vi PREFACE TO THE SECOND EDITION. 
comparative elevation of the land in the United Kingdom and the 
depth of the surrounding seas ; while, although on a small scale, it will 
serve as'a guide to the relative positions of the various groups of 
islands. It may also remind the reader that, owing to the indenta- 
tions of our coast, very few places in the British Islands are fifty 
miles distant in a straight line from tidal or brackish water: a cir- 
cumstance which exercises a modifying influence on our climate— 
and consequently on our bird-life—during the winter months, and is 
in strong contrast with the extreme conditions prevalent over 
compact Continental areas, even further to the south. The North 
Polar Chart embodies the latest discoveries by Dr. Nansen and 
others, and it is hoped that it will be of assistance in estimating 
the range of the birds which breed in the Arctic regions. 
The letter-press has required considerable alteration, owing to the 
large amount of information rendered accessible during the last 
nine years by such works as the ‘ Faunas of the Inner Hebrides and 
Argyll,’ of the ‘Orkneys,’ and of the ‘Moray Basin,’ all three by 
Messrs. Harvie-Brown and T. E. Buckley; the ‘ Birds of Devon,’ by 
Messrs. D’Urban and Mathew; the ‘Birds of Pembrokeshire,’ by 
the Rev. M. A. Mathew; the ‘Fauna of Lakeland,’ by the Rev. 
H. A. Macpherson ; the ‘ Birds of Northamptonshire,’ by the much- 
regretted Lord Lilford, and other works ; not to mention various 
compilations, in which there is material of value. In 1896 appeared 
Mr. W. Eagle Clarke’s digest of the ‘Observations on the Migra- 
tions of Birds at Light-houses and Light-vessels from 1880-1887,’ 
a marvel of condensed facts; and some of these observations are 
very destructive of former beliefs. For instance, it used to be 
supposed that the regular east-to-west migration which reached 
Heligoland in autumn would be in some degree continued to the 
British Islands, and that a reflex movement would take place in 
spring ; but the abstract shows that such intermigrations are the 
rare exception and not the rule. It is proved, however, that there 
is much movement from the south-east and east towards the north- 
west and west in autumn—and reversely in spring—across the 
narrowest portion of the North Sea. Another former fancy was that 
the migration of many species of birds depended upon the direc- 
tion of the wind; but this, again, is only true to a very limited 
extent, and it has been demonstrated that certain meteorological con- 
ditions at the point of departure are the prime factors controlling 
the seasonal movements. Pyactically the wind is not of great im- 
portance, for although birds cannot fly in the teeth of an absolute 
gale, they can sail uncommonly close to any reasonable wind, 
