ROLE OF PRE DAT ION 



315 



together with data indicating an inverse relationship between the abundance of small mam- 

 mals and the degree of activity among predators. 



In figure 25 is shown the correlation between the degree of activity of foxes from year to 

 year and nest losses during the corresponding season on the Connecticut Hill area. The simi- 

 larity of the two trends is striking. Apparently they are directly related, although in 1941 

 some other influence became controlling. Thus under the conditions studied foxes must be 

 considered to have been a major factor in determining grouse nest failure, and, in turn, the 

 pressure exerted by them has been greater when small mammals have been scarce than when 

 they have been numerous. 



Reference to figure 24 shows a high nest loss on Connecticut Hill in 193,S. While com- 

 parable data for buffers are not available prior to 1934 general records indicate a lower 

 buffer abundance during that year than at any other time except the spring of 1937. 



It is not surprising that a substantial proportion of the grouse nests attempted each year 

 should l>e found by predators and destroyed. A ground neslcr the female commences to lay 

 during the latter part of April and does not bring off her brood until about June 1. Thus 

 for a period of some six weeks or more the eggs are in constant danger of discovery by the 

 numerous animals which would welcome such a ( hange in diet. At this season these species 

 spend considerable time hunting, either to recuperate from winter privations or to supply 

 their growing young of the year. True, the coloration of the female when on her nest blends 

 remarkably with that of the forest floor. But when she is not sitting the eggs are usually 

 more conspicuous, since it is only accidentally that leaves tend to camouflage them*. 



The Brood Period 



Commencing with the hatching of the eggs, the brood period has been considered to extend 

 through August 31. Unlike nests, however, grouse chicks do not "stay ])ut". Sur\ ival records 

 were therefore secured largely from those areas where summer census surveys were regu- 

 larly conducted, namely, the Connecticut Hill and Adirondack areas. An average of 42 and 12 

 broods were studied each season on those tracts, respectiyely. Table 37 presents the per- 

 centage mortality"^ observed each year. 



TABLE 37. 



BROOD MORTALITY RLC.ORDLD ON CONNECTICUT HILL AND 

 ADIRONDACK STUDY AREAS— 1930-1912 



It is evident that losses during this period have been proportionately greater than with 

 respect to nests. There has also been a remarkable similarity both in trend and degree from 

 year to year on the two widely separated areas. Yet an adequate appraisal of the relative 

 importance of the various factors' involved represents one of the most perplexing problems the 

 Investigation has encountered. 



* See Chapter V. p. 288. 



A .'^ItlHMigli teriin'ii hrmxl riiuitalitv. percentages refer to the aggregate loss of chicks, 



t See Chapter Xll, p. 528. 



