Vol. 9, No. 10 
Page 3 
3- Factors Inf1uencinq Distribution and Abundance of Pheasants W. L. Anderson 
In the two previous reports (Monthly Wildlife Research Letters, August and 
September, 1966), it was demonstrated that the body weight of the "average" hen 
pheasant in the better pheasant range in Illinois decreases as the egg-laying and 
egg-incubating periods progress. Further analyses, employing statistical tests 
of linear regressions, indicate that an inverse relationship also existed between 
the body weight of hens and the number of eggs they were incubating (Table 3)* The 
decrease in body weight per incubated egg ( 19*6 grams) was significant at the 95 
percent level of confidence. Decreases in the weights of sternal muscles and of 
the fat strip were also statistically significant. Unfortunately, the reasons for 
these relationships are not readily apparent. No significant relationship was 
found between the number of eggs in incubated nests and the number of ruptured 
follicles counted in ovaries removed from the hens (t^ = 1.165^ not significant at 
the 90 percent level of confidence; Ref. _t = 2.201 with 11 df). Thus, the light 
weight of hens incubating large numbers of eggs, as compared with the weight of 
hens incubating lesser numbers of eggs, apparently was not related to the total 
number of eggs produced. 
The apparent inverse relationship between the body weight of hen pheasants 
and the number of eggs they were incubating might be linked to the age of the birds. 
The hen segment of the population is usually composed of one to two juveniles per 
adult during winter and early spring. If juvenile hens, whose average weight is 
less than that of adult hens, tend to incubate larger numbers of eggs than adults, 
the reason for this relationship becomes apparent. Additional data collected in 
future years should prove or disprove this explanation. 
Table 3» Relationships, as determined by statistical tests of linear regressions, 
between the numbers of eggs in incubated nests and weights or measurements of the 
carcasses, muscles, fat deposits, and internal organs of 13 hen pheasants collected 
in Ford and Livingston counties during the egg-incubating period of 1966. The 13 
hens were incubating an average of 10.410.8 eggs. 
Samp 1e 
S i ze 
Mean Weight or 
Mean Length 
Sample Regression 
Coefficient* 
_t Value 
Carcass 
13 
837 g 
-19.57 
2.816+ 
Muscles 
Leg 
13 
172.5 g 
- 2.28 
1.328 ns 
Sternal 
13 
210.8 g 
- 6.42 
3.470+ 
Fat Deposits 
Fat Strip 
13 
0.9 g 
- 0.08 
1.947* 
Visceral Fat 
13 
5-3 g 
- 0.97 
0-789 ns 
Internal Organs 
Heart 
13 
3-5 g 
- 0.08 
l.689 ns 
Liver 
13 
14.5 g 
- 0.12 
0.399 ns 
G i zzard 
13 
13.5 g 
- 0.24 
1.200 ns 
1ntestine 
13 
99.2 mm 
- 0.21 
0.158 ns 
Caecum 
13 
18.5 mm 
+ 0.01 
0.050 ns 
Colon 
13 
10.6 mm 
- 0.19 
2 . 314 + 
* Mean change in weight or length per egg in incubated nest. 
t Significant at the 95 percent level of confidence (Ref. _t = 2.201 with 11 df). 
$ Significant at the 90 percent level of confidence (Ref. Jt = 1-798 with 11 df). 
ns = Not significant. 
