Vol. 9, No. 3 
Page 4 
As determined by aerial census, the prebreeding population on the study area 
declined from 4,043 in 1963 to 1,684 in I 965 , a decrease of over 58 percent (no 
aerial census was possible in 1964). The aerial counts indicated only general 
changes in the breeding population because (1) observation conditions were different 
each time the aerial census was made, (2) it was impossible to distinguish between 
cock and hen pheasants, and (3) the counts were made 2-3 months ahead of the nesting 
season (with the magnitude of mortality between the date of the count and the 
nesting season unknown). The number of adult hens observed during the summer along 
640 miles of standardized roadside transects decreased 15 percent from 1963 to 
1964, 40 percent from 1964 to I 965 , and 49 percent from 1 96 3 to 1965- 
Nest density on seeded plots showed an increase of almost 30 percent from 1 96 3 
to 1964, while the decrease in the number of adult hens observed on brood# runs 
was slight. However, there was only a 10 percent decrease in the density of nests 
on seeded plots in 1965 as compared with 196 3, in spite of an apparently much 
larger decrease in the breeding population on the study area. 
These data suggest that seeded roadsides may make up an increasingly important 
segment of the nesting habitat on the study area as the amount of hayfield cover 
continues to decrease, even during periods of relatively low populations. 
3- Factors I nf1uencinq Distribution and Abundance of Pheasants W. L. Anderson 
Seven hen pheasants (three juveniles and four adults) were collected in 
Livingston County during February and were dissected to determine, among other 
things, weights of muscles and of fat deposits. Muscles weighed occurred in two 
distinct groups: sternal muscles ( pectora1is , sup racoracoideus , and coracobrachia 1 i s 
anterio r), and leg muscles (all muscles attached to the femur and tibiotarsus). 
Fat deposits weighed were the fat strip, located on the posteroventral surface of 
the pectoral muscle, and visceral fat, found in the abdominal cavity, primarily 
in the greater omentum. The weights of these muscles and fat deposits are 
summarized in Table 3- The sternal and leg muscles collectively constituted 45-50 
percent of the total body weight. Weights of the fat deposits were found to vary 
considerably, those of the fat strip ranging from 0.4 to 2.1 grams and those of 
visceral fat from 1.4 to 8.9 grams. As the birds were collected from the better 
pheasant range in the state, and as weather conditions during the past winter were 
comparatively mild, it is thought that these weights of muscles and of fat deposits 
are representative of healthy hen pheasants during the winter months. 
Table 3- Mean weights of muscles and of fat deposits of seven hen pheasants 
(three juveniles and four adults) collected in Livingston County, Illinois, during 
February 1 966 . 
Weight 
(qrams) 
Percent of 
Ent i re Ca rca: 
Mean 
Range 
Mean 
Range 
Entire Carcass 
906 
775-1 ,002 
— 
— 
Muscles 
Sternal 
257 
241 -278 
28.5 
26.6-31.1 
Leg 
165 
134-185 
18.3 
17.3-19.6 
Fat Deposits 
Fat Strip 
1 .1 
0.4-2.1 
0.1 2 
0.05-0.23 
Visceral Fat 
4.7 
1.4-8.9 
0.51 
0 . 18 - 0.96 
