394 LARIDA: 
On the Scottish Islands! it is the Arctic Tern which forms 
numerous colonies. 
All round the Ivish 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 Shgo. 
Fic. 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? 
' 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. 
