CHAR. Eyes directed laterally, and eyelids provided with lashes. Toes
invariably naked, and tarsus usually naked and scutellate (feathered
only in _Aquila_ and _Archibuteo_). Outer toe not reversible (except in
_Pandion_). Head never with ear-tufts, and never wholly naked (except in
the _Vulturinæ_, of the Old World).
The above characters are about the only readily observable points in the
external anatomy in which the _Falconidæ_ differ strikingly from the
_Strigidæ_ and _Cathartidæ_, and may serve to distinguish the birds of
this family from those of the two others. The osteological characters,
however, as expressed on page 1328, are more decided and important in
a taxonomic point of view, and serve to separate the Hawk family as a
well-defined group.
In the following treatment of the North American _Falconidæ_, I confine
that part relating to the systematic arrangement strictly to the species
embraced within the province of our work, for the reason that in a
forthcoming monograph of all the American species I hope to present a
systematic classification based upon the species of the whole world.
All preliminary details regarding the general characteristics and
distinctive peculiarities of the family, as well as all discussions and
generalizations upon the subject, will therefore be omitted here.
The following synopsis of the North American genera is intended as an
artificial arrangement which may enable the student to identify, by
simple and readily understood characters, the forms belonging to this
country.[40]
Genera.
=A.= Nasal bones almost completely ossified, the nostril being a small
orifice, with a conspicuous central bony tubercle; its form nearly or
quite circular, or linear and oblique (in Polyborus), with its upper
end the posterior one …
_Falconinæ._
1. =Falco.= Nostril circular. Commissure with a prominent tooth
and notch; lower mandible abruptly truncated and notched.
Primaries stiff and hard, and more or less pointed, the first to
the second longest, and the outer one or two with their inner
webs cut, the angular emargination being near the end of the
quill. Middle toe much more than half as long as the tarsus;
claws strongly curved, very acute.
2. =Polyborus.= Nostril linear, oblique, the upper end the
posterior one; commissure without prominent tooth nor notch;
lower mandible not distinctly truncated or notched. Primaries
soft, obtuse, the third longest, and the outer four or five with
their inner webs cut, the shallow sinuation being toward the
middle of the quill. Middle toe less than half the tarsus; claws
weakly curved, very obtuse. Face and cheeks naked, and scantily
haired.
=B.= Nasal bones very incompletely ossified, the nostril being a
large, more or less oval, opening, of oblique direction, its lower end
being invariably the posterior one; without a bony tubercle, and never
perfectly circular. (_Accipitrinæ._)
_a._ Sides of the head densely feathered close up to the eyelids.
3. =Pandion.= Outer toe reversible; claws contracted and
rounded on their under surface, and not graduated in size.[41]
Wing long, third quill longest; outer four with inner webs
emarginated. Tail rather short, rounded.
4. =Nauclerus.= Outer toe not reversible; claws not contracted
or rounded on under side, and graduated in size. Wing long,
third quill longest; outer two with inner webs sinuated. Tail
excessively lengthened and forked, the lateral pair of feathers
more than twice as long as the middle pair.
_b._ Sides of the head with a more scantily feathered orbital space,
with a projecting superciliary “shield” covered with a naked skin.
* A well-developed membrane, or “web,” between the outer and
middle toes at the base.
† Tarsus about equal to the middle toe.
§ Claws short and robust; two outer quills with their inner webs
cut.
5. =Ictinia.= Commissure irregularly toothed and notched; front
of tarsus with transverse scutellæ. Tail emarginated; third
quill longest.
6. =Elanus.= Commissure without irregularities; front of tarsus
with minute roundish scales. Tail double-rounded; second quill
longest.
§§ Claws long and slender; five outer quills with inner webs cut.
7. =Rostrhamus.= End of bill bent downward, with a long pendent
hook; inner edge of middle claw slightly pectinated, or
serrated. Tail emarginated; third or fourth quill longest.
†† Tarsus very much longer than the middle toe.
¶ Front of tarsus unfeathered, and, with the posterior face,
covered with a continuous series of broad transverse scutellæ.
α. Form very long and slender, the head small, the tail and legs
long and claws excessively acute; bill weak, compressed, very
high through the base, the culmen greatly ascending basally, and
the cere much arched; commissure usually with a very prominent
“festoon.”
8. =Circus.= Face surrounded by a “ruff” of stiffened,
differently formed feathers, as in the Owls. Tarsus more than
twice as long as the middle toe. Wing very long, hardly concave
beneath; third to fourth quill longest; outer four with inner
webs sinuated.
9. =Nisus.= Face not surrounded by a ruff. Tarsus less than
twice as long as the middle toe. Wing short, very concave
beneath, the outer quill much bowed; third to fifth quills
longest; outer five with inner webs sinuated.
