452 BUSTARDS, THICKNEES, AND CRANES. 
breast-bone by the bases of the metacoracoids, they are distinguished from the 
game-birds. From the rails they may be distinguished by the circumstance that 
when their nostrils are oval (holorhinal) either the number of toes is reduced to 
three, or if four toes are present either the breast-bone has no notch, or the 
oil-gland is naked ; while from both the pigeons and sand-grouse they are separated 
by the upper end of the humerus being of normal form; the condition in which 
the young are born also forming a point of distinction between the former of those 
two groups. Briefly, then, the Alectorides may be approximately defined as 
including those schizognathous birds with active young, 2 in which the humerus has 
no process at the lower end, and the angle of the lower jaw is truncated ; the 
nostrils being either schizorhinal or holorhinal, but, when the latter, either the 
number of the toes is reduced to three, or the sternum is entire, or the oil-gland 
naked; the upper end of the humerus being always of normal form. Such characters 
may seem not only trivial, but in some cases difficult to understand, although, 
when dealing with groups of such nearly allied birds, they are almost the only ones 
available. Like the orders treated in the two preceding chapters, the members 
of this group either have the toes free, or but partially connected by webs. 
The Bustard Tribe. 
Family OlIDIDJE. 
The stoutly built birds known as bustards and floricans agree with the rails 
in having the nasal openings in the skull of an oval shape (holorhinal); but they 
differ in having only three toes to each foot, and likewise in the absence of bare 
tracts in the plumage of the sides of the neck, and of an oil-gland. In their 
skeleton the breast-bone has two notches in its hinder border; and the furcula is 
U-shaped. Externally they are characterised by the relatively short beak, in 
which the oval nostrils are placed near the base, the stout and moderately long 
legs, in which the metatarsus is shorter than the tibia, the long wings, and the 
short tail; the number of primary quills being ten, and that of the tail-feathers 
twelve. They undergo a complete moult in autumn, and often a partial one in 
spring; and the plumage of the two sexes may be nearly similar, or considerably 
different. The bustards are confined to the Old World, where they are represented 
by between thirty and forty species, of which a considerable proportion are natives 
of Africa south of the Sahara. Essentially terrestrial birds, and chiefly in¬ 
habitants of open plains and steppes, the bustards are admirably adapted for 
running and walking, although they are likewise powerful and rapid in flight. 
Their mottled plumage of brown, black, and grey, harmonises with the colora¬ 
tion of their surroundings. In some the food is chiefly vegetable, although supple¬ 
mented by insects and reptiles, but in others it consists mostly of animal matter. 
The True The great bustard (Otis tarda), which formerly inhabited manj^ 
Bustards. 0 f t,] ie wilder, open districts of Britain in large flocks, is the type of 
a genus which may be taken to include two species, and is characterised by the 
shortness of the beak and the absence of a crest on the head. The legs are 
1 In tlie sun-bittern the young are helpless, while those of the kagu are unknown. 
