SCRATCHING BIRDS. 165 
This digestive apparatus, described in Chapter XIL., is 
seen very completely developed in the birds of this order. 
270. Most of the Scratchers do not associate in pairs. 
The male birds have nothing to do with taking care of 
the young, which are hatched with their eyes open, and 
are generally able to run about at once in search of food, 
instead of being dependent for some time on the parent 
for their supply. They can, for the most part, be domes- 
ticated, and they are the most useful to man of all the 
birds, affording him quite a large portion of his food. 
The plumage of the male birds is usually gay, and they 
often have crests or some other ornaments on the head. 
The females commonly differ from the males in a marked 
manner in these respects. 
271. There is a striking analogy between these birds 
and the Ruminant Quadrupeds in several points. In 
both the food is vegetable, and in both there is a special 
provision for breaking it up and moistening it, so that 
the gastric juice may readily act upon it. The crop in 
the fowl answers to the paunch in the Ruminant, and the 
crushing by the gizzard to the grinding in rumination, 
each following the maceration. Then, too, these birds 
and the Ruminants are both, for the most part, easily do- 
mesticated, and domestication produces in both great va- 
riety in breeds. There are seven families: 1. The Pigeon 
family. 2.The Curassows. 3. The Pheasants. 4. The 
Grouse. 5. The Sheath-bills. 6. The Tinamous family. 
7. The Greatfoots. 
272. The family of Pigeons includes both those birds 
called by this name and those which are called Doves. 
These birds differ from those of the other families of this 
order in pairing; in living on trees, and, much of the time, 
on the wing, for which they are adapted by the large 
size of the wing-muscles ; and in having the hinder toe on 
a level with the others, as in the Perchers, instead of be- 
ing above them, as we see it in the common fowl and in 
all the other families. On these accounts some have been 
