Description.—Blackish slate-colour; head and wing-feathers black; rump white; tail white, with a broad band occupying the apical half, but leaving the tail end greyish; bill orange, apical half black; feet orange-brown, claws black: whole length 17·0 inches, wings 13·0, tail 7·5. Female similar, but rather larger.
Hab. South America.
This Hawk in size and manner of flight resembles a Buzzard, but in its habits and the form of its slender and very sharply hooked beak it differs widely from that bird. The name of Sociable Marsh-Hawk, which Azara gave to this species, is very appropriate, for they invariably live in flocks of from twenty to a hundred individuals, and migrate and even breed in company. In Buenos Ayres they appear in September and resort to marshes and streams abounding in large water-snails (Ampullaria), on which they feed exclusively. Each bird has a favourite perch or spot of ground to which it carries every snail it captures, and after skilfully extracting the animal with its curiously modified beak, it drops the shell on the mound. When disturbed or persecuted by other birds they utter a peculiar cry, resembling the shrill neighing of a horse. In disposition they are most peaceable, and where they are abundant all other birds soon discover that they are not as other Hawks are and pay no attention to them. When soaring, which is their favourite pastime, the flight is singularly slow, the bird frequently remaining motionless for long intervals in one place; but the expanded tail is all the time twisted about in the most singular manner, moved from side to side, and turned up until its edge is nearly at a right angle with the plane of the body. These tail-movements appear to enable it to remain stationary in the air without the rapid vibratory wing-motions practised by Elanus leucurus and other hovering birds; and I should think that the vertebræ of the tail must have been somewhat modified by such a habit.
Concerning its breeding-habits Mr. Gibson writes:—“In the year 1873 I was so fortunate as to find a breeding colony in one of our largest and deepest swamps. There were probably twenty or thirty nests, placed a few yards apart, in the deepest and most lonely part of the whole ‘cañadon.’ They were slightly built platforms, supported on the rushes and two or three feet above the water, with the cup-shaped hollow lined with pieces of grass and water-rush. The eggs never exceeded three in a nest; the ground-colour generally bluish white, blotched and clouded very irregularly with dull red-brown, the rufous tint sometimes being replaced with ash-grey.”
[308.] SPIZIAPTERYX CIRCUMCINCTUS (Kaup).
(SPOT-WINGED FALCON.)
Falco circumcinctus, Scl. Ibis, 1862, p. 23, pl. ii. Spiziapteryx circumcinctus, Scl. et Salv. Nomencl. p. 122; White, P. Z. S. 1882, p. 623 (Catamarca); Sharpe, Cat. B. i. p. 371. Falco punctipennis, Burm. J. f. O. 1860, p. 242. Hemiiërax circumcinctus, Burm. La-Plata Reise, ii. p. 438.
Description.—Above brown, with black shaft-stripes; head black, with brown stripes and white superciliaries, which join round the nape, forming an ill-defined nuchal band; rump pure white; wings black, with white oval spots on the outer and white bars on the inner webs; tail black, all the lateral rectrices crossed by five or six broad white bars: beneath white, breast regularly striped with narrow black shaft stripes; bill plumbeous, lower mandible yellow, except at the tip; feet greenish, nails black: whole length 11 inches, wing 6·5, tail 5·0. Female similar, but rather larger.
Hab. Argentina.
This small Hawk is sometimes met with in the woods of La Plata, near the river; it is rare, but owing to its curious violent flight, with the short blunt wings rapidly beating all the time, it is very conspicuous in the air and well known to the natives, who call it Rey de los Pajaros (King of the Birds), and entertain a very high opinion of its courage and strength. I have never seen it taking its prey, and do not believe that it ever attempts to capture anything in the air, its short blunt wings and peculiar manner of flight being unsuited for such a purpose. Probably it captures birds by a sudden dash when they mob it on its perch; and I do not know any raptor more persistently run after and mobbed by small birds. I once watched one for upwards of an hour as it sat on a tree attended by a large flock of Guira Cuckoos, all excitedly screaming and bent on dislodging it from its position. So long as they kept away five or six feet from it the Hawk remained motionless, only hissing and snapping occasionally as a warning; but whenever a Cuckoo ventured a little nearer and into the charmed circle, it would make a sudden rapid dash and buffet the intruder violently back to a proper distance, returning afterwards to its own stand.