THE VALUE OF EDGES 



171 



Effect of Edges on Adult Grouse Distribution 



In the old pastures and farm woodlots which characterized three of the four study areas, 

 the axe and the plow had been quite successful in breaking down the original forest into an 

 infinite variety of cover. Faced with the problem of classifying the vegetative groups, the 

 Investigation recognized 12 major types as heretofore described. To determine the "edge 

 eflect" of each type on grouse distribution, the location of each adult, brood and nest found 

 over the 13 years of the study was plotted as accurately as possible on large scale maps. 



A copy of a single section, chosen at random but representing adult flushes for all seasons 

 of the year, is here reproduced (figure 14). No strong tendency for the birds to be found 

 along cover type edges is to be observed on many of these maps. 



figure 14. distribution of adult 

 grouse flushes on one compart- 

 ment of the CONNECTICUT HILL 

 study area — ALL SEASONS, 1932- 

 1940. EACH DOT ON THE MAP REP- 

 RESENTS THREE FLUSHES 



OPEN HAROWOOO HARDWOOD B MUDWOOOS HftROWOODS 



BflUSH CCniFCn BRUSH 3*- <2* B CONIFERS 



A further test was then employed. On the cover type maps of 12 sections of the Connect- 

 icut Hill study area, a series of 20 random lines* were run. From the number of type edges 

 crossed by each line an index of edge frequency for each section was obtained. These, 

 tabulated with the corresponding average spring population densities for the period 1930- 

 1942, are indicated in table 16. Studying this, one finds that, in general, the larger the 

 number of edges, the higher the average population of grouse the areas will support. 



* The posilion and direction of each line was eBtablished by Btatisticallv valid random sampling methods. 



