however, does not quite exhaust the number

of representative species or forms that have been thus
isolated, and more or less perfectly segregated from

tite NalA CIAL RANGE ‘CONTRACTION, ETC. °73

British resident species. For in the Italian peninsula
and on some of the various islands of the West Medi-
terranean—which during the Glacial Epoch were not
islands at all, as a glance at the map of this Refuge
Area will show—there are other local species or races.
None of these islands are yet thoroughly explored, and
probably other forms still remain to be discovered. As
may naturally be expected, the representative species or
forms in this area are neither numerous nor striking,
due partly to the enormous amount of migration taking
place over that area, which tends to check segregation
by the intermixing of individuals, and to its far less
‘complete isolation from continental Europe. The most
characteristic instance known to me is the island form
of the Nuthatch (Sz¢ta cesza), confined so far as has yet
been ascertained to Corsica, and known as S7z¢ta white-
headi. A second instance is Passer ztali@, the Corsican
and Italian representative of the Common Sparrow
(Passer domesticus).

In a considerable number of the instances tabulated
above there can be little if any doubt that the southern
races or species are the oldest, the parent races, the
northern forms being of more recent segregation, because
the young in first plumage of the latter resemble the
adults of the former—recapitulate in this portion of the
course of their development the stages through which
the species has passed in its evolution. I have been
unable to get the requisite particulars in some cases, but
in the following instances confirmation of the fact is
forthcoming.

74 THE MIGRATION

OF BRITISH BIRDS

PARENT SPECIES.
ADULT.

NORTHERN DEVELOPMENT.
YOUNG,

Buteo desertorun.
Smaller : tail bars nearly obsolete.

Corvus tingitanus.
Smaller : breast hackles wanting.

Pica maurttanica.

Smaller: no light rump patch.

Fringilla spodiogena.
Underparts much paler.

aris ledouct.

Nape and cheeks yellow.

Acredula irbit.
No rosy tinge on scapulars, which
are grey.
Anthus berthelote,

Smaller: underparts narrowly stri-
ated: no green tints in plumage.

Gectnus viridis vaillantii et shar pic.
No black on forehead and round eye.

Picus numidicus.

Scarlet on breast.

Picus ledouct.

Underparts ‘strongly suffused with
brown.

Equally suggestive is the

Buteo vulgaris.
Smaller: tail bars less in number.

Corvus corax.

Smaller : breast hackles wanting.

Pica caudata.

| Smaller: rump patch much less in

extent.
Fringilla calebs.

Underparts much paler.

Parus ater.

Nape and cheeks yellow.

Acredula caudata et rosea.

No rosy tinge on scapulars.

Anthus pratensis.

Smaller : very buff in general color-
ation: striations on underparts
smaller.

Gecinus viridis.

Black absent from ear coyverts, lores,

and round eye.
Picus major.

Occasional reversions to red on

breast.

Picus minor.

Underparts not so pure in colour.

fact that of the remaining

species no fewer than 64, or nearly two-thirds of the

entire number of resident B

ritish species, are still resi-

dent in the Iberian Peninsula, in the Balearic Islands,

in Corsica and in Sardinia,
Canaries, and do not presen
northern individuals of the

North-West Africa, or the
t any differences from the

same species. Their dis-

THE GEACIAL RANGE CONTRACTION, ETC. 75

tribution is continuous throughout the area, and has
probably always been so during the entire period over
which our present investigation extends, their range
contracting southwards by extermination and expand-
ing northwards by colonization contemporaneous with,
and in obedience to, the changes of climate. The fol-
lowing table will serve readily to demonstrate these
interesting facts.

RESIDENTS IN BRITISH ISLANDS. IBERIA, j N. W. AFRICA. | CANARY ISL.
Aquila chrysaétus eet sl x
Milvus regalis ae x x
FAGGIPICGMISUS! ne) ees ses | x *
Asio otus SRS Tart (as x x
‘Shasovibhonl Glee) sae eaea abe x |

Corvus corone
! Corvus cornix

Corvus monedula eae x x

Pyrrhocorax graculus... ... | x x x
Loxia curvirostra ees ae x x

Pyrrhula vulgaris Sean eed | x

Linota cannabina Pas: es x x x
aurnenilarcarduelis! 2. |... x x x
Coccothraustes vulgaris... x

Passer domesticus Ba) ce lil ss

Passer montanus... ... ... | x x

Emberiza miliaria ... ... % x x
Emberiza cirlus ... ... 2... | x x |
Emberiza citrinella ... ... | : | x

Alauda arvensis... ... «a. | x x |
laudararbOred... «2. «5 | 3

Certhia familiaris ao ee x

Sin, Caan A ee hee x |

Parus cristatus
Parus major...
Panurus biarmicus

Sylvia provincialis on x
‘Turdus viscivorus ee x x
3 Turdus musicus... oe x a x

Merula merula
Accentor modularis
Troglodytes parvulus ...

wa

1 Resident in Balearic Islands, Corsica, Sardinia, Italy, and Sicily.
2 Recorded by Mr. Scott Elliot from an elevation of 10,000 feet (Mt. ‘‘ Ruwenzori”’)
See the Albert Edward Nyanza (conf. Nature, 1895, v. 271).
% This species now only reaches the Canary Islands, the extreme southern portion of
its refuge area in Western Europe, as a winter visitor in varying numbers, having ceased
to breed therein.

76 THE MIGRATION OF BRITISH BIRDS
RESIDENTS IN BRITISH ISLANDS. | IBERIA. N. W. AFRICA on CANARY ISL.

Alcedoispida ... ... ... oe x

1Anser cinereus ... ... .-- x

Tadorma cornuta... ... ... x

MAMASIDOSCHAS: || 'e-5) =-) oss x x

Amasiclypeata. (2... <3. 0 =} x | x

Anas crecca... x

Anas strepera x

1 Fuligula ferina ... x x

2 Vanellus cristatus x x

2 Totanus calidris x x

1 Tringa alpina ioe x

Scolopax rusticula. ...... x %

@Otasstardass:.- = eee x x

Botaurus stellaris sae Sine x } x

Phalacrocorax carbo ... ... x x

Phalacrocorax graculus... x x

Uria troile x

y
A

Puffinus anglorum ae
Procellaria pelagica ..._... x | x x
* Larus fuscus

' Larus ridibundus
Podiceps cristatus af
Podiceps minor 2. 2.3 >-= >
* Gallinula chloropus ...
* Fulica atra...

Rallus aquaticus ...

{XX

x X X

Se NL Se Se

=i Crexipallloninns. sees x ;

Columbus palumbus ... ... x x |
Columbus zenas ... a x x

[Reding cINerea sere ax

Tetrao urogallus... ... ... x

WEACOPUSMMULUS gs. Gen er: x

1 These species only occasionally breed as far south as Iberia; the habit having nearly
lapsed owing to the Post-Glacial northern extension of range.

2 These species now only reach the Canary Islands, the extreme southern portion of
their refuge area in Western Europe, as winter visitors in varying numbers, having ceased
to breed therein.

Continuing our investigations still further we find that
out of the resident birds, or species, to be met with in
some part of the British Islands throughout the year,
no less than 29 resort to Refuge Area II. in winter,
indicating a former range base, many of them there can
be little doubt being individuals from our islands whose
place in them at that season is taken by other individuals

visiting us from more northerly or easterly areas, and

DEE GRACTAI KANGE CONTRACTION, LTC. “77

which regard our islands as their refuge because it is
the area from which they emigrated north or east to
colonize other lands in past ages. These species are
indicated in the following table.

ue
SPECIES. IBERIA. N. W. AFRICA. | CANARY ISL.

Falco tinnunculus

|
Falconesalon’ ... 2:. -2- x x
Gircusicyanus) (2.0 ces. ase x | x
Haliaétus albicilla ...... x | x |
Stumuspvitlearisiss. .0- --- x x |
Motacilla yarrellli ... ... | x x
Fringilla spinus ... 0... ... | x | X (rare) |

Corvus frugilegus
Ardea cinerea

Sula bassana Bese ey Nee. x x
Procellaria leachi eae ne x x
PATIAS PACU EA sees ose) ese) las x x
Amasspenclope .....:. ... | x x X (rare)

Bligulaieristatacs) ce. | «> |
Fuligula nigra ete ME.
IMIG OUISESEDALOT sc ves | x
Mergus merganser

Podiceps cornutus ae
Colymbus septentrionalis ...

ay
x x

Alca torda . x x x
Numenius arquata x x x
Limosa melanura Soa =| x x x
Totanus glottis x x
Scolopax gallinago x | x
Heematopus ostralegus x x
Larus canus... Bog, Pee x | x x
Larus tridactylus dee GER x | x

Stercorarius richardsoni_... x | xx

Stercorarius catarrhactes ... | x | x

Passing from the species that are resident in our
islands, or found in them throughout the year, we shall
still find the same significant facts presented by those
species that are only observed in our area as Winter
Visitors. Of these regular winter migrants individuals
of the following tabulated species prolong their flight
southwards to Iberia, North Africa, and the Canaries,
which indicates an ancient range base of those species

78 THE MIGRATION OF BRITISH BIRDS

and where such species were preserved from extinction
in Western Europe during the glaciation of northern
lands, and from which they started as emigrants on
their northward extension with the change of climate.

SPECIES. | IBERIA. N. AFRICA. | CANARY ISL.

Archibuteo lagopus... ... | x

Fringilla montifringilla ae S

Turdus pilaris x x
Turdus iliacus ; x

1 Charadrius helveticus .. | x x
Strepsilas interpres ee || x x
Galidzisiarenartajge geen x x x
AST MOSAnU tage eee ee x x

|

Scolopax gallinula Wer erste al x x

Phalaropus fulicarius ... ... x x

Tringa maritima ... ... ... x x

Tringa canutus Teen Sor x >

Stercorarius buffoni ... ... | x x

Stercorarius pomatorhinus ... | x x

Larus glaucus ban sie traci x x

Manus munutus sn) eek ae s

Gyonus MmUsICuUS) | ese x x

Gyenus Dewick in aacll nme x x

MiG venus OlOE es” xref eee ee | x x

Anser segetum Me ss

Anser albifrons “6 x

Mergus albellus x x

Fuligula fusca “

Fuligula marila Ss

Clangula glaucion x

Botaurus stellaris ... x x x

1 It isa very remarkable fact that both these species do not go south of the Equator in
Africa, but individuals of the former prolong their migrations in Asia as far south as
Australia, and of the latter as far south even as New Zealand! The Black-tailed Godwit
and Common Sandpiper are other instances.

2 It is only in winter that this species visits us in a thoroughly wild state.

There are five other species which might almost be
included in the above table of our winter migrants ; but
there can be little doubt that the Goshawk (Astu7
palumbarius), the Black Redstart (Rutzcilla tithys), the
Firecrest (Regulus zgnicapillus), the Little Bustard (Ofzs
tetrax), and the Red-necked Grebe (Podiceps rubricollis)

PAE GLACIAL RANGE CONTRACTION, ETC. 79

are only abnormal winter visitors to the British Islands,
or, what is much more likely, may have once bred there
and become exterminated (conf. pp. 183—186). If this
be not a true interpretation of the facts, we are con-
fronted with an insurmountable difficulty of Distribution,
for we should find the anomaly of five species breeding
and wintering south of us in Iberia, North-west Africa,
and elsewhere, but wintering only in our area. The
mild southern counties of our country enable individuals
of these species to winter at or near the northern limit
of their distribution. There can be little doubt that the
two Passerine species would ultimately become residents
again in our area if left unmolested; the three larger
species would possibly become so if our islands were not
so thickly populated, or the individuals that reach us
were not so promptly exterminated. I may here also
take the opportunity of remarking that we have not a
single species wintering in the British Islands and South-
eastern Europe, and absent from South-western Europe
and North-western Africa (although many of course
winter in both), which is a most suggestive fact, indicat-
ing the sources of our avifauna and its Refuge Areas
or Range Bases during glacial times.

When we come to deal with the Summer Visitors to
the British Islands, the vast importance of Refuge Area
II. is demonstrated in no uncertain way. This Refuge
Area continues down to the present time to be the
winter home of almost every bird that migrates to our
country in spring to breed. The following table indi-
cates the species and the precise winter habitat of each,
or, in cases of wider dispersal, of the individuals of such
species that breed in Western Europe.

80 THE MIGRATION

SPECIES.

Falco subbuteo
Pernis apivorus

A Circus cineraceus

Pandion haliaétus

>

Muscicapa atricapilla

Motacilla alba ...
Anthus arboreus
Merula torquatus

Erithacus luscinia

B Ruticilla phoenicurus
Pratincola rubetra ...

B Saxicola cenanthe

Acrocephalus phragmitis

Acrocephalus arundinaceus

Sylvia hortensis

Sylvia curruca ...

Sylvia cinerea ...

Sylvia atricapilla

Locustella locustella

Locustella luscinoides

Phylloscopus sibilatrix

Phylloscopus trochilus

Phylloscopus rufus ...

Upupa epops ...

lynx torquilla ...

Crex pratensis ...

Crex porzana a

Coturnix communis ...

Botaurus minutus

Platalea leucorodia... .. :
(extinct as a by ceding species).

B Grus communis - :

(extinct as a breeding species).

(Edicnemus crepitans =
Eudromias morinellus
Egialophilus cantianus ...

B Recurvirostra avocetta ea
(extinct as a breeding species).

Numenius phzeopus...

Limosa melanurus ... .
(extinct as a breeding species).

Totanus hypoleucus

Totanus glareola 5
(e. vtinct as a by edi ng spec is),

Totanus ochropus or

Totanus pugnax

=
os)

> &

> pwd p> >

wo

o~)

Sy,
a &

uw

OF BRITISH BILDS

Iberia; N.

WINTER AREA.

Iberia : breeds and winters.
Iberia (breeds and winters) ; North
and West Africa.

Iberia (breeds and winters); N.
Africa.
Iberia; N.
winters.

Africa: breeds and

Africa (few breed in
Algeria).

| Iberia (few breed) ; N.W. Africa.

| Iberia: N.W. Africa.

Iberia (breeds and winters); N.W.
Africa.

N.W. Africa: few breed.
N.W. Africa.
N.W. Africa.
N.W. Africa: few breed.
N.W. Africa.
N.W. Africa.
N.W. Africa.
Iberia; N.W. Africa.
N.W. Africa.
Iberia ; N.W. Africa.

| Iberia; N. W. Africa.

| Iberia; N.W. Africa.

| N.W. Africa.

| Iberia; N.W. Africa.
Iberia ; N.W. Africa.
N.W. Africa ; Canary Islands.

| N.W. Africa.

| N.W. Africa.

| Iberia; N.W. Africa.
Iberia; N.W. Africa.
N.W. Africa.
N.W. Africa.
Iberia ; N. W. Africa.
Iberia; N. W. Africa.
N.W. Africa.
Iberia ; N.W. Africa.

| NW.

Africa.

N.W. Africa ;

Canary Islands,
Iberia ; N. W.

Africa.
.W.

Iberia ; N Africa.

N.W. Africa.

Iberia ; N.W.
N.W. Africa.

Africa.

CHE WGLACAL RANGE CONTRACTION, HTC. “81

SPECIES. WINTER AREA.
Sterna nigra... bors OE N. W. Kose
extinct ¢ as a b7 ceding species).
Stemaycantiacaa. see. csc West coasts of Africa.
Sterna iaerindowy cee Sate NEES West coasts of Africa.
Sterna dougalli... ... ... ... West coasts of Africa.
Stemmaranrcticasw.a) Gea lien) a | West coasts of Africa.
Sterna minuta . ‘ er et | West coasts of Africa.
Stercorarius miehardsonis Bee he | West coasts of Africa.
raterculaarctica aise) oe | N.W. Africa.
B Anas circia ee i hae ae N. Africa.

The species marked A in the above table winter, or
winter and breed, in Iberia or North-west Africa, or
both, but only winter in or pass through South-east
Europe, Asia Minor, Palestine, and North-east Africa
on passage to regions further south to spend the cold
season, extending in some cases even to the Cape Colony.
This circumstance appears to me to prove two facts.
First, that the ancient Sahara Sea barred further pro-
gress to the south in the western portions of Africa, as it
had previously barred northern progress say in Pliocene
ages ; and second, that North-west Africa and Iberia
formed the glacial Refuge Area or Range Base of the
British or West European portion of those species ;
the individuals breeding further north in the eastern
portions of the continent than in the western portions,
perhaps, during Pre-Glacial ages, and even continuing
to do so during the progress of the Glacial Epoch, as
we have already seen the extension southwards of the
ice-sheets in the east was much less than in the west
(conf. p. 28), thus leaving a wider expanse of breeding
area northwards during the successive cold periods.
By applying the well-established Law of Migration,

that the birds that breed the furthest north winter the
G

82 THE MIGRATION OF BRITISH BIRDS

furthest south, we can readily understand why eastern
individuals of the same species visit the Cape in winter, ©
whilst western individuals go no further south than
North-west Africa and the Canary Islands—their base
of northern extension. ;

The species marked B in the above table are birds
that go much further to the south in East Africa than
in West Africa ; not necessarily because they breed any
further north in East Europe or West Asia than in West
Europe, but because the passage up or down the Nile
valley has always been a more continuous one, whilst in
West Africa the Sahara Sea or its now sandy wastes
were an insurmountable barrier to emigration. The
Terns, being thoroughly oceanic species, do not come
within the scope of these remarks. The evidence also
seems to suggest that some of these migrants, after
going down the Nile valley, spread westwards across
the Soudan, even to the Atlantic sea-board, as if they
were following the southern coast-lines of the ancient
sea !

There is another small group of Summer Migrants to
the British Islands which appears to me to have unques-
tionably dwelt in Refuge Area III. during the Glacial
Epoch. The winter quarters of these birds may be
either in the Mediterranean basin or in Tropical Africa.
They appear to reach those districts by way of Iberia,
thence eastwards through Algeria and Tripoli, and
southwards down the Nile valley. This class of sum-
mer migrants illustrates very vividly the intricate paths
followed by birds on passage, and demonstrates how in
the remote past the colonists gradually extended their
range, first eastwards and westwards across the Soudan,

LIE ANGLA CIAL RANGE CONLRACTION, £TC. $3

round the southern borders of the Sahara Sea or Desert,
and then northwards up the valley of the Nile, ultimately
following the more recently-formed coast-area of Tripoli,
as the sea receded, colonizing Algeria, and ultimately
spreading northwards into Iberia, into France, and
eventually the British Area. The line of Emigration
followed by those species in the past continues to be the
route of Migration in the present. <A few individuals of
some of the species tabulated below may possibly win-
ter in Algeria and Tripoli, as, for instance, the Swallow,
but the great majority pass on to Tropical Africa, even
to West Africa and the Atlantic sea-board, by this
circuitous route! It is a very significant fact that the
majority of these migrants are late to arrive at their
breeding grounds, as is customary with most if not all
species from the south-east. The only exceptions are
those of species the British individuals of which may
probably winter in Algeria—the three Swallows, and
the Yellow Wagtail. It is a still more significant and
suggestive fact—confirming the views above expressed
—that with the solitary exception of the Turtle Dove
not one of the species is common on migration at the
Canary Islands, as we should reasonably expect to be
the case did the birds journey north from Tropical
Africa by this route. Nay more, such common species
as the Yellow Wagtail, the Swift, the Goatsucker, and
the Garganey have never been noticed at the islands at
all; whilst such wide-spread birds as the Cuckoo, the
Sand and House Martins, the Golden Oriole, and the
Spotted Flycatcher are only noted as stragglers to the
group. The Turtle Dove, however, is a very common
summer visitor to the Canaries, but there is no doubt

84 THE MIGRATION OF BRITISH BIRDS

whatever that it reaches the islands from the east, from
the Soudan, and not from the south, inasmuch that the
bird is unknown in South Africa, and is closely allied
to the Central African Zurtur zsabellinus, a regular
summer visitor down the Nile valley to North-east
Africa. The various species with their winter quarters
—once their glacial Refuge Area—are indicated below.

SPECIES. | WINTER AREA.

N. Africa (?) : Tropical Africa, and
south to Cape.

Muscicapa grisola

Oriolus galbula .., ... ... .... | Tropical Africa, and south to Natal.

Motacilla raii ... ... ... ... | Algeria, Tripoli (?): Tropical Africa,
and south to Transvaal.

Hirundo rustica... ... ... .... | Algeria, Tripoli (?): Tropical Africa,

| and south to Cape.

Chelidon urbica ... ....., ..._| Algeria, Tripoli (?): Tropical Africa,

Cotyleimiparian sts, mee atone. Algeria, Tripoli (?): Tropical Africa,
and south to Transvaal.

Crculus Canorusicanes tees cree Tropical and South Africa.

(Cy pPseluslapusma sccm tee Tropical and South Africa.

Caprimulgus europeeus'! ... ... Algeria, Tripoli (?): Tropical A frica,
and south to Natal.

Turtur communis SORE Ghote sere Tropical Africa.

1 This species is a very late migrant—a fact which seems to prove that the bird is #of a
winter resident in any part of North Africa.

There is yet another and smaller group of Summer
Migrants to the British Islands, descendants of birds
that also dwelt in Refuge Area III., and whose route of
Migration at the present time indicates the line of Emi-
gration taken by the species in past ages, as the breeding
or summer range was increased when the ungenial
climatic conditions passed away. They areas follows :—

SPECIES. | WINTER AREA.

Lanius collurio ... ... ... ... | Greece on passage; South Africa,
vid the Nile Valley.

Acrocephalus palustris... ... ....| Nile Valley; Tropical Africa, and

south to Natal.
Phalaropus hyperboreus —...._.... Black Sea Basin ; Persia; India.

AE NGILACIAE RANGE CONTRACTION, ETC 85

These species appear to reach the British Islands by
way of the Danube and Rhine valleys. They are also,
significantly enough, unknown in the Iberian Peninsula,
although two of them, the Red-backed Shrike and the
Marsh Warbler, are common enough in France during
summer. Mr. Dresser professes to have identified
Marsh Warblers from Malaga, but Mr. Howard Saun-
ders, in whose collection they were, very rightly con-
siders them to be nothing but Reed Warblers, Acro-
cephalus arundinaceus, This shows how important a
correct knowledge of Migration may be, even in the
identification of specimens. ‘These birds are all very
late migrants (amongst the last species to appear in
spring), as we have already seen is the case with birds
from the south-east. All summer birds of passage from
the south-east to Western Europe are late migrants;
and this fact seems to suggest that the habit was ac-
quired during the passing away of the vast glaciers
from Central Europe, when the summers were probably
shorter than they are now—the migration then par-
taking of the character which is the present feature of
the phenomenon in the Arctic regions, where the season
is very late and very short. Species from the direct
south—from North-west Africa and Iberia—had in
those remote ages (and as they still continue to have) a
much earlier route open to them, enabling them to push
northwards sooner in the spring (a habit which is still
continued), owing to the ameliorating influence of the
Gulf Stream and the milder glacial conditions. It may
also be remarked that none of these late migrants from
the south-east are dominant or widely dispersed in the
British area—the Red-backed Shrike being principally

86 THE MIGRATION OF BRITISH BIRDS

confined to the southern and central counties of Eng-
land, the Marsh Warbler to one or two of the southern
counties only, the Red-necked Phalarope chiefly to the
Shetlands, Orkneys, and Outer Hebrides. We shall also
find that even with resident birds that have emigrated
from the south-east, extremely few are widely distributed
or dominant species in our area (cof. pp. 88—-91).

It will thus be seen that of the 63 species that
may be fairly classed as regular summer visitors to
the British Islands (or some part of them), no less
than 60 species may be said, almost with absolute
certainty, to have reached them by way of the Iberian
Peninsula and France, and but three species can be
reasonably presumed, judging from their present geo-
graphical limits, to have reached them by no other
way than from the south-east, most probably vzd@ the
valleys of the Danube and the Rhine. Could any-
thing testify more eloquently or more significantly
to the source whence the British avifauna has been
derived ?

Whilst dealing with species obviously of south-eastern
origin, it may be advisable here to treat with another
croup of birds resident in or wanderers on nomadic or
abnormal flight to the British Islands—birds whose
range base during the Glacial Epoch extended to
Refuge Area III., or which have gradually extended
their range to Western Europe from Asia after the
Ice Age had passed away.

Pe MA CAL RANGE CONTRACTION, LTC:

87

SPECIES.

Loxia bifasciata ...

Pinicola enucleator ...;Conifer region

Carpodacus erythrinus

Calcarius lapponicus

Emberiza melanocephala,

Emberiza pusilla ...
Emberiza rustica ...

Otocoris alpestris...

Anthus cervinus
Lanius minor

Ampelis garrulus...

Muscicapa parva...
Erithacus suecica
Sylvia nisoria

Hypolais icterina

Falco vespertinus

Surnia funerea .,.,
Nyctala tengmalmi
Tetrao tetrix Hee

* Scolopax major...

* Tringa temmincki
>

* Tringa minuta ...

|
|
|
|
|
|
=r)

.|Pine forests of N.

Russia.

near
Arctic Circle.

Breeds as far west as
the Baltic Provinces.
.|Breeds as far west as

Norway.

Breeds as far west as
Italy.

.| Breeds as far west as|
Archangel.

Breeds as far west as|
the Baltic.

.. Scandinavia, N. Russia.

Breeds as far west
Scandinavia.
3reeds as far
E. France.

.| Arctic forests.

west

.| Breeds as far west
Germany.

..| Breeds as far
Scandinavia.
Breeds as far
S. Sweden.
.| Breeds as far
N. France.

west

west

west

.| Breeds as far west

Hungary.

as

..| Pine forests of Scandi-
navia and N. Russia.
..|Arctic pine forests,
Alps, Carpathians.

.| Pineand birch forests of |
N. and Cent. Europe. |
.| Breeds as far west as|
Holland.

EUROPEAN SUMMER AREA, |

INE.

.|Breeds as far west as!

WINTER AREA.

S. Sweden to N. France
and N. Italy; Austria,
Poland, S. Russia, and
S. Siberia.

S. Norway, Denmark, N,
Germany ; S. Siberia.

India and Burma,

Mongolia and China.

Western and Central
India.

India, Burma, China.

Russian Turkestan,
China, Japan.

S. Europe (except Iberia),
S. Siberia, S.W. Turk-
estan, N. China.

Egypt, Nubia, and
Abyssinia.
Nile Valley to S. Africa,

Central Europe W. to
France and E. to Turkey;
S. Siberia.

N.E. Africa, Persia,
India, and China.

|N.E. Africa.

Africa, passage ;
Central Africa, winter.

|S.E. Europe, N.E, Africa

on passage; S. Africa,
winter.

S.E. Europe, N.E. Africa,
passage 5; S. Africa,
winter.

N. Germany, Central and
S. Russia, S. Siberia.
N. France, Germany,
Cent. Russia, S. Siberia.

Sedentary.

Few in basin of Mediter-
ranean ; S. Africa.
Few in Iberia, Algeria ;

Scandinavia.

majority in Nile Valley ;
India, Burma, China,
Malaysia, etc.

..|Breeds as far west as|Few in N.W. Africa;

N. Norway.

bulk in S, Africa, Persia,
India, Burma.

88 THE MIGRATION OF BRITISH BIRDS

SPECIES. EUROPEAN SUMMER AREA. WINTER AREA.

oe | : Sa E
“ Tringa subarquata ...!Breeding area un-/Ethiopian, Oriental, and
| known. Australian Regions ; few

in basin of Mediter-

ranean,

Tringa platyrhyncha ... Breeds as far west as|E. Mediterranean basin ;

Scandinavia. N.E. Africa to Mada-

| gascar, Meckran coast,

| N. India, Malay Archi-

| pelago, etc.

* Totanus fuscus ... ... Breeds as far west as| Africa N. of Equator;
| Scandinavia. | few S. to Cape, India,

| | Burma, China.

With the few exceptions shortly to be noted, none of
these birds are known to visit Iberia normally, no more
than they are known to visit us. So far as the British
Area is concerned the Black Grouse (Zetrao tetrix) is
the only normal species, and in this case it is possible
that a portion of this species refuged in Area II. during
the Glacial Epoch, or so near to it (in the N.W. portions
of Refuge Area III.) that they began to emigrate across
France and Britain at the earliest favourable moment,
yet comparatively late, as the absence of the species
from Ireland suggests. The birds, then, tabulated above
are all species of Eastern origin, those with closely allied
forms or representative species all inhabiting the east
and south-east, or, as in the case of the Bluethroat
(Erithacus suecica), for example, they are actually the
eastern representative of the West European species,
which has succeeded to a great extent in encroaching
upon the area of its ally. Thus Loria d7fasciata is
most nearly allied to the Loxta leucoptera which is
found across North America from Alaska to Labrador,
and perhaps South Greenland ; Pznzcola enucleator
with its allied species P. subhimachalus inhabiting the
Himalayas ; Carpodacus erythrinus with its several allies

PAE AGWACTAL RANGE CONTRACTION, ETC. 89

in Palestine, the Caucasus, Turkestan, South Siberia,
and the Himalayas; Cadlcarius lapponicus, with its
nearest allies in North America; Ofocoris alpestris
with its various allies in South-east Europe and South-
east and Central Asia, notably O. dz/opha which in-
habits the deserts of Arabia and North Africa ; Ampelis
garrulus with its close ally A. phantcoptera of Japan,
and A. cedrorum of North America; Muscicapa parva
with its representative species J/. hyperythra in India ;
Falco vespertinus with its eastern representative F.
amurensis confined to East Siberia, East Mongolia,
and N. China during the breeding season; Swruza
Sunerea with its allies S. dolzata in Siberia, and S. z7zsoria
in North America ; 7etrao tetrzx with its only allied form
IT. mlokostewzrcst inhabiting the Caucasus; and 77znga
metnuta with its closely allied races 7. rujficollzs of Eastern
Siberia and 7. sudimenuta of Eastern Siberia and Behring
Island, leading on to the 7. mznutella of Arctic America.

I might here take the opportunity of remarking upon
the very interesting instance of geographical distribution,
as showing the influence of competing species, presented
by the Icterine Warbler Ayfolazs icterina. This bird
breeds in North France, Belgium, Holland, Denmark,
and North Germany, and visits Scandinavia beyond the
arctic circle for nesting purposes (conf. /dzs, 1894, p.
229), yet, as it is decidedly a south-eastern species, it
has not reached our area. It seems, however, to have

' In my opinion the utter absence of this species from Iberia is
a very conclusive proof that the Post-Glacial emigrations of the
Shore Lark started from the South-east. There is no trace what-
ever, geographically, between Ofocorés alpestris and O. bilopha in

the West, but ample evidence (through allied races especially) of
their former continuity of area (and community of origin) in the East.

go THE MIGRATION OF BRITISH BIRDS

prevented the Iberian and North-West African Hyfolazs
polyglotta from extending its range north of the Seine
and reaching our islands, as normally we should have
expected it to have done. It is possible that similar
influences may have succeeded in preventing such forms
as Emberiza hortulana, Acrocephalus turdoides, and A.
aquaticus from extending their breeding range to us.
Again, not one of the species tabulated above can be
fairly regarded as dominant or widely dispersed in the
British Area. The reason these species are not domi-
nant in South-west and West-central Europe, except
in one or two isolated cases which only tend to prove
the rule, is probably because they were prevented by
climatic and glacial conditions from reaching that area
until the vast northern Emigration of birds from Refuge
Area II. had taken place, which we have every reason
to believe occurred earlier and under more favourable
auspices—due to Gulf Stream influence—than was the
case with birds whose emigrations progressed from the
south-east. Before these south-eastern species had suc-
ceeded in colonizing West Europe, or before they had
crossed the once glaciated portions of Central Europe,
these temperate western lands were occupied by wide-
spread and dominant species from the south which had
become well established (or it may be the sea had
separated Britain from continental Europe) before they
arrived so far to the north-west—two powerful checks to
the western progress of these eastern birds. We have
every reason to believe that had these birds come up
from the south, instead of from the remote south-east,
they would either have been regular visitors to or
residents in our area; unquestionably their most im-

TAPE CEACTALE RANGE “CONTRACTION, ETC. O1

portant line of North-western Emigration was to the
east of Italy. We must also bear in mind our law (conf.
p- 60) that a species in the Northern Hemisphere never
normally increases its breeding range in a southerly
direction—hence undoubtedly the absence of such south-
eastern species not only from Iberia, and France (in
some cases), but practically from the British Area, their
lines of Emigration following such a course as to entail
a southern—and I maintain an impossible—extension
of range in order to reach such countries, from which,
however, we already know they are normally entirely
absent. We see by the instances tabulated above how
birds can spread from the south-east even to Scandi-
navia, to Germany, and even to France, and yet be
rare or abnormal with us and in Iberia, the dominant
line of their migrations trending south-eastwards in
the exact direction of their ancient north-western lines
of emigration. These species have no claim whatever
to be regarded as part of our avifauna; they are all
of them uncommon with us, and most probably will
ever remain so.

It is a most astonishing fact that there is not a single
common or dominant species passing the British Islands
on migration which does not either winter or breed in
that area or in Refuge Area I]. The great number of
birds that occur in our islands sparingly or irregularly
every year, neither staying to breed nor to winter, are
really migrants out of their usual course, and belong to
species whose dominant line of flight normally trends
south-east. Comparatively speaking, a few individuals
of the species in the above table, marked with an
asterisk, regularly pass down the west coasts of Europe

g2 THE MIGRATION OF BRITISH BIRDS

—including the British Islands—by way of Iberia to
North-west Africa to winter ; but it seems very probable
that the ancient Emigration of the ancestors of these
individuals was originally from east to west along the
Mediterranean basin, and thence north up West Europe,
inasmuch as the Migration of their descendants at the
present time does not extend far down the African con-
tinent (probably not beyond the limits of Refuge Area
II., as these species are unknown in or only irregular
stragglers to the Canary Islands) in the west, but the
Migrations of the descendants of eastern individuals
extend down that continent on its eastern portions even
to the Cape. Moreover, the birds that winter in the west
are few, and often irregular in appearance; the great
bulk of the species wintering in south-eastern areas.
It must always remain a moot point whether, in the
course of their Post-Glacial emigration or extension
northward of breeding area with the change of climate,
by this route, any or all of these five species bred in the
British Area when that region was of an Arctic or sub-
Arctic character: probably they did so very sparingly.
I may also remark ere leaving the subject that there are,
of course, vast numbers of individuals of other species
that breed or winter with us which pass our islands only
on passage to breed further north or winter further
south, but their movements do not materially affect the
question we have been discussing. The significance of
the above facts in relation to the past geographical
conditions of Refuge Area II and of continental Africa
in glacial ages cannot be too strongly impressed upon
the reader.

We now come to deal with those species of which

LHEBGLACTAL KANGE (CONTRACTION, ETC, “63

the range base of a portion was undoubtedly in Iberia
and North-west Africa, many of them with southern
representatives remaining as evidence of that olden
habitat, and most of which continue to visit that area
in winter, or breed from North-west Africa or Iberia
north to areas as high as the British Islands or even
yet higher latitudes, but which, from a variety of
reasons dealt with below, do not breed in our area,
and can only be regarded as abnormal visitors to it.

N. LIMITS|

SPECIES. AREA NEAR BRITISH ISLES. |IN EUROPE. | REMARKS.
Nucifraga caryo-| Black Forest ; S. Scandi- | 67° | An Eastern Em-
catactes navia. | igrant, with
| allies in Asia.
A Emberiza hortu-| N. France ; Holland. 664°
lana | |
( Several races
A Galerita cristata] N. France; S. Holland. 60° iT Nines
( Africa.
| ( South African
A Anthus campes-| N. France; Holland. Bie {race Azthus
tris | pyrrhonotius
A Motacilla flava | N. France; Belgium; Hol-| 60° An Eastern Emi-
land. grant.
A Acrocephalus |N. France (Calais); Bel-| 53° All near allies in
turdoides gium ; Holland. far East.
A Acrocephalus |N. France ; Holland. 55:
aquaticus
A Coracias garru-|N. France; N. Germany; 61°
lus Belgium ; Holland ; Den-
mark.
Nyctea nyctea! | Scandinavia. WS.
Bubo maximus!| France; Denmark; Ger-| 71°
many.
A Athene noctua | France; Belgium; Holland.| 56° Allies ) in) Ne
| Africa and
Asia.
A Scops scops_...) N. France; Belgium; Hol-| 53° | Resident races
land. | in N. and 5.
| Africa.
A Milvus ater ...| Germany. 60° Allies in N.E.
Africa and in
Asia.

1 It is probable that these species were once indigenous to the British Area, although
now extinet (conf. /é7s, 18901, pp. 385, 386).

94 THE MIGRATION OF BRITISH BIRDS

SPECIES. | AREA NEAR BRITISH ISLES. Leeeiess REMARKS.
oa |— — — ——— —
A Fuligula nyroca | Holland ; Germany. Som
A Ciconia alba ...] Holland; Germany. 59° Alliesin E. Asia.
A Ciconia nigra ...| Holland ; Germany. 56° Allies in Orien-

tal and Ethio-
pian Regions,
A Sterna caspia .,.| Holland (?) ; Island of Sylt.| 59°(?) |

A Sterna anglica {Island of Sylt. 59°(?)

A Podiceps nigri-| Holland; Denmark; Ger-| 50° |
collis many.

A Crex parva ,..| Denmark; Holland(?);Cen-) 56°

tral France ; Belgium (?). |

Before making any comment upon the species tabu-
lated above, it is necessary for us to deal with another
group of birds, a study of whose geographical distri-
bution and migratory movements will assist us, I think,
in demonstrating the philosophy of a very intricate and
hitherto inexplicable phenomenon: viz. the absence of
certain species from the British Islands which are
common and widely dispersed in continental areas
almost within sight of them. Various ingenious sug-
gestions have been made by naturalists in their attempts
to explain what looks like an anomaly of distribution,
but, as I hope presently to show, the curious fact is
perfectly regular and conforms in every way to the
known laws of avian dispersal. This group will be com-
posed of species whose northern range in the ertreme
zest of continental Europe, or in all Europe, does not
reach the British Islands, or say latitude 50°.

ee ee

RANGE BASE OR REFUGE AREA Il

CHAPMAN & HALL, LISTED.

THE GLACTAT RANGE CONTKACTION, ETC, 95

SVECIES. | N. LIMIT IN WEST. | N. LIMIT IN EAST.

A Anthus spipoletta ... | lelaudiza IMGs, Gee Urals vee Mts, 50°.

64°.
Calandrella _ brachy- | France, S. of 474°. Is. W. Siberia 473°.
dactyla | |
Accentor alpinus’ ...| Alps; Carpathians 49°?| Turkestan, limit un-
known.
Sylvie ouphea ees wee Pnance SO. On Aor S. Russia 48° (?).
Aédon galactodes_ ... Iberia up to 42°. | Turkestan.
A Monticola saxatilis ...; Hartz Mts. 52°. Lake Baikal 55°.
Caprimulgus ruficollis! |S. half of Iberian Pen.

A Merops apiaster __... |S. of France, Alps. | Carpathians ; Russia
| 523° (which is as high
| N. as Yorkshire).

A Cypselus melba ess oblat. so. | Urals 55°.

A Falco cenchris ..._ ...| Pyrenees 42”. Russia 46° (an Ethio-

pian species).

A Tadorna casarca__,..| W. Europe 43°. E. Europe 50°; Asia 55°.

A Fuligula rufina... ...| Lat. 50°. Lat. 50°.

A Pheenicopterus roseus | W. Europe 43”. Asia 50°.

A Plegadis falcinellus ...|S. France 43°; Sclavo-| Volga, S.W. Siberia 48°.

een Ge
Ardea bubulcus —_... |S. half of Iberian Pen. |An Ethiopian _ species
| | spread W. along N,
| Africa.
Ardea comata ..,_...| Iberian Pen. 42”. |S. Russia, Caspian ‘47°,
Ardea garzetta.., ...| W. Europe 43°(?). |E. Europe 46°.
Ardea alba ea mOnASy. 47° to 50° (2).
Ardea purpurea _—_,.,| W.. Europe 47°. Siberia 55° fide Pallas.
A Glareola pratincola |S. France 43°. | Siberia 46°.
A Himantopus melano-|S. France 43°. | Hungary 48° ; E. Russia
pterus 46°.
Hydrochelidon hybri-|S. France 43°. 's. Russia 46°,
da

A Hydrochelidon leuco-|S. France 43°. Poland 52°; Siberia 50°.

ptera |

it Winter quarters unknown. I presume the line of migration to extend eastwards
through Tunis and Tripoli, and thence round the desert to Central Africa. It is decidedly
a species of Eastern origin.

The species contained in the two preceding tables are
mostly birds that have spread northwards or north-
westwards from a Glacial Refuge or Range Base in
Greece, Asia Minor, Palestine, and Africa from Tripoli
to Egypt in the north, south on that continent to
varying limits down to the Cape Colony. They are
the descendants of the individuals of the species that

96 THE MIGRATION OF BRITISH BIRDS

occupied Refuge Area III.; whilst those—if any—
that inhabited the extreme west of Europe (France,
Holland, British Area) were exterminated, except such
as occupied Iberia and North-west Africa. By a
reference to the map of Europe it will be seen how
a species could extend its northern area, with the
return of milder climatal conditions, even to Belgium
and Holland from the eastern Refuge Area, and yet
be effectually barred by the wide stretch of sea from
spreading westwards to our islands, especially as ground
to the north was open to the settlers. This to my mind
also explains why so many of these species range into
Scandinavia and Russia (the further north they go in
the west the wider becoming the barrier of sea separat-
ing them from the British Islands), and are yet absent
from our area. We also find that in many cases these
species go much further south to winter in Africa in the
east than they do in the west. We must also remember
that the area of country composing the eastern Refuge
Area or Range Base (III.) is vastly more extensive
than that of the western Refuge Area or Range
Base (II.), and reaches many degrees further north, If
we follow the probable lines of Emigration after the
Glacial Epoch passed away taken by these apparently
abnormal species, we shall find that to reach our
islands at all from the eastern Refuge Area—taking
into consideration especially the glaciated condition
of the Alps—az exténsion of range southwards would
have had to have been made, and that is utterly
opposed to known facts and to the Law already pro-
pounded. If we accept such an explanation of the pheno-
menon of distribution now presented by these species

TE \GEACIAE KANGE CONTRACTION, ETC. 97

we can then understand why it is that species breeding
commonly in Holland, Belgium, Germany, and even in
some instances Scandinavia and North-central Russia,
do not inhabit our area. Of the three British species
that regularly migrate south-east in autumn (conf. p. 84)
it is a most significant fact that they are common in
France (directly south of the British Isles) or Central
Europe, either as summer visitors or passing migrants,
yet are rare or abnormal in Iberia. Of the various
abnormal visitors to Britain, whose range in West
Europe does not reach as high as the British Isles, no
less than eight breed to the north of some part of our
area east say of Ostend, and where the North Sea is
150 miles or more across; whilst others that breed a
long way south of us in the west approach us much
more closely in latitude in the east. Now all this
appears to suggest that the species breeding so close
and yet not visiting us are descended from the emigrants
that re-peopled Europe after the glaciers retreated from
Refuge Areas east say of E. long. 8°, spread slightly
to the west of that longitude in the north in one or two
instances, and in many instances attaining a higher
latitude than our own in districts directly north of that
Refuge Area—and present winter home. The individuals
of these species breeding in Iberia or North-west Africa
probably never ranged as high as our area in Pre-Glacial
times ; if they did, the Ice Age exterminated them, or
they were entirely absent from Western Europe, which
then extended down to the Canary Islands. Or did
they inhabit that area, we may presume that they were
sedentary as they are to-day, in the sense of not leaving

it in summer or winter; or, yet again, the much smaller
H

98 THE MIGRATION OF BRITISH BIRDS

size of that Refuge Area (II.), and consequently fewer
number of individuals, would not demand such a wide
extension of northern range in Post-Glacial times, as
amongst the much more numerous individuals that
occupied the eastern Refuge (III.). It is even possible
that the Glacial Epoch did not affect the individuals
of these species in Refuge Arca II. at all.

The White Stork (Czconza alba), for instance, breeds
commonly in Iberia and North-west Africa. It also
breeds in Holland, Germany, and South Sweden, but
misses the British Islands. Why? There can be little
doubt that the birds breeding in Iberia were never
affected by the Glacial Epoch, but the birds breeding in
Holland, Germany, and Sweden undoubtedly were, and
were all exterminated, especially through their inability
to rear offspring. A portion of the species, however,
occupied Refuge Area III., and from those Storks
that peopled that area the individuals have descended
that breed in North-west Europe to-day, as is to my
mind surely indicated by the line of their migration at
the present time, namely, across France, Italy (where
they are not known to breed), and down the Danube
valley, across Turkey and Asia Minor. Significantly
enough, the Storks that migrate south-east from
northern areas winter the furthest south in Africa, pene-
trating down the Nile valley to the Cape; whereas
those breeding in North-west Africa and Iberia—a
much more southerly area—only appear to draw south
to West Africa, and in my opinion reach that locality
by coasting round the Sahara east, south, and west
again, as they did when that area was a sea: as is usual
in such cases, the White Stork is only an abnormal

tHE -GEACIAL RANGE CONTRACTION, ETC. 99

and very irregular migrant to the Canary Islands,
Did the individuals breeding in Holland and South
Sweden migrate down West Europe,—of which, how-
ever, we have no evidence,—then by a well-known law
they should go to the Cape; but as they are birds
breeding at the limits of the northern range, they go the
furthest south, and by a route which misses South-west
Europe altogether! Very similar remarks apply to the
Black Stork. The Red-crested Pochard (Fuligula
vujina) may be cited as another instance. There can
be little or no doubt that the individuals of this species
breeding in Europe north of Italy and east of France
are the descendants of emigrants from the far east,
inasmuch that the bird is very rare in the East Mediter-
ranean and in Egypt, but can be traced through the
basins of the Black and Caspian Seas to Turkestan and
North Persia, thence through Afghanistan to the Refuge
Area or pre-glacial Range Base in India. The indi-
viduals breeding in Spain, Sicily, Sardinia, and Southern
Italy form part of the colony whose pre-glacial range
extended to North-west Africa, where they are also
residents.

Very interesting evidence in support of this line of
Emigration is furnished by the Blue-headed Wagtail
(Motacilla flava), and its several allied forms. The
Blue-headed Wagtail is only an abnormal migrant to
the British Islands, which are entirely beyond the con-

1 There can be no doubt whatever that the Knots (7Z7zzga
canutus), passing our coasts on migration, reach their winter
quarters in Africa by a route east along the Mediterranean and
south-west across Africa to the west coasts as far as Damara Land.
It is significant that this bird is unknown on the Canaries.

100 THE MIGRATION OF BRITISH BIRDS

fines of its distribution. It is, however, one of the
commonest birds in summer across the English Channel
in France and Holland. It breeds in Western Europe,
say from Denmark to Iberia, and probably in North-
west Africa, but, as is usual in such cases in the far
east, it does not breed so far south. It passes South-
east Europe and North-east Africa on migration, and
winters in South Africa. The Arctic form of this
Wagtail (Motacilla cinereocapilla) is a summer visitor to
North Europe (as far west as Scandinavia) and Asia
(ranging from lat. 63° to lat. 68°), the European indi-
viduals passing through Central and Southern Europe
and North-east Africa on migration, and wintering in
Equatorial Africa; but, as if still further to indicate
this dominant line of North-western Emigration, we find
a colony of this race established in the Lombard Alps!
Again, another race, JZ. melanocephala, is a summer
visitor to Italy, Greece, Asia Minor, the Caucasus,
Persia, and Turkestan, the birds breeding in Europe
migrating south-east to winter in North-east Africa.
Both these races are, of course, entirely unknown in
Iberia and North-west Africa, and strictly abnormal
wanderers to any part of West Europe say west of
Denmark. The migrations of the Blue-headed Wagtail
to and from North-west Europe, even to Holland and
France, trend to the south-east ; the migrations of the
individuals breeding in Iberia, and possibly North-west
Africa, are limited within that area, and do not even
extend so far south as the Canary Islands. I may also
remark that this Wagtail is a very late migrant to West
Europe, as is usual with migrants from the south-east,
appearing in Holland, etc. late in April, a month or

THE GLACIAL RANGE CONTRACTION, ETC. 101

more later than the White Wagtail, which we know
winters in the south-west !

Excluding Wyctea nyctea and Lubo maximus, out of
41 species no less than 29 (marked A in the tables)
conform to this rule of Emigration and Migration, and
of the remaining 12, eleven do not range to as high a
latitude as our islands in any part of their distribution !
I may here remark that in a great number of cases I
have found that western species, from Range Bases or
Refuge Areas I. and II., go furthest north in the west,
their range having a strong tendency to drop in the
east; whilst eastern species, from Range Base or Refuge
Area III., go further north in the east, their range
having a similar tendency to drop in the west.

