(CASSIN'S TERN.)
+Sterna hirundinacea+, _Saund. P. Z. S._ 1876, p. 647; _Durnford,
Ibis_, 1878, p. 404 (Centr. Patagonia). +Sterna cassini+, _Scl.
et Salv. Nomencl._ p. 147; _iid. P. Z. S._ 1871, p. 570;
_Durnford, Ibis_, 1877, p. 201 (Buenos Ayres).
_Description._--Head and nape black; mantle and wings grey,
darker on the quills; rump white; tail pearl-white, darker on the
outer streamers; underparts greyish white; bill blood-red; feet
orange-crimson: whole length 15·0 inches, wing 11·5. _Young_:
streaked on the head and mottled on the upper parts with blackish.
_Hab._ Patagonia, Chili, Peru, Argentina, Brazil, and Falkland Islands,
up to Rio.
This is a black-headed Tern with a blood-red bill, which is found
abundantly on the coast of Patagonia, and extends up the Atlantic coast
to Rio. It was noticed by Durnford near Buenos Ayres, and found breeding
by the same excellent observer at Tombo Point, about sixty miles to the
south of Chupat, in December 1877. He tells us:--
"I was prepared when I visited this place in December to see a
considerable quantity of birds; but the number that met my eyes
fairly staggered me. Their nests covered an area about 150 yards
square. Allowing three nests and five eggs for every square yard (a
very moderate computation, it being difficult to walk without treading
on the eggs), we arrive at the extraordinary number of 67,500 nests,
135,000 birds, and 112,500 eggs; and, wonderful as these figures may
appear, I feel sure that I have rather understated than overstated the
numbers. The nests were mere hollows in the fine gravel or shingle,
and contained one, two, and sometimes three eggs. The latter generally
have the appearance of the eggs of the Sandwich Tern, though of course
smaller; and out of many hundreds I did not see two alike."