274 STUDIES IN BIRD-MIGRATION 



larks, Tree-Sparrows, and Chaffinches not unfrequently 

 departing at the same time. 



Prior to their departure, numbers of these emigrants 

 have been observed passing southwards, occasionally 

 accompanied by Grey Crows, on both the Yorkshire and 

 Norfolk coasts, en route for particular points of embarka- 

 tion, whence the passage of the North Sea^ is made. 



Spring Emigj^atioii to North- Western Etirope. — The 

 Rooks from Scandinavia which have wintered in our 

 islands return north in March, April, and the first half 

 of May ; and (as in the autumn) are mainly observed on 

 passage in the Orkneys and Shetlands, including Sule 

 Skerry and Fair Isle. Some appear in these northern 

 islands as early as the first days of March, but 

 the chief movements take place during its latter days 

 and the early days of April. Their movements in 1904 

 seem to have been an exception to the rule, for I am 

 informed by Dr Edmondston Saxby that a small flock 

 arrived in Unst on 14th February. Their numbers 

 were greatly increased on 23rd March, and on 20th 

 April enormous numbers were present over the whole 

 island, some of which remained until loth May.^ These 

 travellers arrive during the night occasionally in large 

 flocks, and are sometimes accompanied by Grey Crows 

 and Daws. The emigrants appear at stations widely 

 scattered over both Orkney and Shetland, and usually 

 tarry for a few days before proceeding northwards. 



* At Somerton, on the Norfolk coast, on 20th March 1886, Rooks were 

 flying due south in a continuous stream from 10.30 a.m. to 6 p.m., never 

 fewer than 1000 being in sight at the same time. 



^ Stragglers have been observed as late as i6th May, and some of a party 

 which arrived in Unst, the northernmost of the British Isles, on 4th March 

 1901, remained until 23rd July (Dr Saxby), and probably did not proceed 

 beyond the limits of the British Isles. 



