228 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



bert Ozan on St. Ambrose Island, in the St. Felix group, off the 

 coast of Chile, on December 17, 1907. The nests were mere hollows 

 scraped in the sand among bowlders without any material of any 

 kind or any lining in the nests. The " birds were close sitters^ perch- 

 ing on rocks only 10 feet away while the eggs were secured. The 

 male bird was killed by a stone thrown by a companion," according 

 to the collector's notes. There are seven eggs in the series — one set 

 of three and two sets of two. The eggs are not distinguishable from 

 certain types of common tern's eggs. The ground color varies from 

 " Isabella color " to " deep olive buff." Some are uniformly spotted 

 or blotched with dark browns, and some are more heavily blotched 

 at the larger end. One set is spotted with the lighter shades of 

 brown and olive. Some of the eggs show underlying spots of drab 

 or lilac. The shape is ovate. The measurements of these eggs and 

 of three furnished by Rev. F. C. R. Jourdain, 10 in all, average 41.7 

 by 30.6 millimeters; the eggs showing the four extremes measure 

 46.4 by 30.4, 44.7 by 31, 39 by 30.5, and 39.5 by 30 millimeters. 



Plumages. — Nothing seems to be known about the downy young 

 or the immature plumages. The full nuptial plumage is well illus- 

 trated in Audubon's plate. Two birds in my collection taken in 

 Argentina on October 17 and 27 are just completing the molt of 

 the primaries, but otherwise are in full fresh winter plumage ; proba- 

 bly they are young birds, for adults should be molting into the 

 nuptial plumage at this time. Dr. L. C. Sanford, from whom I 

 obtained my specimens, has quite a series in this plumage collected 

 by Mr. R. H. Beck in the same locality at about the same time, but 

 there are no adults in nuptial plumage among them. The winter 

 plumage is strikingly like that of Forster's tern, but Trudeau's 

 tern may be distinguished by the much shorter and much less deeply 

 forked tail, the long streamers of the outer rectrices being ve*y 

 conspicuous in the Forster's tern. The bill in Trudeau's tern, espe- 

 cially in adults, is also longer and slenderer than in the commoner 

 species, and it is tipped with yellow. 



Behavior. — As to the habits, behavior, and life history of Tru- 

 deau's tern there is nothing more to be said at present. 



DISTRIBUTION. 



Breeding range. — Known to breed only in Argentina (Estancia 

 Espartilla, Ajo district, etc.) and off the coast of Chile (St. Ambrose 

 Island) . 



Winter range. — Unknown. 



Migrations. — Not definitely known. Argentina records: Estancia 

 Espartilla, September to February ; La Plata River, March ; Mar del 

 Plata, October 17 to 27; Punta Lara, October; Buenos Aires, Sep- 



