The largest caracara--Polyborus Braziliensis--ranges the grassy
savannahs of La Plata. Across the desert, between the rivers Negro and
Colorado, numbers constantly attend the line of road, to devour the
carcasses of the exhausted animals which chance to perish from fatigue
and thirst. It also attends the estancias and slaughtering-houses,
accompanied by its smaller relative, the chimango. "When an animal dies
on the plain the gallinaso commences the feast, and then the two species
of polyborus pick the bones clean," says Darwin. These birds, although
thus commonly feeding together, are far from being friends. When the
caracara is quietly seated on the branch of a tree or on the ground, the
chimango often continues for a long time flying backwards and forwards,
up and down, in a semicircle, trying each time at the bottom of the
curve to strike its larger relative. The caracara takes little notice,
except by bobbing its head. The caracaras are crafty, and steal numbers
of eggs; they also attempt, together with the chimango, to pick off the
scabs from the sore backs of horses and mules. These false eagles
rarely kill any living bird or animal; and their vulture-like,
necrophagous habits are very evident to any one who has fallen asleep on
the desolate plains; for, when he awakes, he will see on each
surrounding hillock one of these birds patiently watching him with an
evil eye. If a party of men go out hunting with dogs and horses, they
will be accompanied during the day by several of these attendants.
The flight of the caracara is heavy and slow, and it is generally an
inactive, tame, and cowardly bird. It destroys young lambs, by tearing
the umbilical cord; and it pursues the gallinaso till that bird is
compelled to vomit up the carrion it may have recently gorged. It is
said, also, that several caracaras will unite in chase of large birds,
even such as herons.
The chimango is tame and fearless; and when an animal is killed a number
soon collect, and patiently wait, standing on the ground on all sides.
Darwin describes seeing one pounce on a dog which was lying asleep close
to one of a party of sportsmen. They had difficulty in preventing their
canine companion from being seized before their eyes.
It will frequently wait, as does the caracara, at the mouth of a
rabbit-hole, and seize on the animal when it comes out. It is also very
mischievous and inquisitive. It will pick up almost anything from the
ground: a large black glazed hat was carried nearly a mile, as were a
pair of heavy bolas. On another occasion a small Kater's compass in a
red morocco case was carried off, and never recovered. These birds are,
moreover, quarrelsome and very passionate, tearing up the grass with
their bills in their rage. They are noisy, too, uttering several harsh
cries--one of them like that of the English rook.