THE FOOD OF THE RED GROUSE 111 



its grits, the second bird was not pressed to a similar 

 finish. 



It is therefore probable that in the ordinary course of a 

 Grouse's life the daily loss of small grits is considerable, and 

 that this loss is replaced by an equally regular supply picked up 

 day by day upon the sides of moor roads, or in " scrapes," 

 or along the channel of a burn. 



But, in the event of a heavy snowfall it appears very probable 

 that the Grouse soon recognise that the loss is exceeding the 

 amount which can be made good day by day, and that in such 

 a case they can, in some unexplained way, place a check upon 

 further loss. It cannot for a moment be imagined that the 

 bird has any sort of voluntary control over the passage of grits 

 from the gizzard, But it is quite conceivable that the gizzard 

 itself will allow a certain careless loss of any surplus number, 

 especially of the smaller pieces, so long as there is still a suffi- 

 ciency of larger grits in the gizzard. 



When the supply, however, is straitened, and the bird fails 

 to find more grits to swallow, it may be that less food is eaten 

 as well, and thus the loss of grits is automatically reduced. 

 This is probably the explanation which comes nearest to the 

 truth, and it is a significant fact that a bird not only loses weight, 

 but may actually die when only half of its normal supply of 

 gizzard grits has been lost, and when the dejecta show that this 

 amount of grit is still capable of grinding up the food, given to it. 



Under normal conditions the character of the grit required 

 differs with the nature of the food that is being eaten. Heather, 

 oats, and oat husks are all efficiently dealt with by the quartz 

 grit normally found in a Grouse's gizzard, but large ha*rd seeds 

 are not, and are passed undigested. These seeds are sufficient 

 in themselves to pulp fruits so long as fruits only are being 

 eaten. But as soon as heather or other fibrous vegetable matter 

 is eaten, quartz or other stone grit becomes essential. 



In the Blackcock the gizzard with its quartz pebbles 

 can crush hawthorn pips, but the Grouse apparently cannot 

 crush any of the pips of even much smaller berries, such as 



