CHANGES IN THE WINTER DISTRIBUTION OF THE ROUGH-LEGGED HAWK 
(Figure 4). Red-tailed Hawk numbers increased in each successive period. 
Red-tailed Hawk abundance in the South Intermountain West was also rela- 
tively high and increased slightly. The number of days with significant snow 
cover decreased substantially in the North Intermountain West but remained 
fairly stable in the South Intermountain West. Both Intermountain West 
regions had large increases in human population in the counties associated 
with the CBC circles (30% for the North Intermountain West; 62% for the 
South Inter mountain West). 
Plains Regions 
The increase in Rough-legged Hawk abundance in the North Plains was 
paralleled by a similar increase in the Red-tailed Hawk (Figure 5). In both 
14-year periods, however, the abundance of the Red-tailed in this region 
was consistently lower than in any other region. Rough-legged Hawk abun- 
dance in the North Plains increased in each successive 7-year period with 
abundance in the last period (45 birds/100 party hours) exceeding that of 
the North Intermountain West (43 birds/100 party hrs). The number of days 
with significant snow cover in the North Plains decreased in each 7-year 
period. In the South Plains the abundance of the Red-tailed Hawk increased 
dramatically, doubling from less than 50 birds/100 party hours in the first 
7-year period to nearly 100 in the last 7-year period, while Rough-legged 
Period 
Figure 5. Average numbers of the Rough-legged Hawk (RLHA) and Red-tailed 
Hawk (RTHA) per 100 party hours and number of December days with snow cover 
in excess of 5 cm in four successive 7-year periods (1, count years 79-85; 2, count 
years 86-92; 3, count years 93-99; 4, count years 100-106) for the North and 
South Plains regions. 
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