586 BRITISH GENERAL MIGRATORY MOVEMENTS 



species is sedentary and the continental form touches our shores as a bird of passage ; thus they 

 fall as species into the second class of residents, those which are stationary and migratory. 

 The great- titmouse and hedge-sparrow are birds which appear to show this racial difference in 

 habit. Insular segregation has reached its height in the sedentary red-grouse ; it has become 

 restricted in area in the Irish races of the jay and dipper, and still more in the two wrens which 

 are confined to the island groups of St. Kilda and Shetland. But a nominally British subspecies 

 is not necessarily non-migratory ; there is considerable evidence to support the conclusion that 

 the so-called British forms of the redbreast and song-thrush are also regular migrants, however 

 sedentary some individuals of these races may be. 



The difficult work of tracing the complicated movements of certain species was accomplished 

 by Mr. Eagle Clarke, 1 and his results put an entirely new aspect of the subject before the ornitho- 



GENERAL AUTUMN MOVEMENTS OF THE STARLING. 



->- British nesting bird. 

 > > Immigration from Central Europe. 



- Immigration from North-west Kurope. 



Passage from Northern to Southern Europe. 



The arrows do not indicate actual routes, but merely 

 general direction of movements. 



GENERAL SPRING MOVEMENTS OF THE STABLING. 



Immigration of birds which nest in Britain. 

 Emigration of Winter Visitors to Central Europe. 

 Emigration of Winter Visitors and Birds of 

 Passage to North-west Europe. 



The arrows do not indicate actual routes, but only general 

 direction. Spring emigration is less noticeable than 

 autumn immigration. 



logical public. Birds like the song-thrush and starling, to mention two, though resident as 

 species (in the sense that they are always present in the country), were shown to perform, as 

 individuals, complicated and varied movements. As individuals they were stationary, sedentary, 

 or performing local and restricted migrations ; they were summer visitors, winter visitors, and 

 birds of passage. The complication of these movements is perhaps most noticeable on our 

 south-eastern shores, for at the Kentish Knock Lightship birds of the same species are to be 

 seen travelling in directly opposite directions an emigratory stream travelling in a south- 

 easterly direction meeting and passing an immigratory stream which is flowing west or north- 

 west. The recovery of ringed birds proves that with some species the song-thrush is a good 

 example individuals from a given area may not all follow the same route or even partake 



1912. 



1 First published, British Association Reports, 1900-1903 ; revised and enlarged, Studies in Bird Migration, 



