THALASSEUS POLIOCERCUS, Gow.

Bass’s Straits’ Tern.

Sterna poliocerca, Gould in Proc. of Zool. Soc., Part V. p. 26; and in Syn. Birds of Australia, Part II.
Sylochelidon poliocerca, List of Birds in Brit. Mus. Coll., part ii. p. 175.

 

No species of ‘Tern is so abundant in Van Diemen’s Land and New South Wales during the months of winter
as the present bird, which then inhabits the bays and inlets of the sea, and ascends high up the rivers in
flocks of from ten to fifty in number, for the purpose of securing the abundant supply of food afforded by
the shoals of fish which there abound ; at this season of the year the heads of all are mottled with black
and white, a style of plumage which gives place to an intensely jet-black hue in summer, as represented in
the accompanying Plate: the only part of Australia from whence I have received specimens in this latter
state is the southern coast, where both sexes and the eggs were procured, and sent to me by my late friend
J. B. Harvey, Esq., of Port Lincoln.

It is about the size of, or perhaps rather larger than the Kentish Tern of England, and has many habits
in common with that species.

The eggs vary considerably in colour, some being of a stone-grey and others of a buffy hue, all more or
less marked with brown, the markings in some being large and irregular blotches, in others streaks and spots,
in others in the form of Chinese or Hindustanee characters ; others again are freckled and blotched all over
with brown; and some have the markings so thick at the larger end that they blend into each other and
form a broad zone.

Crown of the head and occipital crest jet-black ; forehead, back of the neck and all the under surface
silky white; back, wings and tail grey; secondaries tipped with white; shafts of the wings and tail white ;
bill yellow; irides black ; legs and feet brownish black.

The figures represent the bird in the summer and winter plumage, of the natural size.