Vo 1 * 10, No. 2 
Page 2 
52.5, prenesting--55-1, iaying--45-8, incubating--48. 1, brooding--55-6, and fall-- 
49 . 9 . Although there has been considerable disagreement regarding the proper 
interpretation of thyroid weights--their relation to thyroid activity (metabolic 
rate) - an illuminating critique of the subject has recently been published. It 
appears that within any species of birds the weight and volume of the thyroids are 
useful indices of thyroid activity, and that size is inversely correlated with 
activity. It also appears that, at least in passerine birds, weights and volume 
of thyroids decrease (increased activity) in autumn, winter, and early spring, and 
increase (decreased activity) during most of the spring, summer, and early autumn. 
The weight data for thyroids removed from pheasants superficially appear to disagree 
with these published findings. If, however, the laying and incubating periods are 
not considered, the seasonal changes in weights of the pheasant thyroids are 
similar to those of passerine birds; the thyroids from pheasants were heavier in 
spring (prenesting) and summer (brooding) than in fall and winter. Therefore, it 
is concluded that in pheasants the metabolic demands of egg production, and possibly 
of incubation, are of sufficient magnitude to increase thyroid activity to levels 
that exceed those characteristic of the colder (fall and winter) periods. 
4. Responses of Bobwhites to Habitat Manipulation J. A. Ellis, K. P. Thomas 
Since 1963 the sex ratio of quail during the fall on the Forbes and Oale areas 
has been determined by using data from the harvest, nightlighting, and baited 
traps. (The latter two methods were discontinued on Dale after 1964.) The sex 
ratio of juveniles on Forbes varied from 2.0 cocks per hen, using data from baited 
traps, to 1.2 cocks per hen, using harvest data, with a median ratio of 1.2 cocks 
per hen, obtained from nightlighting data in I 966 . 
Prior to 1966 the adult sex ratio has favored cocks, whereas the juvenile 
segment has contained more hens than cocks. In I 966 the adult sex ratio continued 
to favor cocks on both areas (Forbes, 1.2:1 and Dale, 2.2:1), but the juvenile sex 
ratio reversed to favor cocks (Forbes, 1.3:1 and Dale, 1.2:1). This reversal in 
the juvenile sex ratio has coincided with a concomitant increase in the fall popu¬ 
lations. 
5. Responses of Prairie Chickens to Habitat Manipulation R. L. Westemeier 
Redtop grass ( Aqrostis alba ) has long been recognized by some as an ideal type 
of nesting cover for prairie chickens in southern Illinois. For this reason red- 
top is used almost exclusively for the rapid establishment of nesting cover on the 
prairie chicken sanctuaries at Bogota. What has not been recognized is that there 
can be differences in the degree of use among various age-classes of redtop sod. 
During the 4-year period, 1963 - 66 , 33 prairie chicken nests have been found 
in a cumulative total of 517*6 acres of grassland dominated by redtop. This red- 
top acreage was categorized into five classes ranging from 1 to 4 years of age, 
with fields over 4 years of age considered as old sod. As expected, first-year 
sod ranked lowest, with only two nests found in 77 acres. The most striking 
difference existed between 45-5 acres of 2-year sod having 13 nests (28.6 nests 
per 100 acres) and 324 acres of old sod having 13 nests (4.0 nests per 100 acres). 
