36 THE GROUSE IN HEALTH AND IN DISEASE 



to be considered the most dangerous month of the whole year 

 for infection with Strongylosis. 



As the hen sits, her weight, even in health, rapidly diminishes. 

 She is living largely upon her reserve material, and has, in 

 addition to produce from eight to ten eggs. This must be a 

 considerable drain upon her system, since each egg weighs 

 about an ounce, and each ounce so lost to her is an ounce of 

 her " flesh and blood," the whole amounting sometimes to nearly 

 half her eventual total weight. By the end of June, thanks 

 also to the trials of a family, she reaches an average weight of 

 less than 20 ounces, and by the end of July sometimes falls to 

 19 '5 ounces, whereas the cock, benefiting daily by the improv- 

 ing food and weather, gradually rises from 19 or 20 ounces 

 in March to an average of 24 ounces in August. 1 



It will perhaps throw light on the cause of the marked 

 changes which appear in the Table if an attempt is made to 

 account for them month by month. 



The sudden drop in the weight of the cock in February 

 and March, for example, must be due to courtship rather than 

 to shortage of food, for though food is scarce at this time the 

 shortage makes no difference worth noticing in the case of the 

 hens. This argument is borne out by the almost equally sudden 

 rise as soon as the mating is over. 



The post-nuptial moult in the male takes place in April and 

 May. It is complete in June, therefore any loss of weight in the 

 replacing of new feathers would make itself felt in the earlier 

 of these three months. From April to August the food supply 

 is improving daily, and the weight of the cock Grouse gradually 

 increases. And it is by no means easy to see why there should 

 be a sudden drop in September unless it is due to the complete 

 (male) moult to the winter plumage. As there is no correspond- 

 ing drop in the hen, and, as we know, no similar moult, we are 

 probably right in thus attributing the September fall in the 

 weight of the male to this autumn moult. 2 



In June the hen undergoes a complete post-nuptial moult, 



1 Vide p. 33. 2 See chap. ii. pp. 42 el seq. 



