THI<: ARCTIC TERN. 
325 
IV. LARIBjK 
THE AECTIC TEllN. 
Sterna arctica. 
TARROCK — PICCATARRIES. 
This species is plentiful throughout Shetland, usually arriv- 
ing in Unst about the third week in May, though sometimes 
earlier, and leaving towards the beginning of September. It 
occasionally happens that a small party of Terns will suddenly 
appear some weeks after the islands have apparently been 
altogether clear of them, but these pass on at once, not, indeed, 
staying over the day. 
After the arrival of the Terns in spring they seem to be 
fond of keeping about fresh water for a week or two, possibly 
finding some favourite kind of food at that season. The 
small loch in front of the house at Halligarth was thus re- 
sorted to every year by a single pair, which would remain for 
several weeks, but which never bred there. Young trout were 
abundant in the loch, and I thus had continual opportunity of 
watching the process of capture. The birds always appeared 
to know how deep the water was over which they were hovering 
on the look-out for fish. If there was plenty of water beneath 
them, they would dash down upon their prey with sufficient 
force to bury themselves completely out of sight, nearly always 
reappearing with a fish in the bill. In the shallower parts of 
the loch they would be more cautious, and drop only from 
an inconsiderable height. They took good care to keep off 
any poachers from their preserve. I once saw them fairly 
beat off even the tame Great Black-backed Gull which belongs 
to Buness, as he was going to the loch for his morning dip. 
Indeed, the Terns are among the bravest of little birds. I once 
saw a single Tern attack and put to flight a Eaven which hap- 
pened to pass near the holm at Helyer Water, where the Tern 
