CHAPTER XII 



PRODUCTIVITY OF GROUSE POPULATIONS 



By Robert W. Darrow 



POPULATION CHARACTERISTICS 



Composition — According to Age — Sex Ratios — Grouse Densities — Nest Densities 

 — Brood Densities — Adult Densities — Sati RATION Point — Rate of Spread — Car- 

 rying Capacity 



PRODUCTIVITY OF POPULATIONS 



Breeding Success — Survival During E\cn Life Period — Nest Period — Brood 

 Period — Adult Period — Net Productivity — Life Equations 



THE BIOLOGICAL BALANCE SHEET 



& 



SUMMARY 



In the same way that individual grouse exhii>it certain peculiarities of l)eha\icir sn also do 

 grouse populations have characteristic reactions to various influences and circumstances, 

 (p. 513). 



Grouse productivity is the result of a continual tug-of-war between the forces tending to 

 increase the population and those tending to rcdiici' it. I p. 551). 



The factors of increase include primarily the various components of the reproductive poten- 

 tial of the species. Factors such as shelter, food and weather fall in this category only 

 insofar as they are favorable. I p. 551 I. 



Decimating factors include predalion, disease, hunting and accidents, (p. 551 I. 



When one limiting factor (such as predation) is eliminated, others tend to take its 

 ]>lace. ( p. 552 ) . 



It is jjrobably the cumulative effect of a number of small factors becoming active at the same 

 time, rather than any one of them alone, that most often causes marked variations in 

 grouse populations. ( p. 5.51 ) . 



Relative productivity from year to year tends to vary inversely with the density of the breed- 

 ing population, (p. 540). 



When a fall grouse population numbers at least twice the corresponding breeding population 

 it may be considered to represent a good crop. (p. 539). 



