PATAGONIAN EXPEDITIONS I ZOOLOGY. 



Immature birds in autumn and winter vary from adults at these sea- 

 sons in having the centers of the long inner secondaries ashy-grey. The 

 eye streak is more pronounced and deeper in color. The bill is dull yel- 

 lowish brown at the base and yellow at the tip. 



Young birds, first flight, have the eye streak longer with an indication 

 of a grey crescentic band across the nape. The crown is greyish, slightly 

 mottled with buffy brown, as are the feathers of the mantle. The tail 

 feathers are dark ashy grey with defined white edgings. The bill is yel- 

 lowish brown at the base and dusky or blackish for the rest of its length 

 without a yellow tip. The legs and feet are yellowish flesh color. 



Geographical Range. Atlantic coast of South America from Rio Jan- 

 eiro to Argentina, and north casually to the United States (Long Island 

 and New Jersey). On the Pacific coast of South America the Chilian 

 coast north to Southern Peru. 



Trudeau's tern was not obtained by the Princeton Expeditions to Pata- 

 gonia and, while it is known to occur on the northern portion of the coast, 

 it is very rare, if found at all, far south in the region. 



The descriptions are based on the material in the British Museum of 

 Natural History. 



Curiously, this South American species which must be regarded as acci- 

 dental in the United States, was first described by John James Audubon 

 in his Ornithological Autobiography. He says (t. c. p. 125): "This 

 beautiful Tern, which has not hitherto been described, was procured at 

 Great Egg Harbour in New Jersey, by my much esteemed and talented 

 friend, J. Trudeau, Esq., of Louisiana, to whom I have great pleasure in 

 dedicating it. Nothing is known as to its range, or even the particular 

 habits in which it may differ from other species. The individual obtained 

 was in the company of a few others of the same kind. I have received 

 from Mr. Trudeau an intimation of the occurrence of several individuals 

 on Long Island." 



In its winter plumage, which was that of the type described by Audubon, 

 Trudeau's Tern somewhat resembles the winter plumage of Sterna for steri, 

 but this last bird always shows more marked coloration on the crown. The 

 eye bar of Sterna forsteri is darker and better defined in winter and. the bill 

 of S.forsteriftevtr has a yellow tip. I have before me forty-one examples 