If we glance at the relative position of the British
Islands to continental Europe, we shall see that wide
areas of water now bar the way to all northern exten-
sions of southern forms, and even at the narrow Strait
of Dover a line of Emigration due west would have to
be followed to reach our area—a direction of extension,
be it remarked, rarely made across a wide water area, as
a study of our avifauna and its past emigrations and
present migrations abundantly proves. No part of
the British area is now situated directly north of con-
tinental land without a sea-passage of nearly 20 miles
separating our islands from Cape Grisnez to the South
Foreland, and even in this case a route several points
west of north would have to be followed. If we takea
route direct north from continental land, the narrowest
sea-passage varies from about 60 miles between Cape
la Hague and St. Albans Head to nearly 120 miles
between the north coast of Finisterre and the entrance to

102 THE MIGRATION OF BRITISH BIRDS

Plymouth Sound. As a general rule, even narrow seas
are an effectual bar to Emigration (in many cases wide
rivers are equally effective barriers), and their area
appears generally to have been crossed by these avian
colonists whilst such seas were dry land, and previous
to submergence, in such instances where we find an
abundant avifauna now separated from that of adjoining
districts by water areas. On the other hand, existing
water areas even of comparatively wide extent are in
the majority of instances no barrier to Migration or
Season Flight, inasmuch as the fly-lines of migratory
birds are followed with amazing persistence, and con-
tinue to be followed across recent seas, or seas slowly
becoming wider as submergence progresses. There can
be no doubt that at the time these routes were formed
the land surface was continuous, or nearly so; indeed,
in a very great number of cases the geological evidence
confirms its continuity, and as birds only know, and
always and invariably follow, the one route by which
their area has been extended from winter quarters,
refuge areas, range bases, or centres of dispersal in
past ages, they must of necessity continue to follow
that route, notwithstanding the gradually widening
seas, or the formation of entirely new water areas,
which we know has taken place during a by no
means very remote past even in our own area, on
that route which lies between their breeding grounds
and their winter refuge.

As showing the impassable nature of a sea-barrier,
and its influence on the avifauna of a sea-encircled area,
I may mention that no less than 36 species of birds
breed in West continental Europe within the parallels

IHE GLACIAL RANGE CONTRACTION, ETC. 103

of our latitude, or in some cases much to the north of
them, which are only known as rare and abnormal
migrants to us, and which it may be interesting to
tabulate as follows.

See lleaal eae 2] 3
ze Seon Nae a
SPECIES. & 2 5 =) mB] 0 <s REMARKS,

3) Zz a % s| 4 me

= i} a : ° a ms

2 a = z = a z

n

Nucifraga caryocatactes | x le Nomadic Migrant.
Carpodacus erythrinus x Migrant.
Emberiza hortulana ... | x | x | x | x | x | x | » Migrant.
Galerita cristata... ... | x | x | x | x | x | x | x | Partial Migrant,
Anthus campestris ... | x | x | x x |x ]x Migrant.
Motacilla flava ... x | X eS || BS 3 Migrant.
Lanius minor x x | Xx Migrant.
Muscicapa parva x Migrant.
Erithacus leucocyana x || BS || ee Migrant.
Ruticilla tithys x 25: |) PS.) Bc Migrant.
Sylvia nisoria ... x x Migrant.
Acrocephalus turdoides | x | x xX |x | x Migrant.
Acrocephalus aquaticus | x | x x Migrant.
Hypolais hypolais || Se || Se S|} bS |] oS Migrant.
Picus tridactylus aa x Resident.
Picus medius..., x Resident.
Picus leuconotus x Resident.
Picus martius... x Balle: x Resident.
Coracias garrulus x | xX | x x | xX | x Migrant.
Athene noctua x ZS | 2S) ex Migrant.
Scops scops x xX |X | x Migrant.
Bubo maximus 2S |)525 | 251/72 x Resident.
Milvus ater ... x Migrant.
Aquila neevia x Migrant.
Astur palumbarius eee | A SX | Partial’ Misrant.
Tetrao bonasia x Resident.
@iconiaalba ;.. x | xX | Xx x |x Migrant.
Ciconia nigra x x Migrant.
Scolopax major ... 2S eS || BSH Ss |) Be Migrant.
Tringa platyrhyncha .. x | X Migrant.
Totanus fuscus x | x Migrant.
Fuligula nyroca . a || eS i) 2x x | x Partial Migrant.
Podiceps nigricollis Pal Posal 3 x Partial Migrant.
Sterna caspia x x Migrant.
Sterna anal? ase x Migrant.
Crex parva . x x 1X | x Migrant.

a RE ee ee ee a a
More suggestive still is the evidence furnished by the
Mammalia and Reptilia. As Dr. Wallace remarks

104 THE MIGRATION. OF BRITISH BIRDS

(Island Life, second edition, p. 339): “Germany, for
example, possesses nearly 90 species of land mam-
malia, and even Scandinavia about 60, while Britain

has only 4o, and Ireland only 22. The depth of
the Irish Sea being somewhat greater than that of

the German Ocean, the connecting land would there
probably be of small extent and of less duration, thus
offering an additional barrier to migration [emigra-
tion], whence has arisen the comparative zoological
poverty of Ireland.” The Reptiles furnish even more
significant evidence, owing to their more limited
powers of dispersal. Belgium has some 22 species.
of reptiles and amphibia, Britain but 13, and Ireland
only 4! Again, if seas were not such an important
check to Emigration, we may very naturally ask why
no continental species attempt to colonize the British
Islands during historic time ; why do none of the birds
breeding so commonly almost within sight. of our woods
and pastures ever seek to extend their area tous? So
far as I am aware there is no evidence whatever to
suggest that any one species of bird has extended its
range to the British Islands since their final severance
from continental land at the Strait of Dover; but on
the other hand we have ample proof that many species
have increased their range within our limits even during
historic time, as we shall learn in a future chapter (conf
p. 168). It follows, then, that our present avifauna was
established here during land connection with Europe;
not merely by the Strait of Dover, but. during such
time that the Engiish Channel formed one unbroken
land surface with the north of France. Even within
our area we have further confirmation of this interesting

© es

THE GLACIAL RANGE CONTRACTION, ETC. 1095

fact in the comparative poorness of the avifauna of
Ireland and England, especially as regards southern
types; or even, yet again, the poorness of the south-
west of England, in summer migrants especially, as
compared with the eastern counties—a subject which
also will be referred to in greater detail in a later
chapter. I should say in every case the probability is
that the abnormal migrants to our area of the species
tabulated above are from the East. They belong to
species of an eastern origin, which to reach our islands
normally would either have to increase or extend their
range southwards—contrary to Law—or to have crossed
wide expanses of sea, which all our experience of
migration and of the laws which govern the dispersal
of birds over the earth’s surface tend to show they are
most averse to do.

In an earlier chapter I alluded to a greater extension
of land area between Greenland and Europe during
Post-Glacial time ; it now becomes necessary, in order
to render this portion of our subject tolerably complete,
to enter more fully into this question and to inquire
whether during post-glacial time any Palearctic species
has had a purely Nearctic origin. As may naturally be
inferred by a reference to the map, Greenland—the great
central land mass between Europe and America—is much
too isolated from what is now continental land and too
ice-clad to possess a very extensive avifauna. Avian
Emigration to Greenland appears to have been as
difficult from America as from Europe, even more so, the
wide, deep water areas (600 miles across) of the south
proving so effectual a barrier to extension of area in this
direction that not a single purely American land bird

106 THE MIGRATION OF BRITISH BIRDS

(with two very doubtful exceptions) has succeeded in
extending its area to the country, whilst the Wheatear
is the one solitary representative of Palearctic land
birds that regularly breeds therein. On the whole, the
facilities—few and meagre as they were—have been
more favourable for the Emigration of Palearctic birds
to Greenland than for Nearctic species ; the Faroes and
Iceland indicating a once more continuous land surface
between Europe and that isolated country. Equally
unfavourable has this route been for the Emigration of
Nearctic species eastwards into the extreme west of
Europe ; not a single American bird has extended its
range to the Faroes, such a line of extension being
contrary to the Law we have already promulgated, and
but two have prolonged their emigrations beyond
Greenland as far as Iceland. These are Barrow’s
Golden Eye (Clangula tslandica), and the Harlequin Duck
(Fuligula histrtonica) ; both these species are aquatic,
and both breed commonly in South Greenland. It is
interesting to note that South Greenland is situated in
a lower latitude than the Faroes; had the Emigration
of these Ducks been from Refuge Areas I. and II., there
can be no doubt whatever that they would have bred
from the Faroes northwards to Iceland, just as we find
some species whose Emigrations started from South-west
Europe which have extended their range to and breed
in Iceland, but do not breed in South Greenland, as
most assuredly they would have done had their line of
Emigration been from Labrador northwards. Of Ne-
arctic origin, however, and governed by the Law which
forbids an extension of breeding area southwards, both
these Ducks are only abnormal visitors to any other

22 ——————

THE GLACIAL RANGE CONTRACTION, ETC. 107

part of Europe. There can be little doubt that had the
same facilities for Emigration existed between Labrador
and Greenland as between the British Isles and Ice-
land, the latter island would have possessed a much
more heterogeneous avifauna, and that it would have
been an area in which the ranges of many Palzarctic
and Nearctic species would have coalesced. I cannot
find that a single species (excluding the Wheatear)
breeds in South Greenland and in Iceland that does not
go further south in the Nearctic Region to winter—
proof that some portion of the species had a range base
there from which it emigrated northwards. It isacurious
fact that the Wheatear is a comparatively common
summer visitor to the extreme south of Greenland. The
individuals that breed in Greenland, say south of Jat.
65°, most certainly do not reach their summer area by
way of Iceland, but must enter the country either from
the south-east, south-west, or west. It is most im-
probable that the Wheatears breeding in South Green-
land cross the Atlantic from North-west Ireland to Cape
Farewell; it is even more improbable that they reach
their breeding area by way of the coast of Labrador ;
not only because, so far as we can ascertain, the species
had no base in the Nearctic region during the Glacial
Epoch, but because the individuals that have been ob-
served in Labrador are extremely few, and can only be
classed as abnormal migrants there. We are therefore
forced to the conclusion that the Wheatears breeding in
the extreme south of Greenland are the descendants of
individuals that have extended their area from Eastern
Asia across Behring Sea—when dry ]land—into the Ne-
arctic region. These individuals fly nearly due west

108 THE MIGRATION OF BRITISH BIRDS

across Canada and winter in Mongolia! That the
Wheatear is a species of great colonizing power is
proved by the enormous extent of its breeding area,
which extends from the south temperate zone to the
highest known limits of land.!. The Knots that reach us
from Greenland never pass south of say lat. 65° in that
country, and come vzé Iceland to the British Islands.
Here I may remark that the fact of the Great
Northern Diver (Colymbus glacialis) breeding in the
Faroes—and possibly within the British Isles (Shetlands)
—is to my mind overwhelming and positive proof that
some portion, if comparatively but a few individuals, of
this species dwelt in Refuge Area I. during the Glacial
Epoch, and from which their descendants passed north
with the return of a milder climate and open water.
It may seem rather an anomalous fact that a species
dwelling in Refuge Area I. should not breed in Scandi-
navia, but this Diver is thoroughly a marine bird, or one
only able to exist on or near to open water, and its Emi-
erations northwards appear to have been restricted to the
western portions of the British Area; at the time they
were taking place the English Channel and the North
Sea were dry land, and possibly still covered with ice
and snow, whilst a land connection between Scotland
and Iceland, by barring the progress of the warm ocean
currents, kept the climate of Scandinavia and the seas
adjoining too severe for the existence of any birds at all.
The disappearance of the ancient isthmus or peninsula

1 Strong evidence that the Wheatears breeding in Greenland do
not reach the country vzé@ Iceland is furnished in the fact that birds
have been observed in autumn to pass the extreme south of Green-
land as late as the 5th of October, after having apparently been
entirely absent from that district for several weeks.

THE GEACIAL RANGE CONTRACTION, ETC. 109

between Scotland, Iceland, and perhaps Greenland, and
the consequent entrance into the area beyond it of the
Gulf Stream was a much later event, as I think we have
some evidence to prove. Broadly speaking, the Post-
Glacial Emigration of birds in West Europe from the
south appears to have spread in two well-defined direc-
tions, one, which we may call Route 4, by way of the
British Area, the Faroes, and Iceland to Greenland ;
the other, which we will term Route 2, by way of
Holland, Belgium, and Denmark to Scandinavia. The
former stream of emigration took place most probably
in advance of the latter, owing to the genial influences
of warm oceancurrents. The birds therefore that breed
or winter in the British area followed this A route north;
the birds that followed the 4, or continental route, north
are only abnormal visitors to our shores... Of course it
must be clearly understood that many species—or the
individuals of many species—reached Scandinavia by
an emigration across the British Area and the once dry
land of the North Sea, and it is the descendants of
these individuals that still continue to reach us either as
passing migrants or as winter visitors from that country.
The following table contains West.European species
that breed in or visit the various specified island areas
between the British Isles and Greenland, and which
form very interesting evidence, not only suggestive of
an ancient coast-line between the two countries, but of
a route of past Emigration and Migration. Owing to
the vast submergences which have taken’ place on this
route, it is nothing near so important a highway for
Migrants as was once the case. Sufficient evidence,
however, exists to testify to its former importance.

110 THE MIGRATION OF BRITISH BIRDS

Notre.—One x signifies Winter Visitant; two x x’s Breeding; M
signifies Passing on Migration ; Mx signifies Passing on Migration and
Winter Visitant ; AM signifies Abnormal Migrant.

5 A , ‘ s
SPECIES. 5 a © $ z
: : : a ae
° oc Co %
na cS
MUATGUSHItACUS Meese lee “és és XK BS 3K
Saxicola cenanthe... ... a xe Se pane xx cans
Motacillavalbay cna. M M x 3 SoS
Anthus pratensis... ... ye x x se SK x AM
Anthus obscurus ... ... xe x me SK
Hirundo rustica ... ... xe xe xx AM
Chelidon urbica ... ... sex x Sean Se er) |
Plectrophenax nivalis ... ae xe Se x xx | xx
Sturnus vulgaris ... .., sax xe 3K ox AM AM
Coryusicordx eee geese Se Ne x X 52, 38 xx
Corvus comixas teers se Sg Se x AM
Alauda arvensis ... ... Sa Sax <x
Niycteamiyctea tumeremilee¢ x Se x * SoS
Haliaétus albicilla? ... ax SCX XS CISC eis
Haleorcesaloniy -<s are x X x xX x X eS AM
Phalacrocorax carbo .., ex ax x ee getie | bd oe
Phalacrocorax graculus xe Ss x Sess se
Silaubassanavel wees tase x xX So
Anser albifrons ... «+. x x 2 38 <x
Anser brachyrhynchus.., pe
Bernicla leucopsis ... AM AM Sher ce
Bernicla brenta ... ... M M M S32
Cygnus musicus ... s MX MX Mx xs rie
Anas boschas uel ese Xie <x ne Si xox xx
PASISELE PEL AN Nese tess x x M xe SS
IATIASACHtAl set ingen ieee x M eS <i AM
IAMASICKECCAl Swag Neca ers ex xT se xe Se
Anas penelope ... ... Me Ne S235 se 3K I< AM
Fuligula cristata ... ... x Be oS
Fuligula marila ... ... x x aod SCC
Fuligula glacialis... ... x Gear >< Scrc) | eee
Fuligula nigra... x M xM x M 3 8
Somateria mollissima .., soo NE Ne xe SS ax ne
Somateria spectabilis ... x x xM 4 ary
Mergus merganser_.... xM xM xM eee
Mergus serrator .. « aa ex Dox x a
Columba livia Sse)... ye Bd Sc xix
Coturnix communis... x x xg be ee
Crex pratensis 5 «.. pax “2 Se AM
Rallus aquaticus ... ... a bone Sen nex
Kilicavatta eeunsre ies x xX AM aS AM AM
fEgialitis hiaticula... M M M oS x x

1 The Ravens that breed in South Greenland are colonists from the Nearctic region,
and perhaps subspecifically distinct—another indication of the route by which this area
has been invaded by birds.

2 Probably Halietus leucocephalus in South Greenland

tit. GEACKAIS KANGE CONTRACTION, ETC. 11%

g a
SPECIES. ra a = < 2
4 & < 2 a
Q im U Leaf .
° = %
a c)
Charadrius fulvus.., ... sex ea MMS es Ne AM
Strepsilas interpres_... x M x M x x? x Bg Se
Heematopus ostralegus xi ax x 2K AM
Phalaropus hyperboreus x Bs x X Sai xe 2 BS
Scolopax gallinago... mg 6 Se xx x x AM
Tringa alpina ,,, ... xe Se See cx meee || | Be
Tringa maritima .., ... x) x M ne OK Be 5K xix
(irinsaycanutus) Wyse.) a: M M M M a
Tringa arenaria ... ... M M M X ee ae 3
Totanus calidris ,.._ ... x x oe St fl ne Oe x x
Limosa melanura... ... AM AM x ne
Numenius pheopus ... xx se x x xX AM
DEEMAALCHEA © tvex oe 5a SK eee, sen ne es
Pagophila eburnea_... x x | x ny || aes ae
Larus ridibundus... ... x i See Ih Be Se |
BUaEUSCANUS 05) pc.) ces x x Mee | esc
Larus argentatus... ... a Sot
NAGS TUSCUSIs-= gor oo a x6 BS Sox
Larus marinus ,.. ... xe x X xX 5% SS
Larus glaucus... ... xM xM xM ey
Larus tridactylus... ... xe x ee Be xX
Stercorarius catarrhactes x orem uN xc
Stercorarius richardsoni XS 8 x x Sax Me Se
PA Cant@rdagmeres! eesti aes ax en x Se
(Uittattrcilemio-m e.sce en SB Ex xX x
Uarraronylleme tesco. x x x X ME) AGE
Mersulus alle 7, 2. xM xM xM aX Se
Fratercula arctica... ,.. ax xx a a
Colymbus glacialis... x x eae: xX
Colymbus septentrionali Ba 3 ras SOS ESCs XK
Podiceps cornutus... xM x M M x x
Puffinus anglorum__.... Se 3 MRS x x | x
Procellaria pelagica ... aX xe Beso Wibecee SS

Nore.—None of the species have colonized Greenland south of say lat. 65° w7é Iceland -
those breeding in South Greenland have reached the country from Nearctic bases, or, in
the case of sedentary forms, when the North Atlantic, as low as lat. 60°, was dry land.
Their range extension has never taken a southern trend into this area normally. If the
White-tailed Eagle is a resident in South Greenland, then its ancestors reached the
country when dry land extended as low as lat. 60°. There can also be no doubt that
Ee gialitis semipalmatus and not “gialitis hiaticula is the Ringed Plover breeding in
the extreme south of Greenland. There is no evidence whatever to show that the Palz-
arctic Ringed Plover breeds south of Cumberland Bay across Davis Strait, which is not
quite so far south as the southern extremity of Iceland. It is significant that Hagerup
did not meet with the Semipalmated Plover. The Palzarctic Ringed Plover does not
winter in any part of the Nearctic Region, whilst its Nearctic ally, though it breeds from
Greenland across America to North-east Asia, winters nowhere in the Palzarctic Region
—facts entirely in accord with the Law of their dispersal. I may also remark that the
Lapland Buntings breeding in Greenland are from a Nearctic base—this species is un-
known in Iceland.

ElsO ih BA

THE GLACIAL RANGE CONTRACTION AND POST-
GLACIAL EMIGRATION OF BRITISH BIRDS (contznued).

Anomalous Facts—Analysis of the Facts suggested by preceding
Table—Table demonstrating the two Dominant Lines of Post-
Glacial Emigration in the extreme West of Europe—Analysis
of Table—Variations in the Northern Limits of Species—
Ancient Line of Emigration from the British Area Eastwards
into Continental Europe—The North Sea Plains—Their
gradual Submergence and its Effect on Birds—Table of East
and North-east Emigrants—Analysis of Table—Influence of
Temperature on Birds—Effects on Birds of Isolation of British
Area from Continental Land—Professor Geikie on Emigration
to the British Area—Emigration to Ireland—Impossibility of
Southern Emigration to this Area from Scotland—Migration
of Birds in the Valley of the Petchora—Emigration of Birds
within the British Archipelago—Resident Species—Table of
Resident Species—Analysis of Table—Absence of Birds from
Ireland—Summer Migrants—Table of Summer Migrants—
Analysis of Table—Table of Autumn Migrants to, and Coasting
Migrants over, the British Islands—Analysis of Table—Table
showing the Proportional Distribution of Species over the
British Area—Deductions from the Facts— Table of Endemic
British Species and Races—/ésumé of Present and Preceding
Chapters—Importance of New Law of Dispersal—Extermin-
ating Effects of Glacial Epoch—Effects of Cold Winters—-The
Dartford Warbler—Importance of Southern Range Bases.

ONE or two facts embodied in the table at the close of
the preceding chapter call for special mention. It may
be remarked as somewhat anomalous, for instance, that
the Gannet (Sz/a bassana) breeds on the Faroes and

THE NGELACTAL RANGE CONTRACTION, ETC. 'r13

Iceland, but does not visit the Orkneys and the Shet-
lands for that purpose ; the Pink-footed Goose (Azser
brachyrhynchus) breeds on Iceland, but is absent from
the Faroes, the Orkneys, and the Shetlands ; the Bernacle
Goose (Bernicla leucopsis) is only an abnormal migrant
to the Faroes and the Shetlands, yet probably breeds
on Iceland. There can be little doubt that these species
keep well out to sea in performing their annual migra-
tions southwards, inasmuch as they are well-known
visitors to the coasts of the British mainland. Again,
the common occurrence of the Bean Goose (Auser
segetum) and Bewick’s Swan (Cygnus bewickt) off the
British coasts in winter, and their absence from Iceland,
suggest unknown breeding grounds due north of these
areas in North-east Greenland, or in undiscovered land
between Emperor William Land and _ Spitzbergen.
Another interesting fact is presented in the migration
of the Black-tailed Godwit (Lzimosa melanura) to Iceland
and the Faroes. In its north-western migration this
species misses the British Islands entirely, and appears
to follow a route directly up the North Sea—probably
the river valley which once occupied the ancient land
between Britain and the continent—a vanished land
which was once the breeding ground of this Godwit, as
it slowly emigrated north. Godwits seem to be ex-
ceptionaliy attached to old routes of passage. The Bar-
tailed Godwits (Lzmosa rufa) passing up our coasts in
spring apparently go no further north than Spurn, and
then strike out to sea as if following an ancient and sub-
merged coast-line, or a continuation eastwards of the
Humber valley (see Map, p. 21); whilst the eastern
form of this Godwit (Lzmosa rufa uropygialis) appears
I

114 THE MIGRATION :OF BRITISH “BIRDS

to follow a similar sunken coast between New Caledonia
and New Zealand (W/zgration of Birds, pp. 99, 100).
The significance of the facts suggested in the above
table cannot be ignored by any student of Migration
and Avian dispersal. Out of the 75 species enumerated,
the breeding range of no less than 14 species is absolutely
continuous between the two extreme areas, and these
species breed in this direction from the British Islands
to Greenland wherever land occurs. Taking Iceland as
the next most remote area on this line of dispersal, we
find (including one or two doubtfuls) that no fewer
than 58 species, or about eight-tenths of the whole,
resort to it to breed; whilst almost exactly the same
number of species (57) breed on the Faroes. In two
cases at least we find that the highest northern emi-
gration of the species throughout the world has been
made along this route, which fact seems almost incredible
when we bear in mind the geographical conditions of
the area,and the comparative ease of a continental
extension. The Gadwall (Auzas strepera) breeds in Ice-
land, certainly north of lat. 64°, but only reaches lat.
57° in Scandinavia, and lat. 60° in the Stanavoi Moun-
tains in Siberia; the Kock Dove (Columba livia) breeds
in lat. 62° in the Faroes, but only does so up to lat.
59° in Scandinavia, its highest known northern limit
elsewhere. The Chough (Pyrrhocorax graculus) and the
Nightingale (Hrzthacus duscinia) attain their highest

1 More information on this intricate subject is badly needed;
We want particulars respecting the birds of East Greenland especi-
ally from lat. 65° northwards through Egedes Land, before we can
come to any absolutely correct conclusion respecting Avian Emi-+
gration from Europe in this direction,

THE GEACTAL RANGE CONTRACTION, ETC. 115

known northern limits in the British Islands. The
migrations of the Knot (Z7zuga canutus), the Sanderling
(Tringa arenaria), the Snow Bunting (Plectrophenax
nivalis), and the Wheatear (Saxzcola wnanthe), are
perhaps more northerly in this direction, more dominant,
stronger, than in any other part of Europe. Again, the
Great Skua (Stercorarius catarrhactes) and the Manx
Shearwater (Pufinus anglorum) range along this route to
Iceland, and the Stormy Petrel (Procellaria pelagica) to
Greenland, yet all three species are absent from the
Scandinavian Peninsula—a fact which suggests a land or
ice barrier to eastern progress beyond the longitude of the
Shetlands in remote ages when the emigration north of
these species was in progress, These are profoundly
interesting facts. They admit of but one interpretation
—a greater extension of land surface between Greenland
and the British Area during earlier ages. The ques-
tion of the ancient land areas in the North Atlantic
scarcely comes into the subject of this work, but if the
present dispersal of birds be any guide to past physical
changes, there can be no doubt that a vast extension
of land southwards between America and Europe once
existed, and that too possibly during Tertiary time.

Our next table will indicate the two dominant lines of
Post-Glacial Emigration in the extreme west of Europe
—one extending to, and by way of, the British Islands
to Scandinavia, principally to Norway; the other by
way of Belgium, Holland, and West Germany to Den-
mark and Scandinavia, principally to Sweden.

THE MIGRATION OF BRITISH BIRDS

116

*v[[AISNIO[ V[[A}sNI0'T
‘suysnyjed snpvydoo0.y
‘snoovurpunie sneydaoo10y

‘stytusvasyd snpeydaoo1sy
‘snyna sndoosoy[4y gq
‘snqiyoo.1y sudossoyAy gq
*xLuyepiqis sndooso [Ay

eqpidvouye viapfs
*SISUdJIOY BIATAS
*eondInd viatss
*BIIOUTI VIA[AS
“CIUTOSUT SHOVY LAG
*epnoaqna snovuyygy
‘snanotuayd vyppiornyy
*EfOdIqNIA v[OoUTVA F
eIJAqUI VOILA
*OYJULUAD VIODIXVS
eyenbio} BpnAzayy
*e[NAIUL B[NII TY
‘srizjid snpany,
‘snovT[L SNPAN J,
*SnoISUU SUpAN T,
*SHAIOAIOSIA SPIN,

*“SHIDAdS

XX X-
x X xX

x XXX
x xX XX

ORM ZR, oN VOR On OK TaNNRU On
xX XX KX KK XK XK K XK XK

Pat Pes
5

WM

xX X
x X

“‘WOISTsHA

x XX
x XX

xX XX
xX X XX

XX XX XK XK XK KX X
XX XK XK XK XK XK K K XK XK X

“GNVTIOH

x XX
x XX

x XXX

xXx XXX

X KX XXX XK XK XK XK XK
xX XX XX XK KX XK KK KX

Ss x
=

WM

x
x

xX xX

“ANVWUYAD “MM

nm
POSES 2 od
pax

x XX
x X X

x XXX
xXx XXX

xX XXX
x xX x XXX

x

= xX
=x

WA
xX X
x X

“MUVANAT

x
in X

08

x xxx
xxx xx x x x

xX XX Xo

x xX
xX X

xX XXX XK XK XK X
xX XXX KX XK XK X

“NAG aMS

NUAHLYO

“VIAVNIGNVOS

*SLINTT

x

x

x xX

“AVMUON

n

WA
WAL

“SONVILAHS

n

WM
WAAL

“SAANUNO

“OJULAA UT To[dSvYS MS + paceig pur
JOJUTAA X XM £0} AVPPSvIYS § f19,ULAA PUL UONVASITY WA { UOTWTISIPY UO W £ JO}ISTA 19}UTA\ AL f Spoa1g saylusis sx x OMT —"SLON

xXx xX XK X
x X XX

x XXX
xX X XX

PO hr, PRS
ROKK ON KS

x

WM
WA
x Xx
xX X

“ANVILOOS

x XX
x xX XxX

xX XX X
xX X XX

xX XK XX XK XK XK KX XK XK
MIKO KE OK OK Ge PE GG

x

WAV
WM

xX X

“ANVIONGA

“8 BL[aISNIOT VI[A}sNI0"T
stjsnjed snjeydaoo1ny
snaovurpuniv sneydaoo10y

sytuseiyd snpeydaso1iny
“+ snynt sndossoi[ Ay gq
snjry90.13 sndoosoyAy q
xtyqviiqis sndoosoy fy gq

29 eypidvonye viapss
a sisua}10y BIA[AS
<< "* voNIIND VIATAS
“a0 "* BaraUutd BIA|AG
“a8 BIUINSN] SNOVYILAST
"* -BpNdaqNI snovyILay
“ snanoiuaeyd vyponnyy
"* -Bjoziqns vpoounVig
* -BIjaqns vjoounrig
ae ayUBUADd BOTXLS
ae eyenb10} vpnsayy
as BINIAUW VpNIIPY
as “+ sued snpiny,
ue ** snoel[t Snpin f,
“° SNOISNUL SNp.iN
see SILIOAIOSIA Snpin yz,

“SH1IDadS

117

PEG,

Yr
?

THE GLACIAL RANGE CONTRACTION

"e[[ISULYNUOU VT[TULT
*sqojao By[IsULLy
*sHO[Y v{[IsULL

*SHIBSINA saj}snesyjoI0_
*snue}UOU Jasseg

*snoljsawiop jasstq
*B.I]SOMAIN BIXO'T
*SLIBS(NA VINYAUIA
ettedtt afAjo9
*eoTq.M UOpTayD
“eOT|SN.I OPUNATFT
*eypidvorsye vdvoiosnyy
*ejostis Vdvorosnyy
‘snanosqo snyuy
‘sisuajyeid snyjuy
*snaroqie snyuy
*(aoueI yy) Wet VypIOV}O
*eainydyns v][Ioevjoyy

“ECV VI[IOVIO PAT

‘poured v][OVIOFy
“SLeT[IWey VIyyIAD
‘snared sayApoysory,
RISB V}}IS
*snyeystIo snaivg
‘snopes snieg
‘rofeul snivg
‘stajsnyed snieg
‘snoienbe snjoutsg
*sNn}eISHIO sninsdoyy
‘sLIv]Npow 10}UIDIV

=

RG OK OK ORK eK OG KR OS
x KX KX KK KK KK KK KK KX

x
x

x
xX

RON Oe OK KX OX OS SSS
Re OCIS KOR IS CUS

2

x KX K XK XK XK XK XK XK OK OX OXK OXK OX OX

x
x

x
x

RR OS EX) EXT! IX) OK) OK 15C
KX XX XX XK KX

x

EKG OK OK OK XK OK XK OK OS 6

x
=

x XX XK XK

KX XK KK XK KX XK KK XK X

x

x
x

x
x

2S 2S PSS BS ES ong wre oven bed ve
FGI IK XOX OK OK

Pe PO OR) SN OS KTS RO) OG

M

xXx XX XK XK X
xX X XK XK XK XK

DEES OS PeStuead eoguee need
XXX KK XK XK XK

°
+
WwW

XX
x x

>S 2 2S 24 Ps OM
EX KOK ES OK

x xX
x xX

| ee ise eee
KI XK KEK KC | OS ORK Ox.

x X

x xX KK X

xXx xX xX

x

W
M
W

W
MOJ

W

M

Moy

MA

x
x

S

PS PSS SSA en Pos! PS CDS eae
PS IOS PSEC PAS CSE Gup Le DVS De bY

KX XX x X X

> oe ee Ge, Sate Ee
x KX KX

=
>

EE OR OR ON OK IKK KS OSC
TOT ERE URE EEK OK SK) OOK

V[SuLyUOW BypLSUrTT

ms Sqa[ao visu
oat SLLOTYS vI[ISUTI
SUVB[NA sajsnviyjoo00D
gs snuvj}UOUl Jasseq
"* snorjsawop Jasstg
see VIJSOMAIND VIXO'T
One suvspna vpnywdg
aus “ viiedtt afAjog
ove voIqin uoplayD
We BOYSNI OpunATyT

“* eypideoye vdvorosnyy
of vjosiis edvoisnyyy

999 sninosqo snyyuy
oe stsuajyeid snyjuy
000 snoioqie snyjuy

WEEE AUTO Al
“* vomydyns eB[lovjopy

see “ Bq[v BI[IOvJOPY

se qypoared eypIoVjOPY
ae SHIVIPIULZ VIYIIOD
* snnared sayAposory,
BISBI BIWS

eae * snjeysi19 sued
et snapniad snivg
sel “* jofeuw snivg
ace stysnied snaeg
ay snorjenbe snout
pe SNye}sIId snpnse xT

“ srivjnpow JoJUsDDy

THE MIGRATION OF BRITISH BIRDS

118

“eyinb10} xudT
*sneedoino snspnutides

*snde snjasd&>

*ealoqie vpneyy

*SISUDAIR BPNLLY
“sno Lon snAIOd
*9UOIOD SNAIOD
*XIUI09 SNAIOD
*X¥.109 SNAIOD)
*e[NpouoUI sNAIOD
‘eyepneo VIG
*SNIIVpULIS sn[nuesy

*sLIes[NA snuinjs
‘sI[vAlu xevusydo.j9a]q

*sn[oluaoyos VzLoquiy
"E][OULI}IO VzLaquy
"BIIVI[IUL VZLIIq UI
*sud.SAyN VJOULT
*SIIJSOITALYE VOUT
*eUIqVUUvS vjOUNT
‘snurds v][Isutt jy

*sI[aNpavo vI[LSUL

“SAINadS

x Xe
x XXX
xX XX
xX XXX
xX XXX
xX X X X

x
x
x
x
x
x

x
x
x
x
x
x

x
x
x
x
x
x

x XXX
xXx XXX
x X XX
x XXX
> a a aa
xX XXX

x
x

x xX X
Bx x

x XX

“AN

“WOISTaa
“GNVTIOCH

“ANVAYAD

xXx XXX
x xX XX

x X
x X

M
x X
x X
xX X

“HAVWNAG

Xo GReS
xXx XXX
an

x
x
x

x
x
x

DOR XS ORS
x XX XX
xX X

x xX

x

x xX

“NAGAMS
NYAHHLYON
*"VIAVNIGNVOS

“AVMUON
*“SGNVTILAHS
*“SAANMUO

“SLINIT

May

xX XXKXXXKXKXXXKX

XXKXXKXXXyK KX KKK KK XK XK XK XK
-

xXx XXX XX XK X

“ANVILODS

wee ees "+ gtmbi0} xusT
. snadoina snspnwided
288 so * sndv snjasdsa
ate ae voloqie epneyy

x XXX
x xX XX

ue fee SISUDAIV LpPNLLY
oh ae snoo|tsnayy SNA1OD
ie £2 $** QUOIOD SNAIOD
se fis *** xI1UIOD SNAIOD
ais ace "** -xBI09 SMAIOD
v[Npauow snaiod
oe es “ -eyepned vg
on “* snuepurys snpuues
2 2t snjnovis xe1os0yAg
aa ie SleS[NA SNU.IN}S
stjeatu xvuoydoj99] J

KM He KC Hoe ee
SUC SC SOIC NCE

be

mee “** snpolueoyos Bzi1eq Wa
3 we BlPeULAIO VZLIeq uy
VIIVI[IW VZ119q WIT
se “ee SUDDSAJNA VOUT
ree wee SLUSOMAR]} COUNT
*P te pre BUIGeUUBS POULT
AM | Pte eee snurds v][tSour]
x xX | os " SIfanpavo VBI|LOULI YT

x xX X KX XK X
XXX XK XK X

*“SHIOAdS

“ANVTIONA

119

THE GLACIAL RANGE CONTRACTION, ETC.

*sn[novas XvIOdOIOL]LY I
"OqIVD XVIOIOION|LY
‘snjavipey WoIpueg
*snjnounuUl) Od|e J
snutiso.1ed oo[vy
"UO]VSAX Od[V
*oaynqqns oo|e yy
ssnioaide stusag
*sI[eso1 SNATIT

‘snstu ra} 1d109V
HEM NS TMS
“snjavsXayo vjinby

*sndosvy oaynqiyd1y

“SLIvS|NA OaINg

*snouvAd snoilg

*snsoulsnia Snot

*snodvADUID SNOITD
“SNUIXvUL OGng
*eaqoAu voyOANT

*OONTL XLS
*snjyokyoviq OISy

‘snjo OISW
*SnOWWeL} OON[V

*sniouvs snjnonsd
“epidst opao| Vv
*SNINIIVS SVIOVIOD
*SIPLITA Snuroar)
“IOUIU SNOT
‘ro[ew snoig

XxXXXXE
SCX) Ge CI

xX XX

XXXXXXKX
—

xX XX XX XK XX

x
x

M

xX X
x X

x XX
x XX

x x K Se eee
=

x
x

Xx
x

x
x

x
x

x
x

xX XXX XK X
xX KX XK XK X

xXx XXXXXK XK X

M
xX X
xX X
x X
xX X
x Xx
x X
x X
xX X
xXx X
xX X
x X
M
xX X
xX X
xX X
xX X
xX X
M
x X
x X
x X
xX X
x xX
xX X
xX X
x X
x X

nin

32 Ok be XE EK Ce KOE XO Xe RE CE
ST BSS SESE ESSE SCE GRID OEE

xXx X XX

x
x

LS

Xo
x

xXx XXX
x XXX

IZ
1Z

ol
£9

of

ol

199

OR Nt oe nM ON
x XX XX

x

S

xX XX
x XX

n

n

M

x X
xX X
M

xXx XXXXX
xX XX XK XK X

xX X XK XK XK X
XXX XK XK XK

M

xX XX
x XX

snpnovad xv1od0rV[eY J

eee

oqivd xv1Od0INL [VY
snjaeley UoIpuey
snjnounuur} O9/e 47
snutiseiod ooe sy

"+ UOT eS O9]v,T
oaNgqns O9/e.T
snioalde siuiag

"* SITvoOI SNATITAL

* snstu rayidiooyw
AULEMC I SUE GIRL
snjoeskiyo vyinby

sndosvy oaynq yoy

" sLiBs[nA Oayng.

** snouvdd sno.ild

snsoursniw snoi1d

snaov1oUld Snot
* SnUUIXBUL Oqng
** goqoAu vaqOA NT
"= Gone XI4S

snjokyoriq oIsy

sce snj}O OISW
snowury only

sniouvs snjnong
“+ epidst opao[ Vv
SnNsvs Selov1oD
*** SIPIIIA SNUIDA4)
“s JOU SNOT
‘rs gofeut snort

THE MIGRATION OF BRITISH BIRDS

120

*eIOIID SVUY
"e99910 SeUy
‘ejnov stuy
*eyeaddo sveuy
“eiodoaijs svuy

“seyosoq svuy
*vNUIOD VULOPLT,
*‘DypoImaq snusia
*snorsnut snusf9

“eyUaIG vlOTUIOg
‘stsdoona] vpoutag

‘snyoudyadyouiq 1asuy
“unjasas Iosuy
*SNJNUTW sUOIjIG]e IasUy
*SUOJJIG]e JasUYy
‘shai0ulo Jasuy

*slIv][9}S snanvjog
"eoIOUID voply

"eursseq vjNS

“Sa1IDadS

M
M

WwW
M
MA
M

MIN
xX X
x X

M

“wold Tad

M
M

WwW

M
M
M

MW
xX
x X

xX X

“dNVTIOH

x xX XXX
xX XXX

x X
x xX

xX

xX X

“ANVWHYAD “MM

xX XXX
x XX XX

x xX
x xX

MA

W
A

M

M

M
xX X

x X

x xX

“MUVWNAG

x XX XX

xX Xo

iL
1Z

1Z

©
ioe)
No)

Ww
W

W

“NHdaMS

N

“SLINIT NYAHLUO
“VIAVNIGNVOS

“AVMUON

s Ss Ss
PaGe race {lavas ba Se | fees.
Ww MA xX X
S X X
Ron) al eet Ped mes
ST We, Sees a leks a
é xX X\é X X| XK X
M M M
M M AV
Ww

A M M
Ss A
M

Ss S M
Ss 5) M
S Ss xX X
x Xx
Ss Ss x X
M M a
n 7)
<= ° fe)

ra
ne ewe y

M
M

M
M
M
M
Mw

“ANVTONaA

PIOIIN seUYy
e009 seu
einov seuy
eyvaddjo seuy
viadoijs seuy

eee wee wee

wee one eee

seyosoq seuy
VINUIOD BUIOpL J,
TypotMaq snusf{>
snoisnu snusk>

ae aoe

aoe ate

vyUaIq vpIMIEd
Ae ** sisdoonay] vpotusagy
**snyoudyrhyoviq rasuy
a, *** unjasos Josuy
SN}NUIW SUO.YIq|e Jasuy
Ores ws *“SUuOYIq]e Jasuy
rie SneVUuld JOsuUYy

SUP]]A}S snanvjog
"** BaI9UID vaply

vursseq vNS
See rere te

*“saidads

121

THE GLACIAL RANGE CONTRACTION, ETC.

*snoijenbe sie yy
‘TUO][Teq xoIg
“euvziod xa19

‘sisuayeid Xo19d
*sTUNUUWUOD XTUINJOD
‘valu XIpPlag

‘snjnut sndosey
*sH[VoOIN OVI}AT,

*X11J9} OVI}O J,
‘shjuMe Injziny,

‘svuce equinjod
‘snqunyed vquinjod
*IOJVAIIS SNDII]Y
“JOSULSIOU SNSIIPY

"eOSHy V|NSI[N
*BIDIU VINDI[N

*stiqeqoads viazeW0Sg

*RUUISST]JOU VITO}
"SI[BIOR[S Vplaie py

‘uolone]s vpnsury>
“RILVUL VpNSI[UT
*B}VISIID VINSIN
*RULIIJ VINSI[N

‘adojaued svuy

x i ex

xX XXX y X

M
MA

DAG Anon on
xX XX XX XK

x
x

M
M

NM
M

Secale
Be BS
XX |x
mex
xX ile
4 Peell pax
Wass Sx
Laxq
Ne 8
alee
xX eX
SS NS Ibs ox
M M
Nien cae
M M
M M
s
M xX X
M M
ANE \e33 es
M M
De SS ox
M
aS ll Se 58
So Be |b bse Se

x
x

xX XXX
x X XX

x
x

x
x

x

xXx X XX

x X

IZ
1Z

ol
ol

§99
£9
Te

W
x xX
M

M
M

XX |XX
s x X
xX X |X X
xX | XX
Xx X1XX
O1UT
xX X
x xX
x X
Ss Ss
XX |XX
s x X
W x X
> i, ial PPG
M xX X
M
M M
M x X
M
M M
s s
XxX |XX
M M
M M
M M
M x X
M
M | X X
A
PSP Paw llc 245

xX XX XK XK XK
XXX XXX

snonenbe snqyeyy
“ TuOT]Ieq xo.179
euvz10d xa19
** stsuajyeid xo19
SIUNWIUOD xTUINJOD
** BaIOUID XIPIO

**snjnut sndosv’T
sn]][vsom ovaja J,

“* XE1}9} OvIjaT,
“ snjzLine anjiny,
*** VIAIT BquIN]OD
** svua equinjod

snqunyjed equinjog

JOPAIDS SNBIIPY
JSULSIAW SNB19 py

‘ wosny vpNSIN 7
* BADIM BINH

stjiqvjoads eriajyew0s

CUIISST[|OW LIID}VUIOG
SI[VIOV]S eploavyy
uorne|s epnsur[D
BILMVUL BINSI[N J
BJVISHO VjVOTN

*' BULIOJ VMOTN AT

‘+ adojaued svuy

122

THE’ MIGRATION OF BRITISH BIRDS

*xeusnd sojyyovyN

elude SLIpleD
*snynUuvo VOUT],
CUTIVE VSUTAT,
eurldye vsuly,

“ejnurtjes xedojoog
‘osvures xedojoos
"gjoorsna xvdojoos
‘snoioqaiaddy sndoivpey
*B]9OOAL VAJSOIAINIIY

*sndarvijso sndoyewma yy]
*saidaaqur seytsda14g
‘snjv]sHo snyjoue A
‘sI[eranyd snipravyy
*‘snuvijuvo snjrydoyersyy
"eoTyVIY SICH
*SnIJIULIOWL svTULOAPN

‘epIv} SO

*STUNWIWOD SsnIr)
"BIL LOIN
*sndo1oyo vnury|ery)

*“SH1IDdS

PROG oes o-} Niebas up. 5 If esSiiead ([Messaras

W W Ww W
Ww W Ww W
M M M MS, || 225%
M 7 eae [as cabal In abl bc
M M M Me lexex
M |X X|iX Xld XX} X X
éX X\d X X > SPS > ap 4 Pens
x X
x X xs. hy oS KK
xX X EX Pine aS xX X x X
MW MW Ww xX X x xX
xX X x X x X x X Po Pes
MW | MAW | MW | X X | X X
xX X xX X x X x X x xX
W W Ww Ww |x x
W W W W |xx
Ss Ss xX X XxX X EK
098
W WwW W w | xx
x X Pres x X xX X x X
x X xX X PG OS xX X Ko
z
Shall Sete Eva dh istee lie
5 = S| Z ts
< rail Pes |oaeer cas
=) 4 > a CA
5 5 Z in .
Z ?

1Z

1Z
1/4

IZ
_oL
199

1Z

Ue
1Z
§99
iL

1Z
1Z

“SLINIT NYAHLYON
“VIAVYNIGNW)OS

x X XX

x
x

x

xX XX xX

“AVMUON

ae ee

x XX

x
x

x X
x X

nn e

“SANVTLAHS

W
xX X
xX X

“SAANMYO

W
XX
Ww
x XxX
youn
Ww |
os
D <a>, 4

x xX
Ww

Ww
MN

4x]
xX X
MW

“ANVTILODS

ANV TONGA

xvudnd sajayovyy

eLeUaIv SUple9

snjnuvo vouL yf,
BUTLIVU VOUT TY,
‘ eurdje vou y,

enuiyjes xedojoog
osvurjed xedojoos
ejoonsni xvdojoos
sige snazoqiaddy sndoivjey gq
£}JOIOAV VIJSOITAINIEY

eee wee

snde[erjso sndojeua yy
saadaojut svptsdasys
snyv}slio snpjeuv A,
‘ stqerantd sntpeiryd
snuvijuvo snprydoyerssy
BINDIILIY SHILIO GY
SnpJeULIowW svIMOIpNy

eee

a epiv} sNO
STUNWIWOD SnId
VIZL VIN
sndosoyyo vpnurjesy

wee

*SaIDadS

123

IME

THE GLACIAL RANGE CONTRACTION,

*snorjoiw snqwos
*BOIJOAV VINIIIJCAY
*a[[AIS BIE)

*Q]10.1] BII/)

"TTB SNNS.AI JA

“epdo} BolT W

*TUOPN SNIAV1OIIA}S
*TUOSPIVYIA SNIIIOII9}S
*SOJIVYAIVJVI SNLAVIOIII}S
‘snpAjouply snav’yT
‘snoneys shiv]
*SHULIVUL SIv'T
*snosny snie'y
*sn}vjUadIV SHIv'T
*snuvo snie'y
‘snpunqIpu snieT
"ENUIUL VUII}S
"BOIJOIG BUII]S
“OpuniIY UII}
“eidsvo VUIa]S
“eoeTJUVS VUIO]S

"BOI SUB BUII}S
*eISIU UOpIyayoompA FY

‘sndoxwyd sntusun
*eyenbiv sniuacn
“BINULTAW BSOULL'T
*SI}JO[S snuvj}O f,
*snosny Ssnuvjo
*SLIPI[vo SnUvO J,
‘sndo1yoo snuv}o J,
*BlOIIV[S SNUL}O f,
*snonajoddy snuvjoy,

SBaAaaAS

M

M
M

dM

s<
>
ian 3

a.

PS oS) Pas end Ov 5 eS UeAS

ee GIG DR IOS OOK, 2S

x xaax
Bie et

M
M

DS Pe Ons CAS Das
xX XX XX

x
x

x
x

x
x

x XXX XK XK KX XK
x XX XK XK KK XK

lf
IZ
ui/é
1Z

iff
1Z

IZ
1Z
14
1Z
IZ
if
6S

xX XXX
Meta ne.3

x

xX XX XK XK XK
XX KX XK XK X

xX XX XK xX

xX XX XK X
PIES SASS BAS ASI

xX XX XK XK XK XK

x
x

M

X XXX XK XK XK X
XXX XK XK XK XK X

x
Xx

‘ss snorjorv snquidjoa
wes BIT}OIB B[NIIIJCLT
9g se oad v1

a]Io vy)
oe “* oT]e snnsiayl
ee rite Bp1l0} VITVW

*** TUOWJNG SNIIVI0II9}G
TUOSPACYITI SNIIV10II19}
SOJIVYATVJVI SNIIVIOIIO]G

a snjAyoepiy sna’
Gou " snoneys snivT
oes "* SHULIBUL SHIT
oe ‘ snosny sniv’T
a8 snjyvjUeoIe snie’y
Oe “* snued snieTy
He snpunqIpit snieTy
ne “"* BINUIL BUIO}S
Ee "* BOTJDIB VUIDIS
ays *“OpunITY vU1a}S
ar " erdsvo vulas
oy BOVIJULI VUIO}S
one "* BOT[SUB VUII}S

"* BIS WOpTpayooIpA Fy

* sndoayd snruown
siole eyenbre sntusuin yy
see eINUL[OW BSOULT
OG ***SI]]0[5 snuv}o J,
ni0 *** snosny snuejo y,
aus slIpljvo snuvjoy,
ace sndoiys0 snuvjo J,
000 BIOSIS SNUL}O J,
*** snonejodAy snuvjoy,

Y
&
=
:
S
fe
gQ
ky,
1)
ee
9
8
:
S
=
Q)
.

