394 



On the Scottish Islands 1 it is the Arctic Tern which forms 

 numerous colonies. 



All round the Irish coast this species is plentiful in 

 summer. In many localities, especially in the south, it 

 breeds in company with the Common Tern. But the former, 

 more maritime in its habits, far exceeds and even replaces 

 its congener on some of the marine islands of the north and 

 west. Mr. Ussher mentions that vast colonies, apparently 

 unmixed with other species, resort to the islands off Donegal 

 and Sligo. 



FIG. 53. ARCTIC TERN. 



I have seen large assemblages on the Blasket Islands 

 off Western Kerry. Rockabill, on the Dublin coast, is 

 no longer a breeding-station, yet I have observed large 

 numbers in the vicinity of Dublin Bay in autumn prior 

 to migration. In Thompson's time this used to be the 

 most abundant species of Tern on the east coast of Ireland. 

 Over the flat and shingly shores of Killala Bay, it has in- 

 creased as a nesting-species (Warren). Moreover, Ireland 2 



1 Though according to Mr. Harvie-Brown the Arctic Tern is dimin- 

 ishing as a breeding-species on the Outer Hebrides as the Common Tern 

 is on the increase. 



2 Also Scandinavia and Arctic America 



