390 LARIDAL 
AVERAGE MEASUREMENTS. 
ToTaL LENGTH a on08 De bSe me 
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BEAK S.. es Ne. oes.” Sohne 
TARSO-METATARSUS ... cng HORS ee 
EGe PP <p im 
COMMON TERN. Sterna fluvialitis (Naumann). 
Coloured Figures.—Gould, ‘ Birds of Great Britain,’ vol. v, pl. 
70; Dresser, ‘ Birds of Europe,’ vol. viii, pl. 580; Lilford, — 
‘ Coloured Figures,’ vol. vi, pl. 8. 
The Common ‘Tern, familiarly known as the ‘Sea- 
swallow,’ is plentifully distributed in summer along our 
coasts, and about the shores and islands of inland lakes. 
On the whole, it is probably the most abundant of British 
Terns, though the succeeding species predominates on the 
coasts and marine islands of North Britain, and is also 
the most numerous in Ireland. North of the Moray Firth 
on the east, and of the Island of Skye on the west of 
Scotland, it becomes much scarcer, and previous to the 
year 1901 there was no substantiated evidence to show 
that it bred in the Shetlands (Hagle Clarke, Ann. Scot. 
Nat. Hist., 1902, p. 121). Im the Orkneys and Outer 
Hebrides colonies are now known to exist. 
The majority of Common Terns reach us about the end 
of April or beginning of May, departing gradually during 
August and September for more southern latitudes. During 
early October, limited numbers pass along the British coasts, 
while I have seen a few solitary birds on inland waters at 
that time of year. In the autumn, young and old consort 
together, flying for miles along the coast in pursuit of the 
‘schools’ of herring- and mackerel-fry. 
Flight.——Most of us have seen these beautiful and 
clamorous birds wing their way, some by the edge of the 
breakers, others further out from the shore. One after 
another, they poise with quivering pinions, hovering like 
Kestrels, searching for their prey which moves beneath 
them. 
What keen sight they must possess, seeing as they can, 
the little fish under the surface of the water! Like minia- 
ture Gannets they precipitate themselves fearlessly with a 
