Vol. 22, No. 7 
Page 3 
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However, a comparison of nest numbers and nest densities of prairie chickens 
relative to other nesting fauna reveals the dependence by prairie chickens on 
associated grassland species that act as buffers to predation. Nest densities 
are used as an index of population levels for 12 species of birds and 3 species 
of mammals (Table 1). In 1978, prairie chicken nests found on sanctuaries 
were 129 % of the mean for the 12 -year period of 1966 - 77 . this figure was 
exceeded only by percentages for the pheasant and the endangered upland sandpiper. 
By contrast, quail, mourning dove, meadowlark, and grasshopper sparrow showed 
record low densities among the species that nest on the ground. 
Among 5 species that nest off the ground in grasses and forbs, only the 
red-winged blackbird approached an average nest density. Densities of cottontail 
nests in 1978 were 200% above the 12-year mean. However, by excluding a 
"hot spot"—a prairie restoration area (Walters 40) that was searched for the 
first time in l978--cottontaiIs were 93% of the long-term mean. Nest densities 
for small mammals (prairie vole and bog lenming) were 119 % of the long-term mean. 
These data suggest that prairie chickens at Bogota are not doing badly 
compared with other birds and mammals nesting on the sanctuaries. The current 
low densities of 9 species of birds are apparently the result of low breeding 
populations due to the past 3 severe winters. A previous report (MWRL 20(12):3) 
showed that as the proportion of prairie chicken nests to nests of other ground 
nesters increased, nest success of prairie chickens declined (£ = - 0 . 692 ). 
Hatching success of prairie chickens above the critical 50% level and a recovery 
in the population level are not likely until average or greater densities of 
nests of the buffer species are attained. 
Table 1. Numbers and densities of bird and mammal nests found on prairie 
chicken sanctuaries, Bogota Study Area, 1 966 - 78 . A cumulative total of 4,676 
acres ( 357 -acre annual mean) was searched. 
Species 
Tota 1 
Nests 
Annual Means 
for 1966-77 
Nests/ 
Nests 10 A. 
Nests 
1978 
Nests/ 
10 A. 
Percent 
of 
1966-77 
BIRDS; 
Prairie chicken 
599 
45.3 
1.26 
55 
1.62 
128.6 
Quai 1 
297 
24.3 
0.68 
5 
0.15 
22.1 
Pheasant 
63 
4.2 
0.12 
13 
0.38 
316.7 
Mourning dove 
175 
14.5 
0.40 
1 
0.03 
7.5 
E. meadowlark 
764 
62.5 
1.74 
14 
0.41 
23.6 
Upland sandpiper 
25 
1.3 
0.05 
3 
0.09 
180.0 
Grasshopper sparrow 
49 
4.0 
0 . 11 
J_ 
0.03 
-IZii 
All ground nests 
1,972 
156.7 
4.37 
92 
2.71 
62.0 
