650 ARCTIC TERN. 
On migration it can be traced along the Atlantic sea-board to the 
Canaries and the Azores, a straggler occasionally penetrating into 
the Mediterranean as far as Italy ; it descends the coast of Africa to 
Table Bay ; and specimens obtained at sea to the south-east of 
Madagascar, and even in lat. 66°S., far beyond New Zealand, are in 
the British Museum. The islands of the Southern Ocean are in- 
habited by two nearly-allied but well-defined species, while there is 
a third representative on both sides of South America ; but on the 
Pacific coast Staff-Commr. MacFarlane, when in H.M.S. ‘Constance,’ 
obtained an Arctic Tern off Arica. It occurs in Kamchatka and 
Amur-land; but there, as well as in Japan, and in Eastern Siberia as 
far as Lake Baikal, the representative species is S. Zongifennis, which 
is intermediate between the Arctic and Common Tern, and has a 
black bill, small ruddy legs and feet, with grey under-plumage. 
In Ireland, Scandinavia, and Arctic America this bird has been 
found nesting by fresh-water lakes, but its breeding-places are usually 
by the sea. The eggs, laid in a depression of the sand or on scanty 
herbage, or even on the bare rock just out of reach of the waves, are 
sometimes 3 but often only 2 in number; they are slightly smaller 
than those of the Common Tern, measuring about 1°6 by 1 in., and 
are subject to more variations, those with a pale bluish-green ground- 
colour being frequent, while a rich ochre-red with rufous-brown spots 
is occasionally found. In defence of its nest the bird is very bold, 
sometimes striking the intruder sharply with its beak, and a flock has 
been seen to mob and drown a Hooded Crow. In food and general 
habits it does not differ materially from the preceding species, and 
both may be seen dashing down with such force as to raise a cloud 
of spray and completely submerge themselves. 
The adult in summer may be distinguished from the Common 
Tern by its blood-red bill, distinctly pearl grey under-parts (without 
any vinaceous tint), and longer lateral tail-feathers. At all ages its 
shorter tarsi are characteristic, though the difference is not invari- 
ably so great as some writers have supposed ; a better distinction 
being the narrowness and pale colour of the stripe next the shaft on 
the inner web of each of the long primaries: this stripe being much 
broader in S. fluviatilis. The young of both species go through 
similar seasonal changes. The legs and feet are coral-red in spring 
—duller in the young—and nearly black in winter. Birds which 
are a year old have a dark bar on the carpal joint until the autumn 
moult ; they breed in the following June. Length r4°5 in. (bill 1°6, 
tail 7°5 to 8), wing ro in. 
