SPECIAL TECHNIQUES 709 



Buffer Abundance 



Rabbits, mice, and to some extent, squirrels, are the principle buffer species with respect 

 to grouse. When these foods become scarce, predators are forced to turn to other sources and 

 grouse suffer accordingly. Thus fluctuations in the abundance of buffers are of importance 

 in evaluating the effect on grouse of changing numbers or activity of predators. 



It was found that rabbit, squirrel, mouse and shrew tracks were too numerous to be 

 accurately recorded by the regular survey crews. Accordingly, a controlled tracking system, 

 based on trail counts, was organized. 



Trails, each one-half mile in length, were laid out through representative cover types on a 

 study area*, care being taken that the locations chosen would change as little as possible in 

 cover relationshi|)s during the course of study. Each trail was marked in such a manner that 

 an identical jtath could be followed during each working and in subsequent years. 



Tracks were observed and counted along the.se trails in a controlled manner. Approxi- 

 mated 24 hours after a fresh snow, the trails were traversed })v a single man and alwa\s in 

 the same order. In practice, a day was judged to be suitable if it had stojjped snowing the 

 previous day between the hours of 10 a. m. and I p. m. The character of weather during the 

 time since snowing ceased was recorded, together with the character of the snow. All tracks 

 which crossed or touched the trail made by the oi)scrvers" feet were counted as individual 

 tracks. If an animal walked direclK along the trail, it was counted as a single track, but if 

 it deviated from the trail h\ more than one foot and then returned to ihe trail, it was counted 

 a second time. This was done to eliminate the personal element to ihc greatest possible 

 extent. 



The trails were co\ered as man\ times during the winter period as the above-mentioned 

 snow conditions occurred. Ilowe\er. an attempt was made to cover the set of trails at least 

 four times each year. 



Trail track count data was analyzed bv the method of covariance by adjusting the number 

 of tracks recorded for the number of times worked. Individual trails were used for repetition. 



Food Hahils oj Predators 



In order that the true iniportam e of predators be understood, a picture of the seasonal 

 and yearly changes in their normal food was necessary. This was obtained through the analysis 

 of stomach specimens from the State as a whole as well as drop])ings and j)ellets collected b\ 

 the regular survey personnel on the study areas during all seasons over the entire period of 

 the Investigation. Collections of the latter t\pe were often large, with such items as fox 

 drop|)ings (.scats) sometimes running to 600 specimens for a single season. When examined 

 and sununarized. \earl\ and seasonal clianges in the occurrence of items eaten were revealed. 

 Correlations were also made with known fluctuations in the abundance of some of the more 

 important foods, such as rabbits and mice. 



This material was examined b\ the laboratory personnel conducting the food habits studies. 



Predators Responsible jor Grouse Rills and .XrsI Des/ruction^ 



An accurate knowledge of the predators responsible for the observed mortality of grouse 

 during the stages of their develo|)ment is also of importance. Early in the Investigation, 



* Eight such trails were used on the Connecticut Hill area. 

 A By R. W. Darrow. 



