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POPULAR HISTOHY OV BIEDS. 
Order COLUMB^. The Pigeons. 
This order contains but one family^ the Columbid^^ or 
Pigeons; — an extensive group, very generally distributed 
over the world, and containing species some nearly as 
large as the turkey, while others are not much larger than 
a sparrow. They are all characterized by their vaulted 
beak, the nostrils being placed in a membranous space 
and covered with a cartilaginous scale. The crop is very 
large, and expands on each side of the oesophagus, — a 
peculiarity in this order of birds ; it is in the crop that the 
food is elaborated before it is conveyed to the young, and 
mixed with a milk-like secretion, which flows from its inner 
surface only during the incubation of the young; the giz- 
zard, as in the birds of the next order, is very muscular ; the 
feet have four toes, three in front, divided to the base, and 
one behind, which springs from the bottom of the tarsus, 
at the same level with the other toes, and takes a firm 
grasp of the branch in perching ; the wings are strong and 
concave, and the tail consists of twelve feathers. These 
birds differ widely from the GallincBj with which they have 
