184 



DOMESTIC PIGEONS 



Chap. V. 



As faucy pigeons are general!." confined in aviaries of moderate 

 size, and as even when not confined they do not search for their own 

 food, they must during many generations have used their wings 

 incomparably less than the wild rock-pigeon. Hence it seemed to 

 me probable that all the parts of the skeleton subservient to flight 

 would be found to be reduced in size. With respect to the sternum, 

 I have carefully m.easured its extreme length in twelve birds of 

 different breeds, and in two wild rock-pigeons from the Shetland 

 Islands. For the proportional comjiarison I have tried three 

 standards of measiirement, with all twelve birds namely, the length 

 from the base of the beak to the oil-gland, to the end of the tail, 

 and from the extreme tip to tip of wings. The result has been in 

 each case nearly the same, the sternum being invariably found to 

 be shorter than in the wild rock-pigeon. I will give only a single 

 table, as calculated by the standard from the base of the beak to 

 the oil-gland ; for the result in this case is nearly the mean between 

 the results obtained by the two other standards. 



Length of Sternum. 



This table shows that in these twelve breeds the sternum is of 

 an average one-third of an inch (exactly "332) shorter than in the 

 rock-pigeon, proportionally with the size of their bodies ; so that 

 the sternum has been reduced by between one-seventh and one- 

 eighth of its entire length ; and this is a considerable reduction. 



I have also measured in twenty-one birds, including the above 

 dozen, the prominence of the crest of the sternum relatively to its 

 length, independently of the size of the body. In two of the twenty- 

 one birds the crest was prominent in the same relative degree as 

 in the rock-pigeon; in seven it was more prominent; but in five 

 out of these seven, namely, in a Fantail, two Scanderoons, and two 

 English Carriers, this greater prominence may to a certain extent 

 be explained, as a prominent breast is admired and selected by 

 fanciers; in the remaining twelve birds the prominence was less. 

 Hence it follows that the crest exhibits a slight, though uncertain, 

 tendency to be reduced in prominence in a greater degree than does 

 the length of the sternum relatively to the size of body, in comparison 

 with the rock-pigeon. 



I have measured the length of the scapula in nine different large 