β. Form short and heavy, the head larger, the tail shorter, the
legs more robust. Bill stronger, less compressed, lower through
the base, the upper outline less ascending basally, and the cere
less arched. Commissure variable.
10. =Antenor.= Form heavy, the wings and tail moderately long,
and feet very robust; bill rather elongated, the commissural
lobe prominent, and the base of the culmen somewhat depressed.
Fourth quill longest; outer five with inner webs cut. Lores
naked, and almost destitute of bristles.
11. =Onychotes.= Outstretched feet reaching beyond end of tail;
tibial plumes short, close, not reaching below the joint. Wing
short, rounded, very concave beneath, the fourth quill longest;
outer five with inner webs sinuated. Tail short, but little
more than half the wing, slightly rounded. Claws very long, and
extremely acute.
12. =Asturina.= Bill and feet as in _Antenor_; lores densely
bristled; wing short, rounded, concave beneath, the third to
fourth quills longest; outer four with their inner webs cut.
13. =Buteo.= Form of _Antenor_, but primaries longer and more
pointed, the fourth usually longest, and the outer three or
four with inner webs cut. Bill and feet as in _Asturina_. Tail
moderate, or rather short, nearly even, or slightly rounded.
¶¶ Front of the tarsus densely feathered down to the base of the
toes.
14. =Archibuteo.= Feathering of the tarsus interrupted behind by
a bare strip along the full length; middle toe less than half as
long as the tarsus. Nostril broadly oval, obliquely horizontal;
bill weak, the upper outline of the cere much ascending basally.
Feathers of the nape normal, blended. Third to fourth quills
longest; outer four or five with inner webs cut.
15. =Aquila.= Feathering of the tarsus uninterrupted behind;
middle toe more than half as long as the tarsus. Nostril
narrowly oval, obliquely vertical; bill strong, the upper
outline of the cere nearly parallel with the lower. Feathers of
the nape lanceolate, distinct. Fourth quill longest; five to six
with inner webs cut.
** No trace of membrane between outer and middle toes.
16. =Haliætus.= Tarsus feathered in front one third, or more, of
the way down; the naked portion with an imperfectly continuous
frontal, and less well defined posterior, series of transverse
plates, and covered elsewhere with roundish granular scales.
Feathers of the neck, all round, lanceolate, distinct. Bill very
large, the chord of the culmen more than twice as long as the
cere on top; nostril oval, obliquely vertical. Third to fifth
quills longest; outer six with inner webs cut. Tail rounded or
cuneate, sometimes consisting of fourteen feathers.
The foregoing diagnoses embrace merely the more conspicuous external
characters whereby the genera may be most readily distinguished by
the student. The following table presents additional accompanying
characters afforded by the osteological and anatomical structure, of
more importance in defining with precision the several groups embraced
in our fauna.
=A.= Scapular process of the coracoid produced forward so as to meet
the clavicle[42] (HUXLEY). Nasal bones almost completely ossified,
the nostril being a small, usually circular opening, with a raised
or “rimmed” margin, and conspicuous, usually central, bony tubercle.
Inferior surface of the supermaxillary bone with a prominent median
angular ridge. Superciliary process of the lachrymal consisting of a
single piece. (_Falconinæ._[43])
=B.= Scapular process of the coracoid not produced forward so as
to meet the clavicle (HUXLEY). Nasal bones incompletely ossified,
the nostrils being very large, and without bony rim or tubercle.
Inferior surface of the supramaxillary bone without a median ridge.
Superciliary process of the lachrymal variable. (_Accipitrinæ._)
_a._ Superciliary process of the lachrymal composed of a single,
excessively abbreviated piece;[44] posterior margin of the sternum
with a pair of indentations, and without foramina. (_Pandion_ and
_Nauclerus_.)
_b._ Superciliary process of the lachrymal double, or composed
of two pieces, joined by a cartilaginous “hinge,” and reaching
nearly across the orbit. Posterior margin of the sternum without
indentations, and usually with a pair of foramina. (All except
_Pandion_ and _Nauclerus_.)
† Septum of the orbits and nostrils incompletely ossified (the
former always and the latter usually) and with foramina; posterior
margin of the sternum most produced backwards laterally, and
incompletely ossified, there being usually a pair of foramina.
Intestinal canal short, broad, with the duodenum simple, forming a
single loop (MCGILLVRAY). A well-developed “web” between the outer
and middle toes. (All but _Haliætus_.)
†† Septum of the orbits and nostrils completely ossified, and
without any trace of foramina; posterior margin of the sternum
produced medially into a convex lobe, and without any trace of
foramina. Intestinal canal extremely elongated, attenuated, with
the duodenum arranged in several convolutions (MCGILLVRAY). No
trace of a web between outer and middle toes. (_Haliætus._)