FAMILY COLUMBID^E, OR PIGEONS. 



475 



respects from the general type of the Rasores, and approaches to 

 the Perching Birds.* The bill is formed upon the plan of that 

 of the Gallinaceae ; but the wings, feet, and tail more resemble 

 those of the Insessores ; and they live more among trees than upon 

 the ground. They associate invariably in pairs ; their nests are 

 constructed in trees, or in the holes of rocks ; and both parents sit 

 upon the eggs. The Pigeons are also remarkable for the peculiar 

 mode in which the young are fed. The crop, instead of being 

 an expansion of the oesophagus on the right side only, as in other 

 Birds, is double; and its walls are furnished with numerous 

 glands, which become developed in both sexes during the period 

 of incubation. These glands secrete a sort of milky substance, with 

 which the food that passes into the crop is moistened ; and the 

 food, saturated with this secretion, is disgorged by the parents 

 for the nourishment of their young. In Fig. 269 is represented 

 the double craw of the Pigeon; 

 one side (a) exhibiting its usual 

 aspect, and the other side (b) 

 showing its appearance in 

 Pigeons which have newly- 

 hatched young. The true 

 Pigeons are found in most parts 

 of the "World ; and in some they 

 multiply to an enormous extent. 

 In Britain there are four native 

 species : the Ring-Dove, Cushat, 

 or Wood-Pigeon, which is the 

 largest of these ; the Rock- 

 Pigeon, which is the original of 

 all our domesticated breeds; 

 the Stock-Dove, which, like the 

 Ring-Dove, chiefly frequents 

 coppices and groves ; and the 

 Turtle-Dove, which is the smallest, the most elegantly formed, 

 and the most beautifully coloured. Among the Pigeons of other 



* It is now generally regarded as forming a distinct order, that of the Co- 

 LTTMBJE, intermediate between the Rasorial and Perching Birds. 



Pro. 26&*-PiGJEON'8 CRAW. 



