Vol. 9, No. 7 
Page 5 
booming ground (Klier) declined from seven cocks in February to only one occasionally- 
present cock in early April (Table 5) -- the time when the ground should have been 
active with at least the seven original cocks. The apparent reason for the collapse 
of this ground was not due to habitat deterioration but to harassment by raptors, 
particularly harriers ( C i reus cyaneus ). As shown in Table 5 , an unusual concentra¬ 
tion of raptors was observed on or within about £ mile of the booming ground. All 
of the counts shown in Table 5 were made during the first hour of daylight, during 
which as many as 13 raptors were seen on or near the ground, and on the evening 
of March 17 at least 20 raptors were counted. 
No evidence was found that the raptors were actually killing prairie chickens 
on the Klier booming ground, but the harassment pressure by harriers was persistent 
enough through constant flushing and chasing of the cocks to prevent them from 
establishing booming territories. An unusual concentration of short-eared owls 
( Asio f1ammeus ) also wintered in the vicinity of the Klier booming ground. Uni ike 
the harriers, however, the shortears were generally on or near the booming ground 
but were not seen diving at the cocks. 
The large concentration of raptors present at Bogota during the winter of 
1965-66 may have resulted from an apparently high population of meadow mice 
( Microtus sp.), which may be a temporary phenomenon. If similar situations develop 
in future booming seasons, special raptor-control measures may be justifiable to 
safeguard the welfare of the remnant flock of prairie chickens at Bogota. 
Table 5- Counts of prairie chickens and of raptors made during the first hour of 
daylight on or within £ mile of the traditional Klier booming ground during 1 966 . 
Prairie Chickens 
Date 
Cocks Hens 
Raptors 
2/7 
5 
0 
2/21 
7 
8 
2/23 
7 
0 
2/25 
4 
7 
3/1 
2 
13 
3/2 
5 
12 
3/8 
6 
0 
3/16 
4 
9 
3/21 
4 
11 
3/25 
3 1 ? 
7 
3/26 
0 
7 
3/27 
3 
3 
3/31 
0 
4 
4/3 
2 1 
0 
4/4 
0 
9 
4/6 
1 
4 
4/9 
1 
2 
4/15 
0 
0 
4/17 
0 
0 
4/23 
0 
0 
4/30 
1 
1 
