xii Preface 



SHELTER 



Fundamental to the environment that supports grouse is the 

 vegetation that provides its home. Shelter includes the trees, shrubs, 

 and herbs that compose the crown cover, imdergrowth, and ground 

 cover as well as the surface litter on the ground, and occasionally 

 boulders, ground holes, and other protective materials. For the 

 grouse, the evergreen conifers and broad-leaved trees and shrubs 

 are important shelter, especially in the winter. Brush piles, fallen 

 tree tops, and deep snow also furnish important winter protection. 

 In the summer the leaf litter and vine and brier tangles are important 

 shelter. Shelter must furnish not only protection from the elements 

 and from mortal enemies, but the medium for all of life's functions 

 including nesting, coiui;ing, sunning and dusting. 



FOOD 



Probably the most obvious factor affecting abundance is the food 

 supply— an ample supply for good health at all seasons of the year. 

 Water and grit requirements are a part of this factor. With the 

 grouse, food as an independent factor is not often as limiting in 

 effect as it is with many animals. Cover which furnishes adequate 

 shelter usually possesses considerable numbers of grouse food plants. 

 But the distribution and quality of grouse foods has a vital bearing 

 on the distribution of the birds, even though grouse rarely succumb 

 directly from diet deficiencies. 



The cover which furnishes both shelter and food for grouse is 

 termed the habitat, and is the foundation of the environment. 



PREDATORS AND OTHER ANIMALS 



Those creatures other than man that utilize the grouse for 

 food are its predators. Primarily mammals and birds, they are the 

 most common immediate cause of death for adult grouse. However, 

 in considering the importance of the predators and other animals in 

 determining grouse abundance, the correlation with other factors 

 must also be considered. Most of the other factors of abundance are 

 closely associated with predation. The snow that makes the roosting 

 grouse vulnerable for attack, the parasite that weakens its flight, 



