SPECIAL TECHNIQUES 711 



(2) Shell having a large "bite" taken from one side 

 about midway between the ends and extending 

 from one-half to three-quarters the way around; 

 opening sometimes smaller but inward punctures 

 made by the canine teeth can usually be found 

 in the opposite side Red Fox, Gray Fox 



b. Shell not retaining shape, one-half or more usually 

 eaten away along the long axis; edge of remaining 

 portion very finely chewed but the fragments large- 

 ly held together by the membrane; shell remains 

 frequently left under a log, projecting root or sim- 

 ilar shelter, often several at the same place Weasel*, Mink 



2. Whole eggs buried in runways under or near nest Mice^ 



C. Shell remains in or close beside nest, latter often torn apart 



1. Nest torn apart, completely crushed eggshells mixed with the 



debris Skunk 



2. Nest intact or very slightly disturbed 



a. Shell remains usually retaining much of their spherical 

 shape, one end bitten oS, most frequently the smaller one; 

 if broken to a greater extent the fragments neither held 

 together by membrane nor mixed with debris Raccoon 



1). Shell remains well crushed 



(1) Remains, much chewed but fragments held to- 

 gether by nieiiibrane, largely in nest, latter not 



disturbed Bobcat, House Cat 



(2) Remains largely absent, but small bits of shell 

 usually scattered in and beside nest 



Dog, Opossum, Woodchuck^ 



* Either Musu-la novaboracensis or M. cicognanii, 



A Except that they may have been involved in some of the few instances of this kind, the Investigation has found no evidence that 



chipmunks disturb grouse nests. 

 t Little dilTercntiatioii is possible between these species except on a circumstantial basis. Dogs mure frequently paw up the nest 



but lliere is considerable variation between breeds as well as individuals. 



The majority of broken-up nests were examined only by the authors throughout the In- 

 vestigation in order to eliminate the personal element to the greatest extent. Their reports, 

 together with all the evidence that could be gathered was in turn checked by one individual 

 to reduce further the possibility of error. 



The same author also decided which predator, if any, was responsible for each grouse 

 found dead. Tlie field evidence was noted on an appropriate data sheet. The feathers, bones 

 or other remains were placed in a bag. The specimen and the sheet were then checked in 

 light of the results of experiments as well as field experience. 



Unfortunately, judging the predators or cause responsible for adult grouse kills does not 

 lend itself to being summarized in key form since circumstantial evidence is involved, and 

 space does not permit the detailed discussion which would otherwise be necessary. 



