SYLOCHELIDON STRENUUS, Gowda.

Powerful Tern.

Sterna (Sylochelidon) strenuus, Gould in Proc. of Zool. Soc., Feb. 24, 1846.

 

To a casual observer the present bird would appear to be identical with the Sterna Caspia; but on com-
parison it will be found to differ from that species in its larger size and its more richly coloured bill :
hence I have been induced to consider it as distinct ; and as it is by far the most powerful species of the
genus yet discovered, its average weight being one pound and six ounces, the specific term s¢renuus which
I have assigned to it may not be deemed inappropriate. The two species form beautiful representatives of
each other in the countries they respectively inhabit.

The Sylochelidon strenuus frequents every part of the southern shores of the Australian continent, but is
perhaps more numerous on the islands in Bass’s Straits and Van Diemen’s Land than elsewhere. Its
favourite breeding-places are the prom ontories of small islands, spits of land running out from the shores
of the mainland, extensive flats at the entrances of large rivers, and all similar situations. I never
observed it breeding in company, and seldom met with more than a pair on an island, unless it was one of
considerable extent. It lays two eggs on the bare ground, often within a very short distance of the water's
edge. No bird watches its eggs with greater assiduity, or defends them with greater courage, and woe
betides the unlucky gull or other natural enemy that may wander within the precincts of its breeding-place.
I could always discover its eggs by the clamorous cackling screeching note which it constantly utters
while flying over the place where they are deposited. The breeding-season comprises the months of
August, September and October, during which period the crown of the head is of a deep black, which
colour gives place to a spotted appearance at other seasons. Both sexes are subject to precisely the same
changes, and so much are they alike, that it is only by the somewhat smaller size of the female that they
can be distinguished: the accompanying Plate represents the bird at opposite seasons of the year, and will
at once show the nature of the changes I have referred to. The extensive development of the wings gives
this fine species immense powers of flight: it plunges into the water with the greatest impetuosity, and
brings from beneath the surface fishes of a very considerable size, which are swallowed entire, and in which
state I found several in the capacious stomachs of those I dissected.

The eggs are of a stone-colour, marked all over with large and small blotches of umber-brown, a great
portion of which appear as if beneath the surface of the shell; they are two inches and five-eighths long by
one inch and three-quarters broad.

Forehead, crown and nape deep glossy black; back, wings and tail pale ashy grey, becoming lighter on
the tail and deepening into dark grey on the primaries, the shafts of which are white ; remainder of the
plumage pure white ; irides black ; bill scarlet, stained with yellow on the sides and tip, and with greenish
yellow near the extremity.

The figures are of the natural size.