68 ANNALS OF SCOTTISH NATURAL HISTORY 



Lesser Whitethroat, Chiff- Chaff, Bluethroat, Stonechat, 

 Spotted and Pied Flycatchers, Shelduck, Green Sandpiper, 

 and Pomatorhine Skua, are reckoned as quite uncommon as 

 visitors to the northern isles. 



The occurrences of rare birds have always had a peculiar 

 charm for British ornithologists, but to the student of bird- 

 migration their irregular, and in some instances erratic 

 appearances, are not helpful in connection with his re- 

 searches ; indeed they are often distracting, and present 

 problems which admit of no satisfactory explanation. 



Though the period (the whole of September and the first 

 week of October) covered by our 1906 visit coincided 

 as to date with that of 1905, yet quite a number of 

 migrants came under notice during the past autumn which 

 were not observed by us in the previous year. On the 

 other hand, only one of the birds of passage of 1905, the 

 Ruff, was not detected in 1906. 



It has been suggested to me that Fair Isle must possess 

 some peculiar and special advantages over other northern 

 islands, and thus render it much visited by migratory 

 birds. In my opinion such is not the case. It has, how- 

 ever, decided advantages for the observer. The secret, if 

 secret it be, of its superiority as our observing station over 

 the Isles of the Orkney and Shetland groups, lies in its 

 detached position and its small size. This results in (i) 

 some concentration at Fair Isle, whereas the isles of both 

 the groups named are many, large, and not far apart, 

 and thus the migrants visiting them are widely and thinly 

 scattered ; while (2) its small size renders it possible to ascer- 

 tain, with some degree of completeness, what species are 

 present each day. In this latter respect, however, even 

 Fair Isle, with its two and a half miles of varied surface, is 

 too extensive for a couple of observers, and there were days 

 on which feathered visitors were abundant when we were 

 conscious that, in spite of our utmost endeavours, we had 

 missed many birds. 



The experience gained during many holidays devoted to 

 bird watching has convinced me that, with all our great army 

 of trained observers, we in Britain see only an infinitesimal 

 number of the migrants which visit our shores: far fewer than is 



