_Polyborus_, VIEILL. 1816. (Type, _Falco brasiliensis_, GMELIN. _P.
tharus_, MOLINA.)
_Caracara_, CUVIER, 1817. (Same type.)
GEN. CHAR. General aspect somewhat vulturine, but bearing and manners
almost gallinaceous. Neck and legs very long. Bill very high and much
compressed, the commissure very straight and regular, and nearly
parallel with the superior outline; cere very narrow, its anterior
outline vertical and straight. Nostril very small, linear, obliquely
vertical, its upper end being the posterior one; situated in the upper
anterior corner of the cere. Lateral and under portions of the head
naked and scantily haired, the skin bright-colored (reddish or yellow
in life). Occipital feathers elongated. Wings and tail long, the
latter rounded; five outer quills with inner webs sinuated; third to
the fourth longest; first shorter than the sixth, sometimes shorter
than the seventh. Feet almost gallinaceous, the tarsus nearly twice as
long as the middle toe, but stout; outer toe longer than the inner;
posterior toe much the shortest; claws long, but slender, weakly curved,
and obtuse. Tarsus with a frontal series of large transverse scutellæ,
the lower fourth to sixth forming a single row, the others disposed in
two parallel series of alternating plates; the other parts covered by
smaller hexagonal scales.
[Illustration:
=37871=, ♀. NAT. SIZE.
=37871=, ♀. ¼
=37871=, ♀. ¼
=37871=, ♀. ¼
_Wing and tail._
_Polyborus auduboni._]
This well-marked genus contains but a single species, the _P. tharus_,
Mol., which extends its range over the whole of tropical and subtropical
America, exclusive of some of the West India Islands. North and south
of the Isthmus it is modified into geographical races, the southern of
which is var. _tharus_, Mol., and the northern var. _auduboni_, Cass.
The closely related genera _Phalcobænas_, _Milvago_, _Ibycter_, and
_Daptrius_ are peculiar to South America and the southern portion of
Middle America, most of them being represented by two or more species.
They all form a well-marked and peculiarly American group, for which I
shall retain Schlegel’s term _Polybori_.
Their habits are quite different in many respects from those of other
_Falconidæ_, for they combine in many respects the habits of the
gallinaceous birds and those of the Vultures. They are terrestrial,
running and walking gracefully, with the exception of the species of
_Ibycter_ and _Daptrius_, which are more arboreal than the others, and
are said also to feed chiefly upon insects, instead of carrion.
Species and Races.
=P. tharus.= Wing, 14.50–17.70; tail, 10.00–11.00; culmen, 1.20–1.48;
tarsus, 3.20–4.20; middle toe, 1.75–2.30.
_Adult._ Forehead, crown, occiput, back, rump, abdomen, sides, and
tibiæ, and terminal zone of the tail, dull black. Neck, breast,
tail-coverts, and tail, dingy whitish. Interscapulars, breast, and
tail with transverse dusky bars.
_Young._ Blackish areas replaced by dull brown; region of the
transverse bars marked, instead, with longitudinal stripes.
_Adult._ Whole body, with middle wing-coverts, variegated with
transverse bars of black and white; tail-coverts barred. Terminal
zone of the tail about 2.00 wide. _Young._ Longitudinal stripes over
the whole head and body, except throat, cheeks, and tail-coverts;
tail-coverts transversely barred. _Hab._ South America …
var. _tharus_.[67]
_Adult._ Transverse bars confined to the breast and interscapulars;
rest of body continuous black; tail-coverts without bars;
wing-coverts unvariegated. Terminal zone of tail about 2.50
wide. _Young._ Longitudinal stripes confined to the breast and
interscapulars; rest of the body continuous brown. Tail-coverts
without bars. _Hab._ Middle America, and southern border of United
States, from Florida to Cape St. Lucas …
var. _auduboni_.
Polyborus tharus, var. auduboni, CASSIN.