Bulletin - United States National Museum - si-pddr - Smithsonian ...

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,
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