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

BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 277
The stick nests of the present species were seen everywhere in
their range and were of remarkable construction. Thorny twigs
were woven in an irregular form, entirely inclosed, with an entrance
opening frequently in the form of a short tunnel. These structures
were placed in low, often thorny, trees, or occasionally in thistles.
It was not unusual to see them built about the wires on the cross
arms of telephone and telegraph poles, and occasionally one was
built in the head of a railroad semaphore. In one such instance that
came under my observation the birds had filled a space between iron
uprights 4 feet long and were still busily engaged in carrying sticks
up to 10 meters in the air, though lower nesting sites abounded.
(PI. 10.)
On one occasion I observed a pair that had evidently just chosen
the site for a new home. The birds had selected a slight opening
among more or less horizontal limbs of a thorny tree, where they
hopped about a few inches apart as they examined the space criti-
cally, or rested near together and pecked and pulled at near-by
twigs. At intervals the male sang in a low tone. Nest construction
is apparently a prolonged process and the birds seem to work at it
when not in breeding condition. As the nests are firmly woven
and durable they last for several years. Though ordinarily peace-
ful, males fight savagely in defense of their chosen territory, battling
with intruders until exhausted.
The peculiar song of this species, given at times by the female
as well as the male, may be represented as chick chick chick chee-ee-
ee-ee-ee^ uttered in a rapid monotone, with an effort that shakes the
whole body. It is repeated frequently and is often heard from a
nest. The call note is a sharp tschick. In the Chaco the guira
anumbi of Azara was know^n in Guarani as huituitui in imitation of
the song while the Anguete Indians knew it as kas mis ka now ah.
Tlie development of the skull with age in the Tracheophone mesomyodi
seems less rapid than in the Oscines, so that the usual age
criterion for our smaller Passeriformes of the extent of cancellation
between the plates of the cranium may not be trusted. On March
6, 1 killed four Anumbms^ an adult pair and two fully grown imma-
ture birds. In the adult male the top of the skull was entirely
covered with cancellations. In its mate, an adult female, the top of
the skull was still open, as it was in the two young, the offspring of
the adult pair.
An adult male, taken August 23, had the maxilla and tip of
mandible cinnamon drab; base of mandible pale drab gray; iris
liver brown ; tarsus drab gray ; toes smoke gray. An immature male,
taken March 6, had the maxilla and tip of the mandible slightly
darker than hair brown ; extreme tip of culmen shading to chaetura