394 BRITISH BIRDS. 
Family COLUMBIDA, or PIGEONS. 
The Pigeons are a large and well-defined group of birds which are some- 
what isolated. Sclater and Gadow regard them as allied to the Gallina- 
ceous birds through the Sand-Grouse ; but Forbes traced their relationship 
through the Sand-Grouse and Pratincoles to the Plovers. The sternum of 
the Pigeons resembles in many respects that of the Game Birds. There 
are two notches on each side of the posterior margin of the sternum ; but 
the internal pair are small and generally closed at the entrance (the gulf 
thus becoming a lake), and the external pair are very deep and wide. The 
cranial bones of the Pigeons present a moditication different from that to 
be found in any family of which we have hitherto treated. The Pigeons 
are said by Huxley to be schizognathous, like the Game Birds, Sandpipers, 
Gulls, Auks, &c. (Gadow, however, assures me that many species of Birds 
of Prey and Owls are also schizognathous). In their pterylosis the 
Pigeons partake of the characters of both the Sandpipers and some of the 
Game Birds, which latter family they also somewhat resemble in their 
digestive organs, and still more closely in their myology. 
In spite of what has been written by Naumann, Meves, and others on 
this subject, there can be no doubt that, in a wild state, Pigeons moult 
twice in the year, in spring and autumn, as carefully dated specimens 
in my own collection abundantly prove. Young Pigeons are covered 
with yellow down when they are first hatched, but are born blind. 
The most striking external character of the Pigeons is the bill, which 
is thinnest in the middle, expanding towards the poimt, as in the 
Plovers; the basal portion is covered by a soft skin, in which the nostrils 
are situated. The hind toe and claw are small, as in Picarian birds. 
The Pigeons are divided into several subfamilies, which show considerable 
modification both of the wings and tail. The number of primaries in the 
former is ten, but the feathers in the latter vary considerably in this 
respect. 
The number of species of Pigeons probably exceeds 350, which are dis- 
tributed all over the world, except in the Arctic regions. They are rarest 
in the Palearctic and Nearctic Regions, and most abundant in Australia. 
