STERNA 317 



and Arabian Seas, the Indian Ocean, Malaysia, China Seas up to Japan, Polynesia and the 

 islands of the Pacific up to the Hawaii Archipelago." He further states there^^ : — " In this fine 

 Sea Tern the variation in size and in the tint of the upper parts in individuals is considerable, 

 and this has given rise to tlie institution of several supposed species, which I cannot consider 

 as valid. As regards size the smallest are those from the south of Australia, where the 

 conditions of life are probably unfavourable to full development, though even in Tasmania some 

 individuals have a wing-measurement of 14 inches. In North Australia the birds are nearly as 

 large as those from the Red Sea and iMekran Coast, and there is every gradation over the area 

 frequented. In colour the birds with the darkest upper parts are those from the Red (SU-rmi 

 vclox) and Arabian Seas and the Bay of Bengal, and these dark birds — slightly falling off in size — 

 run down to the northern part of Australia (S. pclecaiwides). There and in the Moluccas they 

 meet and blend with the smaller and greyer southern race (.S\ polioccrcus), from which they 

 gradually become indistinguishable. In birds from South Africa and the Mascarene Islands the 

 size of the Indian form is maintained, but the tint of the upper part is of a purer grey, without 

 the brownish tinge, and this holds good of most of the Polynesian examples, though the latter 

 show a slight diminution in size. The contrast between extremes of these Terns may seem 

 striking at the first glance, but even this, when examined, appears capable of explanation. 

 Under the hot sun of the Arabian and Indian Seas the grey feathers of the mantle and tail soon 

 acquire a brownish tinge at their edges, and brown is a very assertive colour, whereas in the 

 Southern Seas and in the Pacific the sun's direct force is much feebler. Food also may have 

 some influence on the tint, as it undoubtedly has upon the size and shape of the bill, which is 

 often worn down in front of the angle of the genys." 



The wing-measurement of a number of adult specimens now before me varies from 13-3 

 inches in North Australian birds to 1275 inches in South Australian and Tasmanian birds. 

 The eggs do not exhibit the constant difference in size one would expect between these two 

 forms, for although Tasmanian and Bass Strait eggs are as a rule slightly smaller, as i\Ir. 

 Howard Saunders has pointed out with the wing-measurements of the Tasmanian birds are 

 nearly equal to those of the largest form of .S. hen^ii, so are some southern eggs equal in size to 

 specimens taken on islands in North Australian waters. 



This species of Tern is probably better known than any other to most residents of Australia 

 and Tasmania, for it frequents most of the seas, contiguous islands and bays and harbours of all 

 the States. In New South Wales waters it is common, breeding on the adjacent islands and 

 frequently its bays and inlets. It is found throughout the year on Sydney Harbour, and may 

 be seen more often between the Heads and about Middle Head and on Middle Harbour, and 

 from there in decreasing numbers to Lavender Bay, and the entrance to Parramatta and Lane 

 Cove Rivers. Frequently it may be seen from the Milson Point and other contiguous ferries 

 at Circular Quay, flying over the harbour, the head and bill carried at right angles to the 

 body, carefully scrutinising the water below. These birds were remarkably common in this 

 part of Port Jackson in January and February, igii, when fur the first time, at the end 

 of the latter month, in their aerial evolutions, I saw two flying over the contiguous wood 

 block paving of Sydney, opposite the Custom House. It is remarkable, however, that the birds 

 were all in winter or immature plumage, and I cannot recollect ever seeing one in full breeding 

 plumage, all the specimens, too, received by the Trustees of the Australian Museum, procured 

 near Sydney, are in winter or immature plumage. In winter adult birds have the black feathers 

 of the crown of the head edged or streaked with white. Immature birds are similar, but may be 

 distinguished by their dark grey quills, by a large amount of white on their upper wing-coverts 

 and scapulars, and which with the mantle is spotted and streaked with brownish-black and buff; 

 the apical portion of the tail-feathers are dark grey tipped with white, and the upper tail-coverts 



Cat. Bds. Brit. Mus., Vol. XXV., p. 92-3 (1S96). 



