584 BRITISH GENERAL MIGRATORY MOVEMENTS 



Spring and Summer. 



(a) Immigration of species which nest in the British Islands, travelling from Southern 

 Europe and Africa via the Iberian Peninsula and France, or from the south-east. 



(6) Emigration of species which have 

 spent the winter in the British Islands, and 

 are departing to North Europe and Siberia 

 to breed. 



(c) Emigration of winter visitors towards 

 Central and Eastern Europe. 



(d) Emigration of winter visitors towards 

 Iceland, Greenland, and the Arctic to the 

 north or north-west. 



(e, f, g) Immigration and emigration of 

 birds of passage, passing along our coasts 

 or crossing the country on their way from 

 winter quarters to the south of Britain 

 towards the same destinations as b, c, 

 and d. 



(h) Internal movements within OUr islands, 



B.B. wintersitors ana Bird, of Passage to Northern Kurope. and intermigration between GreatBritain and 



C. F. Winter Visitors and Birds of Passage to Central Europe. T_ p l n J Tk p m nvpm pn ts of hi rd S wll i P Vl hot h 



Ireland. 



winter and nest within the British area. 



(\) Irregular movements. 



GENERAL SPRING .MIGRATION. 

 A.E. F.G. Summer Visitors and Birds of Passage from Africa and Southern 



D.G. Winter Visitors and Birds of Passage to Greenland, Iceland, and 



the North-west. 



The arrows do not indicate routes, but only the general direction of 

 the immigrants and emigrants. 



Autumn and Winter. 



Practically the reversal of all movements 

 especially between Great Britain and Ireland, 

 due to the influence of greater climatic 

 variations during the colder months. 



Irruptions or the excessive migration 

 of certain species, due to influences at work 

 over a large extra-British area, may occur 

 at any season, but are perhaps most frequent 

 in spring and summer. The spring immi- 

 gration of the summer visitors is more 

 noticeable than the autumn departure of 

 the same species. The field-naturalist is 

 always ready to welcome the first swallow, 

 to listen again to the sweet voice of the 

 willow-wren, and often far too eager to hear 

 the incoming cuckoo. The autumn depar- 

 ture takes place when many of the birds 

 are silent, and although the numbers which 

 leave are larger than those which arrived, 

 due to the presence of the season's young, 

 the birds slip quietly away they may be 

 far on their journey before they are missed. 

 Indeed, at all seasons immigration is more 



to h, with an increase in irregular movements, 



GENERAL AUTUMN MIGRATION. 



A. Emigration of Summer Visitors and Birds of Passage to Southern 



Euroi>e and Africa. >".-" 



B. Immigration of Winter Visitors and Birds of Passage from Northern 



Europe. 



C. Immigration of Winter Visitors and Birds of Passage from Central 



and Eastern Europe. .-* 



I). Immigration of Winter Visitors and Birds of Passage from Iceland, 



Greenland, and the North-west. 



The arrows do not represent actual routes, but only indicate tlje 

 general direction of fight. 



noticeable than emigration; we have not seen 