124

“IOUIA UT IoTSBeNS Ms f posig pure ; tee
JOJUTAA X XM £07 JapFSeIS ¢ f sOUTAA pu VONVATTY WAL { UONLISTPY UO W ¢ AOZISTA TOIUTAA M + Spot SOYIUSIS SX X OMT —"ALON

‘TYOVo] VIIV]JoNOIg | M M M M x |e 7 oe TpIVIy VIULIJIIOI
‘eoloejod viieyja001g | M M M M SEK |S Se eS voisejod viieyja001g
‘wnsopsue snuyng | AX M | MA M Ta\ee| fesse Gat | os een esd gi | oadaera Say Pena ‘* wumiojsue snuggng
Ss

‘rout sdaoipog | x x |x x|xx]|xx|xxP zopxx}| Mm [xx] xx) xx)" A Jourw sioed
‘snynuioo sdesipog | M | M | M | xx] xx gorxx | m | M | A] M ae prloares s poreea
*sijjoolisiu sdastpog | x x | xX X | x X [ex x s S s Ss < StJOOLS1U sdooHeed
*SIT]OO' IQns sdooipog | M |X xX|xxX|xx {xx £99 s Ss M AM s: es sijeeugy pe ae!
‘snyvysiio’ sdaoipog | X x | x X | xx |x x] x x xx eo snje}su9 sdao1pog
; : LS mM
= eee
‘syfeuorquajdas snquéjod | a | M | M M{|xxi] owlyxx|xx|xx|xx)] M steuorjuajdas snquixjop
= | a ee es 2
= 26 v
wo = es iS} a 3 > Z is 2 a s
@ o Qa 8 = m2 ° res ° a
i 3 aI 2 Boy poy 2 . 2 < c *saldaas
*SsaIDadsS 9) iS a = c gs 2 sg Z iS 2
ot > S > Z ie3] >
S Z = is 2 nb > Z 2 Z Zz
= 9 e A = ae eee 5 PA fe I
s sin 2
j Kd

THE GLACIAL RANGE CONTRACTION, ETC. 125

The above table brings to light some profoundly
interesting facts. Taking France and Germany, say, as
our base, the symbols attached to the various birds on
the left side of the table indicate the emigrations of
these species in the British Islands, or entirely across
that area to Norway; whilst the symbols attached to
the same species on the right side of the table indicate
the emigrations of other individuals of the same species
across Belgium and Holland to Denmark, Sweden, and
Norway in that direction. These latter symbols may
also indicate emigrations from more southern areas east
say of E. long. 10°. The table contains 211 species.
Ninety of these have unquestionably reached Scandinavia
by Emigration across the British area, as well as by way
of Belgium, Holland, and Denmark, as is proved by the
present lines of Migration followed by those species, but
in a few cases the palpable scarcity of the migrants
across our area shows that the dominant line of north-
ward extension was continental, The White Wagtail,
the Black-tailed Godwit, the Crane, and the Sclavonian
Grebe may be cited as instances that confirm this, The
northern Emigration of a very high percentage of
individuals, however, was continental. No less than 85
species have undoubtedly reached Scandinavia by way
of Belgium, Holland, and Denmark only—a fact which
is proved by the absence of those species from the
northern portions of our area, or their northern extension
on both routes not being sufficient to render it by any
possibility continuous at its highest limits. Continuing
the analysis still further, we find that only three species
have succeeded in reaching Scandinavia—or rather
Norway only—by an emigration across our area, a fact
which is proved by the absence of such species from

126 THE MIGRATION OF BRITISH BIRDS

Sweden. These are the Twite, the Pied Wagtail, and
the Rock Dove. We also find that the emigrations of
twelve species have only extended as far north as Den-
mark ; whilst five have only reached the southern shores
of the Baltic. Of these latter, however, it is interesting
to note that no less than four are represented in the
more northern latitudes by closely allied forms from
which it is very doubtful whether they are specifically
distinct, except in one instance. These are the Night-
ingale, represented in Scandinavia and Denmark by
Erithacus philomela, the Dipper in Scandinavia by Cznclus
melanogaster, the Bullfinch in Scandinavia by Pyrrhula
major, and the Carrion Crow by Corvus cornix. Two of
these birds are practically sedentary, their migrations, if
any, being limited ; the Nightingale is a migrant, but its
line of passage is south-east, which almost completely
isolates it from the western race &. /uscinia. Of the
twelve species that only reach Denmark, one is repre-
sented further north by a local race, viz. the Nuthatch,
whose Scandinavian allied form is Sz¢ta europea. Again,
but ten species have extended their emigrations across
the British Area toa higher limit than they have done in
West Continental Europe. They are the Nightingale,
the Gray Wagtail, the Lesser Redpole, the Chough, the
Carrion Crow, the Lesser Tern, the Great Skua, and the
three species of Petrels—all, save one (the Carrion Crow),
it may be remarked, thoroughly western types. On the
other hand, no less than 74 species range lower in our
area than in West Continental Europe. It is to my
mind an astonishing fact of distribution—taking into
consideration the mild climatal conditions of our isolated
area, encircled as it is by the warm waters of the Gulf
Stream—that so vast a percentage of species should

PE GEAGIAL RANGE CONTRACTION, ETC. “127

range higher in continental Europe than they do in the
British Islands. In many cases the difference of northern
limit in the two areas is enormous ; and curiously enough
some of the most striking examples are to be found
amongst such delicate species as the Thrushes and
Warblers! Our Missel Thrush and Song Thrush are
by no means dominant birds in Scotland, yet in Scan-
dinavia they range up to the Arctic Circle ; the Redstart
is only locally distributed in Scotland, but in summer it
ranges in Norway to the North Cape, the Arctic land of
the midnight sun! The two species of Whitethroat are
decidedly rare and local north of the Border, yet in
Scandinavia they are regular summer visitors up to
lat. 64°; whilst the Garden Warbler, local even in the
south of Scotland, prolongs its migrations to the North
Cape in Norway. The Sedge Warbler,! too, goes as far
north in summer, yet does not range as high in our area
to breed as the Orkneys. The Tree Pipit is rare north
of the Clyde, yet is a regular summer visitor to the
extreme north of Norway, fifteen degrees of latitude
higher. Even the delicate fastidious Wood Lark—a typical
English species—ranges up to lat. 60° in Scandinavia.
The Swift does not breed in the Orkneys, yet does so in
Scandinavia in lat. 70°; the Wryneck, unknown in Scot-

1 The Sedge Warbler is said to be absent from the south of
Norway, which is strong evidence that the species entered that
portion of Europe from the south-east, and not by a northern
emigration or range expansion either up what is now west conti-
nental Europe, or across the British Area. From such a South-
eastern base an extension of range southwards or across a wide
water area would be necessary for the species to enter south
Norway—a line of emigration contrary to the law of its dispersal.
Very similar remarks apply to the Wood Wren, which is absent
from Norway altogether, yet breeds in Sweden as far north as
Upsala.

128 THE MIGRATION OF BRITISH BIRDS

land, goes up West Europe to lat. 64°. The three
Woodpeckers only known to breed in England in the
British Area penetrate in Scandinavia to lat. 63° (Gecznus
viridis), to the Arctic Circle (Pzcus major), and to lat.
70° (Picus minor)! The Kentish Plover only breeds on
the south coast of England in our area, but on the
Continent it visits the south of Sweden for that purpose.
The Ruff formerly bred in England—there is no evidence
to suggest that it ever bred further north in our islands
—yet it goes in summer as far north as continental land
extends in West Europe. Even such hardy aquatic
species as the Black-throated Diver and the Common
Tern breed no further north in our area than the
Scottish mainland, perhaps in the Orkneys, yet the
former is found in Scandinavia to the highest limits,
whilst the latter reaches the Arctic Circle.

What is the explanation of these apparently anomal-
ous facts? We have already seen that birds are loth
to extend their emigrations across water areas, and we
might reasonably assume that our isolated position was
a check to any considerable increase of northern range
in that direction ; but I am convinced that these won-
derful variations in the northern limits of so many
species are not due to such a cause. After a prolonged
and careful study of the facts, I consider that this dis-
crepancy of distribution is entirely due to the dominant
line of Emigration followed by these species. The
range base of the vast bulk of the individuals of these
species breeding east say of E. long. 10° was in the
south-east during the Glacial Epoch. Their normal
line of Post-Glacial Emigration north and north-west
from that Range Base or Refuge Area (III.) would
therefore be entirely beyond our limits. The i dividuals

THE (GEACIAE LANGE CONTRACTION, ETC, 129

breeding in our islands refuged in the south-west (I1.)
were fewer in number—as has previously been sug-
gested—and they winter at their ancient base where
they refuged; the ancestors of the individuals of the
same species that range so high in Scandinavia had
their Range Base in the south-east, and they migrate
in autumn south-east towards that ancient refuge area,
none of them normally visiting the British Islands or
South-west Europe at all. Fortunately one or two
species prove, even to demonstration, that a vast emigra-
tion of birds did take place in this direction. The Blue-
throated Warbler (Arzthacus suecica) breeds in Scandi-
navia, passes Central and South-eastern Europe on
migration, and winters in North-east Africa, south to
Abyssinia. The Eastern Nightingale (Ercthacus philo-
mela) breeds in Scandinavia and Denmark, passes
Central Europe on migration, and winters in North-east
Africa. The Black-throated Diver (Colymbus arcticus)
breeds in Scandinavia and the Baltic Provinces, crosses
Iurope in a south-easterly direction on passage to its
winter quarters in the Black Sea, occasionally wander-
ing south to the Italian lakes, the Adriatic, and the
Mediterranean. I may here remark that Mr. George
Lindesay, in his very interesting paper, ‘‘ Rambles in
Norsk Finmarken” (Fortnightly Review, November
1894, p. 674), observed and recorded this strongly
marked direction of the migration of birds in spring
to that area. He says: “Like most of the true birds
of passage, these small birds reach their northern
breeding-ground from the East, coming by way of
Russia and the Baltic Provinces.”

Many of the species tabulated above have ceased to

breed in our islands, some only in the extreme north of
K

130 THE MIGRATION OF BRITTSH BIRDS

them, but they unerringly indicate the line of their
Emigration across this area in earlier ages, when they
undoubtedly did so, by visiting us on passage or re-
maining with us during the winter. There is also some
indication—if now slight—of birds passing along some
of our southern coasts (where the Channel is narrowest)
on their way north to Denmark and Scandinavia—
descendants probably of birds whose emigrations ex-
tended up the Channel when that area was an ancient
land surface, a great river valley.

Before leaving this portion of the subject, it is
necessary to make a brief allusion to an ancient line of
Emigration from the British Islands eastwards into
continental areas. We have already dwelt upon the
probable condition of the North Sea Area during early
Post-Glacial time. That this area at no very remote
time, comparatively speaking, was a broad plain watered
by a central river flowing into the Arctic Ocean between
the Shetlands and Norway, and receiving as its tribu-
taries not only our own eastern rivers but those of
West Europe north of Belgium, there can be no reason-
able doubt whatever. This plain was probably well
wooded, studded with lakes and swamps, and in every
way suited:to the requirements of great numbers of birds,
especially the earliest colonists from the south after the
third glacial period had passed away. We have also
every reason to believe that, owing to the influence of the
Gulf Stream, West France, the English Channel (then
dry land), and the British Area were able to support
arboreal species of birds long before the North Sea
Plains, Belgium, Holland, West Germany, Denmark, and
Scandinavia were in such a condition, owing it may be
to the land connection between Scotland and Iceland

Bie IGhACTAL RANGE CONTRACTION, ETC. 13%

keeping out the warm currents, and the English Channel
and North Sea being then a continuous land mass.!_ With
the return of the more genial climate birds soon began
to emigrate from the southern Refuge Areas (I. and II.),
following the retreating ice and snow-fields north; so
that by the time the climate of the North Sea Plains
and West Continental Europe was sufficiently genial, a
dominant resident avifauna chiefly composed of hardy
species was already established in our area. With the
growth of vegetation on this prehistoric plain and in
West Europe the birds began to extend (or in other
words to emigrate) their range east across that area.
The climate, however, was too severe in winter to allow
of these birds becoming resident ; they merely migrated
in spring further and further east each century to breed,
coming back in autumn to winter in the mild climate of
the Gulf Stream laved west. Conditions favourable to
successful colonization and increase in Europe continued,
and these West to East migrants multiplied accordingly
spreading east and north-east across Europe even to
West Asia, yet compelled by the severer climate of the
north and east to return west every autumn. But
gradually the sea began to encroach upon the land ; the
plains between the Continent and our eastern borders
slowly became more and more water-logged as sub-
mergence went on, and the great central river valley
became perhaps a fjord, which, however, the eastern
migrants found no difficulty in crossing. Slowly each
century this ocean inlet became wider; the water

1 We must also not overlook the fact that the fourth Glacial
Period—the epoch of the Great Baltic Glacier—which did not affect

our area or the continental lands adjoining it to any great extent,
must have had a vast influence on the emigration of species.

132 THE MIGRATION OF BRITISH BIRDS

passage more prolonged, but the migratory birds with
unyielding persistence continued to cross and re-cross it ;
until in the course of ages the North Sea occupied the
land, and the contour of our islands and the opposite
continental coasts gradually became as it exists to-day.
Birds continue to migrate in countless hosts across this
wide sea-passage, their ancestors having done so in the
remote past when dry land replaced the sea; and no
single generation of birds has been able to notice any
portion of the vast change which centuries of submer-
gence has accomplished. This is a sufficient explanation
of the wonderful migration which takes place in spring
and still more marked in late autumn across the North
Sea to our islands now. The principal species that
have emigrated in the past by this route, and which
continue to migrate along it in the present, are specified

below.

Species whose lines of Emigration from our
area extend both East and North-East.

Species whose lines of Emigration from our
area extend East alone.

Merula merula.
Erithacus rubecula.
Regulus cristatus.
Fringilla chloris.

Turdus musicus.
Pratinola rubicola.

|
Turdus viscivorus.
|
Accentor modularis.

Parus ceeruleus. | Fringilla ccelebs.
Parus major. Sturnus vulgaris.
Troglodytes parvulus. Corvus monedula.
Fringilla carduelis. Corvus cornix.
Linota cannabina, Alauda arvensis.
Passer montanus. Asio brachyotus.
Emberiza miliaria. Columba palumbus.
Emberiza citrinella. Vanellus cristatus,
Emberiza schceniclus. | Grus communis.
Garrulus glandarius. Cygnus olor.

Corvus corone.
Corvus frugilegus.
Accipiter nisus.
Otis tarda.
Podiceps rubricollis.
Jotaurus stellaris.

ee

PEGI Gil. RANGE CONTRACTION, ELC, 133

Of the species whose lines of Emigration from the
British Islands extend East alone, not one, it may be
remarked, has succeeded in extending its breeding range
across our area to Scandinavia. They are all species
whose northern breeding range in the British Isles does
not reach the Shetlands, or in the few instances in which
it does reach that locality, the evidence distinctly shows
that they have only done so within recent time. It is
therefore more than doubtful whether any individuals of
these typical Eastern migrants come from continental
areas north or east of the Baltic, or south of Holland.
From how far north in Russia these eastern migrants
may come it is at present impossible even to conjecture.
That the line of Emigration, however, extended into
Western Asia, say as far south as Orenburg, is to some
extent proved by the odd individuals of thoroughly
eastern or Asiatic species that from time to time get
into this western stream of migration and abnormally
turn up on Heligoland, in the British Islands, and else-
where. It may also be remarked that few, if any, of
these typical Eastern migrants are dominant during
winter in the extreme south of Europe, still less so
across the Mediterranean, where some of them are
replaced by nearly allied species or races.

Of the species whose lines of Emigration from the
British Islands extend both East and North-east, it is
significant that in every case they are birds that have
reached Scandinavia by both routes, as is proved by
their breeding dominantly in the Shetlands, and by
their passing our entire eastern area on migration. It
is, however, worthy of remark that in many, if not in all,
cases the North-east migrants are the first to visit us,

134 THE MIGRATION OF BRITISH BIRDS

the Eastern migrants being later in their arrival. Were
it only possible to separate the individuals, I think we
should find that so far as the typical Eastern migrants
are concerned, they all journey practically about the
same time, and come from the same areas. I think this
phenomenon of an East to West migration in autumn
will also explain why such species as the Crane (Gras
communis), the Bittern (Lotaurus stellaris), and the
Great Bustard (Otzs tarda), are now only winter visitors
to our islands. All these species a century or so ago
were common summer visitors to the British Islands,
the individuals breeding in our area migrating south in
autumn to their accustomed winter quarters; but on
the other hand, our islands were visited in winter by other
individuals of these three species that were returning to
their old quarters, from whence their ancestors emigrated
East in past ages, and which they continue even to the
present day to regard as their winter home. Several
other instances confirming the above remarks might
also be given.

Singularly enough, the individuals breeding in the
British Islands of many of the species (perhaps of all)
tabulated above migrate south in autumn, their places
being taken by these migrant individuals of the same
species from the east. This seems to be a strangely
anomalous fact, yet it is one that shows how very com-
plicated the whole subject of Avian Migration undoubt-
edly is. As I said in the Migration of Birds (p. 248), I
am strongly disposed to think that Temperature has a
good deal to do with this very complex movement.
Besides, there can be no doubt that the individuals of
these species that breed in Britain are later arrivals in

S——EeE—eeeEeEeEeEOeeEEeEEeEeEEEOeeeEeEeEeEeEeEeEeEeEeEeEeEeEeEeEeEeEeEE EE ————

BIE GEACIAL KANGE CONTRACTION, ETC. 135

our area from the south, later emigrants, more delicate
of constitution, and requiring a higher winter tempera-
ture than the descendants of the earlier emigrants of
these self-same species that reached us, it may be,
thousands of years before, when the climate was much
more rigorous, and which, as we have seen, extended
their breeding range into the colder regions of the North
and East, after having become thoroughly acclimatized
to our winter temperature by long residence therein.

I may also remark that no birds wintering exclusively
south of our area follow this route, a fact which seems
to prove that our islands were a base of ancient Eastern
Emigration from which resident individuals alone
extended their area east. By the time most of our
Summer Migrants had reached us, the North Sea had
‘probably established a fatal barrier to all Eastern
Emigration of southern forms in this direction. Nota
single Warbler, in fact not a single Passerine or Picarian
species that now visits us only in summer to breed, is
by any strange chance observed normally to follow this
East to West migration in autumn, or West to East
return passage in spring.

Want of space and time, and the sad deficiency of
more exhaustive information, I regret to say, prevent me
from entering into greater detail concerning this particu-
lar line of Flight, which I may add possesses a singular
fascination for me. The subject is too vast and too
complicated to be exhaustively treated in the present
volume, and in the existing state of our knowledge, but
it is a portion of the science of Avian Season Flight
that will have to be faced and thoroughly exhausted
in the near future.

136 THE MIGRATION OF BRITISH BIRDS

We will now proceed to analyze a little more closely
the distribution of birds within the limits of the British
Archipelago, and to ascertain whether the same laws,
the same general conditions of dispersal, have similarly
exerted their influence on the range of species in our
area, as we have already learned they have governed
the distribution of birds elsewhere. We have already
seen that the ultimate isolation of the British Islands
from continental land has had a marked effect upon the
distribution of terrestrial animals ; and in like manner
the isolation of Ireland from the greater land mass of
England and Scotland is significantly indicated by a
similar disparity in its mammalian and reptilian fauna.
I have in the present volume repeatedly insisted upon
the aversion displayed by birds to extend their emigra-
tions, or to increase their range across wide water
areas. Instances innumerable in all parts of the world
might be given in support of this assertion, but for
the present purpose we will confine our confirmatory
evidence to the species composing our own avifauna
alone.

As I have already attempted to show, the land mass
of Ireland became isolated from England before Eng-
land itself became detached from continental land.
There is some evidence to suggest that the north-east
of Ireland continued to be joined to South-west Scot-
land for a much longer period, but as I hope presently
to demonstrate, this connection was of no service in
assisting the emigration of birds or animals to the Irish
area, although it may, and probably did, help them on
their emigrations northwards. The Law propounded at
the beginning of the previous chapter emphatically

i

———

LHE GLACIAL RANGE CONTRACTION, ETC. 137

forbids such a line of extension. Professor Geikie
(Prehistoric Europe, pp. 511-513) very rightly remarks
that “the Scandinavian type in the British Isles, as is
well known, attains its greatest development in the
Scottish Highlands. It is less well represented in the
southern uplands of Scotland, the hilly districts of
Cumberland, and the Welsh mountains, while Ireland
shows a very meagre assemblage of alpine and sub-
alpine forms. The Germanic type, on the other hand,
is everywhere present, overspreading the other floras
and giving a general character to the vegetation.” As
the late Mr. Forbes wrote: “Its scarcer forms are of
much interest, from the clear manner in which they
mark the progress of the flora and the line it took in
its advance westwards. Thus we find a number of
species which are still limited to the eastern counties of
England, while others, which have extended over con-
siderable tracts or into several districts of England or
Scotland, have not found their way to Ireland. It is
remarkable that ‘certain species of this flora which
flourish best on limestone ... are not found in the
limestone districts of Ireland, and in like manner cer-
tain species which everywhere, when found, delight in
sand ... are also wanting in such Irish localities as
are best adapted for them. The fauna which accom-
panies this flora presents the same peculiarities, and
diminishes towards the north and west. This is very
observable both among the native vertebrate and
invertebrate animals. Thus, among quadrupeds the
mole, the squirrel, the dormouse, the polecat, and the
hare (Lefus t2midus) are confined to the English side
of St. Georges Channel, not to mention smaller quad-

138 THE MIGRATION OF BRITISH BIRDS

rupeds. So it is also with the birds of short flight ; so
most remarkably, no less than half the species being
different, with the reptiles; so also with the insects and
the pulmoniferous mollusca.” Professor Geikie, in criti-
cizing Forbes’s remarks, continues: “ These peculiarities
of distribution Forbes has accounted for by supposing
that Ireland was separated from England by the influx
of the Irish Sea before the species, less speedy of dif-
fusion, could make their way into the sister island, and
this view has been repeated by every writer who has
touched upon the question since the appearance of
Forbes’s famous essay. Buta glance at the Admiralty’s
chart of the Irish Sea shows us that there is no necessity
for inferring that the arrestment of the migration [emi-
gration] was due to submergence. Were the whole
British area to be elevated for six hundred feet or
thereabout, the Irish Sea would disappear, but Ireland
would still be separated from England by a great and
deep lake, averaging twenty-five miles at least in
breadth, and extending from what is now the Sound
of Jura in Scotland down through the basin of the
Irish Sea to a point between Braich-y-pwll in Car-
narvon and Greenore Point in Wexford. This lake
receiving the tribute of many Scottish, Irish, and Eng-
lish streams, would discharge a broad river from its
lower end, which might well be impassable by many of
the smaller vertebrates. That it was rather the pre-
sence of this lake and the obstacle of the Welsh
mountains than the premature appearance of the Irish
Sea which arrested the westward migration [emigra-
tion] of plants and animals, is shown by the remarkable
fact pointed out by Professor Leith Adams that the

THE GLACIAL RANGE CONTRACTION, ETC. 139

mammalian fauna of Ireland agrees more closely with
that of Scotland than of England ; while Dr. Buchanan
White has shown that Ireland has probably derived
some of its alpine lepidoptera from Scotland. We may
suppose that the temperate mammals gained admittance
to Ireland from the west of Scotland, between which
and the north of Ireland there was a broad land con-
nection. Some of the larger mammals, however, such
as the great Irish deer (Cervus megaceros), may quite
well have entered Ireland from the south, crossing the
river that flowed south through St. Georges Channel.
But it may be questioned whether the reindeer immi-
grated by the same route. So far as the geological
evidence goes, we have no reason to believe that at the
commencement of the Post-Glacial period the British
area was much more extensive than it is at present.
_ The sea was then retiring, as we know, from the low
grounds of Scandinavia and Scotland, and from the
borders of East Anglia, and thus the probabilities are
that when the Scandinavian flora had commenced its
northward advance St. Georges Channel still separated
England and Ireland. This being so, the reindeer
could not at that time reach the latter country. By
and by, however, the Irish Sea gradually disappeared,
and a land connection took place between Scotland and
Ireland, across which the alpine and sub-alpine flora and
the reindeer would migrate [emigrate]. It is perhaps
owing to the late appearance of this land connection
that the Scandinavian type of vegetation is so poorly
represented in the Hibernian flora. The climate we
may suppose was already becoming milder, and the
high alpine forms were gradually vanishing from the

140 THE MIGRATION OF BRITISH BIRDS

low grounds, so that only a few of these could make
their way south into Ireland.”

The first part of Professor Geikie’s remarks very
forcibly suggests that early Post-Glacial Ireland formed
one land mass in the south with England, and thus
presented no barrier to the emigration to that area of
the various alpine and sub-alpine floree (and of course
the hardiest species of birds), relics of which flor exist
there down to the present time. But as the climate
moderated, this flora, which sought and now occupies
a congenial habitat on the Welsh, English, and Scotch
mountains, would to a very great extent disappear from
Ireland, owing to the absence of such suitable mountain
haunts; and this flora was, as we know, (and still is)
replaced by the dominant and southern Germanic types
which must also have entered Ireland Jefore the con-
necting land masses in the south disappeared. The
fact insisted upon by Professor Geikie in support of
some of his views, that the mammalian fauna of Ireland
agrees more closely with that of Scotland than with
that of England, is due entirely to the smaller amount
of competition to which that fauna has been exposed by
the invading Germanic or southern types which have
established themselves in England so dominantly,
together with the later appearance of that fauna in
England, when the difficulties surrounding emigration
to the Irish area were rapidly increasing, or perhaps
almost insurmountable, due to progressing submergence
and widening of the water ways, as well as to the
similarity of climate and general conditions between
Scotland and Ireland. Singularly enough, Professor
Geikie shortly afterwards states that so far as the floras

EEE :—

PEE GLACIAL RANGE GONTRACTION, ETC. 4%

are concerned, that of Hibernia is very poor in Scan-
dinavian—and by inference Scotch—types. Again,
Professor Geikie supposes that the temperate mammals
as well as many alpine forms of plants, etc., reached
Ireland vzé@ the west of Scotland, when a broad land
connection existed between the two areas,—but what
evidence, I ask, is presented by birds, creatures even of
flight to which a water barrier seems ineffectual, that
any such line of extension was followed? None, abso-
lutely none whatever! As we have already had abun-
dant and convincing proof, and hope still to have more;
the emigration of birds to our area has been from the
south, south-east, or east; not a single species has
entered it during Post-Glacial time from the north, nor
increased its range across it from that direction. One is
astounded to read of Professor Geikie insisting upon a
descent into Ireland of alpine forms from Scotland to
account for their scanty presence in that country. Rather
must we look upon these types as relics, not as the result
of abortive and abnormal emigration, but of the domi-
nant flora that in early Post-Glacial time held the land
until a changing climate destroyed its predominance :
relics I may say that to my mind beyond all doubt
demonstrate that St. Georges Channel and the English
Channel were dry land when the Post-Glacial Emigra-
tion north of the earliest flora and fauna took place.
It is impossible to have a southward extension of range
progressing concurrently with an amelioration of climate.
The very fact that species are advancing north with
favourable conditions north of them, and, of course, in
many cases, by inference, less favourable conditions
south of them, is a fatal objection to any such line of

142 THE MIGRATION OF BRITISH BIRDS

dispersal. Species would not range north of any area.
from which they were absent until conditions in that
area were less suitable, and therefore impossible for
southern extension towards it. The very conditions
that are driving species north, or attracting an emigra-
tion movement, are in like manner prevailing in other
areas immediately east and west, and thus rendering
impossible a southern emigration, or what is better
described as a retrograde movement.

One of the most intensely interesting facts bearing
upon this Law of Northern Extension is that of the
migration of birds in the valley of the Petchora. Messrs.
Seebohm and Harvie Brown, whilst stationed at Ust
Zylma in the spring of 1875, kept careful observation
on the migration of birds north along this river to the
North Russian tundras. They report (Rozdley’s Orn.
Miscell, 1876, i. p. 245) that “there can be no doubt
that Ust Zylma lies somewhat out of the line of migra-
tion.” These gentlemen give a list of no less than 13
species of birds that were all common summer migrants
to the tundra, yet did not pass this station on the great
river. The reason for this is obvious. In the first place,
we must keep in mind the fact that the present line of
Migration of a species follows the past line of Emigra-
tion or range extension of that species, and that this
emigration never takes place in the Northern Hemi-
sphere in a southerly direction (conf. p. 60). If we refer
to the map, we find that the Petchora, in very nearly
north latitude 66°, takes a sudden trend to the south-
west for nearly 150 miles; amounting in the aggregate
to as much as 50 miles south of north. Birds, then, in
emigrating into North Russia from the south-east, and

THEY GLACIAL RANGE CONTRACTION, ETC. 143

following the river valleys, would therefore have been
under the necessity of breaking the Law of their dispersal
by increasing their area south-west had they kept to the
river; but following the normal conditions of their
dispersal, they left the valley entirely at the apex of this
southern trend and began to colonize the tundras north-
wards. To this day their descendants miss the river
valley probably entirely, after reaching its most northerly
trend! These birds were all emigrants from South-west
Asia or South-east Europe. On the other hand, the
great body of migrants to the tundras did pass through
Ust Zylma, but they either did not follow river valleys
so closely (as for instance in the case of the Siberian
Chiffchaff), or most certainly came from more south-
westerly areas (couf. footnote, p. 127).

We will now endeavour to trace more minutely the
emigration of birds within the British Archipelago. We
will deal first with the species that are resident in the
British Islands. For the most part these consist of
hardy birds, numbering amongst them some of ‘the
earliest to reach our area after the third cold period of
the Glacial Epoch. From these early arrivals, as we
should naturally expect to be the case, the dominant
avifauna of Ireland has descended. They represent
species whose emigrations to the British Area took
place whilst that area was much more compact than
it is now; when St. Georges Channel and the English
Channel did not exist, and extension northwards and
westwards was not retarded or absolutely prevented
by wide areas of water. Our resident birds are
tabulated below.

144

Nore.— x signifies Breeding ; vl Breeding, but very locally ; 1 ditto,
w Winter pou ; VLW Very rare and local in Winter only.

but locally ;

THE MIGRATION OF BRITISH BIRDS

RESIDENT SPECIES IN

Pardus musicus (Sonp Thrush)

Turdus viscivorus (Misse! Thrush)

Merula merula (Blackbird)

Pratincola rubicola (Stonechat)

Erithacus rubecula (Robin)

Regulus cristatus (Goldcrest) ; oe
Sylvia provincialis (Dartford W arbler) wae
Accentor modularis (Hedge Accentor)
Cinclus aquaticus (Dipper)

Panurus biarmicus (Bearded Titmouse) ..

Acredula caudata rosea (Long-tailed Titmouse)

Parus major (Great Titmouse)

Parus ater e¢ ater britannicus (Coal Titmouse) .
Parus palustris (Marsh Titmouse)
Parus ceruleus (Blue Titmouse) ...
Parus cristatus (Crested Titmouse)
Sitta ceesia (Nuthatch) x
Troglodytes parvulus (Wren)
Certhia familiaris (Creeper)
Motacilla yarrellii (Pied W agtail)
Motacilla sulpburea (Gray Wagtail)
Anthus pratensis (Meadow Pipit)
Anthus obscurus (Rock Pipit)
Coccothraustes vulgaris (Hawfinch)
Fringilla carduelis (Goldfinch)
Fringilla chloris (Greenfinch)
Fringilla spinus (Siskin) ...
Fringilla coelebs (Chaffinch)

Linota cannabina (Linnet)

Linota rufescens (Lesser Redpole)
Linota flavirostris (Twite)... ‘
Passer domesticus (House Sparrow)
Passer montanus (Tree Sparrow)...
Pyrrhula vulgaris (Bullfinch)

Loxia curvirostra (Crossbill)
Emberiza miliaria (Common Bunting)
Emberiza citrinella (Yellow Bunting)
Emberiza cirlus (Cirl Bunting)
Emberiza scheeniclus (Reed Bunting)
Sturnus vulgaris (Starling)
Pyrrhocorax graculus (Chough)
Garrulus glandarius (Jay) ...

Pica caudata (Magpie)

Corvus monedula (Jackdaw)

Corvus corax (Raven)

Corvus corone (Carrion Crow)
Corvus cornix (Hooded Crow)

|
|
|

ee

SESE IR POM OS, Da ee Ra Sn one Ow

x X X

XX XK XK XK XK XK XK XK XK OX

=

< &
= °
z
x x
x x
Xx x
x x
x Px
x x
x x
x x
x x
x x
< x
x VL
< se
x
x L
x x
x x
x x
* x
x x
x x
x x
x x
x x
Xx x
x x
< x
x x
x x
i L
x x
x x
x x
x x
x se
x x
se x
x >
x x
x x
x *
x x
Ww x

|
|
|

IRELAND.

MX KK OK

x X

THE GLACIAL RANGE CONTRACTION, ETC.

SPECIES RESIDENT IN

ENGLAND,

Corvus frugilegus (Rook) ...

Alauda arvensis (Sky Lark)

Alauda arborea (Wood Lark) :
Gecinus viridis (Green Woodpecker) _ ...
Picus major (Great Spotted Woodpecker)
Picus minor (Lesser Spotted Woodpecker)
Alcedo ispida (Kingfisher) AG Bae
Aluco flammeus (Barn Owl)

Asio otus (Long-eared Owl) boc

Asio brachyotus (Short-eared Owl)

Strix aluco (Tawny Owl) .. Pe

Circus zeruginosus (Marsh Harrier)
Circus cyaneus (Hen Harrier)

Buteo vulgaris (Common Buzzard)

Aquila chrysaétus (Golden Eagle) dG0
Haliaétus albicilla (White-tailed Eagle)
Accipiter nisus (Sparrow Hawk)

Milvus regalis (Kite)

Falco cesalon (Merlin)

Falco tinnunculus (Kestrel)

Falco peregrinus (Peregrine)
Phalacrocorax carbo (Cormorant)
Phalacrocorax gracuius (Shag)

Sula bassana (Gannet)

Ardea cinerea (Heron)

Anser cinereus (Gray-Lag Goose)
Tadorna cornuta (Sheldrake)

Anas boschas (Mallard)

Anas clypeata (Shoveller)

Anas crecca (Teal)

Somateria mollissima (Eider Duck) wae
Mergus serrator (Red-breasted Merganser)
Columba palumbus (Ring Dove) 303
Columba zenas (Stock Dove)

Columba livia (Rock Dove)

Tetrao urogallus (Capercaillie)

Tetrao tetrix (Black Grouse)

Lagopus mutus (Ptarmigan)

Lagopus scoticus (Red Grouse)

Phasianus colchicus (Pheasant)

Perdix cinerea (Partridge)

Rallus aquaticus (Water Rail)

Gallinula chloropus (Waterhen) ... Soc
Fulica atra (Coot) ..

/Egialitis hiaticula major (Greater Ringed Plover)
Charadrius pluvialis (Golden Plover) aon
Vanellus cristatus (Lapwing) ...
Hzematopus osiralegus (Oystercatcher) —
Scolopax rusticola (Woodcock) ee

vy
Pas

W
w

OXON) ON Aon mON OM Owen, OS

XXX KX XK XK KX

WALES.

W
W

KOS, OX

xX KX XK XK X
.

SCOTLAND.

CK DRIER ON, Hor oes Otho

vs
m~ 2

DK SOK sXe One Oe OM ST OS

SKK, KK

xx
A ?

X XXX XK XK X

145

IRELAND.

Cae OS

xX XX

2
=

XXX XK XK XK

XKXKXXKXXKXXKXX

x x X

v
“~

xe

205025) OWEEAS aS CAS PS PT UPAS DA TEAS

146 THE MIGRATION OF BRITISH BIRDS

SPECIES RESIDENT IN

ENGLAND
WALES
SCOTLAND.
IRELAND

Scolopax gallinago (Snipe)

Tringa alpina (Dunlin)

Totanus calidris (Redshank)

Numenius arquata (Curlew) ss
Larus ridibundus (Black-headed Gull) 350
Larus canus (Common Gull)

Larus argentatus (Herring Gull) .. eal
Larus fuscus (Lesser Black- backed Gull) 5; (|
Larus marinus (Greater Black-backed Gull)... |
Larus tridactylus (Kittiwake) 5a
Stercorarius catarrhactes (Great Skua) ae
Alca torda (Razorbill)

Uria troile (Guillemot)

Uria grylle (Black Guillemot) :
Podiceps cristatus (Great-crested Grebe)
Podiceps minor (Little Grebe) B80
Puffinus anglorum (Manx Shearwater) ...
Procellaria leachi (Fork-tailed Petrel)
Procellaria pelagica (Stormy Petrel)

XxS2xxxXxxXSaXXXX*X
BYE oodas| S\Pabede var pve eal bydanve Byes 5.2

a

SOS XO IX
be

6 IKE Uta Sane iis ec antec

xX XX XX
], OR gS i Kk DR SOR IGN ECOSOC uM st LN NINOS RG HEDS

Notre.— x signifies Breeding; vi Breeding, but very locally ; L ditto,
but locally ; W Winter only ; vLW Very rare and local in Winter only.

Of the 115 species, tabulated above, that are resident
in our area, fourteen are entirely absent from Ireland,
whilst another eight cannot in any sense be considered
dominant in the island, but are excessively local. Now it
is a most significant fact that all these fourteen species
(with the solitary exception of the Eider Duck) are
confined chiefly to England and the extreme south of
Scotland, eminently southern species, not ranging north of
France in some cases, not north of the Baltic in others ;
or in the few cases of wide range northwards they are
birds strictly sedentary in their habits, and thus leave no
indication of former residence in Ireland (if such were
ever the case) by a line of Migration thereto. Further,
there can be no question whatever that all these species
were late arrivals, comparatively speaking, in the British

THE GLACIAL RANGE CONTRACTION, ETC. 147

Area, that their emigrations northwards and westwards
did not reach the west of England before the isolation
of Ireland had taken place, and a barrier to extension
in that direction formed; a fact which is absolutely
proved by the line of Emigration followed by those
species, which it will be found in no single case reached
Scandinavia by way of Britain. On the other hand,
nearly half of the species (45 out of 99) resident in
Ireland at the present time emigrated to Scandinavia
by way of the British Islands. The most probable
explanation of the one solitary exception of the Eider
Duck is the fact that Ireland is situated too far south,
and that suitable groups of small islets are not present
off the coast. Most of the resident species absent from
Ireland are birds that become rarer and more local in
the west of England or in Wales, and in at least eight
cases they are also absent from or very local in Scotland.
But three species are resident in Scotland and not in
England, all thoroughly hardy forms (Parus cristatus,
Corvus cornix,and Lagopus miutus); five species breed
in Scotland and Ireland, but not in England (although
at least three formerly did so). Seven species breed
only in England and Wales, but no species breeds
exclusively in Ireland. Of the 115 resident species in
the British Isles, 108 breed in Scotland, 107 in England,
or in England and Wales, and gg in Ireland.

Still more significant are the facts presented by the
Summer Migrants to the British Islands. These are
tabulated on the following page.

148 THE MIGRATION OF BRITISH BIRDS

NoTE.— x signifies Breeding ; L Locally; vi Very Locally; M On
Migration ; vLM Very Locally on Migration ; LM Locally on Migration ;
M x Chiefly on Migration, few Breeding.

e a |s
ae < a 4 A
SUMMER MIGRANTS TO 4 z 4 Ey
2) = & Q
4 = ° %
y 2 i=)
Merula torquata (Ring Ouzel) x x x x
Saxicola cenanthe (Wheatear) x x x2 x
Pratincola rubetra (Whinchat) x x oe x
Ruticilla phoenicurus (Redstart) ... aah osc x
Erithacus luscinia (Nightingale) ... x x
Sylvia cinerea (Whitethroat) 5, x | x x x
Sylvia curruca (Lesser Whitethroat) x x x
Sylvia atricapilla (Blackcap) is x x NAL,
Sylvia hortensis (Garden Warbler) x x <1) wae
Phylloscopus rufus (Chiffchaff) ... x x x i
Phylloscopus trochilus (Willow Wren) . x x x x
Phylloscopus sibilatrix (Wood Wren) x x <n | ave
Acrocephalus arundinaceus (Reed Warbler) x x
Acrocephalus palustris (Marsh Warbler) x
Acrocephalus phragmitis (Sedge Warbler) x x x x
Locustella locustella (Grasshopper Warbler) x x x L
Locustella luscinioides (Savi’s Warbler)... x
Motacilla raii (Yellow Wagtail) ... x x 1 ||) Vie
Motacilla alba (White Wagtail) ... x mare, 3
Anthus trivialis (Tree Pipit) : x I x
Oriolus galbula (Golden Oriole) ... x
Lanius collurio (Red-backed Shrike) x Pa |envale
Muscicapa grisola (Spotted Flycatcher) .. x x x x
Muscicapa atricapilla (Pied Bienes) 3 x x L
Hirundo rustica (Swallow) me x x x x
Chelidon urbica (Martin) .. x x x x
Cotyle riparia (Sand Martin) % x x x
Cypselus apus (Swift) x x os <
Caprimulgus europzeus (Nightjar) x x om x
Tynx torquilla (Wryneck) ... x L
Upupa epops (Hoopoe) x x
Cuculus canorus (Cuckoo)... : 6 x x 54
Circus cineraceus (Montagw’ s Harrier) x x |
Falco subbuteo (Hobby) ... 56 x
Pernis apivorus (Honey Buzzard)... x
Pandion haliaétus (Osprey) M | M x M
Ardetta minuta (Little Bittern) the x
Platalea leucorodia (Spoonbill) extinct ... x
Anas circia (Garganey) * x
Turtur auritus (Turtle Dove) x x x x
Coturnix communis (Quail) x x hile
Crex pratensis (Land Rail) x x xi ee
Crex porzana (Spotted Crake) x x | is
Grus communis (Crane) extinct . Se | VLM
CEdicnemus crepitans (Stone Curlew) x
Eudromias morinellus (Dotterel)... M M | XxX 'VIM

THE GLACIAL RANGE .CONTRACTION, ETC. 149

ra) a ra
SUMMER MIGRANTS TO 2 z FS =
a et 81 8
n
fEgialophilus cantianus (Kentish Plover)
Recurvirostra avocetta (Avocet) . x
Phalaropus hyperboreus (Red- -necked Phalarope) | LM ex
Totanus pugnax (Ruff)... é Mee ee) | VLM
Totanus hypoleucus (Common Sandpiper) Jil liek. 3 x oh lee:
Totanus glareola (Wood Sandpiper) _... ae m Ser:
Totanus ochropus (Green Sandpiper)... ae iP SP GENE
Limosa melanura (Black-tailed Godwit)... Ans i)
Numenius phzopus (Whimbrel) ... ae Sm etn me a oP
Hydrochelidon nigra (Black Tern) extzzect ;
Sterna cantiaca (Sandwich Tern)... :
Sterna dougalli (Roseate Tern) : ie.
Sterna hirundo (Common Tern) ... bs ye Wb xe
Sterna arctica (Arctic Tern) x
Sterna minuta (Lesser Tern) on x x x
Stercorarius richardsoni (Richardson’s Skua) an M M, | x M
Fratercula arctica (Puffin)... eS at A x fee

As will be seen from the table above given these
number 63 species, but two of these, however (the
Osprey and the Dotterel), have now ceased to breed
in England, although they did so say within the last
hundred years, and three others (the Red-necked
Phalarope, the Whimbrel and Richardson’s Skua) now
only pass that country on migration, but there is no
doubt that in earlier ages, when the climate was
sufficiently Arctic, they bred there. Four of these
species also pass Ireland on migration, which is a
safe indication that they formerly occupied that area
as breeding species when extending their range north-
wards after the Glacial Epoch had passed. Exclusive -
of these species, but including the three that have
become extinct purely through man’s interference, we
find that out of the 58 Summer Migrants to the British
Islands no less than 26, or nearly one-half, have cither

150 THE MIGRATION OF BRITISH BIRDS

never been detected in Ireland at all, or have only
occurred there as purely abnormal wanderers! Six
others migrate to Ireland every spring, but are very
locally distributed in the island, and in most cases con-
fined to the eastern and southern districts. It is also
interesting to remark that all these absent species were
late arrivals in our area (presumably when Ireland had
become isolated from England), a fact confirmed by
the absence of any trace of their emigration northwards
to Scandinavia across England and Scotland; whilst
three out of the four species that do visit Ireland
very locally on passage undoubtedly extended their
range vzd our area to Scandinavia, viz. the Crane, the
Dotterel, and the Ruff (cozf table, p. 122). It is also
a significant fact that not one of the three Summer
Migrants that visit us from the south-east (cozf. table,
p. 84) has been known to visit Ireland, except the
Red-backed Shrike, a solitary example of which was
obtained near Belfast on abnormal flight. All but five
of these Summer Migrants to the British Islands breed
in England, and of these five, two did so within com-
paratively recent years, viz. the Osprey and the Dotterel.
Twenty species are also absent from Scotland, but these
are all southern forms whose dominant range in England
itself is not very northerly. All the species that visit
Ireland also range further north into Scotland, with
the exception of the Garganey and the Hoopoe, which
‘ are both decidedly southern types ; and with these two
exceptions all the Summer Migrants to Ireland are
dominant wide-ranging species over the whole of the
British Area. It is to be deplored that we know so
little of the distribution of birds in Ireland. Correct

THE GLACTAL RANGE CONTRACTION, ETC. 15%

detailed information is much to be desired, and will
materially assist us in our study of the Emigration and
Migration of birds within the British Archipelago.

We will next deal with the species that either visit
the British Islands in autumn and pass the winter
therein, or migrate across them in spring and autumn
to winter quarters further south, and breeding-grounds
further north. These species are tabulated below.

Note.—A_ few individuals of some of the species (marked *) breed in
our area, so that some of them may be said to be vestvent therein, but for
obvious reasons they have not all been included with our typical residents.
w signifies Winter Visitor; RW Rare Winter ditto; LW Local Winter
ditto; Mw Migration and Winter, chiefly the former; xM Migration

chiefly, few Breed ; x w Winter chiefly, few Breed ; CM Ceagae Migrant ;
RM Rare on Migration ; AM Abnormal Migrant.

