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108 BULLETIN 133^ UNITED STATES NATIONAL MUSEUM
a tall tree to a perch above the surrounding leaves and peered about,
giving a note resembling whaow in a drawn-out nasal tone. In
Guarani the species was called taguatoi.
Both birds taken are males, one in full plumage, and the other in
process of molt from a lighter, immature dress. This second bird
has the throat white, and is lighter, less distinctly marked below than
the adult. The second specimen, when first killed, had the maxilla
and tip of the mandible black; remainder of mandible and a spot
on the maxilla below the nostril glaucous-graj'^ ; iris marguerite yel-
low; cere deep neutral gray; tarsus and toes carnelian red; nails
black.
CIRCUS CINEREUS Vieillot
Circus cinereus Vieillot, Nouv. Diet. Hist. Nat., vol. 4, 1816, p. 454. (Paraguay
and Rio de la Plata.)
The small marsh hawk was recorded only near Lavalle, Buenos
Aires, where at the Estancia Los Yngleses on October 29, 1920, I
secured a male as it came sailing across a marsh with several
Agelaius thilius in hot protest of its passage. This specimen,
hatched apparently the previous summer, is in brown immature
plumage save for one or two gray clouded feathers in the dorsal
region, and a grayish wash on some of the primaries. In life the
tip of the bill was dull black; base of maxilla light Payne's gray;
base of mandibular rami, gape, and cere light olive yellow, changing
laterally on the cere to asphodel green ; iris pale pinard yellow
tarsus primuline yellow; claws black.
Near the coast below Cape San Antonio in this same region I
found a pair that evidently nested somewhere near at hand in the
rush-covered marshes that here alternated with sand dunes. The
male, an adult bird in full plumage, that appeared very light in
color on the wing, was taken November 6. This species is similar in
appearance and manner of hunting to the North American marsh
hawk and has the same light graceful soaring flight that enables
it to scan the grass closely in its search for food.
CIRCUS BUFFONI (Gmelin)
Falco 'buffoni Gmelin, Syst. Nat., vol. 1, pt. 1, 178S, p. 277. (Cayenne.)
Of two specimens (both males) of this marsh hawk taken, one
was secured at Las Palmas, Chaco, on July 26, 1920, and the second
at the Riacho Pilagu, Formosa, on August 15. The first of these
was an adult bird in full dark plumage, with sexual organs onefourth
developed. The breast and neck are entirely black save for an
obscure white patch on the chin and partly concealed white markings
on the ruff and upper breast, while the abdomen varies from russet to
mars brown, and the thighs and flanks are nearly black. Feathers
;