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

266 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
represented, though two skins from Tucuman appear very slightly
darker than others. Birds in juvenal plumage have the tips of
breast, neck, and upper back feathers more or less faintly veraiicu-
lated with fuscous; the dark markings on the breast in some are
extended down on the abdomen and in others almost obsolete.
Young specimens are often more or less stained. The few taken in
Uruguay appear to have slightly larger bills than those from the
westward. An adult female taken January 29 is molting wing and
tail feathers while the body plumage is worn.
In the present paper I have followed current usage in adopting
the generic term Sijitornis for a broad group of species that with-
out question may be divided into two or more restricted genera.
At this time only a little more than half of the species known in this
assemblage are available to me, sufficient to demonstrate that while
Mr. Cory's treatment of the group ^^ has certain merits, it is far from
conclusive, and in certain respects requires modification as regards
the allotment of species in the genera recognized. Further material
is needed before an intelligent discussion of the matter may
be made.
The present species, one of more active habit than many of its
relatives, frequents groves and thickets often near the borders of
openings and clearings, wdiere it works about from 2 to 10 meters
or more from the ground. In ordinary circumstances the birds are
suggestive of titmice as they clamber and hop about among the
smaller limbs, and the long tail, with its pointed, rather stiffened
feathers, seems almost an encumbrance to their movements, as it is
often held in awkward positions. It may not be used even when the
bird swings around on the underside of a horizontal limb, so that
one comes to wonder at the possible function of the stiffened tip,
when suddenly one of the little birds may start up a tree trunk in
orthodox woodpecker fashion. Should any return be necessary they
are not averse to whirling around and sidling down head first as
acrobatically as any nuthatch, though this is not a usual habit.
The birds are gregarious, and, in addition to traveling tw^o or
three together, have a predilection for association with other small
brush-haunting birds, and form in a way the guides for little
traveling companies of Thamnophilus gilvigaste7\ Picumnus, etc.,
as chickadees do in similar bands in more northern regions.
When excited /S. pyrrhophius comes about with rapid, sputtering
explosive call notes that may be represented as spee-ee-ee-ee or
tsee-ee-ee-a- In the breeding season they utter a low trill, not un-
pleasing in sound, that is suggestive of the song of Synallaxis f.
frontalis^ and is given from the cover of branches-
ssproc. Biol. Soc. Washington, vol. 32, Sept. .30, 1919, pp. 149-160.
^