[327.] PLEGADIS GUARAUNA (Linn.).
(WHITE-FACED IBIS.)
Plegadis guarauna, Baird, Brew., et Ridgw. Water-B. N. A. i. p. 97. Falcinellus guarauna, Elliot, P. Z. S. 1877, p. 505. Ibis falcinellus, Hudson, P. Z. S. 1870, p. 799 (Buenos Ayres). Falcinellus igneus, Durnford, Ibis, 1877, p. 189 (Buenos Ayres). Plegadis falcinellus, Gibson, Ibis, 1880, p. 155 (Buenos Ayres); Barrows, Auk, 1884, p. 272 (Entrerios). Ibis chalcoptera, Burm. La-Plata Reise, ii. p. 511 (Paraná, Mendoza).
Description.—Head, neck, and under surface purplish chestnut, with a white band round the base of the bill; back with metallic reflexions; wings and tail bright green, with bronzy reflexions; band across upper wing-coverts chestnut; bill reddish grey; feet brown: whole length 22·0 inches, wing 9·0, tail 3·0. Female similar.
Hab. Central and South America.
This form of the well-known “Glossy Ibis” of Europe is one of our most abundant waterfowl on the pampas, and appears in spring in flocks; but as their movements are somewhat irregular and many individuals remain with us through the winter, their migrations probably do not extend very far. In summer they are found beside every marsh and watercourse, briskly wading about in the shallow water and plunging their long curved beaks downwards at every step. When taking wing they invariably utter a loud ha ha ha, resembling hearty human laughter, but somewhat nasal in sound. They frequently leave the marshy places and are seen scattered about the grassy plains, feeding like land-birds; and on the pampas they often congregate about the carcass of a dead horse or cow, to feed on the larvæ of the flesh-fly in company with the Milvago and the Hooded Gull.
Their flight is singularly graceful; and during migration the flocks are seen to follow each other in rapid succession, each flock being usually composed of from fifty to a hundred individuals, sometimes of a much larger number. It is most interesting to watch them at such times, now soaring high in the air, displaying the deep chestnut hue of their breasts, then descending with a graceful curve towards the earth, as if to exhibit the dark metallic green and purple reflexions of their upper plumage. The flock is meanwhile continually changing its form or disposition, as if at the signal of a leader. One moment it spreads out in a long straight line; suddenly the birds scatter in disorder, or throw themselves together like a cloud of Starlings; as suddenly they again reform to continue their journey in the figure of a phalanx, half-moon, or triangle. The fanciful notion can scarcely fail to suggest itself to the spectator that the birds go through these unnecessary evolutions intelligently in order to attain a greater proficiency in them by practice, or, perhaps, merely to make a display of their aerial accomplishments. The Glossy Ibis has another remarkable habit when on the wing. At times the flock appears as if suddenly seized with frenzy or panic, every bird rushing wildly away from its fellows, and descending with a violent zigzag flight; in a few moments the mad fit leaves them, they rise again, reassemble in the air, and resume their journey.
[328.] THERISTICUS CAUDATUS (Bodd.).
(BLACK-FACED IBIS.)
Theristicus melanops, Darwin, Zool. Beagle, iii. p. 128 (Patagonia). Geronticus melanopis, Scl. P. Z. S. 1871, p. 261. Theristicus melanopis, Scl. et Salv. Nomencl. p. 127; Durnford, Ibis, 1877, p. 190 (Buenos Ayres), et 1878, p. 400 (Patagonia); Barrows, Auk, 1884, p. 272 (Azul). Theristicus caudatus, Elliot, P. Z. S. 1877, p. 498. Ibis albicollis, Burm. La-Plata Reise, ii. p. 510 (Paraná, Mendoza, Tucuman).