\e/a|2]e
AUTUMN MIGRANTS TO, OR COASTING MIGRANTS OVER | = 2 SI s
Z = ° =
y = =)
Turdus iliacus (Redwing) .. ae ae Be W Ww w |w
Turdus pilaris (Fieldfare) .. Wee 580 w |w | w |ow
Ruticilla tithys (Black Redstart) .. ae He Ww | W | RW] RW
Regulus ignicapillus (Firecrest) ... ae a8 Ww | Lw | LW
Lanius major (Great Gray Shrike) ey Oe Ww Ww w | LW
Ampelis garrulus (Waxwing). ecb =. | W | W | Wl RW
* Plectrophenax nivalis (Snow Bunting). os ADE wi] w | xwil w
Fringilla montifringilla (Brambling) Sat a Ww Ww Ww | w
Otocoris alpestris (Shore ark) ee. BE Meg Ww | Lw | Lw |
Nyctea nyctea (Snowy Owl) ae oie w | w | w
Archibuteo lagopus (Rough- legged Buzzard) ag towel w ow: | ane
Astur palumbarius (Goshawk) ... ee dew | ow lt we |) ane
Hierofalco candicans (White Jer Falcon) ae Ww W w | w
Hierofalco islandus (Iceland Jer Falcon) ta W ? w | Ww
Hierofalco gyrfalco (Scandinavian Jer Falcon)... w |
Anser albifrons (White-fronted Goose) ... aS Ww W w | w
Anser segetum (Bean Goose)... ewe we | we low
Anser brachyrhynchus (Pink- -footed Goose) Verano |fecuvanet
Bernicla leucopsis (Bernacle Goose) tes ve w |w w | Ww
Bernicla brenta (Brent Goose)... cS, on we low |W tw,
Cygnus musicus (Hooper Swan) ... dee oe wi}w lw hw
Cygnus bewicki (Bewick’s Swan)... me ae wilwiw lw
Cygnus olor (Mute Swan)... Bic he =e w | w | w
* Anas strepera (Gadwall)... 5G Bas eee OW || OW [eave wg
* Anas acuta (Pintail Duck) ie a seen OW Wh iS Wenn
* Anas penelope (Wigeon) oe a. ee) |) Waa) Wa eal ata
* Fuligula ferina (Pochard) sf ow ». |xw\| w )xwlxw

152 |. THE MIGRATION OF BRITISH BIRDS

a | a] ee
. ees sy Akane : : < 5 4 <
AUTUMN MIGRANTS TO, OR COASTING MIGRANTS OVER a a E =
Zz =
BI y) =
* Fuligula cristata (Tufted Duck) ae ses | XW] Wo] XW] Xe
Fuligula marila (Scaup) ... 350 a wiwi ww
Fuligula glacialis (Long-tailed Duck) 390 oes TW We eve a
* Fuligula nigra (Common Scoter) tis) (AXEL WE 1 Sas
Fuligula fusca (MelvetiScoter) es. wee ie Wo} wo | ow | aw
Clangula glaucion (Golden Eye) ... see sis wi w | w | w
* Mergus merganser (Goosander)... oe eas w | w | xw] tw
Mergus albellus (Smew) ... =e S58 nn w | w | W | Rw
Botaurus stellaris (Bittern) Sue Bh Ber w iw | WwW / Rw
Otis tarda (Great Bustard) she Boe Sp w | w |] Ww ] RW
Otis tetrax (Little Bustard) ah air Ww Ww | RW
fEgialitis hiaticula (Ringed Plover) se 3 cM | cM | CM | cM
Charadrius helveticus (Gray Plover) 9)". ... | MW | MW | MW | MW
Strepsilas interpres (Turnstone) . sit w | wl] Ww low
Phalaropus fulicarius (Gray Phalarope) .. aN? Ww | RW / RW | RW
+ Scolopax major (Great Snipe) ... Me e2 MGM | RM | RM
Scolopax gallinula (Jack Snipe) ... oe wae fee ee fa i
+ Tringa minuta (Little Stint) ... : aie cM.| CM | CM | cM
+Tringa temmincki (Temminck’s Stint) ... | RM | RM | RM
+ Tringa subarquata (Curlew Sandpiper) -«. | CM | GM | Ch | (em
Tringa maritima (Purple Sandpiper) _... a2 w | w i] wihw
Tringa canutus (Knot)... sae ae ... | MW | Mw | Mw | Mw
Tringa arenaria (Sanderling) AN. ho CM | CM | CM | CM
+ Totanus fuscus (Dusky Redshank) a: oe RM RM | RM
* Totanus glottis (Greenshank) ... aoe ... | CM | CM | XM/ MW
Limosa rufa (Bar-tailed Godwit) ... =a at wil wiwl)w
Larus minutus (Little Gull) ser ao Ba: RW | RW | RW | RW
Larus glaucus (Glaucus Gull) aoe se oe W Ww | Wes
Pagophila eburnea (Iceland Gull) He ... | RW | RW | RW | RW
Stercorarius buffoni (Buffon’s Skua) BS ; CM | CM | CM
Stercorarius pomatorhinus (Pomatorhine Skua) w | w | Ww | RW
Mergulus alle (Little Auk) ae wf}wi|w iw
Colymbus glacialis (Great Northern Diver) Ro w | w |] w ] w
* Colymbus arcticus (Black-throated Diver)... w | w | xw] w
* Colymbus septentrionalis (Red-throated Diver) w ]} sw | xw] xw
Podiceps rubricollis (Red-necked eee sé Ww | wel w
Podiceps cor nutus (Sclavonian Grebe).. oem | OW

t Cony. pp. 87, 88, 91, 92.

When we come to study the species that visit the
British Islands in winter, or pass them on migration, a
very different state of things occurs. The birds that
come into this class number 64 species. Of these the
Firecrest, the Shore Lark, the Scandinavian Jer Falcon,

THE GEACTALE: RANGE, CONTRACTION, ETC. 153

the Mute Swan, the Pink-footed Goose, Temminck’s
Stint, and the Red-necked Grebe are as yet unknown
in Ireland; but as at least four of these birds are
extremely uncommon in all other parts of the British
Area, and the remaining three have a strongly-marked
eastern tendency in their migrations, it is scarcely fair
to take them into consideration in our analysis. Of the
57 species that visit Ireland in winter, or pass over it on
migration to and from the north, it is a very suggestive
fact that no less than 29 breed in Greenland, Iceland,
or the Faroes, or pass the Faroes and Iceland on
migration—the nearest land masses north of the Irish
Area lying beyond the British limits. Of the remaining
28 species, at least four (Bewick’s Swan, Bean Goose,
Pomatorhine Skua, and Buffon’s Skua) spend the
summer in the high north in little known lands between
Greenland and Nova Zembla ; whilst twelve of the rest
breed more or less commonly in Scandinavia, and whose
migrations to our area may be traced in all but one
instance (Colymbus arcticus), by way of the Shetlands
and Orkneys. Four others are known or presumed to
breed in Arctic Russia (the Smew, the Gray Plover, the
Curlew Sandpiper, and the Bar-tailed Godwit), but in
the case of the three latter more western breeding
grounds may yet be discovered; whilst the Smew is
decidedly rare in Ireland. Of the remaining eight
species two (the Rough-legged Buzzard and the Gos-
hawk) are only abnormal wanderers to Ireland, and six
are decidedly rare in any part of the United Kingdom,
viz. the Black Redstart, the Waxwing, the Bittern, the
Great Bustard, the Little Bustard, and the Little Gull
(all rarer in Ireland even than elsewhere), species whose

154 THE MIGRATION OF BRITISH BIRDS

line of Migration in autumn is more southerly than
westerly, and whose breeding grounds in some cases are
for the most part below the parallels of Irish latitude,
and in others whose centre of dispersal was from the
south-east.

These facts prove undoubtedly that the common and
dominant species that exclusively winter in Ireland and
in other portions of the British Islands, or that pass
such areas on migration, are strictly boreal forms, most
of them from the high north or north-east ; the few that
reach us from the east are mostly rare and irregular,
and confine their visits principally to the eastern side of
our islands. Of course I need scarcely state that I do
not include our normal east to west migrants (covf. table,
p. 132) in these remarks. The proportions of the Irish
avifauna to that of England, Wales, and Scotland may
be thus briefly summarized.

tLe BREEDING IN ENGLAND ae ee ae
CLASSIFICATION, RR eae BREEDING IN IRELAND.
Summer migrants, 63. 63. Bes
Resident species, I15. 115. 99.
Winter visitors or coast- | Wintering in or passing | Wintering in or passing
ing migrants : | over England and Scot- over Ireland :
64, less 6 better classed land: 57, less 2 abnormals ;
as abnormal migrants ; 58. total 55.
,
total 58.

The significance of this proportion is apparent when
we study it in relation to the following facts. It may
be stated as an axiom, that as species begin to extend
their breeding or summer range northwards they still
continue to return to winter in the area which they
formerly occupied as residents, until such time as that
extended summer area may be dwelt in permanently

DHE (GEACIAL RANGE CONTRACTION, ETC, 155

owing to an amelioration of climate ; and that as the
range becomes more and more northerly, and less and
less southerly, the intermediate areas are only passed on
migration or occupied by comparatively small numbers
of individuals in summer and winter—a few individuals
breeding in the area, a few wintering; but even then
there is every probability that the former draw south in
winter, and are replaced by individuals breeding further
north. We may thus assume that the species that pass
our islands on migration were the earliest to enter our
area after the Glacial Epoch, and have followed the
ameliorating climate northwards, none of them breeding
in our islands now. We may also assume that the
species that return to our islands to winter therein are
the descendants of birds that were somewhat later in
emigrating northwards after glacial conditions had
lapsed, and as is usual in such cases a few individuals
remain to breed in our area—direct descendants, we
must regard them, of the very last individuals that
moved north to that area, and which we can have
no doubt in many if not in all cases move south of
our islands to winter.

That both the resident species in the British Area, as
well as those that winter therein, or pass over it on
migration, were early emigrants is still further confirmed
by the fact of their being so dominantly distributed in
Ireland. They reached that area when it was joined to
England in the south, and before much of the land was
submerged that is now covered by St. Georges Channel,
the Bristol Channel, and the English Channel. They
continue to winter in Ireland in such proportionate
abundance probably because the land continues to be

156 THE MIGRATION OF BRITISH BIRDS

much more compact and continuous in the north (the
point of egress) than it is now in the south. On the
other hand, there is much evidence to suggest that the
stream of Coasting Migrants across the Irish Area is
much less in volume than the stream that passes over
Scotland and England, which must be due in a great
measure to the wide water areas south of Ireland. Many
instances, moreover, might be given in which a number
of individuals of certain species, which pass Scotland
and England only on migration, spend the winter in the
south of Ireland, as though their southern progress was
arrested by the impassable barrier of the open Atlantic
Ocean. Thus many Knots, Greenshanks, Gray Plovers,
Bar-tailed Godwits, and Short-eared Owls pass the
winter in Ireland; whilst even such typical summer
migrants as the Blackcap Warbler and the Land Rail,
for instance, are frequently known to do so in the south
of that island—Coasting Migrants from the north which
have apparently gone too far west, and whose southern
flight has been abnormally arrested by the wide area of
unknown sea. We often hear of similar phenomena in
the south-west of England, where the sea-passage to the
Continent is very wide. I am not disposed to consider
such instances as due to the milder climate of these
areas tempting a winter sojourn: the individual birds in
question are lost migrants, too far west of their normal
route.

The Summer Migrants represent the species that were
the last to extend their breeding range northwards across
the British Area—then a portion of continental land. As
many of these birds reached the British Islands, we have
every reason to believe that submergence had com-

PAE GLACIAL ‘KANGE CONTRACTION, BTC. . 157

menced, and that Ireland had become separated from
England long before it had received its fair share of the
birds that were spreading across our land as summer
visitors. Thus we have birds that visit England, and
even extend their summer flight to the north of Scot-
land, such as the Redstart, the Lesser Whitethroat, and
the Tree Pipit, but which do not visit Ireland, which
they normally should do, all conditions being equal; the
water areas forming an impassable barrier to extension
of range thereto. These species also furnish another
proof in support of the Law which forbids emigration
southwards, as in the north-east of Ireland the water
passage to Scotland is no wider than the Strait of Dover
between England and France, which these summer birds
must cross and re-cross each year, and therefore no
barrier to emigration to Ireland, if such a line of exten-
sion were a normal one. Ireland is often held up as an
example of zoological poverty, and rightly so, in com-
parison with adjoining areas, but so far as birds are
concerned this poverty only exists among one class of
species alone, the Summer Migrants to our area, which
were prevented from entering the country in past ages
owing to submergence of the connecting land areas, and
because such species were late emigrants in this direc-
tion, arriving in the British Area, we have every reason
to believe, long after the dominant resident avifauna
was established, or the present winter visitors thereto
and coasting migrants across had spread northwards
over it.

In order to render the subject of Avian Emigration to
the British Area fairly complete, I append below a table
of the species and races that are peculiar to this area,

158

THE MIGRATION OF BRITISH BIRDS

and which I propose to discuss in greater detail in a
later chapter (cozf. p. 192 e¢ seq.).

BRITISH RACE.

BRITISH
DISTRIBUTION.

CONTINENTAL OR
EXTRA-BRITISH
PARENT SPECIES.

POINTS OF DISTINCTION
OF BRITISH RACE.

Parus ater britan- | General. Parus ater. Upper parts below
nicus nape, and the flanks,
more suffused with

brown.
Parus palustris | General in| Parus palustris.| General colouration
dresseri England and more dull, and more

Wales ; local

in Scotland

and Ireland.
General.

suffused with sandy
brown.

General colouration
more dull; white
on head confined
to crown; lores
black.

Upper parts below
nape barred with
dark brown; bill
and feet larger.

Quill feathers brown
at all seasons; no
white winter plu-
mage.

Acredula caudata Acredula rosea.

rosea

St. Kilda. Troglodytes

Troglodytes par-
parvulus.

vulus hirtensis

Lagopus scoticus | General. Lagopus albus.

A brief résumé of the facts (and the deductions drawn
from them) contained in the preceding and the present
chapter will perhaps help to simplify what is undoubt-
edly a very intricate subject, and enable the reader
better to grasp the importance of their bearing upon the
question of avian dispersal. We commenced Chapter
III. by propounding a Law of Dispersal, which I think
very closely goveyns the facts set forth in that and
the present chapter. By means of this Law and its
corollaries we are able to explain many apparent
anomalies of avian distribution. For instance, they
will explain why the Arctic Tern actually breeds in
Alaska, yet returns to South-eastern Asia to winter,

MAE GIACTAE RANGE CONTRACTION, ETC. 159

not breeding on any other part of the Pacific shores
of the American continent, because such areas could
only be reached by a flight south in spring. It
explains why the Little Bunting breeds in Siberia
within the same parallels of latitude as the British
Islands, and only in North Russia in Europe; why
the Eastern Nightingale breeds from Asia Minor to
South Sweden, yet is unknown in Western Europe ;
why the Red-backed Shrike breeds throughout the
whole of Europe south of lat. 64°, with the sole ex-
ception of the Iberian Peninsula ; why the Nightingale,
the Reed Warbler, and other birds are absent from the
south-west of England; why TZurdus alicia, Junco
hyemalis, Aigialitis semipalmatus, and Tryngztes rufes-
cens cross over into North-eastern Siberia to breed
yet return to their range bases in America to winter ;
why Phylloscopus borealis and Erithacus suecica, after
spending the summer in Alaska, return to winter exclu-
sively in the Old World; together with scores of other
anomalies of distribution which space alone forbids me
to enumerate. I appeal to naturalists interested in that
fascinating branch of ornithology which embraces
Geographical Distribution and Migration to apply this
Law ; for I am confident that it will lead to important
results, and explain many anomalies; perhaps even
enable us to remodel on a more satisfactory and natural
basis the various regions into which the world has been
divided by zoologists.

We began with the vast change of climate that marked
the closing era of the Pleistocene Period, and endeav-
oured to trace its effects upon the avifauna in particular
of Western Europe ; we have sketched out the probable

160 THE MIGRATION OF BRITISH BIRDS

condition of the British Area during this cold era, and
attempted an outline of the probable resident avifauna
of that and adjoining areas during this period. We
traced out the two other Range Bases or Refuge Areas
during the close of the Glacial Epoch of most of the
species that now compose the avifauna of West
Europe, by the aid of their allied southern and parent
races or representative species left stranded in Iberia,
North-west Africa, the Canary Islands, Malta, ete.
We have also sought to demonstrate not only that
the range of a very large percentage of our resident
species is continuous from our area down to Iberia,
North-west Africa, and the Canary Islands; but also
that a by no means inconsiderable number of species
resident in our islands or met with in them through-
out the year resort to that region (Refuge Area II.)
in winter, as very conclusive evidence of the source
from which our avifauna was derived. Similar con-
firmation of this fact has also been shown to exist
among the species that are only known as winter
visitors to our area, many of them extending their
range at that season to varying limits as far south as
the Canaries. We have also shown that almost all our
Summer Visitors seek winter quarters in this Refuge
Area (II.). Some of these species go much further south
in the east than in the west ; some of them breed as well
as winter in North-west Africa (a most convincing proof
that that was an area of dispersal or base from which
their emigrations northwards commenced), yet only pass
North-east Africa on migration—two apparent anom-
alies for which I think a satisfactory reason has been
given. We have also dealt with the two small groups of

Die GhACGAL RANGE CONTRACTION, ETC. 16%

Summer Migrants to our area, the species in one of
which apparently reach us by way of Algeria and Iberia
(or perhaps Italy and France); the species in the other
sroup by way of a north-west migration across Europe,
as is proved by their absence from North-west Africa
and Iberia. We have then proceeded to deal with
another important class of birds—nomadic migrants and
abnormal wanderers to the British Area—and to ascer-
tain the causes which have prevented these species
reaching our islands during past ages, and becoming a
portion of its dominant avifauna, and the relation of
these facts to past geographical conditions. We then
approached the difficult problem presented by birds
inhabiting West Europe—even in some cases within
sight of our shores—yet absent from the British Area,
and by an application of our Law of Dispersal to many
instances of such avian distribution, have shown that the
curious facts are perfectly normal.

Coming then to the subject of wide water areas as
most effectual barriers to Emigration, and its bearing
on the dispersal of British birds, we have considered at
some length the vast and far-reaching influence of such
a barrier on the avifauna of our area, and have en-
deavoured to show why so many species breeding in
West Europe never attempt to extend their range
across the English Channel. Coming to the question
of a former land connection between Greenland and
Europe, we have dealt with the causes of the
ornithological poverty of Greenland, the reason
why the avifauna of Iceland does not contain more
Nearctic elements, and have endeavoured to demon-

strate the importance of the emigration that in
M

162 THE MIGRATION OF BRITISH BIRDS

long past ages followed this route to the Arctic
regions.

In the beginning of the present chapter we have
discussed the possibility of undiscovered breeding
grounds between Greenland and Spitzbergen of several
northern birds, as an explanation of various apparent
anomalies of distribution ; and by an analysis of the
table containing the species that emigrated in a north-
westerly direction to Iceland and Greenland, we have
shown what a great and significant proportion of
species continue to breed along the entire route from
the British Area to Greenland, and a still greater pro-
portion between Iceland and our area. We have also
shown that in two cases at least the highest northern
emigration of the species throughout the world has been
along this route, We next proceed to discuss the two
dominant lines of Post-Glacial Emigration in West
Europe, illustrating by a table the range extension
northwards of 206 species, and their relation to the
British avifauna. By means of this inquiry we discover
the astonishing fact that a vast percentage of species
range absolutely higher on the Continent than they do
in our area, notwithstanding its much milder climatal
conditions—a discrepancy of distribution due entirely to
the dominant line of Emigration followed in past ages,
and a fact which proves that the individuals of certain
species breeding in North-west Europe (say in Scandi-
navia) are descendants of the individuals that dwelt in
the south-east (Refuge Area III.) ; whilst individuals of
the same species breeding in cur islands, and as far
north as Holland or Denmark, are the descendants of
other individuals that dwelt in the south (Refuge Area

EE GEACGCIAE RANGE CONTRACTION, ETC. 163

II.) ; that in fact the avifauna of these two portions of
West Europe have been derived from two quite distinct
and widely-separated areas. We have then proceeded
to deal with the emigration of species eastwards and
north-eastwards into continental Europe that started
from the British Area as a basis, and which is shown to
be recapitulated even at the present time in the migra-
tions of various birds to and from our area across the
North Sea. We thus see that Emigration is only
attempted across land areas or very narrow water pas-
sages, and that in every case where Migration at the
present time crosses wide stretches of sea it is an
unfailing sign of comparatively recent land submer-
gence, and a sure indication that when the migration
across such areas was being established, the land masses
were continuous, or nearly so.

Passing on to a more detailed study of the distribu-
tion of birds within the British Archipelago, we have
found the same Laws of Dispersal to apply, and the facts
to be thoroughly in harmony with those climatal and
geographical changes which have taken place in this
area during Post-Glacial time. We have discussed at
some length the impossibilities of southern dispersal,
and shown how the views held by Professors Geikie and
Leith Adams are opposed to known facts, and that the
evidence furnished by birds, animals, insects, and plants
leads to the inevitable conclusion that normal extension
in the Northern Hemisphere is never pursued in a
southerly direction,

We have then proceeded by the aid of a series of tables
to demonstrate the emigration of birds to the various
portions of the British Area, dealing with the resident

164 THE MIGRATION OF BRITISH BIRDS

species in, the summer and winter migrants to, and the |

coasting migrants across that area, and to show the
proportionate avifauna of each of the three divisions of
the United Kingdom. Dealing then with the resident
species and each class of Migrant, we have endeavoured
to trace the sequence of their arrival in the British Area ;
and, finally, to append a table of the species and races
of birds that are peculiar to that area. The whole
subject is a most fascinating one, and full of promise ;
an unworked ficld to which I am afraid the somewhat
small limits of the present work have prevented me
from devoting a fuller measure of attention. Sufficient,
I hope, has been discussed to serve as a stimulus to
further inquiry. The new Law of Dispersal, by which I
have attempted to explain what up to the present time
have been universally regarded by naturalists as inex-
plicable phenomena, will, I trust, meet with some small
portion of tentative approval from biologists.

As we remarked in our résumé at the close of Chapter
II.,so we may again repeat here, that the Glacial Epoch
was the cause of extermination of the greater portion of
the fauna and flora of northern and temperate Euro-
Asia. Among this awful wreck of life we must un-
doubtedly include the Birds. Some of these species,
as we know from paleontological evidence, must have
disappeared from the scene for ever; others, the majority
of others, have left no trace behind them. Birds, it
may be urged, could readily escape from such adverse
conditions: as the severe winters came on they could
retire south. But all the available evidence we can
bring to bear upon this question disproves the assump-
tion. In the Northern Hemisphere no bird increases

ee ee Sa

THE GLAGAL RANGE GONTRACTION, ETC. 165

its area of distribution southwards, either in summer
or winter; if it be overtaken by a change to a colder
climate in the north, the individuals of the species
that occupy that area will assuredly perish, and that
portion of the species be eradicated! If, for instance,
the British Islands are visited by an exceptionally
severe winter, birds, instead of flying off south to escape
its terrors, die helplessly in thousands and tens of
thousands; and it has been remarked that certain
localities have been well-nigh depopulated of various
birds, not perhaps regaining their usual strength again
for years. If the birds, instead of perishing from cold
and hunger, had merely emigrated south a little way
(perhaps but a very few miles!) they would have been
safe, and the return of spring weather would have
brought them back in their wonted numbers again.
We have at least some direct evidence that the cold
winters we have been so persistently having of late
years are slowly exterminating the Dartford Warbler.
As a British species it is undoubtedly much rarer than
it was twenty years ago. It is sedentary, and if these
conditions continue nothing can save this little bird
from total extinction in the British Islands. We
observe no extension of range southwards, no “ re-

1 A species may become gradually extinct through the inability
to rear offspring owing to adverse climatic conditions. In some
seasons, for instance, the Brent Goose appears on our coasts
unaccompanied by any young; and it may fairly be presumed
that an unfavourable season (say abnormally cold, backward, or
stormy) in the high latitudes where this species breeds has proved
fatal to the eggs or young. Should these adverse climatic con-
ditions become more pronounced, and continue season after season

(as they must have done during the coming on of a Glacial Period)
the species would most assuredly gradually be exterminated.

166 THE MIGRATION OF BRITISH BIRDS

treat ” to escape the growing inclemency of our English
winters. Now if we take the instance of the Dartford
Warbler and apply it to a Glacial Epoch, what are
the results? The northern individuals would perish ;
the southern representatives of the species would sur-
vive, and by Post-Glacial Emigration would expand
their previously contracted area, and re-stock the
northern lands wherever conditions were favourable
to such extension. Had the species no southern
base beyond the limits of glaciation or the effects
of the severe climate, z¢ must have been extermi-
nated. Did it manage to survive in any favourable
locality in the south, that locality must have been within
its Pre-Glacial range. With Inter-polar (or perhaps
Inter-hemisphere) species, however, the conditions were
different. These species were probably always migra-
tory ; glaciation might curtail their summer or winter
range, and in combination with equinoctial precession
entirely reverse it, but their migratory habits would
preserve them from extinction. The Glacial Epoch,
then, exerted its baneful influence upon all living things
that dwelt permanently within its limits,and mercilessly
if slowly exterminated all species, or the northern por-
tions of all species, wherever they came within its power.
Such species as had no southern Pre-Glacial breeding base
beyond the limits of glacial influence to sustain them
vanished for ever; only those well rooted in more
southerly latitudes preserved themselves, and from these
have descended all the emigrants that have re-peopled
the once devastated northern areas. 1 may here remark,
that by “contraction of range” I mean the complete
extermination of all individuals of a species within the

MAENGEACTAL RANG CONTRACTION, ETC. 167

area affected,! save, of course, in such instances which
purely apply to Inter-polar or Inter-hemisphere species.
Of course it does not come within our present pro-
vince to seek to show how Evolution progressed, and
the segregation of species went on throughout this
awful era, but that it was a means of much differenti-
ation is unquestionable.

1]T may here take the opportunity of pointing out that of the
three small families of birds that have solely survived the Ice Age
in the Nearctic and Palearctic regions (the Alcidz, Colymbidz, and
Panuridee), by far the most extensive group—the Alcidz or Auks—
numbering some thirty species survives in greatest abundance 77
the region where glacial conditions were the least pronounced! This
family of birds may be said to have its head-quarters now round
the coasts of the North Pacific (from California to Japan), where
not only the bulk of the species are found, but where it preserves
the greatest diversity of its surviving development. There can be
little doubt that before the Glacial Epoch the Alcidz were a large
circumpolar family ; during that era they suffered almost complete
extermination, the only survivors being those species or their
ancestral forms whose breeding range extended beyond the adverse
influences associated with that period. By far their most important
range base during the Ice Age must have been the Asiatic coasts
and islands of the North Pacific, and possibly the Aleutian Islands
—areas, be it remarked, that remained for the most part free from
glaciation. A few species, as we have already noted, survived in
the North Atlantic, owing partly, as we have abundant evidence to
suggest, to the fact of their pre-glacial breeding range, or a portion
thereof in the east, having been in the area I have designated
Range Base I. (cof. pp. 65-77).

CHAPTER ¥V.
RECENT EMIGRATION.

Increase, the Ruling Impulse of Life—The Ice Age and Emigration
—Enmigration still in Progress—Effects of Civilization on the
Emigration of Birds—Present Emigration in the British Area
—Enmigration of the Missel Thrush—Effects of Severe Winter
on that Bird—Emigration of Song Thrush and Blackbird—Of
the Redstart—Of the Robin, the Nightingale, the Whitethroat,
the Willow Wren, and the Wood Wren—Absence of Wood
Wren from Norway—Probable Winter Quarters of Individuals
Breeding in Sweden—Emigration of Marsh and Sedge Warb-
lers—Of the Goldcrest—Migration Waves of Goldcrests—
Emigration of Hedge Accentor, Nuthatch, and Tree Pipit—
Of the Greenfinch—Fluctuating Breeding Range of this Species
in the British Area—Emigration of Sparrows—Emigration of
Tree Sparrow to the Faroes—Emigration of Chaffinch and
Bullfinch—Of the Starling, the Jay, the Magpie, and the Rook
—Of the Tawny Owl, the Ring Dove, and the Stock Dove—
Of the Great Crested Grebe and Woodcock—Table of Species
whose Emigrations are still in Progress—Analysis of Table—
Northward Tendency of Emigration—Emigration attended by
Migration—Extinction of British Species—Effects of Law of
Dispersal.

THROUGHOUT the preceding chapters we have en-
deavoured to show upon what a vast scale the emi-
gration of birds took place, from the close of the Glacial
Epoch down to comparatively recent time. We have
seen that birds have spread in endless directions from
certain centres, emigrated north, east, and west, in which-
ever direction an outlet for their increasing numbers
was presented, or in which an amelioration of climate,

RECENT EMIGRATION 169

or a return to more suitable conditions permitted an
extension of area. The one dominant ruling passion of
Life in its endless varying forms is to increase and to
spread. That such an impulse to spread still rules
supreme, though less acutely than in the more remote
Post-Glacial ages, less palpable because the conditions
are so much less strongly marked, less dominant than
during those chaotic eras—is a fact as incontrovertible
as the very existence of Life itself. That the world is
never in a state of absolute rest is another truism
admitted by every scientific observer of nature. These
two facts imply that the Emigration of Life is still in
progress ; that birds, animals, insects, and plants still
continue to colonize new areas, or attempt to do so,
with their surplus individuals or excessive and increasing
population. This colonizing movement is of a much
more restricted nature than it was immediately after the
Glacial Epoch, due to the greater difficulties in the way
of successful extension of range, owing to the much
greater abundance of competing forms, and the much
less extensive arcas supplying the necessary conditions
favourable for such emigration. We can readily under-
stand the impetus given to Emigration by the passing
away of the Ice Age, and the opening out of half a
hemisphere to the remnants of the species dwelling in
the southern areas, vast numbers of which were perhaps
dwelling therein at a disadvantage, and under the least
favourable conditions for maintaining themselves and
for successful increase. We can also understand after
the great exodus north was nearly spent, how the
stimulus to Emigration would become much less acute,
and would therefore progress more slowly, until we can

170 THE MIGRATION OF BRITISH BIRDS

picture the remote future when the northern movement
may die completely away either by a complete change
to a warm and equable climate at the North Pole, or by
the coming on of a new era of glacial conditions. We
should, therefore, if the above remarks are correct,
expect to observe instances of northern emigration
taking place at the present time. This is precisely what
we do find. In many parts of the world, especially in
countries where owing to a high state of civilization the
phenomenon can be carefully observed, Emigration is
undoubtedly still going on. If this Emigration is in
progress in civilized countries we have every reason to
believe that it continues to progress in other parts of
the world where the movement cannot be so easily
detected; but it may be helped or retarded by the
presence or absence of civilization. Thus we have’
many instances where the spread of cultivation has on
the one hand assisted Emigration, whilst on the other
hand similar cultivation has had a directly opposite
effect, and actually decreased or curtailed the range of
many species in certain areas, and, as we know, ulti-
mately banished them from those areas altogether.

In the present chapter I propose to deal exclusively
with those species of which we have absolute proof of
their emigration being actually in progress, within the
limits of the British Archipelago. It will perhaps be
best to deal with each species separately, and to give in
detail the peculiarities of each emigratory movement,
so far as we can trace it, or it has hitherto been observed.
The first species whose emigratory movements we will
endeavour to trace is the Missel Thrush (7urdus vesce-
vorus). This species has very considerably increased its

RECENT EMIGRATION 171

range in our area during the past hundred years. If the
early records of the distribution of tiie Missel Thrush in
the British Islands are reliable, we learn that this bird
towards the close of the last century was chiefly con-
fined to the lowlands and well-cultivated districts.
Whether it was entirely absent from Ireland we have
no means of accurately ascertaining, but the probability
is that the bird was thinly dispersed over that area as it
was in England. Emigration during the past hundred
years has been steadily in progress, and at the present
time this Thrush is generally distributed over our main-
land area. It has also extended its range to the
Hebrides, but not yet to the Orkneys. When in Skye
some years ago I was informed that the Missel Thrush
had become fairly numerous in the island until the
severe winter of 1879-80, which almost exterminated it.
It is now, however, so I am informed, slowly increasing
again in that area. The Song Thrush ( Turdus musicus)
is also extending its range as it increases in numbers in
the northern portions of Scotland, and that this fact is
not due to the spread of cultivation and tree planting
seems proved by the fact of its present rarity in wooded
areas of long standing suitable to its requirements.
The Blackbird (Merula merula) is, comparatively speak-
ing, rapidly extending its range northwards and west-
wards, and even in some districts encroaching upon the
area occupied by the Ring Ouzel, and compelling that
species to retire, as in Ross-shire. Macgillivray records
that in his day the Blackbird did not breed on the
Hebrides ; it is now known to nest on them as far- north
as Lewis. It has also reached the Orkneys, but only
visits the Shetlands as an abnormal migrant. The

172 THE MIGRATION OF BRITISH BIRDS

Redstart (Ruticilla phaenicurus) is known to have spread
northwards in Scotland of late years, and now breeds
sparingly to the very northern limits of the mainland.
To Ireland, however, as we have already seen, it is
purely an abnormal migrant, which shows how strong a
barrier a wide water area is to a successful extension of
range. The same remarks apply to the Shetlands; we
have many species whose range extends to the Orkneys,
but there is little prospect of that range ever normally
reaching the more remote group of islets.

In the same way the Robin (£7rzthacus rubecula) has
steadily extended its northern range in Scotland, and
now breeds rezularly in the Hebrides and the Orkneys,
where formerly it was excessively rare or entirely
unknown. There is some evidence to suggest that the
Nightingale (Z7zthacus luscinia) is extending its range
northwards and westwards; and this species very
curiously illustrates the potency of our Law of Dis-
persal, for there is nct a scrap of evidence to suggest
that its line of Emigration is spreading south of Exeter
—a fact of very great significance, as we shall learn
in a later chapter (conf. pp. 215-217). This species is
extending its range higher in our area than elsewhere,
due perhaps to the absence of the competing form JZ.
philomela. The Whitethroat (Sy/vza cinerea) appears to
be increasing its range in the north of Scotland and
becoming more dominant. The Willow Wren (Phyllo-
scopus trochilus) is undoubtedly increasing its area, and
also becoming more dominant in the north of Scotland ;
whilst the Wood Wren (Phyloscopus sibilatrix) is a yet
more interesting instance, having spread northwards of
late years even to areas at the very extremity of the

RECENT EMIGRATION 173

mainland. In Ireland, too, although excessively local,
a marked and recent northern extension of range is
apparent. It is interesting to remark that’the Wood
Wren is absent from Norway, and there can be little
doubt will never colonize the south of that country, even
if it succeeds in penetrating to districts further north,
say of lat. 60° (conf. footnote, p. 127). The individuals of
this species that breed in Sweden and even as far north
as Archangel winter probably in Abyssinia, hence its
absence from Heligoland on passage—a line of Emi-
gration to which we have already alluded at some length
in the preceding chapter. The Marsh Warbler (Acro-
cephalus palustris) appears also to be spreading north-
wards in England, but as this species is so excessively
local, and its distribution by no means perfectly known,
it is perhaps wisest to discard this as an instance of
recent emigration until we are in possession of fuller
details. The Sedge Warbler (Acrocephalus phragmitis)
has either not been observed in the Orkneys until I
believe it was found by Mr. T. E. Buckley, or has
extended its range to those islands recently. The Gold-
crest (Regulus cristatits) is rapidly becoming more dom-
inant and widely dispersed in Scotland, Gray stating
that seventy years ago the bird was very scarce and
local. It is also a significant fact that the great waves
of migratory individuals of this species from the East in
autumn, and which spread west into Ireland, normally
strike our coasts south of Fife, thus indicating the area
from which their ancestors emigrated east across the
then North Sea Plains in past ages, and when the Gold-
crest must have been a by no means dominant species
in Scotland, although it certainly reached Scandinavia

174 THE MIGRATION OF BRITISH BIRDS

by way of the Orkneys and Shetlands. The Hedge
Accentor (Accentor modularts) is unquestionably increas-
ing its range northwards in Sutherlandshire and Caith-
ness; and it may be remarked is another precisely
similar instance to the preceding one of the Goldcrest—
a species that has emigrated east from England across
-the North Sea Area before it extended its northern
range at all dominantly into Scotland. The Nuthatch
(Sztta cesta) is one of our most local birds, yet there is
evidence to suggest that it is steadily advancing north-
west into Wales, where comparatively recently it was
very rare. The Tree Pipit (Azthus trivialis) has, it is
said, only been detected breeding in Sutherlandshire
within the past twenty years.

The Greenfinch (/rzngilla chloris) must also be re-
garded as another species that has extended its northern
emigration in our islands within recent years. It has
become much more dominant in the northern and wilder
portions of our islands, as the cultivation of trees has
increased, even reaching the Orkneys, where it now
breeds sparingly. It is interesting to remark that this
bird, like the Goldcrest, is only known as a Coasting
Migrant over, or winter visitor to, the Shetlands; and
this fact seems to me to suggest that the favourable
conditions which assisted the emigration of this species
across our area vzd the Orkneys and the Shetlands to
Scandinavia (where it ranges up to lat, 65°), have lapsed
—a variation in the climate of these islands involving
the destruction of forest growth seems to have occurred
(and there is some evidence that such actually took
place), and by extermination driven the breeding range
in our islands southwards for a time (although the

RECENT EMIGRATION 175

area in question has still been crossed on passage by
birds that have continued to breed in Scandinavia) ;
but which, as we have seen, there is now absolute
proof that it is slowly expanding north again with
the return of more favourable conditions, This exten-
sion of area, it should be remarked, is being carried
out by individuals that breed in Scotland, and is quite
independent of the migratory individuals that cross it
on passage to Scandinavia. The increase of the Starling
in Scotland presents very similar facts.

The extension of range of the House Sparrow (Passer
domesticus) has so very much depended upon the spread
of cultivation and the reclamation of waste grounds,
that it is almost impossible to separate the thoroughly
normal increase of area of this species from that which
has solely depended upon artificial aid. However, the
species is one that is unquestionably extending its area
of distribution, due in a great measure to its abnormal
increase in numbers (owing to the extermination of
many of its enemies and its artificial conditions of
existence), and is now common and well established in
many northern areas, where within the range of historic
time it was absolutely unknown. The Tree Sparrow
(Passer montanus) is also extending its range north-
wards, and apparently increasing in numbers; but it is
most significant that this fact does not apply to the
south-west of England—a direction of extension which
would involve a southern emigratory movement. A few
pairs of this Sparrow reached the Faroes some twenty-
five years ago, and have multiplied to such an extent as
literally to become a pest! The Chaffinch (/ringilla
calebs), again, is increasing and spreading northwards in

176 THE MIGRATION OF BRITISH BIRDS

many directions in Scotland, but apparently has not
extended its breeding area yet to the Orkneys, although
it passes those islands and the Shetlands in autumn and
spring, and is found in them in winter—an exactly
analogous instance to that of the Greenfinch and Starling.
The Bullfinch (Pyrrhula vulgaris) of late years has
increased its range northwards to some of the Hebrides,
especially to the south-eastern portions of Skye. The
Starling (Sturnus vulgaris) is a specially noteworthy
instance of current emigration, having within the past
forty years extended its range north and west to an
cnormous extent. More especially has this been the case
in Scotland, where within the past half-century it has
spread into many districts where previously it had been
quite unknown. Much of this range extension is prob-
ably due to the same causes as those which have spread
the House Sparrow so widely during recent time.t The -
Jay (Garrulus glandarius), in spite of decreasing
numbers due to incessant persecution, has extended its
range northwards within a comparatively recent time, and
now breeds at least as far north as Inverness-shire. The
Magpie (Pica caudata) is said to be increasing its area
of distribution in Ireland, although tradition states that
it was originally introduced to the island by artificial

1 For a very exhaustive account of the recent range expansion of
this species in Scotland, I must refer my readers to Mr. Harvie-
Brown’s admirable paper in Zhe Annals of Scottish Natural
History (January 1895). I am inclined to think that the facts in
many cases would bear a very different interpretation. This may
be due perhaps to the distinguished naturalist who has collected
them not being cognizant of what I believe to be is the Law of
Life’s Dispersal. Speaking generally, the phenomenon very closely

accords with that Law of Dispersal as demonstrated in the present
work,

RECENT EMIGRATION 177

means. Another very interesting instance of current
emigration is furnished by the Rook (Corvus frugzlegus).
As usual, this line of extension is mostly northwards,
and has gradually extended until the bird has reached
and occupied the Orkneys, and possibly the Shetlands,
as a breeding species. A north-western line of Emigra-
tion has also been followed, which at present extends
as far as Skye, but there seems every possibility of a
-speedy settlement over the Outer Hebrides.

The Tawny Owl (S¢vzx aluco) within the past half-
century has extended its range northwards over the
greater part of Scotland—including Skye and some
other of the Inner Hebrides—in spite of its decrease in
numbers. It still continues, however, significantly absent
from Ireland, notwithstanding this emigratory movement
elsewhere, and though common enough in the south of
Scotland, it never attempts a southern dispersal in spring
to breed in that island. The Ring Dove (Columba
palumbus) is another very remarkable instance of cur-
rent emigration. Increasing rapidly in numbers, it has
initiated a northward extension of area on a very large
scale, and within the past century has gradually spread
northwards and westwards as a breeding species over
Scotland, even to the Hebrides. This species is in its
emigrations and migrations analogous to the Greenfinch
and the Chaffinch. The Stock Dove (Columba @nas)
in its recent emigrations presents some very interesting
facts which confirm the soundness of our Law of dis-
persal in no uncertain way. Twelve years ago the
Stock Dove was generally though locally distributed
throughout England and Wales, and in the extreme

north-east of Ireland, where, however, it was said to be
N

178 THE MIGRATION OF BRITISH BIRDS

rare. In Scotland at that time but four instances of its
occurrence had been recorded, viz. once in Stirling-
shire, twice in Perthshire, and once as an abnormal
migrant to the Orkneys. Now the bird has gradually
increased its range northwards over Scotland, and is
known to breed at least as far north as the shores of the
Moray and Dornoch Firths! The occurrence of this
species in Ireland in the north-east alone might appear
almost like a southern emigration from Scotland, but
fortunately we have positive evidence that the bird had
not then appeared in the latter country. There is a
strong probability that the range of this Dove in Ireland
is not yet accurately determined. The Great Crested
Grebe (Podiceps cristatus) has within quite recent years
apparently extended its breeding range northwards into
Scotland. The Woodcock (Scolopax rusticula) seems
also to be extending its breeding range in our area, but
this may be due to closer observation on the part of
naturalists. The table opposite contains the species
that are increasing their range in the British Islands.

This list of birds in the actual process of extending
their range numbers twenty-nine species. Of these
eight are Summer Migrants to our islands (indicated
SM in the table opposite), and the remaining twenty-
one are Residents, or species of which individuals
may be found in our area throughout the year (indi-
cated R in the table opposite), Dealing first with the
summer migrants, we find that in all cases the birds
that are so steadily increasing their northern range
in our area did not emigrate across that area to Scan-
dinavia, where, however, in no less than six instances out
of the eight given their range extends much further north

RECENT EMIGRATION 179

even in some cases far beyond the Arctic Circle to the
North Cape, their Post-Glacial Emigration having beena

eh USSD | IN NORTHERN NORTHERN LIMITS
SSIES x oS BRITISH AREAS. | IN WEST EUROPE.
SUMMER M.

Turdus viscivorus ... R Migratory. lat. 663°.
Turdus musicus R Migratory. lat. 663°.
Merula merula R Migratory. lat. 67°.
Ruticilla phoenicurus SM lat. 71°.
Erithacus rubecula R Migratory. lat. 663°.
Erithacus luscinia SM South of Baltic.
sylviaiieinerea 1) i... SM lat. 65°.
Phylloscopus trochilus ... SM lat: For.
Phylloscopus sibilatrix SM lat. 58°.
Acrocephalus palustris SM Denmark.
Acrocephalus phragmitis SM later
Regulus cristatus ... R Migratory. (?) lat. 663°.
Accentor modularis R Migratory. lat. 70°.
Sitta czesia | R Sedentary. Denmark.
Anthus arboreus . | sm lat. 69°.
Fringilla chloris | R Migratory. lat. 65°.
Passer domesticus R Sedentary. lat. 663°.
Passer montanus ... R Sedentary. lat. 67°.
Fringilla ccelebs R Migratory. later
Pyrrhula vulgaris ... R Sedentary. South of Baltic.
Sturnus vulgaris R Migratory. lat. 69°.
Garrulus glandarius R Sedentary. lat. 663°.
Pica caudata ... | R Sedentary. lat. 71°.
Corvus frugilegus ... | R Sedentary. lat. 663°.
Strix aluco be R Sedentary. | lat. 64°.
Columba palumbus R Sedentary. | lat. 66°.
Columba zenas R Sedentary. lat. 61°.
Podiceps cristatus | R Sedentary. | lath 7.
Scolopax rusticula R Sedentary. | lat. 663°.

purely continental one to Scandinavia.

Of the twenty-

one resident species we find that in no less than fifteen
cases the birds that are gradually emigrating northwards
in our islands did not reach Scandinavia by a Post-
Glacial Emigration across our area; whilst in the six
instances of which we have evidence that such a line of
Emigration did actually take place, some change of
climate or of arboreal conditions has for a time lowered
the breeding range in our area by extermination, and the

lost ground is now slowly being recovered. With two

180 THE MIGRATION OF BRITISH. BIRDS

exceptions all these resident birds range much higher in
continental Europe than they do with us. The exceptions
are the Nuthatch and the Bullfinch, represented however
in more northern latitudes by closely allied climatic races.
This fact, as applicable to the Summer Migrants as to
the Residents, shows very clearly that it is only the
indigenous or British individuals of the species that are
endeavouring to expand, and in some cases to regain,
their northern range, the dominant line of Emigration
of the indigenous continental individuals being in the
majority of cases entirely outside our limits, and, in the
remaining few cases, principally so. We may also here
remark that species in which the habit of Migration is.
dominant (although individuals may be sedentary with
us or partly so) appear to extend their range more
rapidly than strictly sedentary species—the migratory
Ring Dove, for instance, advances quicker and more
dominantly than the much more sedentary Stock Dove.

There is one very important fact connected with all
this current emigration, and that is its invariable north-
ward tendency. It may be in an easterly or westerly
direction, but the trend is always north, never south. I
find that in the majority of cases this emigratory move-
ment has been attributed to the spread of cultivation, to
the planting of trees and the making of shrubberies ;
but are we justified in accepting such an explanation,
when we invariably find that this movement has been
ever northerly, and of course in accordance with a
known Law? Has cultivation and tree planting always
been in a northerly direction? surely much of it has
taken place in southerly areas as well; but with no
accompanying signs of Avian Emigration from north to.

tECENT EMIGRATION 181

south! You may fill South Devonshire with reed-beds
and with spinneys, suitable in every way for the Reed
Warbler and the Nightingale, yet the birds will not
emigrate southwards to fill them; you may afforest
Ireland as densely as you like, as indeed much of it has
been afforested, yet you cannot tempt a single Wood-
pecker or a single Tawny Owl or Nuthatch to break
the Law of its dispersal or the conditions of its exten-
sion, either by emigrating south or by crossing a wide
water area to take up its abode in your forests. I do
not deny that this afforestation offers many advantages
of which species have readily availed themselves and
increased their area, but only is such an advantage
seized upon when it is also in harmony with an unvary-
ing Law of dispersal. Depend upon it, it is the same
Law of dispersal that governs the emigrations of species
in our islands now, just as it governed the movements
of species in other areas, and as we know it controlled
their extension in past ages. Not a single instance of
a species increasing its range in our area in a southerly
direction, or from north to south, can be named among
the long list of examples given above. Of course we
except instances of dispersal which may have an appar-
ent southern tendency in such species that have been
introduced into certain areas by artificial means—the
Red-legged Partridge, the Capercaillie, and some others,
that have been brought to the British Islands (and
maintained there) by human agency.

There is another very interesting fact which must be
noticed in connection with this extension of range of so
many species in the British Islands. In no less than
seventeen cases out of the twenty-eight instances of

182 THE MIGRATION OF BRITISH BIRDS

which particulars have been given has this Emigration
been attended by Migration—the latter has helped the
former ; in fact it is doubtful whether a successful exten-
sion could have been established at all had the species re-
mained non-migratory, or had not already been addicted
to migratory habits, for the winter conditions would have
been fatal to the colonists, and the range gained in
summer would have been lost in the following winter.
The sedentary species must therefore have increased
their area more slowly, not extending their range north
into districts until the winter conditions were favour-
abie. The Migration taking place within our islands is
precisely the same as that Migration which progresses
beyond them; the flight south of a Song Thrush in
autumn from the north of Scotland to more southerly
areas in the same country is precisely the same move-
ment as the flight of a Knot from Grinnell Land to South
Africa ; the difference is only one of degree. One can
readily understand how individual birds and their off-
spring gradually extend their range year by year, spring
by spring resorting to a locality to breed, yet compelled
by the severity of the ensuing winter to return to their
more southern base

as the range expands northwards
the migration flight lengthens, until instead perhaps of
a few miles only the journey slowly becomes one of
many miles. The route followed is the line of extension
in which the breeding range has been increased, each
individual bird following a road back in autumn which
it traversed north in spring—a route which has been
slowly acquired by the species mile by mile, even field
by field, or wood by wood, and taught to the young that
journey south in company with the old birds in autumn,

RECENT EMIGKATION 183

or that follow them north again in spring. So far as the
Summer Visitors that are extending their range in our
islands are concerned, the movement is slowly increasing
the length of their journey, and slightly varying the
route that they follow ; with the Resident species it is in
many cases compelling the adoption of local migratory
habits. It may be remarked that this local migration is
much more marked and general on the Continent than it
is in our island area, where the climate is so much milder ;
more species perhaps partake in it, and the flights are
longer and more dominant, and rise to a much greater
degree of importance. Thus we find many species
absolutely migratory in continental areas, no individuals
remaining through the winter that are sedentary or
nearly so with us, in the sense of never being absent
from our islands all the winter through. In the above
table I have indicated the species that are migratory in
the northern portion of their British area, but we need
not stay to enter into greater details of their movements.
Some of these, I may remark, have already been de-
scribed in the J/zgration of Birds, and to that volume I
would refer the reader who may be sufficiently interested
in the subject to desire fuller information.

In order to render the present subject fairly complete
it is now necessary to devote a little space to the con-
sideration of a very different set of facts from those
which we have been studying; to make a brief allusion
to those species which have passed more or less
completely from our avifauna, and whose absence has
been very largely caused by those very improvements
that have been so advantageous to other species. Our
drainage and reclamation of waste lands, our game pre-

184 THE MIGRATION OF BRITISH BIRDS

serving and mania for collecting “British” specimens,
together with our rapid increase of population, have
cost us dear, so far as some of our most interesting
birds are concerned. Many of these species formerly
resident in, or regular migrants to, our islands have
been completely exterminated, or only survive in the
northern thinly populated and least cultivated districts.
As may naturally be surmised, nearly all the smaller
birds have maintained their ground, even in many cases
increased their range and their numbers, but it is at the
expense of larger and perhaps more interesting birds.
The species in question are named below.

* Savis Warbler. Kite. * Crane.
Bearded Titmouse. | Honey Buzzard. * Great Bustard.
Short-eared Owl. | ‘+ Osprey. Dotterel.
Marsh Harrier. eeeebittenns | * Avocet.
Montagu’s Harrier. * Spoonbill. | PF Ruff
+ Golden Eagle. | +Gray-Lag Goose. | * Black-tailed Godwit.
+ White-tailed Eagle. | Capercaillie. | * Black Tern.

