ON BIRD MIGRATION. 301 



These, or perhaps we should say some of them, are, no doubt, the 

 return movements to British haunts of the emigrants observed leaving 

 our shores in the autumn. Other individuals, especially the late arrivals, 

 may be on passage to the Continent, the corresponding autumn passage 

 southwards on the part of foreign immigrants is not obviously recorded 

 in our data, though it possibly occurs. 



Spring Emir/ration fo Central Europe. — As the reverse migration was 

 the main one of the autumn, so is this the most important one of the 

 spring. 



The first departures of the Rooks which have wintered in England 

 are those for Central Europe. As early as the second week of February 

 (the 10th being the earliest record) these great emigrations eastwards set 

 in, reach their maximum during March, and are much in evidence 

 until the middle of April, the 23rd of that month marking their extreme 

 limit in the observations. During this prolonged period vast numbers of 

 emigrants are observed at the lightships between the Humber and the 

 mouth of the Thames (occa.sionally at the Straits of Dover), passing to the 

 south-east and east during the daytime, from 6 a.m. onwards, and some- 

 times flying very high ; Grey Crows, Daws, Skylarks, Tree Sparrows, 

 and Chaffinches not unfrequently departing at the same time. 



Prior to their departure certain of these emigrants have been observed 

 passing southwards, occasionally accompanied by Grey Crows, on both 

 the Yorkshire and Norfolk coasts, en route for some particular points of 

 embarkation for the crossing of the North Sea.' 



Spring Emigration to North- Western Europe. — The Rooks from Scan- 

 dinavia which have wintered in our islands return north in March and 

 April, and (as in the autumn) are mainly observed on passage in the 

 Orkneys and Shetlands. 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, though a few are seen as late as the 

 end of that month. ■^ They 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 Shet- 

 land, and usually tarry for a few days before proceeding northwards. 



There are only a few records relating io these movements northwards 

 on the east coast of Britain, and it would seem as if they but rarely came 

 under notice at any of the mainland stations. Rooks in small numbers 

 are, however, observed annually at the Hebrides, including the Flannan 

 Isles, on passage during March and April. They occur at the Faeroes on 

 passage about the same time (Andersen), and arrive in Norway during 

 the latter part of March or beginning of April (CoUett). 



Irisli Migrations. — The regular migrations of the Rook witnessed in 

 Ireland are of an extremely limited nature, and relate to certain arrivals 

 in the spring. Ireland does not appear to be visited by Continental birds 

 as a winter resort, and hence the movements observed there are chiefly 



Jackdaws, and again saw another flock, also very high, flying northwards ; they were 

 occasionally toying and circling as one sees them in summer and autumn.' 



' At Somerton. on the Norfolk coast, on March 20, 1886, Rooks were flying due 

 south in a continuous stream from 10.30 A.M. to 6 P.M., never fewer than 1,000 being 

 in sight at the same time. (Report, 1885, p. 47.) 



* Stragglers have been observed as late as May 16, and some of a party which 

 arrived iri Unst on March 4, 1901, remained until July 23 (T. E. Saxby),and probably 

 did not proceed beyond the limits of the British Isles. 



