66 THE GKOUSE IN HEALTH AND IN DISEASE 



holding the tip of the lower bill only. The bone of an old bird's jaw easily 



Lower stands this test, but the soft jaw of a young bird of three or four 



months cannot carry its weight, and the jaw either bends or breaks. 



Yet another test often used is that of trying to crush in the skull with the 

 finger and thumb ; in the young bird the soft skull gives way readily, 

 in the old bird it requires very considerable force. 



In judging at a moment's notice whether a young Grouse chick which rises 

 to the dogs on the 12th is of a shootable age and growth or not, the usual 

 Tail rule is probably as good a one as can be found namely, that there 



feathers, should be a very clear view of black tail feathers before the young 

 bird is fit to kill. 



It is only necessary, however, to look at a few young Grouse chicks of 

 various ages to be convinced that more than a little of the black rectrices should 

 appear before the bird is shot. Probably most sportsmen will be guided better 

 by the strength of the bird upon the wing than by the black tail feathers, 

 however clearly visible in a half-grown chick. 



In dissection, the age of an old bird is apparent, perhaps as plainly 

 upon the table as elsewhere. The fibrous tissues all toughen with age 

 and use, and the bones become harder. The grits of the gizzard in an old bird 

 seem to be larger and more worn into rounded pebble shapes, the reason for 

 this has been discussed elsewhere. 1 The question, therefore, of deciding whether 

 a bird is less than a year or more than a year old, is possible, but it seems 

 almost impossible to judge more exactly of the age of an older bird by any 

 sign to be discovered either externally or internally. 



1 Vide chap. iv. p. 95. 



