The Arctic Tern — Sterna Macrura, Naumann
Except in a few minor points of plumage and in its distribution this species is the counterpart of the preceding one. In England it is only met with on migration, though a few pairs may nest in the north, but in Scotland it is the commonest Tern, breeding in increasing numbers northwards. In Ireland it breeds commonly, especially on the wind-swept islets of the north and west. Elsewhere it breeds in circumpolar regions, and has been met with in winter in Antarctic seas, so that it has a latitudinal range of from 82° N. to 74° S., probably the largest range recorded for any one species.
Its nesting habits are similar to those of the Common Tern, and as a rule it collects absolutely no materials for a lining, but lays its eggs in a shallow “scrape” or even on the bare rock. The eggs are indistinguishable in colour from those of the Common Tern, but are on the average slightly smaller. To the experienced ear the note is also rather different, but that difference is too slight to be expressed on paper.
This species may be distinguished from the preceding species by its blood-red bill, which is not darker at the tip, and the shorter tarsi. The under parts, especially in summer, are much darker, and the stripe on the inner web of the flight feathers is narrower and darker than in S. fluviatilis. In other respects these species are almost indistinguishable. Length 14·5 in.; bill 1·6 in.; tail 7·5 in.; wing 10 in.