166 



NATUEAX HISTOET. 



r 



disposed to make the Pigeon tribe an . order by them- 

 selves. The Pigeons are very remarkable for their mode 

 of feeding their young. The crop is double, forming two 



pouches, one on eithfer side 

 of the gullet, as represent- 

 ed at a and h in Fig. 135. 

 Now, while the bird is in- 

 cubating, a curious change 

 takes place in the crop, and 

 for a special purpose. Ordi- 

 narily it is thin and smooth, 

 as seen at a ; but when the 

 bird is about to have young 

 to care for, the crop be- 

 comes thick and full of lit- 

 tle lumps, as represented at 

 h. These lumps are glands, 

 that have now become en- 

 larged, in order to perform 

 their duty of pouring a 

 milky fluid into the crop. The object of this is to soften 

 the food, so that, when this is done, the bird may throw 

 it up out of the crop and give it to its young. It is sin- 

 gular that the same change takes place in the male bird ; 

 and both parents, therefore, engage in feeding their oif- 

 spring. The most conspicuous varieties of the domestic 

 Pigeons are seen in Fig. 136 (p. 167). That large Pig- 

 eon, the Pouter, is able to inflate its crop with air so as 

 almost to hide its head behind it, and it seems to be quite 

 vain of this accomplishment. 



273. This family are found in almost every part of the 

 globe, and in some they multiply to an enormous extent. 

 The most remarkable in this respect is the Piissfenger 

 Pigeon of this country. " The associated numbers of 

 wild Pigeons," says Nuttal, " are without any other par- 

 allel in the feathered race ; they can, indeed, alone be 

 compared to the shoals of herrings, which, descending 



Fig. 135. — Pigeon's Craw. 



