240 



FOOD HABITS AND REQUIREMENTS 



and for tertain factors of the \ itarain B loinplex to be greater than that required hy domestic 

 fowl. Their vitamin G requirement, likewise, was found to be from two to two and one- 

 half times greater than that of white leghorn chicks. That such is the case for grouse does 

 not necessarily follow, but a possibility is here indicated that awaits further investigation. 

 Such is the general picture derived from the chemical analyses of a food item. 



Differences in Chemical Composition 



There are other equally important questions that might well be raised. One of them con- 

 cerns the individual variation in these chemical components within the plant species that 

 supply the food. As has already been pointed out. the character of the soil on which they 

 grow plays an important part in determining the inorganic content of a plant. 



2 TOP OF TREE 



*" NORTH SIDE 



U. BOTTOM 



^ SOUTH SIDE 



U) BOTTOM 



t YOUNG SPROUTS 



it IN THE SUN 



WMmmmmmmimmMM 



IJaisJisiiiSiSJiMiSJi^iP " 





^E 



mmmmMm,m. 



30 40 50 60 70 



PERCENT OF COMPOSITION 



MINERAL [—1 CRUDE I 1 



MATTER L_J PROTEIN I 1 



CRUDE 

 FAT 



NITROGEN-FREE 

 EXTRACT 



□ ?' 



CRUDE 

 IBER 



FIGURE 20. DIFFERENCES IN COMPOSITION OF YELLOW BIRCH BIDS WITH RESPECT TO THE 

 AGE OF THE TREE AND THE P.ART FROM WHICH THEY WERE COLLECTED 



Likewise there are substantial differences in composition between buds gathered from the 

 shady as <()mpared with the sunlit parts of the tree. Results of the analyses of yellow birch 

 buds taken from the top. the bottom on the north and on the south sides (all on the same 

 tree) and from young sprouts of the same species gathered close by, are shown in figure 20. 

 These examinations were made from material collected on April 6. 1942. 



Crousf are in great need of nutritive constituents in their food that produce heat and energy 

 (luring the colder parts of the year. It is fascinating, then, to tind that the highly digestible 

 carbohydrates that make up the nitrogen-free extract are somewhat greater in buds collected 

 from sunn\ than from sha(l\ locations. Investigations by Gauman' " ha\e shown conclusively 

 that this (ondition prevails throughout the year in tlic KurojH-an beech I Fapii.s sylvatica). 

 Twig tips and terminal buds contain higher amounts of carbohydrates than do the branches 

 and axial buds nearer the trunk. Those on the top of the tree ha\e the highest concentration 

 (pf all. Here may be a likeK reason win grouse and deer feed on the buds from the top of 

 ihc tn-i- when a\ailablc rather than fmrn the sliadcd >ide branches. 



F'ast growing sprouts, too, may differ from their slower growing companions as indicaled 

 in table 172. Great variations are also apparent in the amount of crude protein, the buds 

 from the bottom of the tree on both sides containing considerably more than those fnmi the 

 top or fniin \oung sprouts. Seasonal differences, loo. have been noted. All such factors 

 must, of (durse. be considered, in interpreting the residts of chemical anaKses of grouse 

 foods. 



This. then, is a broad outline of the pirliin- that i> jii.-t beginning to take shajie. A large 

 number of grouse foods still remain to be analyzed. The significance of changes in plant 



