The Sand-Grouse, or Pigeon-Grouse as they were appropriately called by Huxley, form a well-marked and distinct group that has been referred by turns to the Columba; and to the Gallinae; but since Huxley (P. Z. S. 1868, p. 302) showed how completely intermediate between the two the Pteroclidae are, they have generally been classed in a separate order. They - are birds of a yellowish-brown or buff colour as a rule, with somewhat the build of Pigeons and even swifter flight, but with very different bills and feet; the bill, though of small size, resembling that of the Gallinae. The characters of the young are quite Galline. Some are migratory, others resident.
In the bill there is no soft base to the upper mandible. The toes are generally four in number, but the hallux is small, and in one genus wanting; all are on the same level; the anterior toes are short and rather broad. Oil-gland present and nude. The contour-feathers have aftershafts. The lateral bare tracts only extend on the shoulders to the base of the neck, not on to it; the dorsal feather-tract has an interscapular fork. Primaries 11, fifth secondary wanting. Tail-feathers 14 to 10.
Palate schizognathous ; basipterygoid processes present. Cervical vertebras 15 or 10. There are usually two notches on each side of the posterior margin of the sternum, but the inner notch is sometimes reduced to a foramen ; keel of sternum very high.
Deep plantar tendons Galline. Ambiens muscle present; other muscles of thigh as in Columba;. Caeca present and large. Gall- . bladder present, and two carotids.
Sand-Grouse live on hard seeds, and are, so far as is known, monogamous. They lay three eggs on the ground, generally without a vestige of nest. The eggs are peculiarly shaped, simply oval, nearly a prolate spheroid, equally rounded at both ends, grey or reddish grey and double-spotted. The young are covered with down, richly marked, and they are able to run on leaving the egg.