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

48 BULLETIN 133^ UNITED STATES NATIONAL MUSEUM
killed, as they seemed less agile in rapid diving than other species of
grebes that I have taken.
An adult male had the bill dull black, more grayish at base; iris
scarlet, with a narrow circle of baryta yellow around the margin of
the pupillar opening; outer face of tarsus, fourth toe, and under
surface of all the toes, dusky neutral gray; inner faces of first and
second toes washed with vinaceous buff; rest of tarsus and toes neu-
tral gray.
AECHMOPHORUS MAJOR (Boddaert)
Colymhus major Boddaert, Tabl. Planch. Enl., 1783, p. 24. ("Cayenne.")
This large grebe, when in full plumage, bears a striking resemblance
to Holboell's grebe in pattern of markings and color. The
bill in general form agrees with Aechmophorus occidentalis (the
type of the genus), but is slightly heavier, while the base of the bill
is somewhat more heavily striated, and the nostril, bordered above
by a stronger membrane, is less elongate in form. In addition
the feathers on the sides of the mandibular rami form a more obtuse
angle and in most specimens do not extend as far forward, while
the streaked plumage of juvenile birds is strikingly different from
that of the plain gray of the chick of occidentalis.
The species was first observed on the Parana River between Holt
and Zarate on October 9, 1920. On October 25 six or eight were
seen on salt water in the mouth of the Rio Ajo, below Lavalle,
Buenos Aires, and three, all in immature dress, were taken. Two of
these, preserved as skins, have indistinct dark streaks on the side of
the head, and lack the full bright color of adults. As my boat approached
in the narrow river, these birds worked to one side and
finally made a long dive to allow me to pass. Three were observed
sleeping as they floated on the water, with the neck drawn back so
that the bill rested on the shoulder at the side of the neck with the
point ahead. As this threw the rounded head in the middle of the
back it produced a curious outline. From this attitude the birds
dived with no loss of time in swinging the bill to the front, an evident
advantage of this attitude over that assumed under similar circum-
stances by the pied-billed grebe in which the bill is turned and inserted
among the feathers of the back. One of the grebes taken here had
the end of one toe and part of the web on another bitten out as
though by a turtle or a small shark. The species seems to range
along the seashore, as on November 6 when I was on the coast below
Cabo San Antonio one washed ashore after a heavy storm, while on
the following day two more, one an adult male, were secured under
similar conditions. These had been dead for two days at least, and
were preserved either as skulls or skeletons.