No less than eight of these (marked by an asterisk)
have become absolutely extinct as breeding species in:
the’ British Islands; five others (marked by an obelisk)
have been banished from England and now only breed
in Scotland; two of them, however, nesting in Ireland.
The remaining eight are very locally distributed, but
still continue to breed in our islands, although there can:
be little doubt that most of them will eventually dis-:
appear if some special ‘means for protecting them are
not quickly devised. Every naturalist must deplore the’
absence of the Bittern, the Spoonbill, the Crane, the
Great Bustard and other interesting birds from our
avifauna ; all the more so, for in perhaps every instance
by a little judicious management the species might

RECENT EMIGRATION 185

have been preserved to us. It is too late now in many
cases for us ever to hope to see these beautiful birds
re-established in their ancient homes, or in what
remnant of their haunts still remains untouched or
unimproved by modern methods. Could we turn half
England once more into a vast morass, the Laws of
dispersal would forbid the Bustard, the Spoonbill, and
the Wild Goose to enter. <As colonists they will never
return again, for now our islands are beyond the limits
of their normal migrations, and our wide water areas,
so long as they continue, will ever act as a barrier to
successful re-emigration. The Golden Eagle, the White-
tailed Eagle, the Dotterel, and the Ruff are the only
species whose lines of migration now cross our islands
at all dominantly, and they are the only species that are
ever likely to re-people the areas from which they have
been banished, although even this is very problematical,
notwithstanding any and every inducement we might
offer them to do so. The Short-eared Owl, the Marsh
Harrier, Montagu’s Harrier, the Kite, the Honey Buz-
zard, the Osprey, the Ruff, the Black-tailed Godwit, and
the Black Tern we might yet save, were strict protec-
tion given them ; but the few individuals that are from
time to time destroyed at their old breeding grounds
are assuredly among the last of their kind that will
ever visit us with the object of reproducing their
species;-and if we still continue to kill them or to
drive them thoughtlessly away, the opportunity of re-
taining them in our land will soon be gone for ever.
They are the last remnants of the individuals whose
lines of emigration extended to our area, and taking
into consideration our insular position, they are the

186 THE MIGRATION OF BRITISH BIRDS

last that will ever essay the attempt. Nothing, then,
short of absolute re-introduction by human aid will
re-establish them in our islands, as we know by ex-
perience. Such sedentary species as the Bearded Tit-
mouse will never again attempt to enter our area
normally. The Capercaillie, also a sedentary species,
would never normally have become a British species
again had not man’s assistance been given, although
we know for an absolute fact that our islands were
and are suited in every way to its requirements, as
experience has shown. Nothing short of re-introduction
by man would ever establish the Gray-Lag Goose in the
lowland counties again; as a breeding species it has
passed north never normally to return. Professor
Newton, in his very interesting paper on the Great
Flood in the Fens during the winter of 1852-3 (77azs.
Norfolk and Norwich Nat. Soc.), records that among
other species that appeared with the return of more
favourable conditions, due to the flooding of the land,
were the Black Tern and the Redshank, which might
seem like instances of pure re-colonization ; but both
these species have not yet been entirely banished from
the district. No return of such utterly banished birds
as Spoonbills, Avocets, Cranes, and Gray Lag Geese
(all completely exterminated) was remarked.

Knowing then what we do of the Laws of Avian
dispersal, let us employ our knowledge while there is
yet time in saving at least a remnant of that rich and
interesting avifauna that has vanished from our shores,
by protecting that remnant jealously from persecution
and wanton, senseless destruction.

ee

CHAELER VIC
ISLAND AVIFAUNAS.

The West Palearctic Islands—Continental Islands—Birds of
Borneo, Formosa, the Philippines, etc.— Ancient Continental
Islands—Birds of the Canaries, Madagascar, Azores, Bermuda,
etc.— Reasons for the Unequal Dispersion of Species—Islands
and Migration—The British Islands—Endemic British Species
—The Red Grouse—Endemic British Races, or Representative
Forms—The St. Kilda Wren—Races of Titmice—Poorness of
British Avifauna in Endemic Species—The Channel Islands
and Heligoland—West Mediterranean Islands—The Canary
Islands—Endemic birds of—Number of Eggs laid by Birds in
Canary Islands—Madeira and the Azores—Japan and the
Bonin Isles—Various Tropical Islands—Endemic Avifaunas of
—Bearing of Migration on Insular Avifaunas—Conclusions
Drawn from Facts—Bearing of Glacial Conditions on Island
Avifaunas.

WE have now reached that stage in our investigations
where it becomes necessary to deal more specially with
the avifaunas of islands, and to ascertain what relation
the birds of the various islets that dot the western limits
of the Palearctic Region bear to the species that inhabit
the large land masses or continental areas adjacent to
such island groups, and the bearing of that fact upon
our whole subject. We may commence by stating that
all the west Palzearctic islands, with two exceptions, are
what are termed Continental Islands, or islands that at
some more or less remote epoch formed part of the

188 THE MIGRATION OF BRITISH BIRDS

continent to which they are adjacent. The two excep-
tions are the Azores and the Madeira groups, which are
oceanic islands, and apparently of volcanic or coralline
origin. The continental islands resolve themselves
again into two distinct classes, viz. those that are of
ancient origin and usually separated from the parent
land mass by deep seas; and those that are of recent
origin, always situated upon submerged banks that con-
nect them with the adjoining continent, and surrounded
by shallow seas. The Canary Islands may be taken as
the only example of ancient continental islands in the
West European Area; whilst the British Isles, the
Channel Isles, Heligoland, the Balearic Isles, Corsica,
Sardinia, Sicily, and Malta all belong to the class of
recent continental islands. The more ancient islands
very often contain the greater number of peculiar
species, due to their longer isolation, and are remark-
able for the fragmentary character of their fauna. The
more recent islands are said to possess few peculiar
species, and to exhibit the general characteristics of the
fauna and flora of the adjacent land mass. The vol-
canic or coralline islands are probably peopled entirely
by fortuitous emigration, by accident, and therefore
often exhibit a somewhat puzzling mixture of species.

In the present chapter it will be my principal aim to
show why these Atlantic and Mediterranean islands are,
and in all probability will continue to be, so poor in pecu-
liar species, and why various other islands in other parts
of the world, irrespective of their age and origin, are
respectively rich or poor in endemic species—a question
which has hitherto, so far as I can determine, never
been grappled from the same standpoint as that which

ISLAND AVIFAUNAS 189

I propose to take. Dealing first with continental islands
of recent origin, why, we may very naturally ask, does
Borneo—presumed to be a recent continental island—
contain so many peculiar birds, whilst the British
Islands, of probably the same geological age, contain
so few endemic species? Why does the Japanese
Archipelago exhibit such a paucity of peculiar forms,
whilst Formosa—only about half the size of Ireland—
is rich to an astonishing degree in endemic species ?
Why should Ireland possess not a single endemic bird,
whilst the Philippines are replete with them ?

Of the 580 species of birds that have hitherto been
found in Borneo, according to the latest available in-
formation, no less than 108 species are peculiar to the
island. In Formosa the late Mr. Swinhoe met with
some 144 species of birds ; subsequent investigation has
shown that no less than 43 species are endemic ; whilst
of the 472 species that have been obtained in the
Philippine Islands, no less than 300 species are peculiar !
On the other hand, the list of birds found normally in
the British Islands contains, say, close upon 250 species,
but out of this number only five are endemic, and four of
these cannot even claim specific rank. Again, the list of
birds found in the Japanese Empire contains some 381
species (fide Seebohm), but only seventeen are known to
be endemic, and of these five at least are not specifically
distinct. The Channel Islands do not contain a single
endemic species; Corsica but one (Sztta whitehead?) ;
none, so far as is known, occur in the Balearic Isles, in
Sardinia, Sicily, Malta, or Heligoland. Of the two
latter islands it is interesting to remark that no less.
than 278 species were recorded by Mr. Wright from

190 THE MIGRATION OF BRITISH BIRDS

Malta ; whilst the more astonishing total of 396 has
been recorded from tiny Heligoland!—yet neither
island can claim a single endemic species or race!
Turning next to continental islands of more ancient
origin, we. find that in the Canaries (the only group
which can claim such a distinction in the West Pale-
arctic Area) the number of species recorded by Mr.
Meade Waldo is 146, of which perhaps ten are endemic,
but most if not all of these are only island forms or
representative races of continental Palearctic species.
On the other hand, Madagascar, another continental
island of ancient origin, contains 238 species, of which
no less than 129 species or races are endemic. Not a
single genus is peculiar to the Canary Islands, but no
less than 35 genera are confined exclusively to Mada-
gascar! As an example of Oceanic Islands we can
compare the Azores and Madeira with say the Bermudas
and the Galapagos. On the Azores some 53 species of
birds have been obtained, 38 of which are residents, and
15 only stragglers to the group: two species are en-
demic, one of which is very closely allied to Canarian
and Madeiran forms. Madeira numbers some _ 100
species, either as residents or abnormal migrants, and
can claim but two endemic birds, one of which at least
is only subspecifically distinct from a Canarian form.
Coming now to the Bermudas, we find that no fewer
than 180 species have been observed on the islands, but

1 This is the number recorded by Gatke, but at least one species
has been shown to have been so in error—Geocichla dauma (conf.
Tbis, 1894, p. 298). Probably some other records are equally
unsatisfactory, so that the total number of Heligoland species may
not be quite so large.

ISLAND AVIFAUNAS 19!

only II are resident, the remainder being abnormal
migrants of more or less frequency. Not a single species
is endemic. The Galapagos can claim 57 species of
birds, and of these no less than 38 are absolutely
endemic, all thé land birds (31 in number) being
peculiar except one species, and more than half generi-
cally so!

The facts briefly stated above are very interesting
ones, and apparently inexplicable by any known laws
of avian dispersal. The anomalies, however, are but
apparent, the difficulties of explanation are far more
imaginary than real. This very large amount of appar-
ently anomalous and unequal dispersion of species over
these island areas is probably entirely due to geo-
graphical causes, correlated with avian migration. I
think it may be safely laid down as a universal rule that
islands situated on a direct and important line of Migra-
tion are never remarkable for a great or predominant
number of endemic species, or even of local races, and it
is the exception to find any such peculiar species at all.
On the other hand, islands remote from any dominant
line of Migration just as invariably contain proportion-
ately or absolutely large numbers of endemic species or
peculiar races. The islands most remarkable for their
number of endemic species are almost without exception
situated in the Southern Hemisphere, or within the
Tropics, where Migration does not prevail to anything
like the extent that it reaches in the Northern Hemi-
sphere, and where—as in the Tropics—the climate is one
of uniform warmth and stability, rendering migratory
movement on any very important scale unnecessary.
Briefly, then, we find the great number of endemic or

¥92 THE MIGRATION OF BRITISH BIRDS

peculiar species where the avifaunas, both on the islands
and in the surrounding areas, are sedentary. Let us
deal with each of these island groups in turn, and see
how the facts they present may be explained by geo-
graphical position, and the absence or presence of any
dominant line of Migration.

First we will consider the British Isles. We have
already dwelt at some length on the emigration of
species to this area, and on the comparison of its avi-
fauna with that of adjacent areas. For the purposes of
the present inquiry it will only be necessary to confine
our attention to the few endemic species or races that
dwell in these islands, to explain their presence in that
area, and to show why the British avifauna is so poor in
peculiar forms. At the close of Chapter IV. (p. 158)
we gave a list of these British endemics. But one of the
five species is absolutely distinct, the remaining four
being races or insular forms, only subspecifically distinct
from continental species. The one exception is so
utterly unique in character that I cannot resist the
opportunity of inquiring somewhat fully into its origin.
The Red Grouse is absolutely peculiar to the British
Archipelago, the one solitary endemic bird entitled to
specific rank. How did it come there? The nearest
ally of the Red Grouse, in fact its continental represen-
tative, is the Willow Grouse (Lagopus albus). There
can be no reasonable doubt that before the Glacial
Epoch the Willow Grouse was the only and dominant
species in West Europe, including what is now the
British Area. Exterminated in the north by the chang-
ing climate, by the snow-fields and the glaciers, the
remainder of the species continued to dwell in South

ISLAND AVIFAUNAS 193

Europe, and the evidence strongly suggests that the
range of this Grouse reached far to the south-east, from
Scandinavia and North Russia as far as the Caucasus
(where it is probable this Grouse will yet be discovered
as an indigenous species ; at least one example has been
obtained there), Asia Minor, and Turkestan. Owing to
its arboreal habits, it soon became exterminated in the
north, its disappearance following that of the willows
and birches. The birds inhabiting what was then the
British portion of continental Europe were likewise
exterminated in the north by the glacial climate, say to
limits that reached from 53° north latitude, down to the
Pyrenees. In the course of time the great glaciers and
snow-fields of Central Europe completely isolated the
two colonies of Grouse. Those in the south-west were
probably never exposed to such a severe climate as the
individuals dwelling in the south-east. Be that as it
may, there can be no doubt that the Willow Grouse that
occupied that portion of the Pre-Glacial range of the
species composing Refuge Area I. during the Ice Age
were the ancestors of the Red Grouse, and must have been
differentiated to a certain extent by their isolation at
that period. During their long sojourn in this area, in
their probably severe struggle to maintain themselves,
they became heath or tundra birds, compelled to give
up their arboreal habits ; and as the climate ameliorated
and their descendants gradually spread north again,
they would naturally keep to those districts that pre-
sented the least changed conditions—the mountainous
areas, the watersheds and moors—as they still continue
to do, not emigrating across the low fertile plains of the
North Sea Area, and perhaps finding no country suited
O

194 THE MIGRATION OF BRITISH BIRDS

to their requirements from North France to Denmark,
those areas being entirely non-mountainous, flat, and
probably of a dense forest or swampy character. That
the dominant line of Post-Glacial Emigration north-
wards of this party of Grouse (whether completely
differentiated then or not being a matter of no con-
sequence) was only across Britain, and did not extend
in that direction to Scandinavia, is proved by the
absence of this bird from the Shetlands. Thatwae
emigrated across our area slowly seems also suggested
by the fact that no trace of an emigration in the
direction of Greenland by way of the Faroes is to be
found. Probably by the time this Grouse had reached
the Orkneys, this north-westerly route was considerably
broken by areas of water,' or conditions favourable
to range extension in this direction were wanting.
The Willow Grouse that now dwell in Scandinavia
have reached that area by a north-westerly line of
emigration, and there is no trace that this extension
was ever west of E. long. 10°. The almost sedentary
habits of these Grouse have been the means of keep-
ing the two colonies distinct, and by isolating the
individuals to allow of the differences—due to changed
conditions of life—to become constant characters of
full specific value. The brown dress of the Red

1 Even had the Red Grouse reached Scandinavia by an emigra-
tion across the British Area (of which there is no evidence) or by
way of Holland and Denmark (which is by no means improbable),
the species must have been exterminated again by the fourth
Glacial Period—the epoch of the Great Baltic Glacier—which, it
will be remembered, only slightly affected the British Area, not
sufficiently to cause the extinction of such a hardy tundra species
as the Red Grouse.

ISLAND AVIFAUNAS 195

Grouse was retained in winter owing to the pluvial
climate of the mild western region—a change which
the bird has been quick to take advantage of as a
means of protecting itself from enemies amongst its
native heath and ling. The propensity of the Red
Grouse to perch occasionally in trees is very interesting,
and unquestionably a relic of the arboreal habits of its
ancestors. The emigrations of the Red and Willow
Grouse, it will be remarked, are almost exactly analogous
to those of the Eastern and Western Nightingales.

Of the remaining four endemic birds, the St. Kilda
Wren (if it can be preserved from extermination) has
probably the best opportunity of asserting finally its
specific distinctness from the Wren that inhabits the rest
of the British Area. It is, however, wrong to presume
that St. Kilda owes its Wren toa party of birds driven
south from Norway in search of a milder winter climate.
In the first place no species, nor single individual of a
species, normally migrates south along an unknown
route which its Post-Glacial emigrations north have not
followed. No bird, no species, emigrates or extends
its area in winter, colonizing movements are prompted
solely by reproduction.! Of course it may be urged

1 One most convincing proof that species do not increase their
area during winter, or retreat by emigration from adverse conditions,
is furnished by the fact that great numbers of species, or portions
of species, resort to winter quarters much further south or more
remote from their breeding grounds than there is any necessity so
to do. To my mind this is proof beyond the possibility of doubt
that these remote winter areas are ancient range-bases from which
the species has been dispersed, and from which it has colonized the
most remote parts of its present area. The Willow Wren, for
instance, goes in some numbers as far south as The Cape to winter,
but many individuals remain in North Africa and even in South

196 THE MIGRATION OF BRITISH BIRDS

that the movement to St. Kilda was perchance a
purely fortuitous one, but the possibility of that being
the case is destroyed at once by the fact that St.
Kilda was completely glaciated during the Ice Age,
and every bird exterminated from its surface. The
Wren reached St. Kilda by the line of Emigration
which we have seen extended from the British Isles to
Greenland, and by which same route the Faroe Isles
and Iceland received their 7voglodytes borealis. That
both these insular Wrens preserve their subspecific
identity, and (if the present conditions continue) may
ultimately attain complete specific rank, is entirely due
to the fact that Migration along this route—so far as
these subspecies are concerned—has ceased ; the Wren
(in its various subspecific forms) is now sedentary, and
isolation is therefore complete. The three subspecies
of Titmice that inhabit the British Area, however, may
very probably never rank higher than they are to-day,
because the migration of the continental (and parent ?)
species continues to pass our area. So long as this
migration and consequent intermixture of individuals
continue, the swamping effects of intercrossing will
prevent complete segregation; were the migration,
however, to lapse, isolation would doubtless soon enable

Europe at that season. Numbers of Chiffchaffs go as far south as
Abyssinia to winter, whilst others spend that season even in the
South of France, Iberia, and Italy. Many Sedge Warblers winter
in Algeria and various parts of North Africa, others journey
thousands of miles further to the south in that continent. It is
nonsense to suggest that these birds are seeking a suitable winter
climate so far to the south, as many individuals of the same species
find suitable winter conditions at a distance measured by thousands
of miles nearer to their breeding grounds. Scores of similar
instances might be given.

— Oe

ISLAND AVIFAUNAS 197

complete distinction to be attained. I cannot admit
what Dr. Wallace asserts to be the case, viz. that in
the British Isles “the process of formation of peculiar
species has only just commenced” (/s/and Life, new ed.,
p. 408), for there is no evidence whatever to show that
these British endemic forms are not of very ancient
origin—dating, it may be, from the close of the Pleis-
tocene Period—to indicate that they are not struggling
with adverse conditions in segregating themselves ; con-
ditions, be it remarked, that will prevent complete
specific distinction so long as they continue.

Now a few words with regard to the poorness of the
British avifauna in endemic species. The geographical
position of our islands is directly opposed to the
establishment of local or peculiar species. They are
situated too far north for many species ever to become
absolutely sedentary within their limits (so long as
climatal conditions continue the same), and they are
adjacent to areas where the conditions for sedentary
residence are even less suitable. The inevitable con-
sequence is that the several avifaunas are constantly
being mixed by the migration taking place over these
various districts ; and to such an extent does this pre-
vail, that probably not more than two or perhaps three
of our indigenous birds are sufficiently isolated from the
remainder of the species to ensure the preservation of
any variation that they might develop. The species
that are the most sedentary show the greatest amount
of local variation. This is specially observable in the
case of the Dipper, the Red Grouse, and the Partridge ;
and could we only isolate sufficiently the various local
types of these species that occur in certain areas, there

198 THE MIGRATION OF BRITISH - BIRDS

can be little doubt that a subspecific and eventually a
specific distinction would result. We may conclude,
therefore, beyond the slightest doubt, that our paucity
of endemic species is due to the vast amount of migra-
tion taking place over our islands ; and so long as the
migration of any and every species continues, so long
shall we remain poor in peculiar forms. Of plants,
insects, fish, and animals, however, whose means of
dispersal are more limited, and whose habits are seden-
tary, we have a fair proportion of endemic species—a
fact which only emphasizes the truth of the foregoing
remarks.

Let us now pass to the Channel Islands and Heligo-
land. So far as the Channel Islands are concerned
precisely the same remarks apply—their geographical
position preventing the establishment of a single en-
demic species. Their avifauna contains a fair proportion
of species, composed of residents, summer migrants,
winter visitors, and coasting migrants ; yet none of the
resident species are isolated from the vast stream of
migratory individuals of the same species regularly
crossing their area, All the species indigenous to them
are continental or British, and none of them are abso-
lutely sedentary. Heligoland, situated about 40 miles
from the mouth of the Elbe, and only about one-fifth
of a square mile in area, is said (on the authority of
Herr Giatke) to have been visited by no less than 396
species,! yet not a single endemic bird is found thereon
—a fact entirely due to the abundance of migratory
birds that so regularly pass over it.

We will now proceed to notice the various West

1 See footnote, p. 190.

ISLAND AVIFAUNAS 199

Palearctic islands in the Mediterranean—the Balearic
Islands, Corsica, Sardinia, Sicily, and Malta. It may
be remarked that all these islands are situated in a
comparatively small and entirely land-locked sea, and
that all of them formed part of continental land at no
very remote era. So far as our knowledge extends at
present, only one of this important series of islands
contains an endemic species. In Corsica we have a
species of Nuthatch (Sz¢ta whitehead7) peculiar to the
island, so far as is known. That endemic species should
be so excessively rare in islands apparently suitable in
every way for the development of insular forms would
appear to be a somewhat anomalous fact, but the
explanation is an extremely simple one. Again, geo-
graphical position is the cause of the absence of endemic
species ; and each one of these islands is situated in the
direct path of a strong migration, indeed acts as a sea-
bridge to its progress. The resident avifaunas of these
several islands are composed of species that range well
into Europe, cross them on their way to Africa, or
reside in them during the winter months. This inter-
mixture of individuals—due to migration—has prevented
any local races becoming established in these islands,
with the sole exception of the Corsican Nuthatch. This
exception, however, is one that proves the rule. The
Common Nuthatch appears everywhere to be a seden-
tary species, and to be absent from Malta, Sardinia, and
Corsica. The descendants of the individuals which in
emigrating north across the Mediterranean after the
Glacial Epoch became stranded residents in Corsica (and
it is probable that S. whzteheadi occurs also in Sar-
dinia), have remained sufficiently isolated to become

200 THE MIGRATION OF BRITISH BIRDS

segregated into a well-marked species. It is very
probable that the Nuthatch of Algeria will be found
to differ from the European type. It is therefore
most significant that the only instance of an endemic
species in these Mediterranean migration-swept islands
is that of one whose parent form is non-migratory, and
thus never interfered (by the intermixture of individuals)
with the process of differentiation.

Passing now to the Canary Islands, we are confronted
with a very different series of facts. As we have already
seen, these islands in remote ages probably formed the
extreme south-western termination of what was then
continental Europe. They formed a part of a great
Range Base of species during the Glacial Epoch, of
which many traces sti]l endure, either in the form of
endemic races or species, or in the annual passage to
and from them of many migratory birds. Their situa-
tion, however, at the very south-western limits or ex-
tremity of a refuge area, or range base on the northern
limits of a wide expanse of water across which we
have no evidence that purely terrestrial species pene-
trated, is a most favourable one for the establishment
of endemic forms. The Canary Islands still continue
to be the resort of a great many northern species in
winter, but there is no evidence of any strong migration
across them from north to south, for reasons which
have already been dwelt upon. This group of islands
within the past few years has received considerable
attention from ornithologists, among whom may be
mentioned Canon Tristram, Mr. Meade Waldo, and Herr
Konig. The result of these investigations has been to
show that the Canary Islands are, comparatively speak-

ee

ee See ee eee

ISLAND AVIFAUNAS 201

ing, singularly rich in endemic forms ; in fact no other
group of islands in the West Palzearctic region can boast
so many peculiar races or such abundant examples of
insular variation. The explanation is a very simple
one, and the facts confirm in no uncertain way the truth
of our general arguments respecting island avifaunas.
The number of endemic races may be taken at ten,
although this does not quite represent the peculiarities
of the islands, for several species and races not included
in that total are apparently common to Madeira and
the Azores as well. Of these ten no less than three are
island forms of two endemic species, confined to various
parts of the Canarian Archipelago, some of which
apparently interbreed among themselves. How have
these endemics become differentiated, and how do they
continue to preserve their characteristics? It will be
remarked that not one of them is an endemic race of a
species that now visits the islands on migration, or at
least that portion of the archipelago inhabited by the
peculiar form. They are all allied either to North-west
African sedentary species, or to birds that breed in
Europe and North-west Africa, yet do not extend their
winter migrations to the islands. When the Canaries
formed one unbroken area with the Atlas, there can be
no reasonable doubt that these endemic species were
not in existence. Being sedentary throughout this area,
they have—as submergence or volcanic action gradually
or suddenly reduced it to an archipelago—continued to
inhabit the localities where they were so isolated, and
have thus been able to preserve the differences which
now entitle them to specific or subspecific rank. It is
interesting to remark that the Canarian form of the

202 THE MIGRATION OF BRITISH BIRDS

Robin (Erithacus superba) is confined to Teneriffe and
Grand Canary, two of the most southerly and remote of
the islands, where the ordinary form of the Robin is
never seen ; and that the individuals of Parus ultrama-
vinus (a sedentary species ranging from Algeria to the
Canaries) present some differences of size and colour.
I may also remark that the Stonechats resident in
Algeria may yet be found to belong to the Canarian
form, or to resemble it more nearly than the migratory
individuals of this species. Whilst dealing with the
birds of the Canaries, I may take the opportunity of
making a few remarks on the number of eggs laid by
various species in the islands. It is a most curious and
interesting fact that many birds breeding in the islands
lay fewer eggs for a sitting than they are known to do
elsewhere. Thus we have the Blackbird with clutches
of two or three, frequently one; the Robin two or
three ; the Canarian Firecrest three to five; the Tits
three to five; the Teydean Chaffinch two; the Barn
Owl two; Bolle’s Pigeon one ; and the Canarian Pigeon
one! This small number to the brood, so general
among so many different species (especially in the case
of the Pigeons), is possibly caused by the scarcity of
food for the nestlings, or difficulty in obtaining it and
conveying it to the nest—the result of a long process of
natural selection.

With Madeira and the Azores we come to a slightly
different class of phenomena. These islands are very
remote from continental land, and their avifaunas are
perhaps entirely derived from fortuitous emigration.
Although Madeira numbers some 100 species, and the
Azores 38, each of these island groups can claim but

ISLAND AVIFAUNAS 203

two endemic forms. No wonder need be expressed at
the paucity of endemic species in Madeira and the
Azores, for they are situated too near the vast migration
that passes the coasts of West Europe, and are therefore
constantly being visited by abnormal migrants, out of
their proper course, which prevent the complete isola-
tion of the island individuals, and destroy by inter-
breeding any tendency towards specific distinctness. I
need scarcely remark that the endemic races are more
closely allied to species that rarely, if ever, reach the
islands. The various connections between the avifaunas
of the Canaries, Madeira, and the Azores are certainly
remarkable, and in some cases scarcely the result of
fortuitous migration. The facts seem to suggest that
these areas were formerly, and at no very remote era,
more extended and in closer proximity than is now
the case.

I might also remark that Japan, with its few endemic
forms, is precisely analogous to the British Islands. It
is situated on or near the direct path of migration that
flows down the extreme east of Asia, and its avifauna is
not sufficiently isolated ever to assume a very endemic
character. It is significant that the Bonin Isles, out of
the line of this dominant stream of continental migra-
tion, contain comparatively a very large number of
endemic forms.

A brief notice of Tropical Islands, remarkable for
their wealth of endemic species, now becomes necessary.
For instance, we have Madagascar with its 129 endemic
species, out of a total avifauna of 238; Borneo with 108
out of 580; the Philippines with 300 out of 472!
Many scores of similar instances might be given,

204 THE MIGRATION OF BRITISH BIRDS

especially from the Malay and Pacific Islands. We need
not inquire how or whence the avifaunas of these various
islands have been derived; all that concerns us is by
what means such a very large percentage of the species
has succeeded in becoming endemic. The indigenous
species of all these areas are sedentary. Vast numbers
of birds may visit these islands in winter, or pass over
them on migration, yet none of such birds are the direct
ancestors of these endemic species. The endemic avi-
fauna stands quite apart; its affinities are exclusively
with the non-migratory species in the more or less
adjacent areas, or with forms that from a variety of
causes have ceased to visit the area occupied by the
peculiar form. It is said that many of these endemic
island species owe their origin to volcanic or seismic
agency, a species often being isolated into various
groups, as a previously compact area has been divided
into various portions by earthquakes or volcanic action.
This is true, but only under certain conditions. Japan
is a great centre of earth disturbance, so are various
parts of the Mediterranean; but we do not find the
same results following upon such earth action as we
find in other areas, as, for instance, in the Pacific—
where almost every island possesses some endemic form
—or in the East Indian Archipelago, where the phe-
nomenon of peculiar species is very apparent and domi-
nant. If the geographical area be situated upon a
migration route, little specific change will result, no
matter how varied the physical disturbance ; if, on the
other hand, the disturbance takes place (even on a
comparatively small scale) in areas where no migration
occurs among the avifauna, or where species are chiefly

ISLAND AVIFAUNAS 205

sedentary, it will lead to the establishment of great
numbers of peculiar forms, proportionate to the amount
of isolation produced by such physical change.

I think, from a careful study of the facts, that we are
perfectly justified in coming to the following conclu-
sions. Firstly, it is only in the Southern Hemisphere
or within the Tropics, where migration is not very
extensive or is entirely absent, that we find islands
remarkable for endemic avifaunas; all the islands in
the Northern Hemisphere probably being Post-Glacial
and recent, so far as their avifaunas are concerned, those
in the Southern Hemisphere being generally of greater
antiquity, and dating to a very large extent faunally
from the last glacial epoch at the South Pole. Secondly,
that endemic sfectes may be established only in such
areas where the migration of the parent form has en-
tirely lapsed: endemic forms or races, not specifically
distinct, exist only in such areas where the migration of
the parent form is only slight, not sufficient entirely to
swamp the differences by interbreeding ; and that such
endemic races or forms are not necessarily evidence of
species just commencing their segregation, for obviously
they may be of considerable antiquity. Thirdly, endemic
species are never closely allied to species that pass their
area on migration. Fourthly, migration tends largely
to preserve the ornithological identity of all areas over
which it is dominant. Fifthly, changed conditions of
environment are to a very large extent powerless to
produce specific change if the geographical position is
unfavourable to complete isolation from a dominant line
of migration of the species affected.

The bearing of glacial conditions on the problem of

206 THE MIGRATION OF BRITISH BIRDS

island avifaunas is a very important one; and it is
probably entirely due to the influence of that recent Ice
Age that the Northern Hemisphere is so utterly poor in
endemic island species, it is a region of climatic forms ;
whilst on the other hand the rarity and shortness of
migratory movement in the Southern Hemisphere, due
to the present high state of glaciation of South Polar
latitudes, together with the greater antiquity of existing
conditions, to some extent explain the abundance of
endemic forms in all isolated areas, from New Zealand
to the limits of the northern tropic.

a PART II._MIGRATION

“

- A STUDY OF THE PHENOMENON OF AVIAN SEASON
_—s FLIGHT = ACROSS THE BRITISH ARCHIPELAGO.

We Muy13009 fo Ney ——~_ WAU Vie

Md
. ow
pean Erie empl
Stns.
bess

>

=

eS. i
"PROPPUY sy aoa

“ =e aang eats
oe ae

TAPP SPU TENE Jo UorMaT

PART II.—MIGRATION.

CEVA ais NTT:
ROUTES OF MIGRATION.

Difficulty of tracing Routes to British Islands—Definition of a
Migration Route—The Gradual Effects of a Changing Climate
on Birds—Impulses to Emigration and Migration—The Turn-
stone and the Rose-coloured Pastor—Ancient Breeding Ranges
—Inter-polar and Inter-hemisphere Species—Breeding Grounds
and Winter Quarters coalescing— Routes followed by Summer
Migrants to British Area—Routes into the South of England—
Species following them—Routes into Ireland—How followed
by Birds—Absence of Routes into Scotland vzé@ Ireland—Past
Physical Changes indicated by Present Routes of Migration—
Persistency shown by Birds in following Migration Routes—
Across the English and St. Georges Channels and the North
Sea—Palmén’s “ Fly Lines”—The North Sea Routes—Origin
of—Effects of Submergence on the Emigration and Migration
of Birds—West to East Migration—Water Areas a Check to
Emigration—Routes followed by Winter Visitors to and Coast-
ing Migrants over the British Islands—The Routes of Migration
that are most followed—Inland Continuation of Migration
Routes—Difficulty of Tracing—Correlation of Routes with
Breeding Grounds.

IT is a somewhat difficult matter to trace the various
routes by which migratory birds enter the British
Islands, especially in the south. This difficulty is en-
tirely due to our want of requisite information. I yield

to no one in my readiness to admit the value of the
P

210 THE MIGRATION OF BRITISH GIRDS

work accomplished by the British Association, respect-
ing the information collected by its committee con-
cerning Migration in the British Archipelago. But one
of the most important points of observation has been
entirely neglected. I allude to the complete absence
of information respecting migration between the Start
Lighthouse in Devonshire and the Varne Light-vessel at
the mouth of the Strait of Dover—the most interesting
stretch of coast-line throughout the entire British Archi-
pelago. Concerning the internal routes followed by
migratory birds, our information is still more meagre.
We now want.a thousand recording stations in inland
districts, with observations extending at least over a
period of five years before we can obtain sufficient
material to suggest very minutely the probable lines of
migration within the British Area. This need be no
difficult task, all that is required being the earnest
co-operation of ornithologists. In the present chapter,
therefore, I cannot treat the subject so fully as I desired ;
but I think we have sufficient material in our possession
to suggest some very important facts.

In the first place, it may serve to simplify matters if
we endeavour to explain What a Route of Migration is,
and How it has been formed. The following remarks,
be it clearly understood, apply as much to British species
as to species in all other parts of the world; and the
facts set forth must be constantly borne in mind by the
student of Avian Dispersal and Migration. In the first
place, then, we may remark that a bird’s breeding
erounds and its winter quarters were once continuous,
no matter how remote one may now be from the other.
The Northern Emigration has slowly progressed purely

ROUTES OF MIGRATION ZEY

by an extension of breeding area, which in many cases
has now ceased to be a breeding area in the extreme
south, owing to a change in the climate, due probably
to equinoctial precession ; but in many more cases the
breeding range and the winter range do still continue
to overlap at the southern extremity of the one and the
northern extremity of the other. The birds that breed
exclusively in the high north required a Polar temper-
ature, and were among the first to cease breeding in
temperate latitudes; but there is perfectly conclusive
evidence to show that when more southerly areas were
Arctic in climate, the breeding range extended over
them, as witness so many Polar birds wintering, if in
small numbers, in comparatively high latitudes, as, for
instance, the Knot in the British Isles.

It is only too popularly believed that the Glacial
Epoch was a saudden phenomenon; that birds left the
Arctic regions at once, as if overtaken by a change of
climate as quick as that which now marks the change
from summer to winter in the Arctic regions; and that
parties of a species, or the entire species, immediately
emigrated this way and that, along that coast-line or
‘down that valley, far south to a refuge from its rigours.
No more erroneous view of the facts could be con-
ceived. Ages most probably elapsed before any per-
ceptible difference could be observable in the northern
range of species, and no one generation of birds would
experience any perceptible change in the climatic con-
ditions. As the glacial climate slowly came on, the
breeding range in response slowly became more and
more southerly as the cold spread southwards. Species
simply retreated by extermination from those glacial

212 THE MIGRATION OF BRITISH BIRDS

conditions along the line of their past emigrations or
extension of range; in other words, the range shrank
back upon itself. Azrds, be 7¢ remarked, do not extend
their range or emigrate to increase the area of their
winter quarters. Paradoxical as it may seem, it is
nevertheless a fact, that BIRDS EMIGRATE AND MIGRATE
SOLELY TO BREED! Extension of range is prompted
exclusively by increase of breeding population, and
therefore takes place in spring, north in the Northern
Hemisphere, south in the Southern Hemisphere. Hence
we find birds much more sparingly dispersed in summer
at their breeding grounds than in winter at their winter
quarters, where they are often gregarious and exceed-
ingly crowded or abundant in small areas, due especially
to the influx of the young. Whether their winter area
is large or small depends entirely upon the localness or
otherwise of those conditions which were favourable to
breeding occupation prevailing during the time their
northern range was curtailed by glacial climates, or as
the breeding range spread across the world. The Turn-
stone, for instance, as an example of past widespread
southern breeding areas, and therefore present extensive
winter range, is a circumpolar species breeding chiefly -
on the shores of the Arctic Ocean; yet in winter its
migrations extend over all the coasts of the Southern
Hemisphere, which it inhabited as a breeding species
in emigrating north, and which there is much evidence
to suggest it still continues occasionally to use for repro-
ductive purposes, for it is said to have bred on Lord
Howe’s Island, Robben Island off the south coast of
Africa, on the coast of South-west Texas, on islands in
the Red Sea, on the Balearic Islands, the Canaries,

ROUTES OF MIGRATION 213

Azores, and Jamaica. On the other hand, as an
example of past local southern breeding areas and
therefore present limited winter range, we have the
Rose-coloured Pastor, a species whose breeding range
now extends from Italy to Lake Saisan in Central Asia,
but whose winter quarters are entirely confined to India.

The southern limit of that ancient breeding range is
now marked in a great many cases by the southern
winter limits of a species. In other cases the southern
limit of the Glacial (and of course Pre-Glacial) breed-
ing range is marked by the area occupied by a
sedentary southern form or representative species,
whose segregation is often due to isolation from the
northern form during the non-breeding season of the
former. With the Inter-polar species such as the Knot,
Turnstone, Curlew, Sandpiper, etc., the birds continue to
go as far south towards what were once their Antarctic
quarters, as they can find land on which to rest ; and
these movements unquestionably indicate that at some
period the migrations of those birds were absolutely
Inter-polar—the birds breeding at one pole and winter-
ing at the other. With Inter-hemisphere species such as
the Swallow, the birds continue to go far south into the
Southern Hemisphere; and their movements also indi-
cate that at some remote Pre-Glacial era their breeding
grounds were situated low down in that hemisphere, say
in South Temperate latitudes, and their winter quarters
high up in the Northern Hemisphere.

At the climax of the Ice Age the breeding grounds of
northern species, and the winter quarters of such species,
no matter how far south they may have extended, were
in the great majority of cases continuous and over-

214 THE MIGRATION OF BRITISH BIRDS

lapped. Migration then would be limited, the birds
that visited the northern areas in the immediate neigh-
bourhood of the ice-sheets and snow-fields during the
short summer, would draw south in winter (just as the
Song Thrushes that now breed in Scotland move south
in winter), but the majority of the individuals would be
more or less sedentary. As the climate:changed, and
a return to more genial conditions commenced, the
northern breeding range gradually expanded by emi-
gration, and the migrations as gradually became longer,
in many cases the breeding and wintering areas becom-
ing discontinuous (although continuous by Migration),
owing to change of climatic conditions, the North
becoming more suitable for successful reproduction
and summer residence, the South less so, but. still
adapted for winter residence.

All these facts tend to prove that Routes of Migration
are not only continuous, but that they were formed
whilst the species was extending its northern area by
emigration, and therefore represent the expansion of
breeding range which has taken place during Post-
Glacial time. The various Routes of Migration to the
British Islands may be divided into several very distinct
classes. First we have the Routes followed by Summer
Migrants—or of birds that come to our area in spring,
and depart from it in autumn. These are all situated
on our southern coasts. Then we have the North Sea
Routes, which are chiefly traversed by the great stream
of east to west migrants that visit us in autumn
and leave us in spring; whilst, lastly, we have the
Routes followed by species that come to our area
to winter, or that pass over it on their way to more

ROUTES OF MIGRATION 21S

southern lands in autumn or to more northern lands in
spring.

We will first consider the Routes followed by our
Summer Migrants, and endeavour to trace the various
points at which these species enter and depart from the
British Archipelago. Unquestionably these routes are
the most difficult of all to trace, owing to our sad lack
of necessary information. In the first place, we must
continually bear in mind the Law that forbids a southern
emigration, and which renders a flight south in spring
impossible. So far as I can at present ascertain, the
bulk of our Summer Migrants enter the British Area
between say Beachy Head and Dover. Less important
points of entry are situated on all the great southern
land projections from Selsey Bill to the Lizard, including
the Isle of Wight, St. Alban’s Head, Portland Bill, and
the whole of South Devonshire (locally known as the
“South Hams”). As we progress west, however, the
Migration gradually assumes a weaker and weaker
character, and probably is extremely slight at the
Lizard. The Migration that enters by the south-west
coast of Ireland, judging from the British Association
Migration Reports, is weak, as we might naturally expect
to be the case, owing to the wide water area between
that district and continental land. We have many
indications that the migration of birds into the south
of England is much weaker in the west, where the sea
is so much wider, than it is in the east, where the sea-
passage isnarrow. But little migration is reported from
the Start Lighthouse, the keeper stating “that very few
birds are observed at his station.” For instance, many
summer migrants are notably rare in the south-west of

216 THE MIGRATION OF BRITISH BIRDS

England, or even absent altogether from that area
which are commonly distributed or at least present in
more easterly localities. Among such species we may
mention the Redstart, which is very local west of
Somerset; the Wheatear, which is only seen sparingly
in spring, although further east it literally swarms all
along the area of the Downs; the Whinchat, which is
equally local in Devon and Cornwall, and only known
on abnormal flight on the Scilly Islands, but abundant
and widely distributed in more easterly localities ; the
Nightingale, absent altogether west of Somerset; the
Lesser Whitethroat, very scarce and local in South Devon,
and only an abnormal migrant to Cornwall; the Reed
Warbler, absent from the entire south-west, except as
an abnormal migrant; the Tree Pipit, decidedly more
rare and local in the south-west than elsewhere; the
Pied Flycatcher, only in limited numbers on migration
(I have seen one example in four years), and might
almost be classed as abnormal; the Wryneck, much
more rare and local in the west than the east; the
Turtle Dove, rare east of Devon ; the Corncrake, much
rarer and more local in the west than the east; the
Kentish Plover, normally entirely absent, although one
might have expected it to pass our entire southern
coasts on migration; the Wood and Green Sandpipers,
much less frequent in the south-west than in the eastern
counties. I may here remark that the species entirely
absent from the south-west of England, and obviously
only entering our area further east, would have to
migrate south in spring to reach that district, an
extension of area contrary to Law; whilst the extreme
localness of other species proves that they do not enter

ROUTES OF MIGRATION 217

further east and then migrate south-west, as the much
wider sea-passage is not only more fatal to the birds
that cross it, but is essayed by a vastly less number of
individuals. If these birds were equally common in the
south-west of England as in more northern and eastern
districts, we should find either a southern movement
after entering our area, or as strong a migration across
the wider portions of the English Channel as across the
narrower portions, slightly more north and much further
east—two assumptions which have no facts whatever to
support them. From the above facts we may safely
draw the inferences that wot a single species exclusively
entering the British Islands east say of Portland Bill
breeds south of Dartmoor, that all species do not breed
anywhere south of their point of entrance; and that all
species breeding in the extreme south-west of England
enter from continental land south of them, probably by
way of Cape la Hague or the Channel Islands. There
can be no doubt whatever that headlands are the great
points of arrival and departure; they are the most
enduring portions of the coast-line ; the most important
land-marks, and easily recognized. From the various
southern promontories the great stream of spring migra-
tion spreads into our islands, fan-like northwards, east
and west.

From the south of England we pass to a consideration
of the Routes to Ireland. This island is far more iso-
lated from continental land than England and Scotland,
and the fact is reflected in the migration of birds to its
area. The only possible points of egress for Summer
Migrants are in the south, and separated by wide water
areas from England. From a careful study of the British

218 THE MIGRATION (OF BRITISH BIROS

Association Reports it is very palpable that there is very
little migration into Ireland in the extreme south-west,
infinitely much less even than that observable in the
south-west of England. Records from Fastnet indicate
that the Wheatear, “Swallows,’ and Whimbrel enter
Ireland by that route, but the migration at this station
is evidently trifling, especially in spring: in autumn more
birds are. observable, but many of them are obviously
abnormal migrants too far west of their usual course
south, or they should be observed in spring as well. At
the next station east (Galley Head) much the same state
of things prevails, the keeper very significantly remark-
ing (Report, v. p. 86) that he has “never been at a station
with less birds about than this one.” The same remarks
practically apply to all the stations on the south coast
of Ireland until we reach the vicinity of St. Georges
Channel, when we begin to obtain conclusive evidence
of a regular and fairly strong migration in spring from
the south. This water area, I need scarcely point out, is
the narrowest sea-passage for all birds entering Ireland
from the south, and is the point of former land connec-
tion between that island and England. It is the one
principal route of Summer Migrants into Ireland ; Holy-
head, St. Bees, and Menai showing no spring route to
Ireland whatever. The route from England either fol-
lows the extreme south-west, perhaps crossing the
Bristol Channel vz@ Lundy, but mostly higher up in the
narrower portions, thence following west through South
Wales to Pembroke, where the sea-passage begins ; or,
it may extend north-westerly from the south coast of
England across the Bristol Channel or the mouth of
the Severn, and thence 77¢@ South Wales by the same

ROUTES OF MIGRATION 219

route. That some birds follow this route to Ireland
exclusively is proved by the date of their arrival in the
extreme west of that island. Unfortunately we have
not much data to go on, but I notice among one or two
other instances that the Spotted Flycatcher does not
reach the west of Ireland until the last half of May, a
fortnight or more after its appearance in the south-west
of England. Did it enter Ireland in the south-west it
would arrive as early as in England. From recording
stations in St. Georges Channel we also have many
records in spring and autumn of such common summer
migrants as Ring Ouzels, “ Swallows,” Willow Wrens,
Wagtails, Cuckoos, and Corncrakes, passing north-west
into Ireland at the former season, south-east on the
return journey at the latter season, v7d England south
to their winter quarters. Unfortunately we know little
of the distribution of birds in South-west Ireland, Juz
there can be no doubt that none of the species that enter
the country exclusively across St. Georges Channel breed
south of lat. 52° 10’. Species that do breed south of
that latitude in Ireland enter the island by way of the
coast of Cork and Waterford. As we have already seen,
very similar conditions prevail in the south-west of
England, the geographical position of the two areas
being almost precisely alike in relation to the nearest
land masses south of each.

I may here again take the opportunity of pointing out,
that notwithstanding the much more favourable geo-
graphical conditions in the north-east of Ireland, not a
single summer migrant is known to enter that area
across the North Channel, another very convincing
proof of the Law which forbids a southern extension of

220 THE MIGRATION OF BRITISH BIRDS

breeding area. It is significantly enough reported by
the keeper of the South Maidens Light, in the very
centre of this North Channel, off the Irish coast, that
“no birds strike the lantern in April and May.” This
fact also implies that none of our summer migrants
reach Scotland by way of Ireland.

The routes followed by these Summer Migrants very
plainly indicate the physical changes which have taken
place in the British Area, and also the approximate date
of the first arrival of such species as emigrants in Britain.
In the first place, we know that migrants continue to
cross wide water areas in such cases where the line of
Migration had become established before submergence
had made any appreciable alteration in the physical
character of such areas—hence the persistent passage of
birds across the North Sea from and to our islands. In
the second place, we have very ample proof that Emigra-
tion or the extension of breeding range is rarely if ever
attempted across wide water areas, such increase of
summer area having perhaps invariably been accom-
plished before submergence took place and such water
divisions came into existence. Keeping in mind these
two very important conditions, we are able to deduct
the following interesting facts from a study of the known
Routes of migratory birds in spring to our islands.
First, that the birds which cross the widest water areas
are the descendants of those species that were the first
to colonize or extend their breeding range to our area
after the Glacial Epoch. At the present day these are
few both in number of species and individuals, and they
are found still to continue to enter Ireland in the
extreme south-west, having reached that area when the

ROUTES OF MIGRATION 22%

land extension southwards was much greater than it now
is. They are hardy northern species, be it remarked, the
Wheatear, “ Swallows,” and Whimbrel for instance, all
birds that have extended their breeding range to the
Arctic regions. The greater difficulties of such a route at
the present time may possibly have reduced the number
of individuals very considerably, and we can almost pre-
dict a future time when all migration by that route may
cease. Jf this should happen, the Wheatear will cease
to breed in the extreme south-west of Ireland. Second,
that the St. Georges Channel land connection with Ire-
land continued to endure for some time after the land
at the extreme south of Ireland had disappeared. At
this time too we may be tolerably certain that much of
the Bristol Channel was then dry land. These facts are
still reflected in the great and almost only Migration
Route to Ireland at the present day across St. Georges
Channel. It marks the point of entrance into Ireland of
most of its avian summer visitors. Wide water areas
were already formed in the north of the Irish Sea, and
submergence was rapidly spreading south down that
sea—checking all emigration from Central and North
Wales to Ireland, even of sedentary species, as the few
last Summer Migrants succeeded in extending their
breeding range to the Irish Area. Complete severance
of Ireland from England must have taken place before
the island received its due share of these summer
visitors, the last land connections in the south across
St. Georges Channel disappearing and checking all
emigration in that direction. Migration, as we know,
would still continue across the slowly widening sea,
for once the habit of visiting Ireland was acquired,

222 THE MIGRATION OF BRITISH BIRDS

no reasonable amount of slow physical change would
arrest it.

