138 BULLETIN 133;, UNITED STATES NATIONAL MUSEUM 



the level expanses of the broad marshes or along some open sea 

 beach they appear plain gray, with light head and a prominent 

 dark mark through the eye. In winter the undersurface of the 

 body is entirely white. At times they were wary but were enticed 

 within range by a white bird or a handkerchief waved in the air. 

 Near Lavalle through inquiry I located a small breeding colony of 

 the gaviotina^ as these terns were known locally, where the birds 

 were associated with gulls, but before I was able to visit it the 

 ternery was raided by boys who sold the eggs to the local baker 

 for use in preparing cakes. 



The two females secured for skins in October and November 

 were in full breeding plumage. In one the back of the crown is 

 washed with gray of the same shade as the back in the form of 

 a transverse bar. In this specimen, an adult, the soft parts were 

 colored as follows: Tip of bill cinnamon buff, base between zinc 

 orange and tawny, band across distal third black; iris Vandyke 

 brown ; tarsus and toes zinc orange, the scutes clouded with fuscous ; 

 nails blackish. In winter plumage the bill is black tipped with 

 yellowish, a condition that suggests Cabot's tern, from which the 

 present species may be distinguished readily in the field by its 

 lack of a nuchal crest. A female, apparently adult, secured on 

 January 31, is in the winter plumage as the bill is black at the base 

 and the undersurface of the body is entirely white. The primaries 

 in part had been renewed recently but the outer ones were much 

 worn and broken. Measurements of the two adult females in full 

 plumage are as follows: Wings, 255-26G; tail, 139-135; exposed 

 culmen, 41.8-42.5 ; tarsus, 24-24.5 mm. 



STERNA HIRUNDINACEA Lesson 



Sterna Mrundmacea Lesson, R. P., Traits d'Ornith., 1831, p. 621. (Coast 

 of Brazil.) 



On November 4, 1920, I found 20 or more on the beach below 

 Cape San Antonio, eastern Buenos Aires, mixed among flocks of 

 Trudeau's tern. The birds were wary and difficult to approach as 

 they rested in close flocks in the sand. At rest or on the wing they 

 suggested Forster's or common terns, but appeared larger. A female 

 secured had the forehead and part of the lores white with slight 

 mottlings of white throughout the otherwise black crown. The 

 wing feathers and tail were considerably worn. The soft parts 

 in this specimen were colored as follows : Bill slightly darker than 

 jasper red, space behind nostril dusky neutral gray; iris natal 

 brown; tarsus and toes jasper red, webs scarlet, nails black. A male 

 secured at the same time is in worn immature plumage, with the 

 nape and upper hind neck clouded with blackish, and the lesser 

 wing coverts dusky. The wing feathers were considerably worn, 



