Bill strong, upper mandible considerably longer than the lower, culmen
much curved, end of bill hooked and its tip perpendicular; basal
portion of bill covered by a membrane or cere, in which the nostrils
are situated; legs large; feet very strong, claws curved and sharp;
general plumage compact; wings long and powerful; tail nearly square,
rarely forked or wedge-shaped.
Suborders.
a1. Claws less curved, that of middle toe describing much less than
a semicircle; outer toe not reversible. ... Accipitres (p. 211)
a2. Claws greatly curved, that of middle toe describing a full
semicircle; outer toe reversible. ... Pandiones (p. 244)
Suborder ACCIPITRES.
This suborder includes all the hawks and eagles except the fish hawks
of the genera Pandion and Polioaëtus; its members are distinguished by
having the outer toe not reversible and all of the claws moderately
curved, that of middle toe describing much less than a semicircle;
concave or under side of each claw hollowed or grooved instead
of rounded.
Family FALCONIDÆ.
Characters same as those given for the Suborder.
Subfamilies.
a1. Tarsus and toes longer and more slender. ... Accipitrinæ (p. 211)
a2. Tarsus and toes shorter and stouter. ... Aquilinæ (p. 222)
Subfamily ACCIPITRINÆ.
In external characters this subfamily differs very little from
Aquilinæ; its members are weaker with body and legs more slender,
wings and tail longer, and plumage less compact.
Genera.
a1. Hinder aspect of tarsus with many hexagonal scales; wing, 300
mm. or more. ... Circus (p. 211)
a2. Hinder aspect of tarsus without hexagonal scales; wing, 200
mm. or less.
b1. Middle toe without claw about twice the culmen from anterior
margin of cere. ... Astur (p. 216)
b2. Middle toe without claw more than twice the culmen from anterior
margin of cere. ... Accipiter (p. 219)
Genus CIRCUS Lacépède, 1799.
Bill moderate or weak, somewhat compressed; margin of upper mandible
slightly sinuate but not toothed; wing very long and pointed, first
primary short, about equal to sixth; secondaries much shorter than
primaries; tail long, slightly graduated or nearly square; tarsus
long and slender, feathered at the base and overhung for about
half its length by the long thigh-feathers; front of tarsus with
transverse plates, sides and most of the hinder aspect with hexagonal
scales; toes long, nails long and much curved; behind ear-coverts and
sometimes across the throat a "ruff" of short, rather stiff feathers,
most conspicuous in the young of melanoleucos and not very evident
in the other species.
The harriers or marsh hawks are noticeable among birds of prey
for their slender form, long slender legs, and slow flight. Adult
birds can be easily identified but the immature specimens present
considerable difficulty.
Species.
(Adult.)
a1. Upper parts black; tail silvery gray; lower breast, abdomen,
and crissum white.
b1. Throat and fore breast white streaked with black. ... spilonotus
(p. 211)
b2. Throat and fore breast black. ... melanoleucos (p. 214)
a2. Upper parts dark brown; tail bluish ash. ... æruginosus (p. 215)
(Immature.)
a1. Facial ruff complete across the throat; smaller, tarsus about 70
mm.; wing, 340 mm. ... melanoleucos (p. 214)
a2. Facial ruff incomplete; tarsus about 90 mm.; wing, 400 mm.
b1. Lighter; general color more rufous-brown. ... spilonotus (p. 212)
b2. Darker; general color more chocolate-brown. ... æruginosus
(p. 215)