We now pass to England. There can be no question
that a land connection endured across the mouth of the
English Channel after the submergence which took place
off the south coast of Ireland, and that which severed
Ireland from England. All the evidence suggests that
this submergence took place, both east and west of the
British Islands, from north to south, as we shall also
learn when we come to study the routes across the
North Sea. Whilst the mouth of the English Channel
remained dry land, a few more of our summer visitors
succeeded in extending their range northwards to Eng-
land—among these later arrivals we may mention the
Redstart and the Tree Pipit, but the Nightingale, the
Reed Warbler, and other eastern species could not have
done so. The Channel Islands remained continental
until the sea had encroached some distance up the-
English Channel. As the sea gradually encroached upon
the land, and the English Channel began to appear,
other birds gradually extended their range northwards
across what are now the narrower portions of the
Channel, and their line of migration was continued
across the widening water area year by year, no single
generation of birds, of course, being able to perceive
the slightest change in their route. Finally, and at a
much later period, when the climate must have grown
considerably milder, the land mass of the Channel
could not have extended much further west of the Isle
of Wight ; and across this narrow neck all the latest
species to arrive made their final entry before the
waters of the Strait of Dover mingled with those of

ROUTES OF MIGRATION 223

the North Sea across the low watershed, of which the
cliffs at Calais and Dover then formed the continuous
highest ridge, and completely isolated the British Islands
from continental land.

With such facts as these before us, surely the cross-
ing of the Channel by migrant birds in spring and
autumn can be nothing very wonderful after all. The
submergence took place very slowly ; the doomed land
perhaps being swampy at first, then gradually studded
with lagoons, and finally becoming open narrow sea,
wider and wider. Throughout all this slow and
gradual change the migration (and emigration) of birds
went on, no single generation noticing a change, until
‘the complete transference of land to water had been
accomplished. The birds with dogged perseverance and
admirable persistency stuck to their old routes—the
only ones, be it remarked, of which they could possibly
have had any knowledge—and continue to stick to
them down to the present day. The Wheatears that
cross the wide expanse of sea to the south-west of
Ireland know of no easier and safer passage; the
Redstarts that land in England on the South Hams of
Devon know of no narrower route further north and
east ; whilst those fortunate individuals that have
descended from the later settlers which entered our
area where the Channel now is narrowest, never experi-
ence normally the greater terrors of the prolonged flight
across that Channel in its wider aspects. I may also
remark that there can be little doubt that the reason the
stream of migration is so dominant at the Strait of
Dover is purely because the land connection there was
coincident with the dominant line of northern extension

224 THE MIGRATION OF BRITISH BIRDS

into our area, and that entrance at this former land
connection was sufficiently south to admit of normal
range extension throughout the greater part of the
British Islands say north of lat. 503?°—a fact which is
proved by the strong migration east and south-east in
autumn towards the Strait of Dover. The same re-
marks apply to the migration (and past emigration)
across St. Georges Channel, only the latitude will then
have to be extended north to 52° 10. Tosay that birds
in autumn, for instance (the same remarks apply to
_ spring ‘as well) are all making for the narrowest sea-
passage to the Continent is absolute nonsense. If birds
were guilty of breaking the Law of their dispersal so
flagrantly, why, I ask, do not the tens of thousands that
cross the wide North Sea each season—between say
Heligoland and Hull—pass south to Calais before they
attempt to make the passage? We know, of course,
that numbers do so cross at that narrow passage, but
the circumstance is entirely due to the line of emigra-
tion followed by the ancestors of those individuals, and
is merely a coincidence.

Palmén’s elaborate system of “Fly Lines,” which he
postulated in his endeavour to trace the Migration
Routes of birds, are myths. No special route of migra-
tion is traversed ; species follow the course that their
range expansion has taken in past ages; and the route
can only be regarded as a comion one (as a “ Fly Line”
in Palmén’s meaning), in the sense that many species
have extended their areas of distribution along it. It
may be urged that in all countries traversed largely by
migrants, there are certain routes which are much more
crowded than others ; that in some districts little or no

ROUTES OF MIGRATION 225

migration is apparent, whilst in others it is palpable even
to the most cursory observation. This is perfectly true,
and is the result of the survival of the fittest, the easiest
routes being occupied season by season, by the descen-
dants of birds that extended their area along them ; the
more dangerous routes being abandoned, because the
perils in following them have been so much greater, and
resulted in the gradual extermination of the individuals
and their descendants that had followed them during
their Post-Glacial emigrations. We may safely presume
that in earlier ages migration was most numerous
and important across certain areas (the mouth of the
English Channel, and to the south and south-west of
Ireland, when dry land) where it is now least appar-
ent and least extensive, seeing that the areas to which
those more ancient routes led were probably colonized
much earlier and in greater abundance by emigrating
or range-expanding species directly after the Ice Age,
than more northern and eastern areas, say where the
English Channel is now the narrowest. As the sea has
encroached, the migration route has become more peril-
ous, with the inevitable result that birds have been
exterminated in their persistent efforts to follow it.
At the present time the most used routes are those
where the passage is attended by the minimum of
danger, and where the conditions of flight are the most
favourable. But this is not choice on the part of the
individuals following these routes, but the accident of
direction of Post-Glacial emigration, the survival of the
fittest. We can thus see why the narrowest seas are
crossed in greatest numbers by migratory birds, why

the most favoured valleys, coast-lines, or mountain
Q

226 THE MIGRATION OF BRITISH BIRDS

passes are followed, why headlands and peninsulas are
more favoured points of arrival and departure than
deeply indented coasts—the simple explanation being
that the more difficult routes have become deserted
through the extinction of the individuals following them,
or continue to be followed by a few survivors, destined,
nevertheless, sooner or later most probably to complete
extermination. Had all routes of passage remained the
same, continued unchanged so far as the dangers are
concerned, Migration would have endured uniform in
character between breeding grounds and winter quarters
or range bases; but the various physical mutations
along the route have minimized or increased the perils
of the journey, and at the same time rendered that
Migration uneven in character, dominant in some places
slight, or even entirely absent in others. Thus the
migration across the North Sea! is general and very
uniform in character; that across the English Channel
is local and most irregular.

The North Sea Routes, which are perhaps most con-
spicuous on the eastern coasts of the British Islands,
have already been dealt with at considerable length in
a previous chapter, so that little more respecting them
need now be said (conf. pp. 130-131). We may, how-
ever, remark that they originated in precisely the same
way as those Routes across the English Channel, and that
the facts they now present are entirely in harmony with

1 It is not improbable that the Migration across the North Sea
may ultimately become of a much weaker character, especially as
regards small Passerine birds. The area which this Migration
drains is many times larger than the British Isles, and consequently
the movement will continue unaffected to any appreciable extent by
adverse conditions for a much longer period.

ROUTES OF MIGRATION 22,

the progress of that vast submergence which brought
the North Sea into connection with the English Channel
across the Strait of Dover. As previously stated, this
submergence undoubtedly took place in a north to south
direction, if the geographical distribution of birds is of
any value as an indication of past physical change. It
follows then that this area, say north of the Humber,
was for the most part a water area between the latter
locality and Denmark, before the emigration of species
eastwards commenced, yet not before a line of north-
east Emigration had progressed towards Scandinavia, as
is proved by the present limits of the great East to West
Migration that now breaks upon the east coast of
England in autumn. The bulk of this migration from
the east strikes our eastern coast-line from Yorkshire
southwards, just as the bulk of our northern migration
in spring of summer visitors is most dominant in the
vicinity of the Strait of Dover—eloquent proof, I take
it, that the North Sea plains endured longer in the
south than in the north. This East to West (or more
correctly speaking, West to East) Migration extends
right across England and Wales to Ireland; and here
we may remark, that there is evidence to prove that the
Irish Sea is crossed in a direct line east to west,’ say
from Holyhead southwards to the north of Pembroke,
which is just what we ought to find if our previous view
of the past physical changes in the British Area is a
correct one. The birds that follow this east to west

1 Here, for instance, is the report of the keeper of the Kish Bank
Light Vessel, stationed off Dublin Bay : “ September and October
are the chief months for the migration of birds from the Welsh
coast” (Report, iv. p. 76).

228 THE MIGRATION OF BRITISH BIRDS

route in autumn are all hardy species which must have
been among the first to enter Britain after the Ice Age
had passed away, and when it was practically a compact
continental area. No Irish Sea then existed ; Ireland
was then probably better suited to the requirements of
all Passerine species than any other part of Britain, due
entirely to its proximity to the open sea and warm
ocean currents, and from there emigration eastwards
undoubtedly commenced, as is proved by the migration
to that area of so many of these east to west species.
The Starling, the Sky Lark, and the Short-eared Owl
are especially good instances of this line of past Emigra-
tion, as they migrate in such vast numbers, palpable to
every observer, right across England to Ireland, where
they are known to occur in enormous quantities in
autumn, starting on their return journey east in spring.
I may also remark, again, that the Short-eared Owl is
not known even to breed in Ireland now, although
common enough there in winter. It may also be stated
that none of this east to west migration is perceptible in
the south-west of England, although there is a con-
siderable amount of the migration from the north-east
observable even down to Land’s End (conf. table, p.
132). Here, then, is eloquent testimony of the impas-
sable nature of a water area to Emigration, and of the
futility of such an obstacle to arrest Migration estab-
lished previous to the submergence! We have seen
how Emigration has been effectually checked by the
comparatively narrow St. Georges Channel, and now
see how the wide Irish and North Seas—formed after
successful emigration—are impotent to arrest the Migra-
tion of species whose range was gradually extended

ROUTES OF MIGRATION 229

over their area when dry land. The submergence
which caused the incroach of the Irish Sea has had no
more visible effect upon this East to West Migration
than the subsidence which drowned the North Sea
plains has had on its progress there. The habit of
crossing those areas has been slowly acquired by an
extension of breeding range, and still continues to be
followed with a persistency as astonishing as that which
characterizes the migrations of the lemming, whose im-
pulse to migrate over the now submerged or effaced lines
of its former emigrations is so dominant that nothing
but death itself can eradicate it! In conclusion, we
may remark that evidence of the north-east to south-
west migration to Ireland is evident at many stations in
the North Channel and in the north of the Irish Sea,
one of the most interesting instances (because so easily
traced by numbers) being that of the Goldcrest; a
species which, we have already shown, extended its
breeding range north-east across the British Area to
Scandinavia. These north-eastern species are specified
in a preceding chapter (couf. p. 132).

We now pass to a consideration of those Routes
followed by species that come to our islands to winter,
or that pass over them on their way to more northerly
or southerly areas. Broadly speaking, these Routes
extend very impartially over the United Kingdom, as
we may very naturally expect to be the case. All these
species are northern in their summer dispersal—hardy
or Polar species that were absolutely the first to extend
their emigrations over the British Area after the climate
of the Ice Age had sufficiently moderated to permit of
successful avian colonization northwards. They are

230 THE MIGRATION OF BRITISH BIRDS

species that at one time bred in our area, and whose
range extended northwards with the changing climate
across it, until Britain was entirely (or nearly) deserted
in summer, as the breeding range more or less com-
pletely passed on to the north. I say “nearly” in some
cases, because a few individuals of such species for
instance as the Wigeon, the Greenshank, etc. (conf.
table, p. 151), still continue to breed in our islands,
but more dominantly to winter in them or to pass them
as coasting migrants. None of the birds whose breed-
ing and winter range overlap in the British Area are
Inter-polar or Inter-hemisphere. Some of these birds,
as for instance the Little Stint, the Sanderling, and the
Ringed Plover, were never resident in our area (no more
than the Swallow is), although their breeding range once
unquestionably extended over it, and as far to the south
of it as the winter quarters once extended north from
south Polar latitudes during the time Antarctica was
occupied. They are dominant Inter-polar species that
must always have passed far to the south or south-east
to winter, and which may be regarded as our earliest
Post-Glacial summer migrants, whose breeding range
now only begins far to the north of us.

During this period the British Area was practically
unbroken and compact, not only far south towards the
Bay of Biscay, but far north in the direction of Iceland,
Greenland, and Scandinavia. The vast submergence
that has taken place has broken much of the continuity
of these Routes of Migration, but they are still followed,
as we have found to be the universal rule. The North
Sea between Scandinavia and Scotland is still swept by
these migrant hosts each season; the wider waters are

ROUTES OF MIGRATION 23m

still crossed between Greenland, Iceland, and the Faroes,
and between the south of Ireland and the Lizard, as
they were in remote ages traversed when dry land, or
nearly continental dry land, replaced them. Most of
these birds, it will be remarked, are aquatic, able to make
long flights across the sea, powerful of wing; and it is
possibly due to these facts that they have been able to
conform to the Law of Migration so successfully and so
long, notwithstanding the enormous change which has
taken place along their recognized routes—now only
rendered visible in some cases by an isolated island here
and there, which may serve as a welcome landmark or a
possible place of rest. We thus see again that the wide
water areas are no obstacle to species that acquired the
habit of crossing them when they were dry land,
although they are barriers to emigration and range
extension which no species attempts to pass.

These Routes unquestionably are most followed along
our eastern coasts, due not only to the greater land
mass of Scandinavia lying nearest to that area, but to
the fact of the Shetlands assisting in deflecting a great
deal of it east. Most of the species that follow them
are coast birds, and they chiefly keep to the coast-lines
on their way to their northern or southern destinations.
We have one important Route from Scandinavia, not
only by way of the Shetlands and Orkneys, but right
across the North Sea in a south-westerly direction to the
Scotch coast. The former portion of this Route divides
at the Orkneys, one continuing down the east coasts of
Scotland and England, the other following the west
coast of Scotland to Ireland and the west coast of
England. Another Route, followed, however, by few

232 THE MIGRATION OF BRITISH BIRDS

land birds, extends from Greenland, vzé@ Iceland, the
Faroes, St. Kilda, and the west coast of Scotland, to
Ireland. I have already dwelt at some length upon
the emigrations of species that followed many of these
Routes, so that it is unnecessary to enter into greater
details here.

Before dismissing the subject of Routes it will now be
advisable to deal a little more fully with their inland
continuations. These, I need scarcely remark, are
extremely difficult to trace, owing to the sad lack of
an all-necessary series of long-continued observations.
There can be little doubt, especially in the case of locally
distributed species, that these Internal Routes are com-
plicated, although they will be found to conform exactly
to those laws which govern the migration of birds else-
where. We have already seen that birds follow most
closely in their present migrations the past line of
Emigration—however complicated and tortuous that
may be. Could we only define the limits of emigration,
we should find them to agree precisely with the present
Routes of Migration. We may safely put down as an
invariable rule that the Internal Routes of migrants
trend in the present direction of suitable breeding
conditions, or over such districts that were once suitable
areas for reproduction. River valleys, as long as they
trend northerly, are certain routes for migrants ; for
there can be no doubt that from earliest times they were
favourable localities for range extension. Mountain
chains will just as surely indicate the routes followed by
other birds whose conditions of successful reproduction
are only to be found in upland districts; whilst lake
systems, swamps, heaths, woodlands, or cultivated dis-

ROUTES OF MIGRATION 233

tricts will all mark the Route of Migration followed by
the several species that reside only in such localities.
The migration routes of the Dotterel, for instance, will,
broadly speaking, follow the mountain uplands; and
this may explain why so little of this species is seen
whilst it is on passage. It is also interesting to remark
that this bird is known to pass on migration the districts
where it formerly bred. The Ring Ouzel, the Wheatear,
and the Merlin will also follow a mountainous route, as
the direction along which their past emigrations were
carried. The routes of such species as Sandpipers and
Ducks will follow rivers and lakes; those of the Rails
and Snipes will follow the northern trend of the swamps ;
those of the Stone Curlew and the Nightjar the heath
systems and the commons; whilst those of such species
as the Hobby and the Honey Buzzard would be confined
to the northern extension of woods. In many cases
these Routes have lapsed as Breeding Routes, either
through modification of climate, as the northern exten-
sion of breeding range spread over our area, or the
disappearance of suitable breeding grounds, as such
have been “improved” away. Such Routes will con-
tinue, however, to be followed by the descendants of
birds that increased their range along them. In the
utter absence of detailed information, I shall refrain
from more closely entering into the subject of Internal
Routes; but I may refer the reader, in addition to the
above information, to what I have already said in the
Migration of Birds (pp. 242-245).

GCEIAP TER oye:
CONDITIONS OF FLIGHT.

Routes of Migration, how followed by Birds—Paley’s Definition
of Instinct—Impulse of Migration—Restlessness of Captive
Birds—Certain Routes followed by Certain Individuals—
How a Route of Migration has been Learnt—Mysterious
Sense of Direction” a Myth—Altitude of Migration: Flight—
Advantages of a Lofty Course—The Order of Migration—A
few Old Birds Migrate as Early as the Young—The Daily
Time of Migration—Amount of Sociability amongst Birds on
Passage—The Perils of Migration.

IN the preceding chapter we endeavoured to ascertain

how a Route of Migration has been formed; it now

becomes necessary to inquire how birds continue to
follow those routes so unerringly, how they manage to
traverse them for such long distances apparently with

so few mistakes. If we define Instinct as Paley did,

and describe it as “a propensity prior to experience and

independent of instruction,” which I think is about as
good a definition of the power as we can ever hope to
possess, then most assuredly Instinct can never control
the performance of avian season-flight. The impulse of
migration may be, and probably is, a very deeply rooted
one, an hereditary impulse even. Captive birds in which
the habit of migration is dominant, have often been
observed to become exceedingly restless as the usual

CONDITIONS OF BEIGE Tf 235

time for their departure approaches, and there is much
evidence to suggest that such restlessness is invariably
increased or further excited by the sight of companions
en route, or by the cries they utter when on flight. We
remark the display of a similar state of restlessness
among birds at liberty upon the eve of their departure,
the gatherings of some birds, the unusual activity of
others. Whether a falling temperature or a failing
food-supply assist in intensifying this impulse we do not
at present know, but there can be little doubt that the
departure is taken when the impulse becomes tco intense
to be longer resisted, whatever be its initiating cause.
_ Once, however, a bird begins its migration all Instinct as
a guiding medium ceases ; memory and knowledge of
locality, in fact experience, assist it to perform that long
journey. Migratory birds follow routes in every case
that indicate the line of their extension of range or past
emigration. These routes have been slowly formed and
are continuous, either from the area where the species
now winters, and where in past ages it formerly bred, or
by the absolute overlapping of the summer and winter
range. The individuals that follow one route by no
strange chance ever follow another ; even though their
own may be fraught with perils and difficulties unknown
to the other, it is still retained ; and even though one
route may be much longer and more tortuous than the
other, it still continues to be followed. If this were not
so, why should some individuals of the Wheatear, for
instance, elect to take a wide ocean passage to the
south-west of Ireland, whilst other individuals cross by
the Strait of Dover? Why should the Redstarts breed-
ing in or passing over Devonshire, cross the English

236 THE MIGRATION OF BRITISH BIRDS

Channel where it is four times as wide as where indi-
viduals breeding in or passing over more eastern counties
cross? There can be but one answer to such a ques-
tion, and that is, that these individual birds follow a
route along which their ancestors increased the range
extension northwards, that they have no knowledge of
any other route, and are not endowed with any instinc-
tive faculty that will help them to migrate by any easier
way. If the route be exceptionally dangerous, or the
difficulties in following it increase, it will still continue
to be followed, until every bird that follows it is exter-
minated ; it can never be changed (conf. pp. 223-226).
The Route has been slowly learnt by the species as
the summer area increased. When the extension of
breeding range commenced the extent could probably
have been measured by yards rather than miles; by a
short flight to a more distant lake or swamp; a visit for
nesting purposes to some outlying grove or forest; or a
trip north along a coast for a little way to a suitable
stretch of sand or shingle, or range of cliffs—prompted
chiefly by overcrowded quarters to the south. As the
species multiplied the range increased. Each year the
journey became longer, more distant from the base or
centre of dispersal; so slowly that perhaps not more
than a mile or so might have been added to the northern
area of a species in a century, as favourable conditions
to extension were gradually presented. ‘The flight back
in autumn was therefore at the beginning a very small
one, and never perhaps included any sea-passage what-
ever. But our Summer Migrants now, we know, cross
the Channel every year; they do so because the line of
their past emigration extended across that area when it

CONDITIONS “OF FLIGHT 237

was dry land; their migration route gradually assumed
its present aspects as submergence progressed, no single
generation of birds having experienced any very sudden
change, the sea-passage becoming imperceptibly wider
and wider as the land vanished, until the present state
of things was reached.

That migration routes are traversed by experience,
and not by inherited impulse, is further proved by the
variability of the habit, some individuals going longer
distances than others, some remaining stationary alto-
gether. Again, if birds are endowed with that mysterious
“sense of direction,’ which popular opinion so readily
ascribes to them, how can that sense explain the endless
routes, the tortuous journeys, the migrations this way
and that to common range bases or centres of dispersal ?
How utterly at fault it must be in those species that
breed in the far north-east and that winter in the
remote south-west ; how impotent in species that breed
in Pomerania and journey south-east all the way to
India to winter, when just as suitable localities are
available directly south and not a quarter of the dis-
tance! Is it not more rational to presume that these
migrant birds are following the route of their ancient
range extension, a route with which they must be
thoroughly familiar, the result of it may be thousands
of years of experience? The very fact that migratory
birds, generally speaking, keep so closely to their normal
areas of distribution is a most convincing proof that they
do not wander from their routes of passage. For this
reason I consider it most absurd to say that a wave of
migration has been deflected this way or that normally.
If it were so, birds would be drifted into country of

238 THE MIGRATION OF BRITISH BIRDS

which they have had no experience, cf which they can
therefore have no knowledge, and would be lost to all
direction or locality. How rarely do we have any proof
of this. It is true migrants are repeatedly driven out of
their usual course by storms and fogs, and this abnormal
deflection from their proper route is fatal to vast numbers
of birds every year. Were birds endowed with this
mysterious inherited sense of direction, most of the
wonderful scenes at our lighthouses in spring and
autumn would never be witnessed at all. But the perils
of the journey are great and constant ; birds blunder to
an almost incredible extent; lose their way or perish
every year in numbers that can only be described as
astounding !

Another very important condition of Migration which
is too often and too persistently ignored by the majority
of people is the altitude at which it is undertaken. I
have already dwelt at considerable length upon this
subject in the MWzgration of Birds (conf. pp. 77-84), to
which I would again refer the reader. The advantages
of such lofty flight are very obvious. Let a person stand
on some moderately lofty hill, say 400 feet or so above
the level of the sea, and let him remark the vast area
of country over which his vision can extend. The more
he increases his altitude, the wider will become the view
—hills, valleys, and coast-lines spreading out before him
in one uninterrupted expanse. Birds flying along a
lofty course will readily recognize the various landmarks
that they and their ancestors have been in the habit of
passing for ages. A headland, a river valley, a wide
reach of sand or shingle, for instance, may mark the
spot where the sea-passage begins; a lofty down, a

CONDITIONS OF FLIGHT 239

similar headland, or a wide expanse of heath or forest
may just as surely indicate the point where that sea-
passage terminates. Inland Routes are followed in
much the same manner, old familiar points being
recognized and passed with amazing precision every
year. I can recall many instances of birds passing
certain moorlands, certain sheets of water, certain woods
and heaths on migration with a regularity that must
surely indicate the appearance every season of the same
individuals or their direct descendants.

A few words now on the Order of Migration. There
is a very generally prevalent idea that the young birds
are the first to migrate in autumn, and this has been
repeatedly brought forward as a most convincing proof
that birds are born with an instinctive knowledge of the
route they must traverse to their winter quarters. That
this order of migration prevails amongst many species
cannot be doubted. The young unquestionably appear
in ‘many localities it may be weeks in advance of the
general migration of adult birds. But let it be remarked
that a few old birds invariably precede as well as
accompany these first flights of the young—old indi-
viduals with a full knowledge of the road that have
acted as guides to the inexperienced. Many young
birds, however, go astray on their autumn journey south,
and it is remarkable that the bulk of abnormal migrants
at that season is composed of young birds that have lost
their way. As I previously pointed out in the Alzgratzon
of Birds, the individuals that are the first to migrate in
autumn are birds that have been prevented from breed-
ing or that have lost their broods. Such individuals
have no parental instinct to restrain them from starting

240 THE MIGRATION OF BRITISH BIRDS

early, and they frequently begin to move south before
their moult is completed. These may be regarded as
the pioneers, and with their departure the flight south
of the young commences. ‘These young often set off as

soon as they can fly, and individuals of certain high
Arctic species have been observed on the British coasts
even with the down of their nestling plumage still
adhering to them. Soon after the departure of the bulk
of the young the adult males begin to leave their —
summer quarters, the females following a little later,
their moult being delayed somewhat by maternal duties.
In the rear of the migration come the laggards—indi-
viduals delayed by accidents to their flight feathers, or
other casualties. The order of return in spring is to
some extent reversed. As usual, the adult males initiate
the migration; then follow the females; the young of
the preceding season follow, and lastly the maimed and
weakly individuals. These and the young (or birds of
the last season) frequently pass the summer some
distance south of the actual breeding grounds, or actually
remain in some cases in the winter quarters.

The daily time of migration also varies considerably.
Some species migrate exclusively by day; others just
as regularly by night ; some by night as well as by day.
The punctuality of their arrival and departure is also
profoundly interesting ; and it will almost invariably be
found to be the rule that the birds that arrive earliest in
spring are the latest to depart in autumn ; the latest to
arrive in spring being the first to take their departure.
I should be disposed to class the former of this class of
migrants as much earlier emigrants to the British Area
than the latter.

CONDITIONS OF FLIGHT 241

The varying amount of sociability in birds whilst on
migration, their gregarious or solitary tendencies, have
all been described at length in the previous volume, and
as the facts apply not only to British birds, but to all
species, we need not repeat them. We have also dwelt
at some length on the duration of the passage and its
varyjng phases of intensity. The migration is usually
characterized by the advent or departure of a few indi-
viduals ; then the flight becomes more strongly marked
up to its greatest phase of intensity, which may or may
not be marked by one or two exceptionally strong
movements, after which the passage of the species for
the season as gradually dies away as it commenced.
The various stages of the journey, and the normal
velocity of flight during passage, have also been de-
scribed. I have nothing further to add at present to
what I have already said in the above-mentioned work
concerning the effects of Wind and Temperature on the
migration of birds. The remarks just as aptly apply to
British birds as to other species. The moulting of birds
before they migrate, and the structure of the wings of
migratory birds, have also been dwelt upon.

Of the perils of migration but little more may be said.
I have already devoted a chapter of my previous work
to the subject. Many more instances of fatalities to
migrants might be given, but they would all partake of
the same general character : sufficient has been furnished
to illustrate very vividly the perils that beset birds
whilst on passage. The mortality connected with
migration can scarcely be realized. The vast numbers
of birds that perish during passage is past belief. And

this not only applies to the British Area but to every
R

242 THE MIGRATION OF BRITISH BIRDS

other part of the world. There can be little doubt that
the passage across seas is attended by the greatest
amount of mortality, and even under the most favourable
circumstances the death-rate must be a high one. Of
the hordes of young birds that are seen on migration in
autumn but a small percentage survive the perils of
the journey, and a still smaller percentage return in the
following spring. If the season of passage chances to
be exceptionally unfavourable—full of storms and fogs
—the death-rate will go higher than its normal average,
and perceptibly reduce the numbers of a species perhaps
for years. An anonymous reviewer of the J/zgratzon of
Birds says that I greatly over-estimate the perils of
migration. Well, after several more years’ close attention
to the subject I will state that in my previous work I
under-estimated the mortality, and that the more I
study migration the more I am convinced of its fatal
consequences.

CHAPTER. 1X:

THE SPRING ASPECTS OF MIGRATION IN THE
BRITISH AREA.

Commencement of Spring Migration in the British Islands—
Departure of Eastern Migrants—Departure of North-eastern
Migrants—Abnormal Lines of Migration from the British Area
— Birds Migrating Too Early—Arrival of First Spring Migrants
from the South—Departure of Winter Visitors to the British
Islands—Coasting Migration in Spring—Migration of various
Northern Birds—Arrival of Summer Migrants in the British
Islands—The Growing Intensity of Spring Migration—Months
of Passage of Various Species—Gradual Advance Northwards
of Migrants—Duration of Spring Migration—Vertical Migra-
tion in Spring—The Various Species performing it—Order of
Migration—Table indicating the Spring Migration of Birds
across the British Islands.

I INTEND to devote the present chapter to a brief
review of the most salient features of the Spring Migra-
tion of Birds as they are presented in the British Archi-
pelago. To the student of British birds, nothing perhaps
is more interesting after a long dreary winter than to
note the first signs of a coming change of season in the
movements of migratory birds. As might naturally be
expected, the first species to display any migratory
tendencies in spring are the hardiest—those birds that
winter in our islands, yet breed in various continental

244. THE MIGRATION OF BRITISH BIRDS

areas east and north of them. This migration in spring
is much less marked than in autumn, and for three
reasons. First, it is always more difficult to note the
departure of a migratory species than to observe its
arrival ; second, the number of individuals that depart
in spring is very much less than the number that arrived
in the previous autumn, owing to the casualties of the
intervening winter; and third, the majority of the
species that take part in the movement are birds that
breed commonly in our area, and it is difficult if not im-
possible to distinguish between the individuals that only
winter here, and those that spend the summer with us.
This migratory movement, in a fairly normal spring,
may be said to commence as early as February, and the
first migrants to go are those that breed in continental
areas east of the British Islands. Amongst these species
we may include the Missel Thrush and the Song Thrush,
the Hedge Accentor, various species of Titmice, the
Wren, the Linnet, and some other Finches, several
species of Bunting, the Jay, the Rook, and the Carrion
Crow. In former years, when the Great Bustard and
the Bittern were common in our islands, these species
also would have been amongst the first migrants to
move towards the Continent. The indication of their
migration is now very slight. For a complete list of the
species partaking in this early spring migration the
reader is referred to the table on p. 132. The next
species to move out of our islands are those whose lines
of Migration trend north-east. It is impossible to
separate the individuals, but many birds of these species
migrate both east and north-east; those travelling in
the latter direction are the last to go. Among these

SPRING MIGRATION IN BRITISH AREA 245

we may include the Blackbird, the Robin, and the Gold-
crest, the Greenfinch, the Chaffinch, and the Starling,
the Jackdaw and the Hooded Crow, the Short-eared
Owl, the Ring Dove, and the Lapwing. Years ago,
before the Crane had been well-nigh exterminated in
the British Islands, it would have left its winter quarters
in our area with this second migratory movement. We
have abundant testimony from the various lighthouses
and light-vessels stationed on our eastern coast, or in
the North Sea, that the migration of all these species is
undoubtedly in progress very early in the spring, con-
tinuing more or less strongly for just upon a couple of
months. Sometimes birds of these species are noticed
passing away from the British Area in great numbers for
days together, but the migration is only in very excep-
tional instances so strongly marked as the return move-
ment in autumn. It has been stated (conf. M/zgration
Reports) that there is apparently a south-eastern de-
parture from our shores in spring, but this, if true, is
utterly abnormal, and due entirely to local conditions.
I for one should require more accurate and positive
proof of this movement than that furnished in support
of it by the entirely unskilled observers that have re-
ported the anomalous migration. It is impossible to
say accurately in what direction a body of migrants
may be going on a dark night, when the birds are
bewildered by adverse weather, and flying dazed and
lost round the lanterns of a lighthouse. We can only
accept the reports as useful when they are made under
fairly normal circumstances, and obviously harmonize
with known Laws of migration and geographical dispersal.
Again, a strong migration from the east and north-east

246 THE MIGRATION OF BRITISH BIRDS

to the British Area in sfvzug has been reported and
described by Mr. Cordeaux as a ‘“‘very anomalous
movement.” If it were perfectly normal it certainly
would deserve such a description. There can be no
doubt whatever that the individuals coming from the
north-east and east (most probably the former) into
England, in the very teeth of the advancing normal
migration from Britain to the Continent, are birds that
have migrated too early, or that a sudden late snap of
winter in their summer quarters, or on the routes to
them, has turned back. We experience precisely the
same phenomenon in the Arctic regions of birds being
too eager to reach their breeding grounds, and having
to return, it may be, many miles, owing to a temporary
recurrence of winter weather. It would be just as
manifestly absurd to say that there was a migration in
the Arctic regions south as well as xorth in spring, as
it is to describe this east to west or north-east to south-
west flight at the same season on and off our eastern
coasts (conf. Wzgration Report, v. pp. 60, 61). It is
suggestive enough that no such “anomaly” occurs in
autumn !

During the earlier part of the time this spring migra-
tion is in progress of birds leaving us for continental
areas, another, if perhaps less perceptible movement of
some of the same species is taking place into our islands
from more southerly areas: individuals that breed with
us and still continue to winter further south. This
movement is not a very ancient one. It is made by the
descendants of individuals of these species that were
among the last to extend their summer area to the
British Islands. It was initiated after Ireland was

SPRING MIGRATION IN BRITISH AREA 247

separated from England, and after much of the Channel
land had been submerged. Hence no trace of that
movement is visible in extreme western and south-
western districts.

Very soon after this early spring migration begins the
birds that are only known in the British Islands as winter
visitors commence to leave and to pass northerly, either
by an easterly trend to the Continent, or by a westerly
trend to the Faroes, Iceland, and Greenland. The Red-
wing and the Fieldfare begin to leave our islands
towards the end of February, the migration of both
species becoming more marked in March, reaching its
fullest strength in April, and ceasing in May. The
Brambling passes north again in March and April, as
also do the Siskins that winter exclusively in our area.
The Snow Buntings begin to leave us even at the end
of January, the migration being more regular in February,
attaining its fullest strength in March, and dying down
completely in April. Such species as the Golden Plover,
the Lapwing, the Curlew, the Redshank, the Woodcock,
the Common and Jack Snipes, individuals of which
winter in our area, begin to pass northwards from it in
February, the migration becoming strongest in March
and April, and dying away again in May, or in some
few cases is prolonged even into June—the latter being
composed chiefly if not entirely of coasting migrants,
individuals that only cross our area on passage. In
February and March great numbers of Ducks and
Geese commence their northern migration from our
islands, the flight continuing through April, and in the
case of the most Arctic species into May and even June,
although the latter migration probably consists entirely

248 THE MIGRATION OF BRITISH BIRDS

of coasting migrants—individuals that merely pass us
from winter quarters in lower latitudes.

This coasting migration begins apparently as soon
as the migration which is exclusively of a departure
character, but is weak until March, and perhaps attains
its greatest strength in April and May. It is impossible
to distinguish with certainty between coasting migrants
and migrants that have passed the winter with us, or in
the case of species that breed in our area; but with
those species—high boreal forms, as a rule—that neither
winter nor breed with us, there is no difficulty, and these
birds generally coast us late in spring. The Whimbrel,
for instance, passes us very regularly towards the end of
April, but the migration of this species is most marked
in May, dying down in June. The Ringed Plover begins
to pass our coasts in March, very sparingly, the great
flights crossing us in April, and lesser numbers again in
May. The Sanderling passes us pretty regularly through-
out April and May, a few in June; the Skuas of various
species coast us chiefly in April. The Little Stint passes
our coasts sparingly in April, but in greater numbers
(although even then by no means dominantly) during
May; as also does the Knot, which perceptibly prolongs
its passage into June. The Curlew Sandpiper, never
very common with us, coasts us in April, May, and
June.

Owing entirely to the fact that all or nearly all this
early spring migration is entirely among species that
breed or winter in the British Islands, no season-flight
is very apparent until the species that visit us exclusively
in spring to breed in our area begin to make their
appearance. While all this other migration which we

SPRING MIGRATION IN BRITISH AREA 249

have been describing is actually in progress—long before
it ceases—with the advent of March in fact, the northern
migration of our summer birds begins. Amongst the
very first of these spring migrants we must class the
Woodcock, which begins to arrive in our area in February,
but the migration is strongest in March and April ;
another early bird to appear is the Pied Wagtail, that
is to say, the individuals that breed with us and winter
further south. The Wheatear and the Chiffchaff, how-
ever, are the two best known species that indicate the
beginning of the exclusively spring migration. Neither
of these birds winters in the British Islands normally,
but they reach us in March. At first the migration is
a weak one, but as April advances the flight becomes
stronger and stronger, and wanes gradually again into
May. But little migration amongst our typical summer
birds, however, is apparent until April. Almost the
only species that are seen to arrive in our islands in
March are perhaps the two just mentioned, together
with the Kestrel, the Ring Ouzel, the Willow Wren,
and the Yellow Wagtail. More rarely a very slight
migration of the Wryneck, the Stone Curlew, and
the Garganey may be observed during March; but
with none of these species does the flight become
dominant until April.

Scarcely without exception the migration of every
species that visits the British Islands in summer begins
to be apparent some time during this latter month. The
most noteworthy exceptions are the Osprey, the Spotted
Flycatcher, and the Marsh Warbler; the two latter
species, as we have already seen, migrate far to the east
and south of our area. With the advent of April, then,

250 THE MIGRATION OF BRITISH BIRDS

migration from the south begins to assume a gradually
increasing strength, which continues to swell in volume
as the month progresses, and with most species to be
continued well into May. Daily the numbers of Chiff-
chaffs, Willow Wrens, Whinchats, Redstarts, Wheatears,
and Warblers increase. It is chiefly owing to the
observations made at the points where migrants enter
our area that we are able to compute the duration of
the flight of these species. From these records, extend-
ing as many of them do over a long series of years, we
are able to judge pretty accurately not only the duration
of the migration of each species, but the time it begins
and ceases. Weare thus able to state that the migration
of all birds that begins in April is continued into May,
and much more exceptionally into June. With such
species, however, as the Honey Buzzard, the Garden
Warbler, the Lesser Whitethroat, the Wood Wren, the
Cuckoo, the Turtle Dove, the Quail, the Red-necked
Phalarope, the Common Sandpiper, and all the Terns,
the migration is much stronger in May than in April.
Probably all the birds that breed in our islands have
reached every part of them towards the end of May.
The migration, however, of some of the common summer
migrants continues into June. We have ample evidence
that such species as the Wheatear, the Swallow, the
House Martin, the Cuckoo, the Dotterel, the Whimbrel,
the Ruff, and the Arctic Tern continue to enter our area
in June (the Swallow especially), but there can be no
doubt whatever that these late individuals are coasting
across the British Islands on their way to more northern
breeding grounds, and in most cases pass by other
individuals of the same species already engaged in the

SPRING MIGRATION IN BRITISH AREA 251

duties of reproduction. It is noteworthy that all these
late coasting individuals not only breed in the high
north, but have extended their emigrations across our
area thereto, as has been already shown (coz/f. table,
p. 116).

The spring migration of birds to the British Islands
is just as gradual as in other localities situated in
temperate latitudes. Birds are almost invariably seen
first in the more southern districts; in cases where this
is not so they must have been overlooked. Nearly if
not quité two months elapse before the remote northern
and western areas are reached. Thus. most of the
summer migrants to Ireland reach that country a week
or even a fortnight later than they appear in the south
of England. In the north of England most migrants
are at least a week later to arrive than they are in the
south, and this is much more marked in some species
than others. The Chiffchaff, for instance, must migrate
very rapidly across our area, as it is generally seen as
soon in the north of England as in the south, at most
but a day or so intervenes. On the other hand, the
Redstart, the Ring Ouzel, and the Corn Crake must
travel slower, for often ten days or a fortnight will
mark the difference in the date of their arrival. A still
greater difference in the date of arrival is almost invari-
ably remarked in Scotland. As a general rule the state
of the season governs the progress of the migration.
If the weather be mild and open birds reach their
northern destinations quicker than if the season be a
cold, stormy, or backward one.

The Spring Migration of Birds to the British Islands
extends over a period of quite four months. It begins

252 THE MIGRATION OF BRITISH BIRDS

in February and certainly lasts until the end of May or
the first week in June. In some cases the migration of
a species extends over the entire period, as for instance
the Wheatear ; in other cases the flight does not cover
more than three months, and even then in a great many
instances the migration is weak at the beginning and
at the close of that period; whilst in other cases the
migration is confined to two months, especially in such
species as the typical Warblers, the Wagtails, and the
Pipits. Other species limit their spring migration to a
month. Among these we may include the Marsh
Warbler, the Red-backed Shrike, the Hoopoe, the Red-
necked Phalarope, and the Greenshank. As a general
rule we might say that the most widely-dispersed species
cover the longest period in their migrations, the most
local birds the shortest period, the length of flight-time
being in the same ratio as the dispersal of the species.
A few words concerning the Vertical Migration in
spring now become necessary. This migration is just
as characteristic and as marked a feature of the spring
in mountain districts as that taking place in a latitudinal
direction. The duration of the period also is about the
same, and lasts for about four months, although it is not
perhaps so marked at the beginning or at the close.
The movement is more contracted, more rapid. Amongst
the earliest of these vertical migrants we may instance
the Stonechat, the Linnet, the Gray Wagtail, the Wood
Lark, the Sky Lark, and the Lapwing. These species
begin to move up the hills in February, but the migration
is much more strongly marked in March, and dies com-
pletely away during April. The next birds to move
are such species as the Merlin, the Linnet, the Twite,

SPRING MIGRATION IN BRITISH AREA 253

the Lesser Redpole, the Pied Wagtail, the Meadow
Pipit, the Golden Plover, the Curlew, and the Dunlin.
beginning in March and continuing into April. With
these species the movement is more contracted, in some
the bulk of the flight taking place in March, in others
in April. Some few species, such as the Linnet, the
Twite, the Lesser Redpole, the Golden Plover, and the
Curlew, prolong their migration into May, but these are
individuals that breed at the highest elevations and in
the most northerly localities. In our islands all vertical
migration ceases in May, but in higher latitudes it is
prolonged even into June.

The following table will indicate the duration of the
principal Migration across the British Archipelago in
Spring.

THE MIGRATION OF BRITISH BIRDS

254

vw
“A

‘anal

x XXX
x bad Sao

|

}

}
x aS Se

x xX
xX Xx
x X
x X
x xX
xX xX

“AVIN
“Ted V
“HAVIN

|
|
l

x
x
x
x
x

x x | | eee | eee eee

<x x
x ae
a sy x

x
xX X Xx XX s
vMwM YM | eee . .
SSC SGC call iis :
Gen se dab Bs ;
NaN On
|
7, xx | 0 a0 sis
|
‘ x x xX X X x X x ae
en's ger xX xX X XK X x ae 7
Xan ok) EO aes ees ;
: a Xx MIS KI KK x si
|
. . | wee | . wee eee
Se re |e tow, as x 4
x X x X x
2
_ _ m
Les] GS a rs > be 5] or]
ist Z iS a nz ist Az
es) ica] < onl a wo &
‘ = = : ,

}
wee | wee eae
. i ee eee
'
eee | .
: - |
|
as
x x x>
x xX xX X x
sa
x x X ee,
SG DR BS Nal] ESS
| x |
4 SEA 5
|
cies isc nd oe
\ ie =
2 =
= | > >
> 7 | ]
< ence | a
De | ar ls br
H he | .

|

“ONILSVOD

“STVAINUV

‘HLYON OL HLAOS WONT

‘HINON OL HLAOS Woy

‘SHUN LYVdAG

‘A ° AN :°N OL

"* TIqIVAA WSpas
JDIQIV AA YSIL]A
* TaIGIEM PIy
WdTM POOM
UdTA\ AMOTITAA

* PEYPYO
Ja[qivA\ Uaprer

tee tee eee deoyorlg
"+ JVOIYJOPY AL 1Oss9°T

“SABRES.
IoJUIDIY ISpayy

vet ayesanysint

" uIqoy
Ivaywoy AA

ure 48 QETIQBTOIS

“ss JeyOUIITAL
JAv}spayy UoMMOD
SABISPo aD TUPLE
“azn Suny

- PAPRES
— eee ahs
eae eee SUM pay

ysniyy, Suos
RBMGL TeSstAl

“SAIOAdS

wn

SPRING MIGRATION IN BRITISH AREA

“a

x X
x X

x

~

x

“~

x

be IL Sie
SA A

A A

S32 SS ONS

x xX

wv
“A

XX XXX xX

A

id

“A

,

,
4

,
.

x

Mv
“

wv
“A

xx x

i, Sastre aie yay AxS
~ Suung mous
“ Suyung poary

“ Sunung uso
Sunung Moya x
Mods oo1J,

BG0 | don “ Surjqueig,

youyyeyd

300 youurT
youyusary

“ * Youyplor)
nee ee SUIM XU AA
uljIeyY pues

ee ins unre],
2 ANG TEAS

gayoyeoAp yy par

“ jayoyeoAp qT poyods

" aYUYS paprq-pry

ayLyS Avin yearn

“* Q[OlIQ, Uapjoryy
guG. 005 ndig da1 J,
“+ qreyde\y Ler

[eySe AA MOTIPA
[eye OPT AA

ses [reySeAA Pad

het tee SE VUISUAN
“* gsnowyry, onig

“ 9snowyly, [209

us ISNOW}FLT, yeaI4)
asnowjLy, poyie}-suo'T
Hee es aor pTON)
loyqiev AA soddoysseary

THE MIGRATION OF BRITISH BIRDS

256

‘anal

ws wo}IE

) { { ! x
xs ; : 4 ; : sc te Set = -AOIGSG)
56x aan é 2 pivzzng Aauoyzy
= BON! a x x | ; | a ; a, Ong
| eee
| XxX | Xx 4 Aqqoy
| | rab | ne JOU] SndvjUOy
x xx ty ae ef % Kx JOWIVyT Uap]
x x Ts | oe pee ly | ss x : plvzzng passal-ysnoy
Sa Saas ey) pes YMVET Momeds
x [Mo 4aous
x xX XXX X , ‘ ‘ x XxX XXX ae [MO peres-}.104S
| x SF amh| (ox “ *** JQYSYSUPyT
ae laa : uss Pe beatae ee pes ay “* ooyong
| cao |e | aodoojxy
eK x yooudr Ay
OOS Tei we bie | Ivhysin
| ASE CON se | | rot nts
xKxxXxXX cL aay <1 §
Sux x | ek eS | "* Yoo
x pee Bae ; Sees aes : ae ae ee ge oS [3s MOLD papoojyT
OB ae, ee Se eae oe x MOID WOLD
5K ICO a es : ames (ne pe dae > Ae 4 ae “* mepyor[
Sm cient | CUCL oct eae : oe PENS | ess Kil a peti | ee “* Surprvyg
a x ms ae : : ete | x xR “+ yay ar0yg
Seales a aca er Ee
2 5 S = ‘< 2 % > 4 ra ne ae ee 4
ee ee aR ole alg |e: la ee oe
—_— Ss *“SH1IDadS
“ONILSVOD “STVAINNV “SHUN LUVdaAG
“HLMON OL HLAOG WOT “HLYON OL HLAOG WOT mi By “AI'N : "'N OL

=)

SPRING MIGRATION IN BRITISH AREA

x

“A
v4
“A

Vv

“~

“~
v
“~

x

v

x
“aA

m4

x X >

‘

vw
A~

x
><
x
x

x X

ova
x~

x

Y

EE NTS

‘
?

