94 APPENDIX F 



It appears from the experiment that when a Grouse is fully supplied with 

 food and grit, much grit is picked up, and much is passed through the bird 

 each day. The ejected grit consists chiefly of the smaller pieces and of the 

 sand which have been formed partly from the rubbing together of the smaller 

 sharp, edged bits. 



If, however, whilst maintaining the same food supply, the grit is 

 suddenly cut off, the gizzard, having no more small pieces and no more sand 

 to pass, will not, on that account, allow the larger pieces to pass. These are 

 retained, and it is only by an accidental passage through the sphincter of the 

 gizzard that a few particles of grits of any size can make their appearance in 

 the intestine lower down, and eventually in the excreta. 



Larger and rather smoother grits are required for permanent use, and these 

 are evidently retained and used for a long period ; hence the smooth, worn, 

 and comparatively big grits in the gizzard of an old Grouse. Smaller, 

 rougher grits are required for immediate use, and are constantly being 

 swallowed, and as constantly passing through, and being replaced by a fresh supply. 



After a snowfall, when all but the roughest and most woody foods are 

 buried out of sight, and no grits can be obtained, the Grouse must starve 

 to some extent, for it is quite conceivable that without the sharp edges of 

 the smaller freshly collected grits the rounder sides of the older and larger 

 grits make but little impression upon the woody fibres of old, dry heather 

 such as alone remains exposed after a heavy snowfall. This is the time 

 when a clearance or two here and there to expose a roadside "scrape" or 

 gravelly bank will make a great difference to the conditions of life for the 

 Grouse. Given grit they can manage to subsist on poor food, but given 

 no grit they will wander in search of it and starve if they do not find either 

 more grit or much softer food. 



Several questions remain still to be answered in this connection, owing to 

 the fact that the two birds experimented upon refused to eat berries with hard 

 Marked seeds, and also refused to eat grits which could be recognised afterwards 

 grits. such as garnets. Samples of these stones were counted and then 

 thrown in amongst the food ; but they were never taken as grits. It is hard to 

 say why they should have been refused, for they were small, and hard and rough 

 and of the same character as the ordinary quartz eaten by the Grouse in nature. 

 The colour alone differed ; but the colour of grits in a Grouse's gizzard varies 

 sufficiently to show that this could not have been the reason for their rejection. 



