396 BIRDS OF AUSTRALIA. 



Young birds have the grey of the upper surface much paler, 

 and the black of the head mottled with white. 



Sp. 602. THALASSEUS POLIOCERCUS, Gould. 



Bass's Straits' Tern. 



Sterna poliocerca, Gould in Proc. of Zool. Soc, part v. p. 26. 

 Syluchelidon ■poliocerca, List of Birds in Brit. Mus. Coll., part iii. p. 175. 

 Pelecanopus poliocercus, Bonap. Compt. Rend, de I'Acad. Sci., torn. xli. 



Thalasseus poliocercus, Gould, Birds of Australia, foL, vol. vii. 

 pi. 24. 



No species of Tern is so abundant on the shores of Tas- 

 mania 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 : the only part of 

 Australia from which I have received specimens in this latter 

 state is Port Lincoln, where both sexes and the eggs were 

 procured, and sent to me by my late friend J. B. Harvey, Esq. 



This bird 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 Hindustance characters ; others again are freckled 

 and blotched all over with brown ; and some have the mark- 

 ings 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 ; forelifead, 