Y
“

vy
“aA

I OK

Xx

x X >

= Se

Me
“a

DEP <

x

v
a

IOAOT] PISulyy
MOpPIMD 90}

" ayvag poyods
2 ER Auer
“' prvysng apy
pavysng jvo.14)
SOOO LIC pene)
DAOC OfANY,
DAO(T SULT
me MOUS

"+ Iopuesoory
9f9-uaplor)

“* 19}09G JOATI A.
I9j09G uowUOD
yond, pate}-suo'T
tee oe tee dneay
yond peyny,

“ preysog

“ UOOST AA
SCOMRACr pequrg
ss TeMpED
rors KOULGILS)
Set yf
oe prereyy
are UBMS ]NIN
“" URMG SIMO
“+ uemg sadoozy
"* gsoory JUdIg
asoor) apovUIog
98004) po}0oj- UI
"* gsoory) uvog

9SOOr) Po}UOY-9IY AMA

THE MIGRATION OF BRITISH BIRDS

258

xxx “xX xx [ eee ae H oe eee ! eae tee
siege mas | sh ee irre ey iu ra
xxx XX ice) aa rl eK SS YE aes
x "| aK | a5" ¢it Bae x x call se anc ae :
53 bos SS | as x 1 eet saint Ih” og oes
A | Keon MO ual eo ok is peter we allie ot at
| . ati: x :
| x x asi
Loe op 2 F
| xxxxx a : : aK ua iise
x ‘> San. ; x a x ° is
asec iliscescnsZ, i ase wee | nee Ay eau (Pern.
x x x xX x | x eee i - | eee | ee eee
[NGS Baeoarrmvaer, ‘2 a i one “in Pe
| | xxx | ae ape
1 ae | eZ a net is Sr il Grich ic at
| x | x . vee
hE | OS oer caechas s Cre
se x Ixxxl xx ox 0 to ea | “2
x yeaket| tee fe ae ts Berge) ecm ie leansee
x eee less Xl Ke xX fu
| | x x x | eee A
b= yy » = | u ] os | » = | a
iu 3 m | Ot a b z 2 | 8
ol A fe Vda) i a
} Wake | e | | uy
“DNILSVOD “STIVALUNYNYV
‘HINON OF HLAOS WONT ‘HLUON OL HLAOS WONT

Brau
WA POL) payie}-ivg
| WMpoOL) payle}-yorpq
E Ge gee

AMa[IND
“* yuvyspayy UOWWOT

yuvysuaelry
yuvyspey Aysnq
jadidpurs uaai5
Jadidpurg poo,
_dadidpurg uowwoy
a ION.
adiug youl
ies adiug uowwoy

[st y909p00 Ay
sonar pexdau-peyy

2 adoavyeyg Aviry
Hs ress Quoysuny,
rete ee aQ90a7
Sr eee UTA
* '* IAOTY USploy
“* oaoTg Avi)
eee ee TOG

IAC YsHUIy

“‘SH1DadS

xX xX X| XX yaa ed
x | xx | x ave | pik
Sg fe | eae le Seraca aaa
Sate Pg oye gh ge Send x
; to |) Soe P| sewer
| | |
| ‘ | i ,
' i ‘
i | x j mais
. . | eee | . .
x A NE a daly x
Ke Se cee x
al Ma's xxxx | x
. | . seca met era sa |
| | | x
ve ie > | x x see
x x xx | xx x x
ak = ||P oae we Cl We Sra x x
ee Ware’ 4 , hors
: _— :
!
|
ei) ES | 2 > =
A ” z= Zz =,
oe ae: B
: =
| ond
‘Saun.LNVdaa
‘a SQN SN OL

259

SPRING MIGRATION IN BRITISH AREA

Gn

“A

yv

%

aqain) ULIUOAL]IS
“* 9qarn pexsau-poy
* TOAIC, poyvoryy-poy
JOAIC, poyeoryy-3ovpq_
JOAIG, UIOYWON Jeary
a yy eT
tee emg
enyG S,uosprvyony
UNAS IulyAo}vWOg

enyS suoyng
‘7p snonepsy
: WD eTArT
mi “U9 [) 1oSsom
CSE SOON OW,
“* Ulay, UOUWIOD
“UIA, 978as0Y

Ua, YOIMpues

SUIpIopurs
tere fe JousT

jedidpuvs ofding
Jodidpuvg moping
JUNG sourwuts 7,
ee JUDG Sia

CrAPTERY

THE AUTUMN ASPECTS OF MIGRATION IN THE
BRITISH AREA.

Migration more Apparent in Autumn than in Spring—Difficulties
of Observing the Phenomenon—Commencement of Autumn
Migration in the British Islands—Arrival of- Birds from the
North and North-east—The Species that are the Earliest to
Arrive—Growing Intensity of the Movement—The Hardier
Species are Latest to Appear—Autumn Migration of Fieldfare
and Redwing—The Earliest Departures from the British
Area—Early Migrants Abnormal—The Growing Intensity of
Southern Migration as Autumn advances— Duration of Migra-
tion Periods—The Migration into the British Area from the
East—General Aspects of the Phenomenon—Abnormal Lines
of Migration in Autumn—Cross Migration in Autumn—Re-
versal of Route by Migratory Birds—Erroneous Interpretation
of the Facts—The True Explanation— Duration of Autumn
Migration—Vertical Migration in Autumn—Order of Migra-
tion—Table indicating the Autumn Migration of Birds across
the British Islands.

THE Spring Migration of birds across the British
Islands has scarcely ceased, before signs of the autumn
passage are visible. The Autumn Migration of birds
from, to, and across the British Archipelago is even
more interesting than the movement which is charac-
teristic of the spring. Autumn migration is more pal-
pable because the individuals engaged in it are so much
more numerous, the old birds being accompanied by

AUTUMN MIGRATION IN BRITISH AREA 261

the young. This grand autumn movement, however, is
most conspicuous amongst species that either winter in
the British Islands or pass over them to more southerly
latitudes. Among our common Summer Migrants, it is
much more difficult to detect migration ; they disappear
one after the other from their accustomed haunts, and
rarely can we give the exact moment of their departure.
Owing also to the impossibility of distinguishing between
individuals, we cannot readily mark the passage south
of a portion of any species that only crosses our area
on migration. Sometimes, however, as I have repeatedly
observed, our regular breeding individuals will all dis-
appear, and perhaps a week or so after the species will
again frequent the district, this time represented by
coasting migrants. These remarks apply most closely
to inland migration ; along the coast the autumn pas-
sage is much more distinct and noticeable. We remark
precisely the same difficulties in spring.

The autumn migration of birds begins to be apparent
in an average season in July. As we might also natur-
ally expect, the first signs of the great Southern Flight
are given by birds that breed in the highest latitudes, or
colder north-eastern continental areas. These species or
individuals experience the advent of winter much sooner
than others inhabiting more southern and western areas.
Autumn migration, therefore, begins not only from the
north, but from the north-east. Among the first
Passerine birds to make their appearance in our area
in July are the Wheatear, the Swallow, the House
Martin, the Pied Wagtail, the Song Thrush, the Robin,
the Goldcrest, the Wren, and the Starling; among
other birds the Cuckoo, the Corn Crake, and the
Dotterel. All the birds that range far north or north-

262 THE MIGRATION OF BRITISH BIRDS

east, in fact, show signs of autumn migration in July.
By the middle of the month flocks of northern waders
begin to appear upon the coasts, mostly composed of
young, but with a few old birds intermixed. As August
comes on, the migration of all these northern and north-
eastern species becomes decidedly stronger, reaching
its climax perhaps during the latter half of that month
and the first half of September; and, generally speak-
ing, dying down again towards the end of the latter
month. Among these migrants must be included many
individuals of species that remain in our islands during
the winter; many others, however, simply pass them
as coasting migrants. The hardier species are later to
arrive. Thus no migration into our area of the Bram-
bling or the Fieldfare is apparent until September, and
even then the passage is slight, not assuming large pro-
portions until October, and even November. The Red-
wings’ migration is apparent in August, stronger in
September, and attains its maximum in October ; but
as we know this Thrush is more of an insect feeder, and
its food is affected by frosts much sooner than that of
the hardier berry- and seed-eating Fieldfare and Bramb-
ling. Coasting migration among the Charadriide, and
the Terns and Skuas, is strongest during September
and October ; but amongst the Ducks and Geese it is
at its maximum in October and November.

Although there is abundant evidence that migration
into or across the British Islands begins in July, there
is little or no evidence to suggest that a southern move-
ment begins at all strongly during that month amongst
individuals that breed in them. There is some evidence
to suggest that a few individuals of such species as
Spotted Flycatchers, Whitethroats, Willow Wrens, and

AUTUMN MIGRATION IN BRITISH AREA — 263

Turtle Doves are on the move during July. As none
of these birds have extended their area north or north-
east across Britain to continental areas or outlying
islands, we can come to no other conclusion than that
they are indigenous individuals moving south from our
area. These very early migrants are probably birds
whose broods have been destroyed or that have not been
breeding at all, just as we know the earliest travellers
from other areas are of a similar character. In August,
however, the departures commence very generally, the
migration assuming its greatest strength in September,
and dying almost entirely away in October, but little
being apparent in November. As the autumn com-
mences we have abundant signs of the approaching
departure of the British Summer Migrants. Nearly all
are moulting, songs have ceased, social and gregarious
tendencies are becoming more and more apparent.
During August the Swifts and Cuckoos depart south,
the migration continuing into September. Swallows
and Martins, most of the young now strong upon the
wing, significantly gather at well-recognized meeting-
places preparatory to departure. Flocks of Terns,
chiefly young, are moving south along the coast-lines.
At first the autumn migration is remarkable for the
preponderance of young ; later the old birds are in the
majority. Slowly as the mellow autumn days creep
on, bird after bird disappears from the old familiar
haunts ; species after species takes its departure along
the well-known routes to the south. Now and then a
general rush of one or two particular species will be re-
marked. No particular hour seems chosen, the migra-
tion progresses day and night pretty evenly, so long
as weather and wind are favourable. In the British

264 THE MIGRATION OF BRITISH BIRDS

Islands the migration of those species that not only
breed in them but pass them is of the longest duration ;
the migration of such species that are confined to our
islands with no ancient lines of emigration across them
is shorter. With the former species individuals con-
tinue to pass right through the autumn, the flight
beginning and ending in a very gradual manner; with
the latter species, once the movement south commences,
it progresses steadily until the end, usually finishing as
abruptly as it began. Thus the migration of the
Wheatear, a species that has emigrated or extended
its range across the British Islands not only to Scan-
dinavia, but to Iceland and Greenland, extends over a
period of five months, beginning in July, and actually
not ceasing before November! On the other hand, the
migration of the Reed Warbler, a species that never
emigrated across the British Islands and whose range
in them is limited, does not extend over more than a
month, beginning say at the middle of August and
closing by the middle of September or thereabouts.
The migration of the Red-necked Phalarope is remark-
ably contracted both in spring and autumn ; so also is
that of the Garganey.

Up to the end of September, the general trend of
migration across or to the British Islands is from the
North or North-east. After that date a very perceptible
change in the general trend takes place, and the pre-
dominating line of Flight falls nearly to due East. This
is the first sign of that gradually approaching wave of
migration from the east, from those continental areas
which were colonized by birds whose emigrations may
be said to have their base in the British Area. Until
the middle of September this migration from eastern

AUTUMN MIGRATION IN BRITISH AREA 265

continental areas is more or less of a desultory charac-
ter. During the latter half of that month it suddenly
assumes a stronger aspect, culminating in a grand and
mighty influx of birds, young predominating, lasting
almost incessantly for perhaps a fortnight ; then a lull
occurs for a week or so; then another grand wave of
not quite the same magnitude and duration, adults
predominating, breaks upon our eastern sea-board,
spreading perceptibly right across England to Ireland ;
after which the great flight is spent, resuming only in
a fitful manner or entirely ceasing, as much of Eastern
Europe and Western Asia become drained of most of
their hardiest non-insectivorous birds. The birds that
chiefly partake in this late migration from eastern areas
are tabulated on a previous page (conf. p. 132). We
have already dwelt at some length on the origin of this
movement. A few remarks on its general character will
now be all that is required. So far as numbers are
concerned this eastern passage is the most important
migration that breaks upon the British coasts in autumn.
The number of species normally is not great. Night
and day the steady inrush of migrants is constant and
prodigious. For weeks birds may be remarked pouring
into our islands by day and by night, or by day or night
alone, the migration of each particular species varying
considerably from year to year, sometimes being com-
pleted in a few weeks, sometimes continuing over as
many months. Three of the most remarkable species
performing this east to west migration in autumn are
the Hooded Crow, the Goldcrest, and the Sky Lark ;
we might also add the Starling. For days and days
together, sometimes, a nearly constant stream pours
into the British Islands from the east. In 1882 it was

266 THE MIGRATION OF BRITISH BIRDS

computed that the migration of the Goldcrest into our
area extended over a period of ninety-two days, com-
mencing in August! It must, however, be remarked
that the earlier arrivals were from the north-east, and
that in computing the duration of the passage of this
tiny species this fact is almost invariably overlooked.
None the less remarkable are the autumn passages of
Sky Larks and Starlings—vast waves of avian life that
only spend themselves in the remote western areas of
Ireland! I have already given many instances of this
grand migratory movement in autumn in the A/zgration
of Birds (pp. 255-258), to which volume I would refer
the reader anxious for greater details.

It has been said that this East to West migration in
autumn sometimes approaches us from points south of
east. If such is actually the case the movement is
entirely abnormal, as no bird whatever migrates in a
northerly direction in autumn. Adverse winds or bad
weather may have driven these migrants a little south
of their normal course, but the reader may rest assured,
if the passage is being undertaken with suitable wind
and weather, the birds will never appear by any chance
from points south of east, nor in a very marked manner
from points north of east. The normal trend of this
movement is east.

There is also just the same cross migration in progress
in autumn as we have already found to be the case in
spring. Birds coasting south across the British Islands
pass almost at right angles the stream that is pouring in
from the east across the North Sea. Every movement
that is observed in spring is again repeated in autumn,
only the directions are exactly reversed. While all this
stream of migration from the east is in progress there is

AUTUMN MIGRATION IN BRITISH AREA 267

another movement going on amongst the same species
toa great extent. These are the individuals that breed
in our islands and pass to more southern areas to winter.
The cause of this double movement has already been
dwelt upon.

It has been asserted that some species reverse their
routes almost entirely in autumn, and travel south by
quite a different fly-line from that which they followed
north in spring. Unfortunately, with too great a respect
for the opinions of other naturalists, I myself have alluded
to this movement in the J/zgratzon of Birds as though it
were a fact. There cannot be the slightest doubt that
this change of route is purely imaginary, for if we look
closely into the facts they will be found to admit of a
very different construction. When I wrote that volume
I regret that the Law of Dispersal which I have
attempted to explain and illustrate in the present work
was then entirely unknown to me. I had accepted the
general belief that a glacial epoch could cause southern
emigration, and I was also labouring under the very
general, if quite erroneous, idea that species were driven
this way and that across the world without any govern-
ing impulse. Let us deal with the few instances known
to me, and which I gave as examples of route reversal.
The first species was the Nightingale. As a proof that
this bird travels by a different route in autumn from
that which it traverses in spring, it is shown that it
passes Heligoland in April and May, but has never been
caught there in autumn. Now Heligoland is situated at
or near the very northern limits of this bird’s distribution.
There is nothing then very remarkable about a few birds
overshooting the mark in spring and visiting the island,
just as we know many southern birds visit our islands

268 THE MIGRATION OF BRITISH BIRDS

at that season under precisely similar circumstances.
It would therefore be a most extraordinary thing indeed
if this bird visited Heligoland in autumn, for to reach
that island from its present normal limits of distribution
it would absolutely have to take a northern flight!
Again, the Dotterel is said not to visit Malta in spring
but to pass regularly enough in autumn. Now the
Dotterel migrates very rapidly in spring, its migration
not lasting much more than a month; in autumn, how-
ever, as is customary with many species, it migrates
more leisurely, the passage extending over four months,
and in fact finds time to visit places it had to pass very
quickly on its flight north. The Turtle Dove is commoner
in spring at Heligoland than in autumn; the Whimbrel
passes the British Islands in greater numbers presumably
in spring than in autumn. But it has been remarked
that the latter bird flies much higher in autumn,
and consequently is disposed to alight less. The same
remarks will probably apply to the Turtle Dove. In
the latter cases, it will be remarked, a complete reversion
of route has not been suggested. We might with equal
propriety say that species of which individuals abnor-
mally appear in our islands only in autumn or spring
change their route according to season. The Little
Bunting, the Rock Thrush, and the Yellow-browed
Warbler are cases in point.

The migration of birds in autumn over, from, and to
the British Islands extends over a period of quite five
months. It begins in July and continues to November
or even into the early part of December. Generally
speaking, the tendency of migration in autumn is
leisurely and more prolonged than in spring. The great
bulk of autumn migration takes place in September and

AUTUMN MIGRATION IN BRITISH AREA 269

October ; the movement in every direction has a southern
trend.

A short allusion to Vertical Migration in autumn will
bring the present chapter to a close. The descent of
mountain species from their upland haunts is just as
characteristic of the autumn migration of birds as that
migration which takes place in a latitudinal direction,
The duration of the period extends over about three
months, namely, from August to October, and is there-
fore much shorter in duration than the autumn migration
of species elsewhere. This is probably due to the more
rapid seasonal changes on mountains than on the low-
lands, more of that sudden nature which marks the
coming on of winter in the Arctic regions. Among the
first birds to leave their mountain summer haunts are
the Merlin, the Linnet, the Twite, the Lesser Redpole,
the Pied Wagtail, the Golden Plover, the Lapwing, the
Curlew, and the Dunlin. In all these species, however,
the migration is only slight in August, and attains its
greatest strength in September, a slight movement
extending into October. The later birds to leave are
the Stonechat, the Gray Wagtail, the Meadow Pipit,
the Wood Lark, and the Sky Lark. With these species
the migration is only slight during September, and
reaches its maximum in October, one species, the Sky
Lark, prolonging its flight into November. In our
latitudes vertical migration is practically over by the
end of October, but in more northern areas it has ceased
for the year months earlier.

The following table will indicate the duration of the
principal Migration across the British Archipelago in
Autumn.

eee eee | es ae nee aIqdeA\ aSpas
| rub ae as i ae nr} eee JarqaBAA YsIEW
| x x x x x { see eee } eee ) wee wee JaTqav AY prey
| x xxx! xx | < Pr wines es aaa UITAA POOA\
< . xx |X xx] xX x a peas | “UDI AL MOTTE AL
= xx xxx] x x te | Rae Fae of See enor)
SS i eg SAR ; f sss JaTqae AA Uapivry
9 < Re See SRI da | (ie cess aso HOETE
ty x X X X x X ; “ )**" JVOIYPPY AA IassaT
es FOE a) She Bt Ne oho : “ee [| t8 8a SVOAI OE AN
S x x aga JoJUIIIW aspayy
3g x Nae onal : apesunysin
ie | | x XX} XX ox uIqoyY
<a) x Sema ISIC | OSX “ x KM aX x eer le ; ser se" Taya AA
a | | ae | "* yvyoauoyS
S x eee atx x Ne NPS EE Mac oe JVYoUIYy A
KKK Xs Wvispay uoulwoy
= | | ( MRISpayy Yui,
> Boel Rye | ik eons [assess caSan i eien
NY | | | | x eee | wee eee eee parq yore
NX 5 5 v . . one . | see one lisie eee eee aIVIP PPL
Re > TS aa ha a) ea se “Sura poy
LQ ? xX X X KG a! : x x x ee med ysniy yp suos
S XxX |XX xX! xXx | x ? se [ses 88 USMIUT, TOSSA
Za ee | | : Ss Se
S ol ee | oval ciel | outa Ges amar: | H | 6 | ¢§
Q < be) 4 | 2 Gly 5 | @ 5 Ha a x
. 4 | |
= enol te SL ota (ae ea wea | oe Ae ‘salads
“ONLLSVOD “SHNOLYA Vda “STVAINUY
S ‘HLNOS OL HLUON WOU ‘HLNOS OL HINON Woug SS MCCH eMCK OT:

271

vv

x

x
——
aan 2

x
x
x

= Xe

AUTUMN MIGRATION IN BRITISH AREA

x

|x x x] x x BY Oa bec sab. ess [eee eS unmags a finan Wace Rita BO gs

| XxxXxXXxX x x ae se fees es Buung Mous
IK > x x oe . “voy WA NZS “eM | see wee Jee eee ¥
eS a as ORGAN | RX | etl sSujung peoy
|XX x| x XxX |XX X| x “os Sunung u1og
Ie =15G rs > ax ES ROM | OX BOTs (oot Surjung Aoy][a x

| xX X|X XxX} xX xX x x 9 Momreds sony)
vasa 5 ET EXE SEX yo Sie mpg nD HoH reaggCalouiai Cg]
SES MNS PRA PAS ecGsaSe || acaGemin |e suai | 2D STUDS IGG 6 fayo hia 466)
x sous <000 youury

youyuso14y

| “* youyplory
x x x aoe see | eae nee wae eee SUIMXU AA.

x
x
x
x
x

3 ps

ae
xX xX
x XK

x
x
x
x
x

Oe ee BS OK ol : 2 Uugie pues
KKX RR KX x ee) | ae Bir ase re fee eel “Uae
oR Se SOR Se Y ob ov bo abe bin Wows. obo

“ MOTTEAMG
wee sae tee ee wee Toyo WwoA Ty pad
: m : ye “|e rayoqeoAp yy pajjods
S| Sense “ Po aan A “+ lo ows payoeq-paryy
; ; PAA SSRs nee x me | es oxtIyS Ava) yeorx)
os ve ve ve ree | ees sf set me fees 58! 31011G uaplox)
| tee . tee tee vee eee wae tee ee clen 1
xxXxKIXxX x onic wie B80 we Nee uit HOD. = 000 peysv Ay Kerry
ee % wee 50 Hae vive nee [reise Ay MOTPA

Wa
“A

x xX X
x
x

x

\
?
?
‘,
?
Mw
x~

x x“ wx | eee vee T1vyBe AA OUI AA
x Xe ED leecace a llbcouescesell Gees Xo es Trerse Ay pergi
| XX |XX X|X XX] x x Se Se Nee CEPTS UANG
Eee, SSI] BX She x | * ssnowjzLy ang

x | XK XX | =X x “sss gsnowjyy [vog

8 WSR S46 Se] Se oe x dc eilene* asNowyy, Wat

[esis ee ae x aSHOW FLT, poyie}-suo'T

Neale lh OC al MS | Gee eee SOTO DOS)

SG Sailing y Boe Biss Ss life gab Ja[qiv A, toddoyssviy

THE MIGRATION OF BRITISH BIRDS

272

eee MIX, OMRON ||| SRS

xX XK X

Pa fara x xX eae
»
n .
3g a o a
a 4 =) a
i i
"SNILSVOD

‘HLAOS OL HINON WOU

ee ee aaa
eee aoe tae faidsQ
“ "* niezang AUOPT
Hee ee uaa
tee nee noe Aqqoy{
“ JOLUBET Ss ndvjUop
oer oe). IOLIIBTT UoyT
pivzzng posdoy-ysnoy
xe yAaryT Moueds

sens na 140 Amous

[MO paiva-}104S
wee wee JOYsysuryy

| eee eee * ooxyony

“* godooyy

fone nae iehysin

,
4

x X X X X
ee Onna
Xx XXX XX

*“Ldas

“LSNONV

x x X x
xX x x xX ree
x X x fie
xx | x na
ave | ene o-
OE LEK Meron 2S, ies
x x X X| XX
x x KX x Xx
x x xX XK x
x x XX XK XK
xX XX x x
x xX X x cae
x X x x x
z

n ’

Camb ten lips
>| 8 a
te

‘SHUN LAVdaAd

‘HLNOS OL HAMON WONT

“A'S +°S OL

He aS
eee see eee Kel
He nt ue yooyr
“* MOIS papooy]
“* MOID UOLURD
tee wee eee Mepspoe[
see nee wae SUTILIS

oe abe yey a10ys

“SaIDadS

AUTUMN MIGRATION IN BRITISH AREA

x
x

x
x

x X

x

2 is
“aA

4

xX xX

x

x

‘,
Pe

x

x

x

x

x

4

‘
?

x

x

xX >

x

S
A

‘

eee

* BACT Pesuryy
“* MapING eU0IS
"* oyvaig panods
eee asa
pleysng apyWwy
“+ pavysng yearn
tee eee tee yen)
“* 9A0q IAN,
He dang, Suryy
roa e MOUS
“* *** JgpuURBsOOr)
an af9-uap]or)
* 19J09G JOATIA
J9}09G uoWUOD
youd peyre}-suo'7
ris oe see dngog
~~ ong peyAy
oi) Sp AByoOr
vee tee UOdSIA\
= eter
es TEMpen
nee ee KOues1ey)
Hee Tea T
sPUITBIN
UBMS JNJ

“ UBMG SOIMog
“* ueMmg sodooFyT
“* gsoory Juaig
as00r) 9[OvUIIg
28004) pajOoj-YUlg
** gsoor) uvag

as004) payuoyy-9}1Y MA

THE MIGRATION OF BRITISH BIRDS

274

x
xX

xX XX

x X X)

x X X

“AON

xx 1xXxx] xx eer ee
ese aN Se Sc! 5c 4 oe xj teat errr’ a
S| SS OX x xe ae x x |x x xX x
x ee eax x Soh Shy PKr an [be core
Sciay ae |< oi pire al eae 4 = Fa i es 6
xx nae xix x Sy. tain
lx x x |x ea x
aie “A vat : Was
x x
x x
Oe ae SM x Jo0 SK DO Sema?
Me (base sell x G6 ae me xe :
goat a seis “i a ;
<r ed ORS 4 BAA : as
x x x x x eee . wee . | of
Cox x xX sials
Perales Z BAe vo vee fons
x Sone xX x pare le .
x x
Miabre ltevgesaiea|| ose x #3 ss 38
See 15K) Seed) x se : ae :
BC ll OE LS OX x ‘ ‘ alae
x XiEXiS x x ee x eg ball Os
x 2 x eX
> >
pealceoneie icranhee 4) (Soh Bia
a 4 a < a 4 a
3 3
“ONILLSVOD “SUMO LNVdaAG

‘HLNOG OL HLNON WONT

‘HILNOG OL HINON WONT

xX |X XX) XX so
Ke Mal Dee HE ENS x
aire?
|
See el ps ne, gah 2d [ae eat x
xx as Kx x
|
; |
|
oe Sag }
x 4 oben’ x |
x x x Dna
1
\x xx} xx | x |
es all bX x
SOUS Ne | ae
x seek nee x
|
: / |
Daal Sle les es St | bse gm | Me
AKT PIXE ioe |e
SSR SSCA ata
n | & x
= BP ace
S = | 5
ee |p s a s
“STVAINNY
"M SAS 5 °S) OF,

wyancy
WMpoy papiej}-1eq
TUMpos paytey-you rg
- salle Webipaietieme Sues ee:

year
|

Maying
“* yueyspay uowuUloy
| sr sts yueysuaary
yuvyspay Aysnq
jadidpurg uaairy

Jadidpurg pooa,
sadidpueg uowwog

my
adrug youl
adiug uowwoy
YOOIPOo AA.
oea paxpeu-pay
ys adosvjeyg Avis)
"* *** Quo}SUIN

“a ya00ay

Surmdey
JIAO|q uapjoy
BACT Y AvID
“ss uanog
sPPACIS ysuay

“SAIDAdS

275

AUTUMN MIGRATION IN BRITISH AREA

x X

Pas PS

xX XK xX)
x X xX

x
x

xX xX X

x

x X

w

x

x xX
x xX

AqaID UIUOALTIS
aqoIr) psa |IeU- PPO

* TOAT] pa}OIY}-payy

JOAICZ po}yVOIY-39vL[_,

JOAIC, WIAYION JwaIryy

ae SVec lial

fewer ung

eNYS S,uospreyorny
ENYS Iury1oyVulog
“* enyg suoyNg

TM) snooneypsy

es RIMS) SURI

"* _ UJd J, 1esse']

Don WHEN], QNAy

“* Tay, UOUOD

“+ UOT, ]vasOY

WI9T, YIMpuLs

ae Sulpiapues

meee Qos

jadidpues ayding

Jadidpueg Maping
wg sspoureia Ty,

oe US Stead

CELA TER: 2X1,

INTERNAL MIGRATIONS AND LOCAL MOVEMENTS IN
THE BRITISH ARCHIPELAGO:

Meagreness of Data bearing on this Question—Local Movement
in Spring and Summer—Internal Migration always takes
place within Normal Areas of Dispersal—Birds do not Wander
from their Areas—Comparative Movements of the Snow
Bunting, the Northern Bullfinch, and the Crested Titmouse—
Emigration only Undertaken during the Season of Reproduction
—Local Movement amenable to Law—Effects of Severe
Winters on Birds—Results of such Movements ineffectual in
extending Area—Redwings and Severe Weather—The Want
of carefully-kept Records—Local Movements at Lighthouses
—lIrruptic Movements—Their Futility as Colonizing Agents.

WE cannot well dismiss the subject of Migration in the
British Islands without some brief allusion to all those
local movements of birds that take place within that
area. The subject is a much more difficult one than
might be suspected. Unfortunately at present the data
are too meagre to allow of much accurate generalization
or deduction. A vast amount of observation has been
made, but the haphazard way in which the facts have
been collected is a very serious detraction from the
value of such observation. Notwithstanding the ap-
parent fortuitous character of much of this internal

INTERNAL MIGRATIONS 277

migration and local movement, I am compelled to
believe that it is governed by law.

In the British Islands these local migrations apparently
are only undertaken in winter. I say apparently, because
it is by no means proved that there is not a considerable
amount of local movement taking place at other seasons
and entirely overlooked. In winter birds are more
gregarious, more easily observed, and the initiating
causes of local migration, such as rises and falls in
temperature and storms, are readily and easily defined.
In spring and summer much of this local movement
might go on, as indeed I strongly suspect it does, with-
out being noticed. Birds both in winter and summer
follow their food, the general area of their distribution
is that in which they can find sustenance, and as this
food-supply varies a good deal according to season,
both in the matter of description and locality, it is only
natural that birds should undertake some local journeys
in quest of it. So far as I can ascertain, a// this internal
migration and local movement takes place within the
normal area of dispersal of every species. There is no
evidence whatever to show that a species will wander
from its normal area in quest of food, and the laws
which govern its dispersal inexorably confine it to that
area, and the species will perish therein if the conditions
change and render existence impossible. As I have
previously shown, species never extend the area of their
dispersal in winter, emigration or range expansion can
only take place in summer or just prior to the season of
reproduction. It must also be remarked, that not a
single species taking part in these local movements in
winter in our area is non-indigenous to that area. No

278 THE MIGRATION OF BRITISH BIRDS

matter how severe the winter may be on the Continent,
the Pine Grosbeak, the Nutcracker, the Crested Lark,
or the Central Russian Blue Tit (Parus pleskiz) will
never normally cross the North Sea in quest of food
in company with the vast flights of Starlings and Sky
Larks, and other well-known indigenous species that we
know even in midwinter pass to and fro in response to
falling temperature or storms. The Siberian Jay, an
inhabitant of the pine forests of North Russia, never
wanders to our area in quest of food, although the
Hooded Crow which frequents the same forests pours
into England to winter, and is known to cross over to
us as lateas December! The Snow Bunting is more or
less on passage to and from our islands and the Continent
all the winter through, but the Shore Lark is only an
abnormal visitor on spring and autumn passage. The
Northern Bullfinch (Pyrrhula major) never visits our
area in winter in company with the hosts of Finches
that cross the North Sea prompted by severe weather.
The Crested Tit never crosses to us from the pine and
oak forests of Germany and Holland, yet the Blue Tit
does so in considerable numbers ; the emigration of the
former species was entirely continental, that of the
latter partly continental and partly from a British base
across the North Sea plains. What I want therefore to
impress upon the reader is that no matter how extensive
this winter movement may be, no matter how birds
may wander to and fro in response to variations of
weather, such journeys all take place within the normal
area of distribution of such species, and within the limits
of their usual migrations. These movements are not in
any sense analogous to what is presumed to have taken

INTERNAL MIGRATIONS 279

~-

place in a Northern Glacial Epoch—that utterly fictitious
southern emigration of life—they are purely local, and
can never extend beyond the geographical limits of the
species partaking in them. Zhe Law of their dispersal,
which forbids southern extension of range either in summer
or winter, and only permits northern extension or emigration
at all during or gust prior to the season of reproduction,
zs znexorable and emmutable.

Having thus placed the subject on what I believe to
be a thoroughly sound and satisfactory basis, we will
pass to a more detailed study of the phenomenon. If
we admit that the whole phenomenon of Local Movement
or Internal Migration is confined within certain limits
and controlled by law to those limits, I think we must
also admit that the individuals partaking in it conform to
certain governing impulses. We have seen how closely
species and individuals and their descendants are con-
fined to certain routes, to certain limits, from which,
broadly speaking, they seldom diverge. It is therefore
difficult to believe that all this winter migration is
entirely fortuitous. Birds, individuals, have certain
routes, inhabit certain areas or districts to which they are
attached. It seems probable, then, that the individuals
partaking in these various winter migrations are moving
to and fro, according to changes of weather in the area
they occupy, along certain routes, which routes indicate
the lines of past emigration or range expansion. Birds
move south or north along a coast, or east and west
across a sea, but there is a certain amount of method in
the flight. Now most of this winter migration, across the
North Sea for instance, takes place within a compara-
tively narrow area. No matter how vast may be the

.

280 THE MIGRATION OF BRITISH BIRDS

winter flights of the Snow Bunting, for instance, we never
observe any of their effects in the extreme west of Eng-
land. Birds of various species may literally swarm along
our eastern coasts ; all winter migrants from the Con-
tinent, yet the more inland districts are not affected. No
matter how abundantly the Hooded Crow may pour
into the districts of the Wash, we never see a corre-
sponding increase of Hooded Crows say in the neighbour-
hood of Sheffield, not 80 miles away, and where the
species is very rare. Wading birds, Ducks and Geese,
may oscillate between the Continent and our eastern
sea-board, but the movement is purely local, confined to
the feeding grounds of those individuals of the species
that frequent the districts affected. To all these local
migrants the route must be familiar; but there is not
the slightest trace of any attempt to increase or prolong
that route into other areas. Birds may seem to be
flying this way and that, entirely at the mercy of the
elements, but there can be no doubt whatever they
know perfectly well where they are going—they are
following familiar routes to other and more open haunts,
anticipating a storm perhaps by hours, or retreating
from a frost that has suddenly sealed their feeding
places. Spasmodic much of this winter migration may
be, fitful as the meteorological changes that initiate
it, but unquestionably in conformity with order and
law.

Every observer of birds must have often remarked
the effects of an unusually severe winter upon them.
Species will then come near to houses or visit localities
where they are never seen under ordinary circumstances.
I have known Red Grouse, when the moors have long

INTERNAL MIGRATIONS 281

been covered with snow, resort to the farmyards, and
even to villages and towns. Scores of similar instances
might be given ; and in some continental districts, where
the weather has been far more severe than with us, still
more extraordinary cases have occurred—of wild birds
visiting civilized places to seek for food. Now in the
first place let it be remarked that however unusual the
locality may be in which such species may appear under
these exceptional circumstances, it is always within the
normal area occupied by that species. A Nutcracker
will never come to an English cottage door for food, no
more than a Robin will ever appear at the threshold of
a Canadian settler. In the second place, the straying of
a species from its accustomed haunts is purely abnormal
—a struggle for life in fact of an individual—and such
an action in the majority of cases would not save the
species from extermination if it succeeded in saving that
individual. The conditions for successful reproduction,
found only in the normal haunts of the species, would be
wanting, and the inevitable result would be a more or
less rapid extinction throughout the area affected.

No matter how an area may abound with food in
winter, it will not be visited normally by any species
whose area of distribution is beyond it. Vast numbers
of birds die during a severe winter in the British
Islands alone, if food fails in the local area of distribution.
I have known our flocks of Redwings, which used to
come to certain localities and remain in them the winter
through, be almost exterminated during an exceptionally
severe season, and not to regain their usual numbers for
years afterwards. And this, mind, in a locality where a
flight of a very few miles would have averted the disaster.

282 THE MIGRATION OF BRITISH BIRDS

But the birds and their descendants that wintered in my

neighbourhood had done so for time out of mind; they |

came there by certain routes; they knew of no more
southerly areas, and each time a severe season overtook
them they were more or less decimated. A study of
the various local movements and internal migrations in
our area alone promises some very interesting results.
We are often told that British ornithology is pretty well
played out; here then is a new field for observation.
We want a carefully-kept record not only of the general
movements of the birds in a district, but of those that
pass through it, combined with keen incessant observ-
ation as to the causes of such movements, their direc-
tion and duration, and the season of the year in which
they are undertaken. Even a record of the summer and
autumn wanderings of such a common species as the
Sparrow will be of service. Of course these observations
are entirely separate from the usual migrations (if any)
of a species to and from any district.

Some very interesting instances of local movement
have been observed at our lighthouses, especially along
the eastern coast-lines. Others occur across the Irish
Sea. Equally interesting movements have been re-
marked along the coasts. It is usually remarked that
these influxes correlate with periods of severe weather
on the Continent, or in the northern British areas. At
Heligoland a great deal of local winter movement takes
place. It is impossible in the present state of our
knowledge to enter into greater details. We do not
possess sufficient data to generalize or deduct very
extensively. At present all we can say with certainty
is, that this local movement is a fact; it has been

INTERNAL MIGRATIONS 283.

observed over a great number of years, but the details
of the migration still remain to be worked out. From
what we have already learned of the emigration or
dispersal of birds, we cannot class Internal Migration
and Local Movement as fortuitous.

A few words on Irruptic Movements will bring the
present chapter to aclose. These movements are entirely
abnormal, and are rarely if ever attended by success.
One of the most remarkable instances of irruptic move-
ment is that furnished by Pallas’s Sand Grouse. Details
of the several irruptions of this species into Western
Europe (in every important invasion, however, be it
remarked, to increase breeding, not wzuter area) need
not be given here; they are doubtless fresh in the minds
of most readers. The last great spasmodic invasion
which may be said to have spread almost entirely
over Europe took place in 1888. The chief point
of interest to us, so far as the present subject is
concerned, is the absolute failure of these birds to
establish themselves in any portion of the area they
invaded. True, many of the birds made more or less
successful attempts to breed, and some individuals may
have lingered on in their new home for several years ;
but I much doubt if a single Sand Grouse out of the
thousands that invaded Europe in 1888 now survives.
Similar irruptions of Jays and Rose-coloured Pastors
have been remarked, but in no case has any permanent
success followed the movement. These movements
very forcibly demonstrate how futile irruptic colonization
is, and how rarely such individuals enter new areas whcre
conditions of life are favourable to them. They are
utterly abnormal means of dispersal, and in the great

284 THE MIGRATION OF BRITISH BIRDS

majority of cases must inevitably end in failure. Some
ornithologists are disposed to explain difficult problems
of geographical dispersal by similar irruptic movements,
but in the face of such damning proof to the contrary
such an explanation should never be invoked, unless
supported by absolute demonstration. Once more let
me assert most emphatically that the dispersal of birds,
nay of all organisms, is governed by Law, not by
chance, that it is not fortuitous but the result of
design.

Once more I repeat, Birds do not increase their range
in winter. J/¢ zs this all-important fact that keeps spectes
to thetr normal areas of dispersal. If winter conditions
led to extension of range or emigration, then species
would wander fortuitously far and wide, and such a
thing as geographical limits would be almost unknown
—especially in temperate and boreal latitudes, where
the food supply is ever a fluctuating one. The more
I study the question, the more I am convinced that
Dispersal or Range Expansion is solely the result of
increase, and that the spasmodic, totally abnormal, wan-
derings of species in quest of sustenance during winter
or the non-breeding season, can never lead to emigration
or permanent extension of area.

Ghia WE -XIT:
SUMMARY AND CONCLUSION.

The Present Volume illustrates the Development and Application
of a New Law of Dispersal— Past Geographical and Climatic
Changes—The Glacial Epoch and its Bearing on the New
Law of Dispersal—Effects of the Glacial Epoch on Species—
Range Bases—Application of the Law of Dispersal to the
Range Contraction and Emigration of British Birds—The
Migration of British Birds—Routes of Migration—Conditions
of Flight—The Spring and Autumn Aspects of Migration in
the British Archipelago— Internal Migrations and Local
Movements in the British Area—Irruptic Movements—The
New Law of Dispersal—Its Bearing on the Arctic Element in
South Temperate Floras—Inter-polar Floras—Impossibility of
Emigration of Plants from North to South— Presence of
Southern Genera in Europe—The Andes as a Route for the
Southern Migration of Plants—The Floras of Mountains in
the Torrid Zone during Pre-Glacial Ages—Arctic Floras could
never have been Developed in the Polar Regions—Dispersal
of Plants North and South from Equatorial Range Bases—
Effects of Glacial Epoch on Northern Floras—Absence of
many Species from Equatorial Range Bases—The “ Retreat ”
of Plants a Myth—Conditions of Successful Dispersal—The
Flora of the Mountains of Asia—Inter-hemisphere Species—
Species in Polar and Temperate Zones—The Distribution of
Plants in Africa—The Temperate Flora of South Africa
Northern Emigration from Antarctic Centres obviously
Erroneous—The Bearing of this New Law of Dispersal on the
Absence of Southern Types from the Northern Hemisphere—
The Dominant Southern Flora—Its Dispersal from Range
Bases South of the Equator—The Problem of Migration and

286 THE MIGRATION OF BRITISH BIRDS

Geographical Dispersal hitherto attacked at the Wrong End
—-Exterminating Influence of Glacial Epochs—Powers of
Organisms to Extend their Areas of Dispersal—This Dispersal
not Fortuitous but governed by Law.

THE subject of the present volume, the Migration and
Dispersal of British Birds, has been selected to illustrate
the development and application of what I believe to
be an entirely new Law governing the Distribution,
Emigration, or Dispersal of Species. In elucidating
this subject a very wide and varied series of phenomena
have had to be dealt with, yet no more than were
absolutely necessary to furnish a satisfactory and toler-
ably complete explanation of the facts. In order to
render the whole subject as clear as possible, it may be
advisable not only to recapitulate the most salient
features in a concluding chapter, but to deal with a few
facts bearing on this new Law of Dispersal that could
not well have been introduced into the general subject
matter of the volume.

In dealing with the Migration and Dispersal of British
Birds, we found it impossible to make any progress until
we had traced out the past geographical and climatic
changes, not only in the British Area itself, but in more
or less adjacent areas, during late Pliocene and through-
out Pleistocene time. We had first to ascertain as
correctly as the state of present knowledge admits, the
condition and the physical aspects, not only of Europe,
but of a great part of Africa, during those periods.
Taking the present distribution of species as a guide, we
ascertained that a great many of those changes of climate
and of geographical conditions upon which astronomers,
physicists, and geologists insist, were in absolute harmony

SUMMARY AND CONCLUSION 287

with such dispersal. We have shown that the gradual
severance of the British Islands from continental land is
also quite in accord with the present distribution of
birds over their area ; whilst the necessity of a former
much greater land extension between Greenland and
Europe is shown to be imperative.

We next pass to a consideration of the Glacial Epoch,
and its results upon the fauna and flora of the regions
affected. By the aid of a new Law of Dispersal, I have
endeavoured to show that the effects of this Glacial
Epoch must have been very different from those which
biologists have universally accepted and described. I
have shown that the conditions of the Ice Age, instead
of being grand incentives to Southern Emigration,
exerted a vast exterminating influence, and that they
must have caused the utter extinction of every species
whose breeding range was entirely confined to the areas
glaciated, or sufficiently within the influence of glaciation .
to render existence impossible. The effects of the Glacial
Epoch on the dominant Euro-Asian fauna are shown to
be exterminating rather than incentive to Southern Emi-
eration. The only species that survived were those that
occupied a southern and continuous range base during
Pre-Glacial time. These southern Range Bases (or what
are perhaps better described as Refuge Areas), so far as
British birds are concerned, are then defined. I then
proceed to show that the breeding range of all surviving
species must have extended at least as far south as these
limits during Pre-Glacial time, and that the Glacial
Epoch exterminated the northern portions of such
species, or contracted the range of such as were migra-
tory, the habit of migration not being acquired during

288 THE MIGRATION OF BRITISH BIRDS

the Glacial Epoch, but a result of range extension from
more southerly areas during favourable intervals of
climate in either hemisphere. Such species were, and
probably always had been, Inter-hemisphere or Inter-
polar, with a more or less ancient Equatorial range base.
An Inter-hemisphere species, for instance, like the Swal-
low, or an Inter-polar species like the Hudsonian Godwit,
could never be exterminated by a Glacial Epoch. As
the summers became colder, the breeding range would
gradually become lower—the species probably suffering
considerably meantime, owing to the increasing adverse
conditions under which the young of the most northerly
breeding birds would be reared, in some seasons perhaps
none at all surviving—and sink back upon itself, until
it was driven as far north or south as the winter quarters
commenced, which represent the centre of dispersal or
range base of the species. If the winter range or range
. base of a species did not extend south of the Equator
the species would never emigrate south, but continue to
occupy that area until a return of more favourable
conditions for northern extension or range expansion
again took place. If the winter range or range base of
a species did not extend north of the Equator, the species
would never emigrate north, but remain stationary until
favourable conditions returned, and permitted a southern
extension or range expansion. If the range base
extended both north and south of the Equator, that
Polar or Temperate area would be occupied by those
Inter-hemisphere and Inter-polar species which pre-
sented the most favourable conditions for reproduction.
At the present time these conditions are almost exclu-
sively in the Northern Hemisphere, but during the last

SUMMARY AND CONCLUSION 289

Glacial Epoch in that hemisphere the Southern Hemi-
sphere would most likely present the most favourable
conditions for successful reproduction, if land extended
southwards. Thus from a common equatorial range
base during the course of ages, would the breeding area
of these Inter-hemisphere and Inter-polar species be to
a varying extent reversed in the former group, and
completely reversed in the latter, the breeding grounds
in one hemisphere becoming the winter quarters in the
other (conf. Wigration of Birds, pp. 149-152). On the
other hand, Northern Hemisphere species living per-
manently in the northern areas, with no southern breed-
ing range base beyond the limits or fatal influence of
glaciation, would gradually be exterminated; or Southern
Hemisphere species living permanently in the southern
areas with no northern range base beyond the limits or
fatal influence of glaciation would also be as surely
exterminated, because the Law governing their dis-
persal forbids retreat. The significance of these facts,
and their bearing on the Arctic element in South
Temperate floras, I hope presently to show.

We then proceeded to apply this Law of Dispersal to
the glacial range contraction and Post-Glacial emigra-
tion of British birds, and endeavoured to show how
existing species were preserved during the Glacial
Epoch ; how such surviving forms emigrated or ex-
panded their range north with the return of more
favourable climatic conditions. Passing, then, from a
study of universal emigration during remote ages to
more local range expansion actually in progress at the
present time, we proceeded to show that the movement

is governed by precisely the same law that controlled it
U

290 THE MIGRATION OF BRITISH BIRDS

in the past. A chapter on Island Avifaunas, their
origin, the conditions under which they are maintained,
and their relation to glacial conditions, bring the first
part of our subject to a close.

Having satisfactorily accounted for the presence of
the British avifauna, we next proceed to a study of its
Migration or Season Flight. Routes of Passage engage
our attention first. We learn how gradually a Route of
Migration has been formed—how slowly a change of
climate might curtail it, or a return to more favourable
conditions assist in its expansion—how species never
extend their winter area, such expansion invariably being
the result of an increase of breeding population—birds
Emigrating and Migrating solely to breed! Then the
various routes of migration to the British Islands are
divided into classes, each being dealt with and described
in turn. First we trace the paths of the Summer
Migrants to that area, and show how the most important
routes are in the closest vicinity to the continental land
masses, the weakest migration taking place in the most
westerly areas. The significant bearing of these facts
upon the distribution of species within the British
Archipelago is next discussed, and many anomalies of
dispersal are satisfactorily explained by law. Passing
on to the migration across the North and Irish Seas,
we endeavour to trace the correlation of routes with
submergence in those areas. We next deal with the
routes of species that winter in our islands or pass over
them as coasting migrants to other lands. A _ brief
account of the inland continuation of these routes,
showing how such were probably formed, brings that
portion of the subject to a close. |

SUMMARY AND CONCLUSION 291

Having shown the origin of these Routes of Migration,
we next proceed to discuss the Conditions of Flight.
Dealing first with the Instinctive impulse of Migration,
we then pass to the question of how birds are able to
traverse these routes with such apparent precision.
Experience rather than Inherited Impulse is shown to
be the guiding influence. The altitude of migration
flight, and the order of migration are next discussed.
The daily time of migration, and the gregariousness or
otherwise of birds on passage are then described ; whilst
finally the perils of migration are briefly treated.

Our next two chapters are devoted to a general
description of the Spring and Autumn Aspects of
Migration in the British Area. We have traced the
phenomenon in spring from its earliest beginning in the
departure of those migrants to the east across the North
Sea that breed in continental areas, and the almost
simultaneous arrival of other migrants, many of the
same species from more southern areas, that breed in
Britain. Later we describe the departure north or
north-east of our winter visitors ; together with the vast
amount of coasting migration that passes over the
British Area, composed of birds that winter to the south
of us and breed to the north. Coming then to the
arrival of spring migrants to the British Islands, we trace
the movement from its beginning onwards through the
months that it continues, until it finally dies away for
the season. A few remarks on the vertical migration
of birds in spring, species that ascend to various eleva-
tions for the purpose of breeding, together with a table
indicating the duration of Flight, bring the spring
aspects of the phenomenon to a close. Entering then

292 THE MIGRATION OF BRITISH BIRDS

upon the Autumn Migration of birds, we trace the first
signs of the movement by migrants entering our area
from the highest and coldest. latitudes as early as July.
As the autumn advances the migration gains in strength,
and our own summer birds begin to take their departure,
that event being more or less directly preceded by the
annual moult, and in many cases by the suggestive
gathering together of individuals. The vast amount of
coasting migration is described, as is also the order of
passage and the duration of flight. In the late autumn
a very noticeable change in the direction of migration is
apparent, and we then proceed to deal with the vast
east to west movement across the North Sea. Various
apparent anomalies of Flight are then discussed, as are
also the presumed change of route and the autumnal
descent of migrants from their mountain breeding places.
The subject will be too fresh in the reader’s mind to
require recapitulation in further detail.

A short chapter dealing with the various Internal
Migrations and Local Movements of birds in the
British Islands introduces us to a very important branch
of the subject, which unfortunately cannot be treated in
a very detailed manner owing to the utter lack of neces-
sary information. We have shown, however, that all this
Internal Migration is purely of a local character, abso-
lutely confined to the areas occupied normally by species
undertaking it, and therefore controlled by that Law of
Dispersal which forbids extension of range during the
season of non-reproduction. We next proceed to discuss
the effects of abnormally severe winters on birds, and
the impotency of such effects to increase or to transpose
seographical area; bringing the subject to a close with a

SUMMARY AND CONCLUSION 293

brief allusion to Irruptic Emigrations, showing their
abnormal character and their failure in the majority of
instances to extend distribution.

