354 REPRODUCTIVE CAPACITY OF THE SPECIES 



The average clutch size in first nests was 11.5 eggs. Fluctuations in average clutch size may 

 result from changes in the proportion of old to young birds in the breeding population. 

 Grouse apparently lay fewer eggs the first year. I p. 3011. 



Grouse whose nests are destroyed while laying or very early during incubation are likely to 

 atlcin])t a second nest, but if their nests are lirokcn uji late in inculiation. the\ rarelv 

 make another attempt, .^ince most nest losses occur late in incubation, renests do not 

 ordinarily contribute largeK to the increase of birds, (p. 3641. 



Renests have averaged about seven and one-half eggs. No yearly variation of importance 

 has been observed. ( jt. 364). 



Egg infertility has varied from one to seven per cent in different years, averaging 2.6 per 

 cent. For renests it has been somewhat higher, averaging 4.3 per cent. This is largely 

 due to occasional renests that are mostly or entirelv infertile, i p. 3651. 



Embryo mortality has been consistently low. Only 1.9 per cent of the fertile eggs in first 

 nests and 3.9 per cent of those in renests failed to hatch. The variations in different 

 years have not been important. ( p. 365). 



Inbreeding probably does not occur to any great extent and when it does, it exerts no ob- 

 servable detrimental influence. I p. 367). 



At some period in the evolution of bird life, the cxait lime and place of whicii is lost in 

 the haze of antiquity, a new species developed that might have been recognized as the proto- 

 type of the ruffed grouse. From the beginning, its survival and increase were, as with any 

 new species in its formative stages, largely dependent upon its ability to adapt itself to the 

 surroundings and to reproduce in numbers at least sufficient to offset its losses. 



Among the factors controlling the abundance of any wildlife species, the capacity to re- 

 ])roduce is fundamental, 'ihe inherent species characteristics that determine this capacity 

 have cvoKcd frnm the adjustment of the forces lending to increase its numbers with those 

 tending to liniil them. So long as these forces remain in balance, tlie species survives, but 

 if reproduction should fail at any time, the species would be threatened with extinction. 



A species like the ruffed grouse, that suffers large normal losses each year, must have a 

 relatively high reproductive capacity. The number of eggs laid and the fertility and hatch- 

 abilit\ of these eggs must be large enough to provide for a sufficient increment each year to 

 absorb these losses if the population is to remain stable. The proportion of female birds 

 that lay eggs, as well as that of tin- males fertilizing them, nmst likewise be high. Other 

 altribulcs of reproduction are similaii\ inipoilanl. 



HKI'RODUCTIVE POTENTIAL 



In order to gi\e a gra|)hii |ii( lure of lln- polciilial pKnlui li\ il\ nf lliis specio it mav be 

 |)ointed out that one pair of grouse and their progen\ would ninnber 33.614 at the end of 

 only five years if sex ratios were equal, all the females laid the average number of eggs* 



* Sincr the numbrr of cgB* per female hai averagcil 11.9 over the Rett of Slate regioii, 12 baa been uaed in llii» calculaliun in 

 oriirr tii avoid decimals. 



