½
¼
Circus hudsonius.
Gen. Char. Form very slender, the wings and tail very long, the head small, bill weak, and feet slender. Face surrounded by a ruff of stiff, compact feathers, as in the Owls (nearly obsolete in some species). Bill weak, much compressed; the upper outline of the cere greatly ascending basally, and arched posteriorly, the commissure with a faint lobe; nostril oval, horizontal. Loral bristles fine and elongated, curving upwards, their ends reaching above the top of the cere. Superciliary shield small, but prominent. Tarsus more than twice the middle toe, slender, and with perfect frontal and posterior continuous series of regular transverse scutellæ; toes slender, the outer longer than the inner; claws strongly curved, very acute. Wings very long, the third or fourth quills longest; first shorter than the sixth; outer three to five with inner webs sinuated. Tail very long, about two thirds the wing; rounded.
The relationships of this well-marked genus are, to Accipiter on the one hand, and Elanus on the other; nearest the former, though it is not very intimately allied to either. I cannot admit the subgenera proposed by various authors (see synonomy above), as I consider the characters upon which they are based to be merely of specific importance, scarcely two species being exactly alike in the minute details of their form.
The species are quite numerous, numbering about twenty, of which only about four (including the climatic sub-species, or geographical races) are American. North America possesses but one (C. hudsonius, Linn.), and this, with the C. cinereus, Vieill., of South America, I consider to be a geographical race of C. cyaneus of Europe.
The birds of this genus frequent open, generally marshy, localities, where they course over the meadows, moors, or marshes, with a steady, gliding flight, seldom flapping, in pursuit of their food, which consists mainly of mice, small birds, and reptiles. Their assault upon the latter is sudden and determined, like the “Swift Hawks,” or the species of Accipiter.
In the following synopsis, I include only the three forms of C. cyaneus, giving the characters of the European race along with those of the two American ones.