138 STUDIES IN BIRD-MIGRATION 



Sometimes during snow a few arrive along with 

 Fieldfares and Redwings. These, no doubt, are birds 

 which have passed the previous portion of the winter in 

 Shetland, and are moving south under the pressure 

 imposed by severe weather conditions. 



In the summer of 1905 a pair reared their young in 

 the face of a ravine, where I saw young birds just able 

 to fly early in September. In 191 1 the bird again 

 nested in the island. 



TuRDUs iLiAcus, Redwing. — Occurs regularly on both 

 passages in considerable, sometimes vast numbers. A 

 few appear during the prevalence of severe winter 

 weather, coming from the north, but do not remain. 



It has been observed on its way north in spring, as 

 early as 23rd March ; but as a rule the passage does not 

 set in until the end of the first week of April, and lasts 

 until the end of that month. A few are sometimes 

 seen early in May, the 15th being the latest date on 

 which they have been observed. In 1906 a single 

 bird appeared amid a rush of migrants on ist June — 

 an exceptional occurrence. 



The average date for first arrivals in the autumn is 

 25th September, the earliest 19th September; and it 

 occurs in numbers, often in great rushes, down to the 

 , third week of November. The cliffs seem to be the 

 chief resorts of this species during its sojourn on the 

 island, but it is also very common in the shelter afforded 

 by turnips. 



TuRDUs PILARIS, Fieldfare. — An abundant species 

 during its spring and autumn migrations. Some also 

 appear in winter, during spells of severe frost or snow, 

 along with Thrushes, Redwings, and Blackbirds, but such 

 visitors only remain a short time on the isle. 