Among the more important points dealt with in the
present volume may be mentioned the following :—

I. A new Law of Dispersal.

II. Polar Dispersal—from either Pole—a myth.

III. Glacial Epochs exterminated Life ; did not cause
Emigration or “ retreat ” from adverse climatic conditions.

IV. The sources or Range Bases whence the British
Post-Glacial Avifauna has been derived.

V. Past geographical Mutations have been shown to
bein harmony with the present geographical Distribution
of Species.

VI. Endemic island species are never produced on
routes of migration of closely-allied parental species.

VII. Emigration or Range-extension is rarely made
across wide water areas ; but Migration, once established
across such, when the land was continuous or nearly so,
is only arrested by extermination.

VIII. The origin of the West to East Migration across
the North Sea.

IX. Additional light has also, I believe, been thrown
on the Migration Routes of Birds.

X. Internal Migrations, Local Movement, Irruptic
Emigration,and Recent Emigration have all been treated
from what I believe to be new points of view.

XI. A short comprehensive account of the Spring
and Autumn Aspects of Migration across the British
Archipelago.

XII. The important bearing of the new Law of Dis-
persal on the Distribution of Floras.

“a

294 THE MIGRATION OF BRITISH BIRDS

XIII. The development of “ Arctic” species.

XIV. Migration a result of Normal Increase, and not
initiated by winter conditions, or retreat from adverse
conditions.

The object of the present work has been to a great
extent to demonstrate a hitherto undiscovered Law
governing the dispersal of species. That Law forbids
the southern emigration of Arctic and North Temperate
forms to Antarctic and South Temperate latitudes. So
far as I can ascertain, every biologist of note insists
upon this Southern Emigration. The “arctic element
in South Temperate floras,” to quote Dr. Wallace, has
been repeatedly brought forward in support of this view ;
and so generally has this interpretation of the facts
been accepted by naturalists, that to question its truth
seems little less than a rank biological heresy. If these
facts have been correctly interpreted, then our Law of
Dispersal cannot apply to floras; animals may bow
submissive to its edicts, but plants may set it at defiance
and demonstrate its impotency. I hope, however, pre-
sently to show that not only does the phenomenon of
“ Arctic” types in the Southern Hemisphere conform to
this Law of Dispersal, but that it actually illustrates it in
no uncertain way.

Sir Joseph Hooker graphically describes a “ continuous
current of vegetation” extending from Scandinavia to
Tasmania ; a second very similar current occurs along
the mountain systems of North and South America ;
whilst a third stretches across the highlands of the
African continent. This flora, which has been described
as the “Scandinavian,” is universally admitted by
botanists to possess astonishing colonizing power, due

SUMMARY AND CONCLUSION 295

perhaps to the exceptional means of dispersal with
which the plants that compose it are endowed. Of the
various means by which this dominant flora has
emigrated from certain centres it is quite unnecessary
here to speak ; that does not concern the point at issue
in the slightest degree, This flora, which is designated
by the excessively inappropriate epithet of “Scandi-
navian,” is in reality an Inter-polar Flora, and occupies
a precisely analogous position to that of the Inter-polar
avifauna, of which various species have from time to
time been mentioned during the course of our investi-
gations. It isan Inter-polar Flora with a well-established
equatorial range base on the mountains and highlands
of the torrid zone—a flora, therefore, which no glacial
epoch at either pole could completely exterminate—a
dominant flora that, notwithstanding the complete exter-
mination which might overtake all those species or
portions of species within the sphere of glacial influence,
would still be preserved on its southern and equatorial
bases, and emigrate north or south again from those
bases towards whichever pole where glacial conditions
were passing away. As we found to be the case with
Inter-polar species of birds, so we also find with this
Inter-polar flora that the Polar region best suited to the
requirements of such avifauna or flora is that where it
predominates. At the present time the Arctic regions
are best adapted to the requirements of this Inter-polar
flora, and consequently there it thrives best, is most
abundant, and most widely dispersed. In the Antarctic
region conditions are unfavourable, therefore this flora
is neither dominant nor abundant, having been extermi-
nated during the last glacial epoch at the Southern Pole,

296 THE MIGRATION OF BRITISH BIRDS

and only lingering on a few northern bases in the
immediate vicinity of that area it once must have
occupied so widely and in such abundance. To describe
this flora as either “northern,” “ Arctic,’ or “Scandi-
navian,” is therefore a most erroneous definition. We
might, with equal propriety, speak of the “Arctic”
element amongst birds, penetrating even to Patagonia,
South Africa, Australia, and New Zealand, and even
more remote latitudes; whereas, as we have already
seen, such birds are Inter-polar and belong as much to
the Antarctic as to the Arctic region.

There can, therefore, have been no emigration of
plants from north to south. The range of the Polar
flora has been contracted by extermination (how many
times we may probably never know) as far as glacial
influences have radiated from either pole ; it has been
expanded from such lower range bases as conditions
favourable to Polar emigration have returned. We have
precisely the same class of phenomena among plants as
we have among birds—in many cases identical species
in both hemispheres of the more Polar ranging types ;
distinct species generically identical, and southern repre-
sentative forms, in the case of the more Temperate
ranging species—both indicating equatorial centres of
dispersal, with little or no isolation or discontinuous
range area in the Inter-polar species, but with varying
degrees of isolation and discontinuity in those we have
already classed as Inter-hemisphere species. It has
been said that some botanical genera now characteristic
of the Southern Hemisphere appear to have been origin-
ally derived from Europe! Now in the first place some
of our most eminent botanists have utterly discounten-

ee ee Oe ee

OO a.

SUMMARY AND CONCLUSION 297

anced such statements; and in the second place, even
admitting the identifications to be correct, there is no
evidence whatever to disprove that these genera have
not spread north and south respectively from an equa-
torial base—suffered extermination in Europe, but still
survive in Australia. I might here take the opportunity
of remarking, that in a great many cases these equa-
torial range bases must for obvious reasons have been
entirely obliterated, as species have moved north and
south from them, and become resident types in higher
latitudes.

The Andes and the Rocky Mountains, stretching in
one almost continuous line from the Arctic to the
Antarctic regions, are stated by Dr. Wallace “to have
formed the most effective agent in aiding the southward
migration of the Arctic and North Temperate vegetation.”
Now, for the sake of argument, we must presume that
the equatorial or torrid portions of this continuous
mountain chain (and also by analogy of a// other moun-
tains and highlands within the torrid zone) held a flora
of some kind, suited to the requirements of a very
elevated cool climate, before any glacial epoch came on
to drive these imaginary Arctic plants southwards. There
is perfectly uncontrovertible evidence to prove that
before glaciation the lands in North Polar latitudes con-
tained a luxuriant flora, even of a semi-tropical char-
acter, and that therefore no “ Arctic” or “ Scandinavian”
flora could have existed dominantly in those latitudes,
ifatall. If they did so exist, “22 xo one case has a single
example of such a fauna or flora been discovered of a date
anterior to the last Glacial Epoch.’ (The italics are mine.)
As the climate slowly changed and cold conditions came

298 THE MIGRATION OF BRITISH BIRDS

on, from where or whence did the “ Arctic” flora arrive ?
True, many of the species—such as the dwarf birch for
instance—are but modified forms of more Temperate
types, and are the result of Post-Glacial invasion from
southern bases; but, paradoxical as it may appear, the
strictly Arctic or Inter-polar flora could never have been
developed within the Polar regions of either hemisphere.
We are forced to the conclusion that it must have had
an origin in a region where cold conditions have existed
unchanged for a vast and indefinite period of time. No
part of the world fulfils these conditions except the
mountains and highlands within the tropics. Here we
can conceive how vegetation slowly crept up these
heights from the equatorial plains, becoming modified
as it reached those zones where cool climates prevailed
—how it spread in strict accordance with the Law of
Dispersal north or south along the mountain chains
towards the poles, entering the Arctic or Antarctic
regions, and becoming dominant as they offered favour-
able conditions for its increase, the altitudinal range
becoming lower as the latitudinal range became higher.
We can also understand how when a change to a warm
climate occurred (a mild inter-glacial period) this flora
dwindled away and perished in these Polar latitudes,
and was only preserved on the higher and more southern
range bases; or in like manner how when the Glacial
Epoch assumed an intense phase it became exterminated
and buried under the ice-sheets and snow-fields, but
maintained its existence through the southern range
bases which preserved those portions of the species that
dwelt in areas beyond glacial influence, supplying fresh
colonists to emigrate towards the glaciated regions, as

SUMMARY AND CONCLUSION 299

soon as conditions became favourable. It is said by Dr.
Wallace (referring to the Andes) that there are “between
sixty and seventy northern genera in Fuegia and
Southern Chile, while about forty of the species are
absolutely identical with those of Europe and the Arctic
regions”; and further, “as only a few of these species
are now found along the line of migration [emigration],
we see that they only occupied such stations tempor-
arily.” There is not a shadow of evidence to support
the latter assumption of short occupation. Species that
reside at high elevations on mountains have necessarily
a somewhat restricted area of distribution, and would
be more quickly exterminated in such localities than in
lower and wider areas; for, as Dr. Wallace himself
suggests, the raising of the snow-line, due to glacial
causes, would not only reduce their area of distribution,
but ultimately cause their extinction even in the very
centres of their dispersal.

With regard to the actual route which this Inter-polar
flora followed, north or south to either Polar continent,
nothing need be said; but we cannot accept Dr.
Wallace’s conclusions, that when. the South Polar con-
tinent became glaciated “these plants would be crowded
towards the outer margins of the Antarctic land and its
islands, and some of them would find their way across
the sea to such countries as offered on their mountain
summits suitable cool stations; and as this process of
alternately receiving plants from Chile and Fuegia, and
transmitting them in all directions from the central
Antarctic land, may have been repeated several times
during the Tertiary period, we have no difficulty in
understanding the general community between the

300 THE MIGRATION OF BRITISH BIRDS

European and Antarctic plants found in all south
temperate lands.” Now it is impossible to understand
how any area could become “crowded” with plants (or
animals) that are retreating from their normal habitat
and entering areas where more or less adverse conditions
of existence must prevail. Is it not more philosophical
to assume that these mountain bases were the points
from which the flora started, and that they are the bases
on which the remnants of that flora will be preserved,
whilst that portion occupying areas beyond them will
perish through an adverse change of climate? Botanists
(and zoologists) are too apt to overlook the fact that no
matter how easily a seed (or in the case of an animal,
an emigrant) may be transmitted from one region to
another, it is perfectly useless as a colonizing or range
extending medium, if the region entered is not adapted
to its requirements and successful propagation. Breed-
ing conditions must therefore always determine and
control range extension.

We have precisely the same phenomena on _ the
mountains of Asia—equatorial range bases and centres
of dispersal of that flora which has spread north and
south into the Arctic regions on the one hand, and into
Australia, New Zealand, and Antarctica on the other.
Just as we found to be the case in birds, the highest
ranging species are the most widely dispersed ; in the
more temperate ranging types the identity is only of a
generic value. This brings us to the consideration of
such species as we have already described as “ Inter-
hemisphere.” They are species that have ranged north
or south from an equatorial base into the Temperate
zones only of either hemisphere. The much greater

sz

SUMMARY AND CONCLUSION 301

difference of conditions prevailing in the two Temperate
zones of the earth, than in the entire Polar zones (either
by altitude or latitude), is reflected in the species occupy-
ing them. In Polar zones conditions are very similar
throughout,—hence we find (especially as regards floras)
various forms preserving specific identity throughout
vast areas; in Temperate zones conditions are almost
endlessly varied, so that species have been modified and
multiplied in conforming to such varying conditions,
and the equatorial range base is very frequently only a
generic one. Thus we find in the floras of Australia
and Europe that species of a Temperate zone in Europe
are represented in Australia by very distinct species.
Both must have sprung from a common equatorial range
base (Borneo, the Moluccas, and New Guinea), one
portion of a species emigrating as far north as Europe,
the other portion as far south as Australia. The con-
ditions which each set of individuals experienced were
totally different, and modification of a specific value was
produced, although in many cases they have both
managed to retain their generic affinity.

When tested by the distribution of plants in Africa
these facts assume even greater significance and sugges-
tiveness. According to Dr. Wallace, there are no less
than 60 genera of North Temperate plants in South
Africa, none of which occur in Australia, and but few of
the species characteristic of Australia, New Zealand, and
Fuegia are found there. South Africa is now isolated
from all the great southern land masses, and appears to
have been so for a comparatively long period, a fact
which has not only arrested the southern emigration of
plants, but caused much modification. The Temperate

302 THE MIGRATION OF BRITISH BIRDS

flora of South Africa has been derived by southern
emigration from range bases on the highlands and
mountains of the equatorial regions, just as Europe has
been so invaded by a northern emigration. But the
southern movement has to a very great extent been
arrested, because South Africa now contains scarcely any
area which can fairly be classed as belonging to a Tem-
perate zone; and this fact explains why the floral links
with Europe are only of a generic character. On the
other hand, nothing arrested the southern extension into —
Temperate climates in Australia, New Zealand, and
South America from common equatorial bases, where the
Temperate zone extends almost to the same (if more
contracted) limits as it does in the Northern Hemisphere ;
and as a natural consequence many of the floral links be-
tween Australia and Europe, and even between America
and Australia, are of a specific character, Dr. Wallace
asserts that this phenomenon is clearly due to a xorthern
emigration from an Antarctic centre of dispersal, which
is obviously erroneous. Were South Africa prolonged
at the present time as far south as say S. lat. 50°, so that
it could present for occupation an equally extensive
South Temperate zone as South America or New Zealand,
there can be little doubt that no such differences would
exist. The comparatively few (and presumably very
ancient) resemblances between the floras of South Africa,
Australia, New Zealand, and temperate South America
cannot be remnants, as Dr. Wallace suggests, of an
ancient vegetation once spread over the Northern
Hemisphere, and driven southwards by pressure of more
specialized types into these isolated areas, but are relics
unquestionably of a dominant flora which started from

SUMMARY AND CONCLUSION 303

an equatorial base, and ranged far south, not necessarily
over continuous land masses south of Africa, although
the probability is that such may have been the case.

We have precisely the same phenomenon among birds
as among plants—Northern and Southern groups which
are strictly confined either to the Northern or the
Southern Hemisphere—north or south of the Equator,
which must have started from an equatorial range base
and spread north or south towards either Pole. Both
Professor Huxley and Professor Parker have described
the dominance of these Northern and Southern groups.
Of course many groups may attain their highest develop-
ment at remote and varying distances from this dividing
line, or be common to both sides, or even become
temperate or polar with little or no trace remaining of
their equatorial origin from remote ancestral forms.
As may be readily surmised, this new Law of Dispersal
demands a continuous land connection equatorially.
But this need not have beena synchronous one, Indeed
the distribution of some groups of birds absolutely
demonstrates that such was not the case. The elevation
necessary to restore Antarctica—say 2,500 fathoms—
would also be sufficient to connect the great land masses
of the globe equatorially, and to a very great extent in
the North Pacific and North Atlantic oceans. But
such an elevation again need not have been synchronous ;
indeed the probabilities are that the Northern Hemi-
sphere continents were united at a much more recent
date than those of the Southern Hemisphere.

If this Law of Dispersal be true, it will explain the
absence of southern types from the Northern Hemi-
sphere, what Dr. Wallace aptly describes as “ the singular

304 THE MIGRATION OF BRITISH BIRDS

want of reciprocity in the migrations of northern and
southern types of vegetation.” This Flora is a dominant
southern one—a flora that has almost entirely spread
from a base south of the Equator. One or two extreme
northern outliers of this southern flora are to be met
with on the Equator, and from such a base a few others
have emigrated as far north as California, India, China,
and the Philippines; but these are in every case ex-
ceptional, and are species or genera that should properly
be excluded from that dominant southern flora, Dr. |
Wallace attempts to account for the “curious inability ”
of this southern flora to penetrate into the Northern
Hemisphere by the totally different distribution of land
in the two hemispheres ; but dispersal, so long as it is
normal, will overcome such difficulties, or at least over-
come them to such an extent as to show some signs of the
intrusion of organisms into adjoining areas, as we have
already had abundant testimony. We can explain this
absence of southern types from the Northern Hemisphere
by one way, and one way alone, namely, that they were
developed from a range base south of the Equator, and
that the Law of Dispersal inexorably keeps those types
to the Southern Hemisphere, and will continue to do so
notwithstanding a change to adverse conditions which
could have one effect only, their total extermination,
just as we have seen to be the case with a once domi-
nant northern fauna and flora. If we take the flora of a
Northern zone, say between the roth and goth parallels
of North Latitude, and compare it with a Southern zone
of equal limits, say between the roth and 4oth parallels
of South Latitude, we shall find the same inability of a
dominant northern flora to establish itself in the south ;

SUMMARY AND CONCLUSION 305

or, in other words, that the flora characteristic of that
one in Europe, Asia, and Africa has not penetrated to
South Africa or Australia, no more than the flora most
characteristic of those countries has penetrated to South
Europe, South Asia, and North Africa.

If this Law of Geographical Distribution be true, Polar
dispersal of species—or in other words from the direction
of the Poles towards the Equator—is a myth. To my
mind we have overwhelming evidence to suggest that
the grand centre of Life’s dispersal across the globe is
an equatorial one; and that from those regions where
the greatest stability of climate, and the most favourable
conditions for the development of animal and vegetable
forms are to be found, Life in two grand streams has
flowed Pole-wards. Glacial Epochs at either Pole have
wrecked and exterminated all living things within their
baneful influence, but on the return of more genial
climatic conditions, Life in its endless forms just as
often has spread northwards again (in the Northern
Hemisphere) vigorous and strong from more southern
bases, to repopulate the ice-freed lands with a fauna
and flora adapting themselves to the diverse conditions
of existence. I freely admit that these vast Polar lands,
under the long-enduring favourable conditions that
palzontological evidence compels us to admit once
prevailed therein, have produced magnificent fauna and
flore of high development, yet the Glacial Epochs have
just as surely exterminated them, the only surviving
relics: being those that were able to maintain themselves
in regions beyond such glacial influences, and where they
MUST have been established before the adverse climates

developed.
x

306 THE MIGRATION OF BRITISH BIRDS

The recent discovery of sub-fossil remains of an extinct
hippopotamus in Madagascar? is an event of profound
and far-reaching importance. The presence of this huge
mammal in Madagascar clearly proves that the southern
emigration of the higher forms of life into the Ethiopian
region could never have taken place at the date Dr.
Wallace ascribes to it, and further proves that these
large mammalia must have had an equatorial or southern
base to survive the climatic vicissitudes of the Ice Age,
as I have already insisted. As Dr. Wallace writes
(sland Life, p. 448), “the most striking and character-—
istic groups of animals now inhabiting Africa are entirely
wanting in Madagascar. Let us first deal with this fact,
of the absence of so many of the most dominant African
groups. The explanation of this deficiency is by no
means difficult, for the rich deposits of fossil mammals
of Miocene or Pliocene Age in France, Germany, Greece,
and North-west India, have demonstrated the fact that
all the great African mammals then inhabited Europe
and temperate Asia. We also know that a little earlier
(in Eocene times) tropical Africa was cut off from
Europe and Asia by a sea stretching from the Atlantic
to the Bay of Bengal, at which time Africa must have
formed a detached island-continent such as Australia is
now, and probably, like it, very poor in the higher forms
of life. Coupling these two facts, the inference seems
clear, that all the higher types of mammalia were
developed in the great Euro-Asiatic continent (which
then included Northern Africa), and that they only
migrated into tropical Africa when the two continents

1 Conf. Heilprin, Geographical and Geological Distrib. of Animals,
Pp. 373; and Nature, January 24, 1895, p. 311.

SUMMARY AND CONCLUSION 307

became united by the upheaval of the sea-bottom, prob-
ably in the latter portion of the Miocene or early in the
Pliocene period. It is clear, therefore, that if Madagascar
had once formed part of Africa, but had been separated
from it before Africa was united to Europe and Asia, it
would not contain any of those kinds of animals which
then first entered the country. But, besides the African
mammals, we know that some birds now confined to
Africa then inhabited Europe, and we may therefore
fairly assume that all the more important groups of
birds, reptiles, and insects, now abundant in Africa, but
absent from Madagascar, formed no part of the original
African fauna, but entered the country only after it was
joined to Europe and Asia.” Now in my opinion this
is an entirely wrong interpretation of the facts as tested
by our Law of Dispersal. Miocene (or any other)
Emigration into Africa from the North, as described by
Professor Huxley and by Dr. Wallace, could never have
taken place. One can almost venture to anticipate
the ultimate discovery of paleontological evidence of
the former existence of these large mammals, even in
isolated Australia.

The facts brought forward in the present volume place
us in a position to understand more fully the futility of
invoking a vast Antarctic continent to explain the
various apparent anomalies of distribution presented in
the Southern Hemisphere.t. The restoration of this sub-
merged or ice-clad Antarctic land mass can never be of
such service in explaining the occurrence of closely
allied forms in the now widely separated lands of the

1 Conf. Fortnightly Review, February 1894, p. 194, and April
1895, p. 640.

308 THE MIGRATION OF BRITISH BIRDS

Southern Hemisphere, as those naturalists that so stren-
uously assert its former existence appear to believe.
The fauna and flora of Antarctica must have been exter-
minated with the destruction of that area—continent
and inhabitants alike perishing together ; the only forms,
nay the only types, that would survive being those that
chanced to have Northern Bases beyond the devastating
influences which have succeeded in destroying pretty
well half the sedentary population of the earth.
Antarctica can therefore never explain the dispersal of
species and types in now wide distant areas of the
Southern Hemisphere; for not a single relic of the
drowned and lost South Polar continent has been pre-
served to us by retreat from the slowly threatening
doom, or by a Northern Emigration contrary to the
inexorable Law of Life’s dispersal. Such widely dis-
persed forms in many cases obviously of common origin
only indicate the bases and the sources from which that
doomed South Polar land has derived its inhabitants,
from a previously much more continuous, more northern,
or even equatorial base. (Conf. p. 57.)

The distribution of Life suggests to me the following
conclusions. Firstly, where the land masses are greatest
south of the Equator we should expect to find, and do
find, the most important and extensive assemblages of
species and types presenting the greatest amount of
differences from such assemblages of types and species
dwelling on the land masses north of the Equator ; and
these assemblages will to a great extent be homogeneous
or otherwise in proportion to longitudinal continuity equa-
torially '! of such Southern Hemisphere areas. Secondly,

| T use the term “equatorially ” more especially in contradistinc-
tion to Polar.

a

SUMMARY AND CONCLUSION 309

where the land masses are greatest north of the Equator,
we should similarly expect to find, and do find, the
most important and extensive assemblages of species
and types presenting the greatest amount of differences
from such assemblages of types and species dwelling on
the land masses south of the Equator ; and these assem-
blages will to a great extent be homogeneous or other-
wise in proportion to longitudinal continuity equatorially
of such Northern Hemisphere areas. Toa great extent
this is quite irrespective of existing equatorial land areas
connecting the Northern and Southern Hemispheres
respectively.

In my opinion we have hitherto attacked the problem
of migration and geographical dispersal at the wrong
end. We have regarded Glacial Epochs, climatic
changes, and physical mutations, as grand distributors
of species, compelling Southern Emigration in one
hemisphere, Northern Emigration in the other, rather
than as vast exterminating influences which have re-
peatedly cleared one dominant flora and fauna after
another from all the areas affected, the only surviving
forms being those whose bases or areas in which
Reproduction took place were beyond the fatal limits of
glacial or other influence. The enormous scope for evo-
lution in the oft-repeated march of life from the tropics
or temperate zones towards the Poles combined with
physical change must be apparent to every reader.
Such periodical emigrations to a great extent account
not only for the origin, but for the geological sequence
of species. This Law of Dispersal will explain why in
past ages we meet with a great extension of range of
forms which are now limited to small areas—eloquent

310 THE MIGRATION OF BRITISH BIRDS

testimony to their inability to escape from adverse con-
ditions, the Law of Dispersal forbidding range extension
in perhaps the only way that safety may have existed.

With so many convincing facts before us, is it too
much to assert that the fascinating science of Geo-
graphical Distribution, or the Dispersal of Life, will
have to be reformed, remodelled on an entirely new
basis, before we can hope to arrive at any uniform or
correct interpretation of the phenomenon as it now
exists ?

We are aware of the wonderful powers possessed by
most organisms to extend their area of dispersal—the
marvellous contrivances of plants, the agency of flight
in bats, birds, and insects, the swimming powers of fish
and other aquatic creatures, all able, one would think, to
emigrate this way and that, as fancy chose or necessity
demanded. But are we to believe that all this range
dispersal is purely of a fortuitous character ; that acci-
dent controls its direction, and that chance shapes its
course? I, for one, cannot bring myself to believe it,
and am compelled to regard this mazy wandering and
endless peregrination of Life across the globe as being
inexorably subservient to Law.

ll ee i a a

INDEX.

Abnormal lines of migration in |

autumn, 266

Absence of large southern mam-
malia from European Post-
Glacial deposits, 21

Absence of pre-glacial relics of
“ Arctic plants” in the North
Polar regions, 297

Absence of West European species
from British Area, reasons for,
95, 96, 97, 98

Accentor modularis, present emi-
grations of, 174

Accipiter melanoleucus, 46

Acrocephalus aguaticus, 90

Acrocephalus palustris, present
emigrations of, 173

Acrocephalus phragmitis,
sent emigrations of, 173

Acrocephalus turdotdes, 90

gialitis hiaticula, 111

Agialitis semipalmatus, 111, 159

Africa, the distribution of plants
in, 301

ALCIDA, survival of the, during
the Ice Age, 167

Algeria, animal remains in the
caves of, 34

Ammomanes cinctura, 46

Ampelis cedrorunt, 89

Ampelts garrulus, 89

Ampelis phenicoptera, 89

Amphibia and Reptiles of British
Area, 104

pre-

Analysis of table of Post-Glacial
Emigrants in West Europe, 125

Anas strepera, northern range of,
114

ANATIDA, 57

Ancient breeding ranges, 213

Ancient emigration up the English
Channel, 130

Ancient land connections between
America and Europe, 115

Andes, a route for the southern
migration of plants, 297

Anomalies of Avian distribution
explained by the Law of Dis-
persal, 158, 159

Anomalous facts, 112

Anser brachyrhynchus, 113

Anser segetum, 113

Antarctic centres, northern emi-
gration from obviously errone-
ous, 302

Antarctica, 303, 307, 308

Anthus trivialis, present emigra-
tions of, 174

Antilope, 34

“Arctic” animals, 55, 56

“Arctic” element among birds,
the, 296

Arctic element in South Temper-
ate Floras, bearing of the Law
of Dispersal on, 294

Arctic Floras, could never have
been developed in the Polar
regions, 298

wat

312 INDEX

Areas of Dispersal, birds do not
wander from, 278

Argillornis, 4

Arrival of birds from north and
north-east, 261, 262

Asia, the Flora of the mountains
of, 300

Asiatic and American forms, in-
termixture of, 61, 62

Autumn and Coasting Migrants,
analysis of Table of, 152—154

Autumn migration, difficulty of
observing, 261

Autumn migration, duration of,
268

Autumn migration, Table indicat-
ing the, 270—275

Autumn, vertical migration in, 269

Avian life, effects of changed
climate on, 52

Azores, birds of the, 190

Baltic glacier, the, 63

Bermudas, birds of, 190

Bernicla leucopsis, 113

Birds, effects of submergence of
North Sea plains on, 132

Birds, gradual effects of a chang-
ing climate on, 211

Birds migrating too early, 246

Birds, northern and_ southern
groups of, 303

Blue-headed. Wagtails, emigra-
tions of, 99, 100

Bonin Isles, birds of, 203

Borneo, birds of, 189

Bos, 34, 57

Breeding-grounds and
quarters coalescing, 213

Breeding ranges, ancient, 213

Brent Goose, effects of unfavour-
able seasons on, 165

British Archipelago, emigration of
birds within, 143

British Area, abnormal migrants
to, 9I

British Area, coast-line of at close
of the Glacial Epoch, 15

British Area, earliest departures
from in autumn, 262, 263

winter

British Area, geographical and
climatic conditions of, 16

British Area, migration into from
the East, 264—266

British Area, present emigration
in, 170

British Area, reasons for absence
of certain species from, 90,
gl

British Area, routes followed by
summer migrants to, 214

British Area, situation of now
unfavourable to emigration, 101

British Area, species do not breed
south of their entry into, 217

British Area, Table showing the
proportional distribution of
species over, 154

British Area, the, 5

British Area, the 15-Fathom Con-
tour of, 18

British Area, the 40-Fathom Cons
tour of, 16

British Area, the 20-Fathom Con-
tour of, 17

British Area, West European
species absent from, 93—95

British Avifauna, poorness of in
endemic species, 197

British Islands, commencement
of autumn migration in, 261

British Islands, summer visitors

to, 79, 80, 81

British Islands, summer visitors
to, winter quarters of in Refuge
Area II., 81

British Islands, Table of autumn
migrants to and coasting mi-
grants over, 151, 152

British Islands, Table of species
increasing their range in, 179

British Islands, Table of Summer

Migrants to, 148

British Isles, the, 192

British Isles, the great submerg-
ence of, 7

British Isles, winter visitors to
that also visit Refuge Area II,

77) 78
British Seas, the, 5, 6

ee SS Se

. ev

’

INDEX 313

British species, extinction of, 183
—186
Bubo maximus, Ll

Calcarius lapponicius, 89

Canaries, birds of, 190

Canary Islands, endemic birds of,
200

Canary Islands, number of eggs
laid by birds in, 202

Canary Islands, the, 42, 43, 44

Cans, 34

Cape Flora, the, 58

Cape Verd Islands, 45

Captive birds, restlessness of, 234

Carpodacus erythrinus, 88

Centropus, 38

Certain routes followed by certain
individuals, 235, 236

Certhilauda desertoruzt, 46

Cervus dicranios, 36

Cervus megaceros, 139

Cervus polignacus, 11, 36

Channel Islands, 189, 198
CHARADRIIDA, 57

* CHARADRIID&, the Pree-Pliocene

ancestor of, 54

Chart of principal Migration
Routes into the British Area,
209

Cicontza alba, 98

Cinclus melanogaster, 126

Clangula tslandica, 23, 106

Climatic change during Post-
Tertiary time, results of, 26, 27

Coasting migrants over the British
Islands, routes followed by, 22
—231

Coasting migration in spring, 247,
248

Cold climates in North Polar

i

latitudes, no pre-glacial evi-
. dence of, 297
Collocalia, 38

Columba @nas, present emigra-

tions of, 177

Columba lvia, northern range of,
114

Columba palumbus, present emi-
gration of, 177

COLYMBID, 167

Colymbus arcticus, 153

Colymbus arcticus, range of, 129

Colymbus glactalis, glacial range
base of, 108

Commingling of Southern and
Temperate forms, 19

Comparative movements of the
Snow Bunting, the Northern
Bullfinch, and the Crested
Titmouse, 278

Competing species,influence of, 89

Continental islands, 188

Continental islands, ancient, 188

Continental islands, recent, 188

Corollaries, 60, 61

Corvus cornix, 126, 147

Corvus corone, 46

Corvus frugilegus, present emi-
grations of, 177

Cossypha, 32

Cross Migration in autumn, 266

Cygnus bewickt, 113

Dartford Warbler, effects of severe
winters on, 165

Deductions from the facts of
proportional distribution, 154,
155

Dispersal, a new law of, 60

Dispersal, conditions of success-
ful, 300

Dispersal not fortuitous, 310

Dispersal of plants from bases
south of the equator, 304

Dispersal of plants north and
south from equatorial range
bases, 298, 299

Diver, Black-throated, range of,
128

Dromolea, 32 °

Early migrants abnormal, 263

Earth’s centre of gravity, changes
in, 14

East Africa, change of climate in,
51

East and North-east Emigrants,
Table of, 132

Eastern migrants,departure of, 244

314

East to West migration, absence
of in south-west of England, 228

Eastward Emigration, ancient
line of from the British Area,
130—132

Elephas meridionalis, 36

Emberiza hortulana, 90

Emigration and reproduction, 279

Emigration attended by Migra-
tion, in British Area, 182

‘Emigration, impulses to, 212

Emigration, northward tendency
of, 180, 181

Emigration of birds, effects of
civilization on, 170

Emigration of plants from North
to South, impossibility of, 296

Emigration of species from South-
eastern Areas, 85

Emigration still in progress, 170

Endemic British species, 192

Endemic British species
races, Table of, 158

English Channel, migration across
the, 223

Equatorial range bases, absence
of many species from, 299

Equus, 34

Erithacus luscinia, 126

Evithacus luscinia, northern range
of, 114

Erithacus luscinta, present emi-
grations of, 172

Evithacus philomela, 126

Erithacus philomela, range of,
129, 072

Erithacus rubecula, present emi-
grations of, 172

Evithacus suecica, 88, 159

Evithacus suecica, range of, 129

Erithacus superba, 202

Europe, condition of during the
Ice Age, 27, 28

Europe, southern genera in, 296

Exit of species down the valley
of the Nile, 35

Exterminating effects of Glacial
Epoch, 35

Extinction of British species, 183
—186

and

INDEX

Falco amurensts, 89

Falco vespertinus, 89

Fieldfare, autumn migration of,
262

Fluctuations of climate during
Glacial Epoch, 63

Forbes on the British Flora, 137

Formosa, birds of, 189

Fossil bird-remains, rarity of, 3

Fringilla chloris, present emigra-
tions of, 174

Fringilla celebs, present emigra-
tions of, 175

Fuligula histrionica, 106

Fuligula rufina, 99

Galapagos, birds of, 191

Garrulus glandartus,
emigrations of, 176

Gastornis klaasseni, 4.

Gecinus viridis, 128

Geikie, Professor J., on Emigra-
tion to the British Area, 137—
140

Geikie, Professor J., on Pliocene
and Pleistotene species, II

Geikie, Professor J., on the effects
of the Glacial Epoch upon the
larger animals, 36, 37

Geocichla dauma, wrongly re-
corded from Heligoland, 190

Geographical Dispersal, problem
of attacked at wrong end, 309

Glacial conditions, bearing of on
island avifaunas, 206

Glacial Epoch, exterminating
effects of, 164, 165

Glaciation correlated with eleva-
tion and subsidence, 14

Goldcrests, migration waves of,
173

Greenfinch, fluctuating breeding
range of, 174, 175

Greenland and Europe, ancient
land between, 6, 105

Greenland and Iceland, emigra-
tion across British Area to, 109
—III

Greenland, Avian Emigration to,
105

present

INDEX

Greenland, Fauna and Flora of,

22,23

Hematopus capensis, 44

Hagerup, on the Birds of Green-
land, 23

flalcyon erythrorhyncha, 46

flalcyon semicerulea, 46

Flalcyornis, 4

flaltaétus leucocephalius, 110

Harvie-Brown on the recent range
extension of the Starling in
Scotland, 176

Heligoland, birds of, 190, 198

Flelornis, 4.

flippopotamius, 34

flippopotamus amphibius, 36

Hippopotamus, sub-fossil in Mad-
agascar, 306

Hye@ia, 34

HHypnum turgescens, 12

fHypolats icterina, 89

fypolats polyglotta, 90

Iberia, absence of species from,
85, 86

Lbidopsis, 4

Ice Age and Emigration, 169

Iceland and Greenland, emigra-
tion across British Area to, 109
—IlI

Iceland, Fauna and Flora of, 23

Increase, the ruling passion of
Life, 169

Insular Avifaunas,
Migration on, 205

Inter-hemisphere — species,
301

Intermixture of Palearctic and
Nearctic species, 61, 62

Internal Migration always within
normal Areas of Dispersal, 277

Internal Routes, meagre informa-
tion respecting, 210

Inter-polar and Inter-hemisphere
species, 213

Inter-polar Floras, 295

Ireland, absence of species from,
147

Ireland, emigration to, 140

bearing of

300,

315

Ireland, impossibility of emigra-
tion to, from Scotland, 140—
142

Ireland, Migration Routes to, 217

Irruptic movement, 283

Irruptic movement, futility of to
increase area, 283, 284

Island Avifaunas, conclusions
drawn from facts, 205

Islands and Migration, 191

Islands, various tropical, birds of,
203

Isolation of British Area, effects
of on birds, 135

Japan, birds of, 203

Japanese Empire, birds of, 189

Jukes-Brown, on a _ boring at
Utrecht, 13

Junco hyemalis, 159

Kentish Plover, range of, 128

Lagopus albus, 192

Lagopus mutius, 147

Law of Dispersal, the, 53—57

Leith Adams, Professor, on the
Mammalia of Ireland, 138

Lepus glactalis, 23

Lepus timidus, 137

Life, Dispersal of, 305

Life, Distribution of, 308, 309

Lighthouses, local movements at,
282

Limunatornis, 38

Limosa melanura, 113

Limosa rufa, 113

Limosa rufa uropygialis, 113

Lindesay, Mr. George, on the
migration of birds in Norsk
Finmarken, 129

Lithornis vulturinus, 4

Local movement governed by
Law, 280

Local movements of __ birds,
meagreness of data on, 276

Loxia bifasciata, 88

Loxta leucoptera, 88

Machatrodus, 11

316

Machairodus latidens, 36

Madagascar, birds of, 190

Madagascar, sub-fossil remains of
hippopotamus in, 306

Madeira and the Azores, birds of,
202, 203

Madeira, birds of, 190

Malta, birds of, 189

Mammalia of West Europe and
British Area, 104

Map showing Range
Refuge Area I., 47

Map showing Range
Refuge Area IIL., 71

Map showing Range
Refuge Area III., 95

Map showing the 40-Fathom, 20-
Fathom, and 15-Fathom Con-
tours of the British Area, 21

Map showing the 1oo-Fathom and
50-Fathom Contours of the
British Area, 5

Mediterranean Area, condition
of during Ice Age, 2

Melierax poly: sons, 41

Merula merula, present emigra-
tions of, 171

Migrants, British summer, from
the South-east, 84

Migrants, circuitous routes of to
West Africa, 82, 83

Migrants, gradual advance north-
wards of in spring, 251

Migration, altitude of, 238

Migration, daily time of, 240

Migration from the British Area,
abnormal lines of, 245, 246

Migration from the East, general
aspects of, 265, 266

Migration, impulse of, 234

Migration, impulses to, 212

Migration in autumn, abnormal
lines of, 267

Migration more apparent in
autumn than in spring, 260

Migration, order of, 239, 240

Migration periods, duration of,
264

Base or
Base or

Base or

Migration Routes, definition saa |

210

INDEX

Migration Routes, inland con-
tinuation of, 232, 2

Migration, Routes of most fol-
lowed, 231

Migration Routes, persistency
shown by birds in following, 223

Migration, the perils of, 241, 242

Milvus ictinus, 46

Months of spring passage of
various species, 248—251

Motacilla cinereocapilla, 100

Motacilla flava, 99

Motacilla melanocephala, 100

Mountains of torrid zone, Flora of _
during pre-glacial ages, 297,
298

Muscicapa hyperythra, 89

Muscicapa parva, 89

Myodes torguatus, 23

Nearctic Emigration, 107

Necrornis, 38

Nectarinia, 32

Newton, Professor, on the Great
Flood in the Fens, 186

North-east Africa, 31

North-eastern Migrants, departure
of, 244, 245

Northern and Southern groups of
birds, 303

Northern birds, spring migration —
of, 248

Northern Emigration from Ant-
arctic centres, obviously erro-
neous, 302

Northern Floras, effects of Glacial
Epoch on, 298

North Russia, emigration of birds
to, 142, 143

North Sea, migration across, 224,
22
226

North Sea Plains, submergence
of, 131

North Sea Plains, the, 131

North Sea Routes, origin of, 227,
228

North-west Africa and Europe,
homogeneity of fauna and flora
of, 32

North-west Africa, during Plio-

INDEX S17

cene and Post-Tertiary time,
2 2
39, 31

NNyctea nyctea, 101

Oceanic Islands, 190

Odontopteryx, 4

Old birds migrating as early as
the young, 239

Organisms, powers of to extend
Areas of Dispersal, 310

Oriental and Ethiopian types in
Europe during Tertiary time,
38
J

Otocoris alpestris, 89

Otocoris bilopha, 89

Ovibos, 22

Palearctic and Ethiopian types,
commingling of, 31, 32, 41

Paley, definition of instinct by,
232

Palmén’s “ Fly Lines,” 224—226

PANURID, 167

Parus cristatus, 147

Parus pleskiz, 278

Parus ultramarinus, 202

Passer domesticus, present emi-
grations of, 175

Passer montanus, present emigra-
tions of, 175

Past physical changes indicated
by present routes of migration,
220—223

Petchora, migration of birds in
the valley of, 142

Philippine Islands, birds of, 189

Phylloscopus borealis, 159

Phylloscopus sibilatrix, present
emigrations of, 172

Phylloscopus trochilus, present
emigrations of, 172

Pica caudata, present emigrations
of, 176

Picus major, 128

Picus minor, 128

Pinicola enucleator, 88

Pinicola subhimachalus, 88

Plectrophenax nivalts, 115

Pleistocene land connections
between Africa and Europe, 33

Pliocene and Pleistocene species,
commingling of, 11, 12

Pochard, Red-crested,
tions of, 99

Podiceps cristatus, present emi-
grations of, 17

Polar dispersal of speciesa myth,
305

Post-Glacial changes of climate,
24,25

Post-Glacial Emigration in West
Europe, Table showing the two
dominant lines of, 116—124

Procellaria pelagita, 115

PROCELLARIIDA, 57

Proherodius, 4

Psittacus, 38

Puffinus anglorum, 115

Pycnonotus, 32

Pyrrhocorax graculus, northern
range of, 114

Pyrrhula major, 126, 278

Pyrrhula vulgaris, present emi-
grations of, 176

Pyrrhulauda nigriceps, 46

emigra-

Range Base or Refuge Area I., 47
Range Base or Refuge Area II.,

Range Base or Refuge Area III.,
50

Range Bases of certain North-
west European birds, 128, 129

Range Bases, variations in climate
of, 51

Recapitulation of facts, 286—292

Recent emigrants, analysis of
Table of, 178—180

Records, want of carefully-kept,
282

Red Grouse and the Great Baltic
Glacier, 194

Red Grouse, the development of,
192—I95

Redwing, autumn migration of,
262

Redwings and severe weather, 281

Refuge Area I., probable avifauna
of, 64—69

Refuge Area II., avifauna of, 71

318

Refuge Area II., British species
resorting to in winter, 76, 77
Refuge Area II., species resident
in, and in British Isles, 74—76

Refuge Area III., Table of
emigrants from, and from Asia,
87, 88

Refuge Area III., winter quarters
of British summer migrants in,
82

Regulus cristatus, present emi-
grations of, 173

Reptiles and Amphibia of British
Area, 104

Resident British birds, analysis
of Table of, 146, 147

Resident British birds, Table of,
144—146

Resident British species, 71

Résumé of Chapters III. and IV.,
158—164

“Retreat ” of plants a myth, 299,
3

Reversal of route by migratory
birds, 267

Rhinoceros, 34

Rhinoceros etruscus, 11, 36

Rhinoceros megarhinus, 36

Rose-coloured Pastor, range of,
213

Route of Migration, how learnt,
236

Routes, difficulty of tracing to
British Islands, 209

Routes into Scotland, absence of
vid Ireland, 219

Routes of Migration continuous,
214, 215

Routes of Migration correlated
with breeding grounds, 232, 233

Routes of Migration, how followed
by birds, 234

Routes, the North Sea, 226

Ruff, range of, 128

Ruticilla phenicurus, recent emi-
grations of, 172

Sahara, colonization of the, 40
Sahara, influence of the, on the
distribution of species, 31

INDEX

|
|
|

Sahara Sea, ancient, a bar to
emigration from the south,
82

St. Georges Channel, migration —
across, 224

St. Kilda Wren, the, 195

Salix polaris, 12

Saxicola enanthe, 23, 115

Saxicola, range of, 24

Scandinavian Flora, the, 295

Scolopax rusticula, present emi-
grations of, 178

Sea-barriers, impassable nature
of, 102

Sedge Warbler, absence of from
South Norway, 127

Seebohm and Harvie-Brown on
the Migration of Birds in the
valley of the Petchora, 142

‘* Sense of direction,” 237

Severe winters, effects of, 165

Severe winters, effects of,
birds, 280, 281

Sitfa c@sia, present emigrations
of, 174

Sitta europea, 126

Sitta whitehead, 189, 199

Sociability during migration, 241

South Africa, the Temperate Flora
of, 301, 302

Southern exodus of life during
Pleistocene time a myth, 53—

on

55

Southern Flora, inability of to
enter Northern Hemisphere,
304

Southern Flora, the dominant,
304

Southern genera in Europe, the
presence of, 296

Southern Migration, growing in-
tensity of, 263

Southern parent species, com-
parative Table of, 74

Southern Range Bases, import-
ance of, 166

Southern representative forms, —
Table of, 72

Southern types, absence of from
Northern Hemisphere, 303, 304

INDEX

South of England, Migration
Routes into, 215

South-west England, weak as-
pects of Migration to, 215—
217

South-west Ireland, weak aspects
of Migration to, 218, 219

Species, earliest to arrive in
autumn, 261

Species, highest range of, 114

Species not increasing their area
during winter, proofs of, 195

Species, unequal dispersion of,
reasons for, 191

Species, variations in the northern
limits of, 126, 127

Spotted Flycatcher, migrations
of to Ireland, 219

Spring and summer, local move-
ment in, 277

Spring Migrants, arrival of first
from the south, 246

Spring Migration, duration of,
251, 252

Spring Migration in the British
Islands, commencement of, 243,
244

Spring Migration, Table indicat-
ing the, 254—259

Spring Migration, the growing
intensity of, 249

Spring, vertical migration in, 252,
253

Stercorarius catarrhactes, 115

Storks, past emigrations of, 98,

Strix aluco, present emigrations
of, 177

Sturnus vulgaris, present emi-
grations of, 176

Submergence, effects of on the
Emigration and Migration of
birds, 228, 229

Sula bassana, 112

Summer Migrants, arrival of in
British Area, 248, 249

Surnia doliata, 89

Surnia funerea, 89

Surnia nisoria, 89

Sus, 57

319

Sylvia atricapilla, migrations of,
45, 46 —

Sylvia cinerea, present emigra-
tions of, 172

Sylvia conspicillata, 46

Table of East and North-east
Emigrants, analysis of, 133, 134

Table of Emigrants to Iceland
and Greenland, IIo, 111

Table of Summer Migrants,
analysis of, 149, 150
Temperature, influence of on

birds, 134, 135

Tern, Common, range of, 128

Tetrao mlokosiewiczt, 89

Tetrao tetrzx, 88, 89

Third cold period of the Glacial
Epoch, 62

Third Glacial Period, physical
changes during, 9

Third Glacial Period, the, 20

Titmice, races of, 196, 197

Tringa arenarta, 115

Tringa canutus, 115

Tringa canutus, absence of from
Canaries, 99

Tringa minuta, 89

Tringa minutilla, 89

Tringa rujicollis, 89

Tringa subminuta, 89

Troglodytes bergensts, 23

Troglodytes borealts, 23, 196

Troglodytes hirtensts, 23

Trogon, 38

Tropical islands, endemic birds
of, 204

Tryngites riufescens, 159

Turdus alici@, 159

Turdus musicus, present emi-
grations of, 171

Turdus viscivorus, present emi-
grations of, 170, 171

Turnstone, migrations of, 212

Turtur tsabellinus, 84

Unequal dispersion of species,
reasons for, 191

Ursus, 34

Ursus arvernensis, 11, 36

320

Valley of the Petchora, Migration
of birds in, 142

Vertical Migration in autumn,
269
Vertical Migration in autumn,

order of, 269

Vertical Migration in spring, 252,
#)

Vertical Migration, order of, 252,
253

Wallace, Dr.; on absence of
animals from Madagascar, 306,
307

Wallace, Dr., on land birds com-
mon to Europe and Japan,
41

Water Areas a check to Emigra-
tion, 228

West Continental Europe, Table
of species breeding in, yet
absent from British Area, 103

Western Europe, geography of,
from late Pliocene to early
Post-Glacial time, 10

West Europe, Post-Glacial Emi-
gration of birds in, 109

INDEX * , ;

West Mediterranean Islands, 189

West Mediterranean Islands,
avifaunz of, 199

West Palzearctic Islands, the, 187

Wheatear, migrations of, 107, 108

Wheatear, migrations of to
Ireland, 221

White, Dr. Buchanan, on Irish
Lepidoptera, 139

Winter, birds never extend their
range during, 284

Winter movement unable to ex-
tend area, 281

Winter visitors to British Area,
routes followed by, 229—231

Winter visitors to the British
Islands, departure of, 247

Wood Wren, absence of from
Norway, 127

Wood Wren, probable winter
quarters of individuals breeding
in Sweden, 173

Young birds, Migration of, 239

| Zones, species in Polar and Tem-
| “perates 307

THE END.

Richard Clay. & Sons, Limited, London & Bungay.

LAY UNIMON

3 9088 0006