The Ibises, Spoonbills, Storks, and Herons have long been classed together, though their relations to each other, and to the Phoenicopteri on one side and the Steganopodes on the other, give rise to a great variety of opinions.
All are marsh birds, and resemble Cranes and Limicolae in having lengthened bills, necks, and legs, and all formed, with those types, part of the old order Grallatores or Waders—the Grallae of Linnaeus. But the Ibises, Storks, and Herons differ widely from Cranes, Rails, Plovers, &c. in anatomy and in their young being helpless when hatched. In this respect and in the characters of the palate, the Herodiones resemble the Steganopodes and the Accipitrine birds, to which they are more nearly allied than to the schizognathous Limicolae and Gralae.
In the Herodiones the skull is desmognathous, and basipterygoid processes are wanting. The nostrils are pervious. There are two carotids ; the caeca are rudimentary; the oil-gland is tufted ; and the wing aquincubital. Plantar tendons galline as a rule, but the vinculum in some Herons and Bitterns is weak or absent, so that the flexor longus hallucis passes freely to the hallux, as in Passeres. Other anatomical characters vary in the different suborders. An aftershaft is generally present, but is wanting in some Storks.
The tibia, except in a few Herons, is partially bare, the toes long, the hind-toe well-developed and not raised above the other toes. Almost all the genera make nests of sticks in trees, and the young remain in the nest for a time and are fed by the parents.
The Indian Herodiones may be arranged in three suborders thus distinguished: —
a. Schizorhinal; accessory femoro-caudal present; sternum with four posterior incisions ; syringeal muscles present……………………PLATALEA.
b. Holorhinal; no accessory femoro-caudal ; sternum with two posterior incisions.
a1. No intrinsic muscles to syrinx; dorsal apterium not extending to neck ……………………CICONIAE.
b1. A pair of intrinsic muscles to syrinx : dorsal apterium extending up back of