180 STUDIES IN BIRD-MIGRATION 



that this bird had not visited Orkney for many years, 

 proceed to say that one was seen off Fair Isle in 

 June 1798. 



Uria troile, Commo7i Guillemot. — The remarks on 

 the Razorbill apply also to this species, except that 

 during the autumn one or two are to be seen resting 

 on the rocks close to the Isle. In early March a 

 considerable increase takes place in the numbers of 

 those observed at sea off the island, clearly indicating 

 arrivals from afar. The cliffs are visited in January, 

 and final residence for the summer is taken up late in 

 May. 



Uria grylle, Black Guillemot. — A common resident 

 and breeding bird. In the autumn and winter it seeks 

 the shelter of the geos and bays. 



Alle alle, Little Azik. — Passes the winter in con- 

 siderable numbers at sea just off the Isle. The earliest 

 recorded date for its appearance is 22nd October; and 

 the latest date for its stay in spring, 14th March. 



Fratercula ARCTiCA, Puffiii. — Is practically a summer 

 visitor, since it is rarely seen in winter at sea off the 

 island. It appears late in March (2 ist earliest) and during 

 early April, but does not finally take up its residence on 

 terra fa^ma until the early days of May. Many leave 

 during the second week of August, and a little later all, 

 save those still feeding young, have departed. 



CoLYMBUS GLACiALis, Great Northern Diver. — Has 

 only been detected on one or two occasions, in October 

 and January. The Fair Isle seas, with their swift- 

 running tidal races and lack of shelter, appear to be 

 shunned by this bird. 



CoLYMBUS SEPTENTRiONALis, Red-throated Diver. — 

 The remarks under the last species apply equally to this. 



