42 STUDIES IN BIRD-MIGRATION 



bird-observatory has been more than realised. Seven 

 years' investigations have made it the most famous 

 bird-observatory in our islands ; indeed it has become 

 the British Heligoland. Quite a number of species 

 which were previously regarded as rare casual visitors 

 to our isles, have, as the result of these observations, 

 been found to be regular migrants. They doubtless occur 

 on the mainland, too, but owing to its broad acres they 

 almost entirely escape notice. In addition, several 

 species have been added to the British and many to the 

 Scottish avifauna through the Fair Isle investigations. 



Though lying midway between the Orkney and 

 Shetland groups. Fair Isle has remained among the least 

 visited of all the numerous inhabited islands in the 

 British seas. This is, no doubt, to be accounted for by 

 there being no regular communication by steamer with 

 the island, a fact which is probably due to the entire 

 absence of a reasonably good natural harbour, and to 

 the fierce tidal streams which rush along its rugged and 

 precipitous coasts. 



The island is situated some 24 miles south-south- 

 west from Sumburgh Head, the southernmost point of 

 the mainland of Shetland, and 26 miles east-north-east 

 of North Ronaldshay, the most northerly of the Orkneys. 

 It is somewhat oblong in form, having an extreme length 

 of about 2f miles from north to south, and averaging 

 about I mile in breadth. Though a circuit of the island 

 may be made by a walk of 9 miles, yet so indented 

 and irregular is the coasdine that its in-and-out circum- 

 ference is not much short of 20 miles. 



Except a small portion of its southern coast, and a 

 litde inlet on the east, the island is everywhere 

 surrounded by a belt of precipitous cliffs, ranging from 



