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130 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
The first species given above, the pomarine jaeger, has in recent
usage been recognized as a monotypic genus Coprotheres^ a distinc-
tion proposed first by Reichenbach in 1850. The second species
farasiticus is the type of the genus Stercorarius of Schaeffer 1789,
while Mathews" has proposed Atalolestris as a subgenus for longi-
caudus. After consideration of the differences indicated it has
seemed that the three small jaegers may be placed in one genus
Stercorarius. In case any further degree of superspecific difference
is desired it may be indicated by the use of subgeneric terms.
On November 4, south of Cabo San Antonio, two parasitic jaegers
came beating down the sea beach from the northward, pausing at
intervals for an agile pursuit of some tern, or to investigate some
other source of food. I secured one and later saw another. On
November 7 several more were seen and two were taken. Though
less abundant than the long-tailed species the parasitic jaeger was
well represented in the migration passing southward at this time,
so that I estimated that they were present in a ratio of 1 to 15 among
the bands of longicaudus. The notes made on the habits of the long-
tailed jaeger apply equally well to the present species.
The female secured in light phase had the tip of the bill and the
gape dull black, the remainder deep mouse gray; iris natal brown;
tarsus and toes black.
STERCOKARIUS LONGICAUDUS Vieillot
Stercorarius longicaudus Vieillot, Nouv. Diet. Hist. Nat., vol. 32, 1819,
p. 157. (Northern Regions.)
Four females and two males were taken on the beaL-h 25 kilometers
south of Cape San Antonio, eastern Buenos Aires, on November 4,
6, and 7, 1920. Of these birds one is a nearly adult male, as it has
only scattering feathers of the immature plumage on the white
upper breast and on the flanks. The remaining five are immature
but seem to be more than 1 year old. The feathers of the upper
surface are more or less margined with white. All are light under-
neath, but vary from deep mouse gray on the throat to white streaked
with deep mouse gray. The wing quills show more or less wear.
A female had the tip of the bill and the gape dull black, the remainder
of the bill deep mouse gray; crus, toes, and webs black;
tarsal joint pale green-blue gray; tarsus pale olive gray, with the
dark and light areas on tarsus and toes sharply delimited. The
blotching of light and dark was conspicuous, so that it attracted
attention in handling the birds. The extent of the light patches
varied considerably, as in some individuals it covered the entire
tarsus and the hind toe with its nail, while in others part of the
" Birds of Australia, vol. 2, pt. 5, .Tan. 81, 1913, p. 500.