34 THE GROUSE IN HEALTH AND IN DISEASE 



January it is 23'58 ounces compared to the hen's 21*52 ounces. 

 These may be considered normal averages, the difference at 

 this time of year being dependent wholly upon a sexual 

 difference of size and build, body and bone. In other words, 

 when the birds are all living under healthy conditions, and 

 when the sexual instincts are in abeyance, the hen being less 

 in all her measurements than the cock has a weight corre- 

 spondingly less by 2 or 3 ounces. 



It is, therefore, essential that average weights, to be of use, 

 should include the sexes separately ; and also if the weights 

 be taken in August, September, and October that every bird 

 taken for an average be adult. 



As winter proceeds, we may assume that, unless the weather 

 is unusually open, food becomes less abundant, or, at any rate, 

 less easily obtained and less nutritious ; " the sap goes out of 

 the heather," as it is generally expressed, and there is a large 

 proportion of dry, dark, woody, weather-bitten shoots. 



Data are elsewhere given to prove that the quantity of 

 such food, both by weight and bulk, found in the crops of full- 

 fed birds in winter, is much in excess of what is usually found 

 in the crops of similar birds in summer. In winter, the crops 

 of Grouse often contain five times as much food-stuff as they 

 ever contain in summer. 1 And, although several factors are 

 at work to produce this difference, one of the most important 

 is the necessity of eating a greater bulk of winter heather in 

 order to arrive at the same total of food value. 



It might be expected that the weight of Grouse would suffer 

 from the shortage of nourishment contained in the winter 

 food : but, as a matter of fact, the average weight of both sexes 

 gradually increases during the winter months until March, 

 the worst and most trying month of the whole year for Grouse. 

 February, March, and April must be considered months of greater 

 or less starvation every year, since the winter food has been 

 picked over, not only by the Grouse themselves, but by cattle, 

 sheep, deer, and hares, and often, too, the whole moor has long 



1 Vide chap. iii. Table I. p. 80. 



