National Museum, 16; Boston Society, 2; Philadelphia Academy, 4; Museum
Comp. Zoöl., 1; R. Ridgway, 2. Total, 25.
_Measurements._
+----+-----------+-----------+---------+---------+-----------+----------+
|Sex.| Wing. | Tail. | Culmen. | Tarsus. |Middle Toe.|Specimens.|
+----+-----------+-----------+---------+---------+-----------+----------+
| ♂ |14.60–16.50| 9.00–10.00|1.20–1.48|3.20–3.60| 1.90–2.00| 6 |
+----+-----------+-----------+---------+---------+-----------+----------+
| ♀ |14.75–16.00| 8.80–10.00|1.20–1.45|3.55–3.75| 2.00–2.10| 8 |
+----+-----------+-----------+---------+---------+-----------+----------+
[Illustration: _Polyborus tharus_, var. _auduboni_.]
HABITS. The Caracara Eagle, as this bird is called, though it seems to
possess, to a large degree, the characteristics of a Vulture, and hardly
any of the true aquiline nature, is found in all the extreme southern
portions of the country, in Florida, Texas, Southern Arizona, and
California. Audubon met with it abundantly in Florida in the winter of
1831. Mr. Boardman has seen it quite common at Enterprise, associating
with the Vultures. Dr. Woodhouse, while encamped on the Rio Saltado,
near San Antonio, in Texas, frequently saw the Caracaras, and always
in company with the Vultures, which he says they greatly resemble in
their habits, excepting that they were much more shy. He could, however,
readily approach them when on horseback. Mr. Dresser also frequently
encountered it in Texas in the vicinity of San Antonio, and speaks of
it as abundant from the Rio Grande to the Guadaloupe, but never noticed
any farther east. In Arizona, Dr. Coues says, it is not a rare bird in
the southern and western portions of that Territory. Lieutenant Couch
likewise describes them as exceedingly abundant from the Rio Grande
to the Sierra Madre. He speaks of killing a male bird on the nest,
which was in a low tree and composed of sticks. He adds that this bird
destroys the Texas field-rats (_Sigmodon berlandieri_) in large numbers.
Dr. Heermann met with this species on the Colorado River, near Fort
Yuma, in company with the _Cathartes aura_. He found it so shy that it
was impossible to procure a specimen. He found it along the Gila River,
and again met with it in Texas wherever there were settlements. At San
Antonio, wherever there were slaughter-houses, he met with them in great
numbers, twenty or thirty being often seen at a time.
Grayson gives the _Caracara_ as quite abundant in the Tres Marias.
Although it subsists mainly on dead animals and other offal, it is said
to sometimes capture young birds, lizards, snakes, and land-crabs. It
generally carries its prey in its beak; but Colonel Grayson states
that he has seen it also bear off its food in its claws, as Hawks do.
It walks with facility on the ground, and was often met with in the
thick woods, walking about in search of snakes. Mr. Xantus found it
nesting at Cape San Lucas, placing its nest on the top of the _Cereus
giganteus_. It occurs also in the West Indies, especially in the island
of Cuba, where it is known to breed. Eggs were obtained and identified
by the late Dr. Berlandier, of Matamoras, in Northern Mexico, on the Rio
Grande, in considerable numbers.
Mr. Salvin (Ibis, I, 214) says the _Caracara_ is universal in its
distribution in Central America, appearing equally abundant everywhere.
At Duenas it was a constant resident, breeding on the surrounding
hills. Its food seemed to consist largely of the ticks that infested
the animals. In Honduras Mr. G. C. Taylor found them very common, quite
tame, and easily shot. They feed on carrion and offal, were often seen
scratching among the half-dry cow-dung, and are “a very low caste bird.”
Mr. E. C. Taylor (Ibis, VI, 79) frequently saw this bird on the shores
of the Orinoco. It was very tame, and generally allowed a near approach,
and when disturbed did not fly far. He did not meet with it in Trinidad.
On the Rio Grande the popular name of this species is _Totache_, while
in Chile the _P. tharus_ is called _Traro_, but its more common name
throughout South America is _Carrancha_.
