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.
Characters same as those given for the Suborder.
a1. Tarsus and toes longer and more slender. ... Accipitrinæ (p. 211) a2. Tarsus and toes shorter and stouter. ... Aquilinæ (p. 222)
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.
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)
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.
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)