178 STUDIES IN BIRD-MIGRATION 



The main body departs in August ; a few, chiefly 

 young birds, are to be seen in September ; and a single 

 bird, an adult, has been observed as late as 22 nd 

 October. 



Larus marinus, Great Black-backed GulL — This 

 bird is numerous as a breeding species, and is present 

 throughout the year. 



Larus glaucus. Glaucous Gull. — Is a winter visitor, 

 and occurs in some numbers. During its sojourn it is 

 frequently seen on the land, like the Herring-Gull. 



The first arrivals are chiefly young birds ; and the 

 earliest date for the appearance of the species is 5th 

 October. There are no precise data relating to its 

 departure, but it appears to leave early in the year. 

 Unusual numbers appeared after the gales of 13th and 

 14th November 19 10. 



Larus leucopterus, Iceland Gull. — The recorded 

 information regarding the visits of this species is far 

 from voluminous, and relates to observations made in the 

 months of November, December, January, and March. 

 The earliest record is for 5th November, when a young 

 male was captured and sent for identification, and the 

 latest on 8th March, which was also sent. 



Rissa tridactyla, Kittiwake. — A resident all the 

 year round, passing the winter at sea off the Isle, and 

 nesting in great numbers on the cliffs. This species has 

 not been known to occur on the land in the roughest of 

 weather. 



Megalestris catarrhactes. Great Skua. — In 1905 

 the natives informed me, in reply to my enquiries, that 

 the " Bonxie " formerly bred on the Isle. They were 

 unable to fix the date, but the information had been 

 handed down to them by their forbears. The accuracy 