According to Audubon, the flight of this bird is at great heights,
is more graceful than that of the Vulture, and consists of alternate
flapping and sailing. It often sails in large circles, gliding in a very
elegant manner, now and then diving downwards and then rising again.
These birds feed on frogs, insects, worms, young alligators, carrion,
and various other forms of animal food. Mr. Audubon states that he has
seen them walk about in the water in search of food, catching frogs,
young alligators, etc. It is harmless and inoffensive, and in the
destruction of vermin renders valuable services. It builds a coarse,
flat nest, composed of flags, reeds, and grass, usually on the tops of
trees, but occasionally, according to Darwin, on a low cliff, or even on
a bush.
Mr. R. Owen, who found this bird breeding near San Geronimo, Guatemala,
April 2 (Ibis, 1861, p. 67), states that the nest was built on the very
crown of a high tree in the plain. It was made of small branches twisted
together, and had a slight lining of coarse grass. It was shallow, and
formed a mass of considerable size. The eggs were four in number, and
are described as measuring 2.15 inches by 1.60, having a light red
ground-color, and spotted and blotched all over with several shades of a
darker red.
Dr. Heermann found the nest of this species on the Medina River. It
was built in an oak, and constructed of coarse twigs and lined with
leaves and roots. It was quite recently finished, and contained no
eggs. Mr. Dresser states that it breeds all over the country about San
Antonio, building a large bulky nest of sticks, lined with small roots
and grass, generally placed in a low mesquite or oak tree, and laying
three or four roundish eggs, similar to those of the Honey Buzzard of
Europe. He found several nests in April and through May, and was told
by the _rancheros_ that its eggs are found as late as June. The nests
found in the collection of Dr. Berlandier, of Matamoras, were coarse
flat structures, composed of flags, reeds, and grass. The nests, though
usually built on the tops of trees, are occasionally found, according
to Darwin, on a low cliff, or even on a bush. The number of the eggs
is rarely, if ever, more than three or four. Four eggs, taken by Dr.
Berlandier near the Rio Grande, exhibit a maximum length of 2.44 inches;
least length, 2.25; average, 2.41. The diameter of the smallest egg
is 1.75 inches; that of the largest, 1.88; average, 1.81. These eggs
not only present the great and unusual variation in their length of
nearly eight per cent, but very striking and anomalous deviations from
uniformity are also noticeable in their ground-color and markings. The
ground-color varies from a nearly pure white to a very deep russet or
tan-color, and the markings, though all of sepia-brown, differ greatly
in their shades. In some, the ground-color is nearly pure white with
a slight pinkish tinge, nearly unspotted at the smaller end, and only
marked by a few light blotches of a sepia-brown. These markings increase
both in size and frequency, and become of a deeper shade, as they are
nearer the larger end, until they become almost black, and around this
extremity they form a large confluent ring of blotches and dashes of
a dark sepia. Others have a ground-color of light russet, or rather
white with a very slight wash of russet, and are marked over the entire
surface, in about equal proportion, with irregular lines and broad
dashes of dark sepia. Again, in others the ground is of the deepest
russet or tan-color, and is marked with deep blotches of a dark sepia,
almost black. The eggs are much more oblong than those of most birds
of prey, and in this respect also show their relation to the Vultures,
rather than to the Hawks or Eagles. They are pyriform, the smaller end
tapers quite abruptly, and varies much more, in its proportions, from
the larger extremity, than the eggs of most true Hawks.
Lieutenant Gilliss found the South American race exceedingly numerous
throughout Central and Southern Chile. It was constantly met with along
the roads, and wherever there was a chance of obtaining a particle of
flesh or offal. At the annual slaughtering of cattle they congregate by
hundreds, and remain without the corral, awaiting their share of the
rejected parts. It was so tame, from not being molested, that it could
be taken with the lasso, but when thus captured, it fights desperately,
and no amount of attention or kindness can reconcile it to the loss of
liberty.
Throughout South America it is one of the most abundant species, its
geographical range extending even to Cape Horn. Mr. Darwin found the
_Polyborus_ nowhere so common as on the grassy savannas of the La Plata,
and says that it is also found on the most desert plains of Patagonia,
even to the rocky and barren shores of the Pacific.