CHANGES IN THE WINTER DISTRIBUTION OF THE ROUGH-LEGGED HAWK 
Hawk abundance declined from 24 to 14 birds/100 party hours. In the South 
Plains snow cover decreased less sharply than in the North Plains. Human 
population growth in the counties associated with the CBC circles in the 
North Plains was low (9%), in the South Plains much higher (43%). 
Great Lakes Regions 
Although Red-tailed Hawk abundance increased in both Great Lakes 
regions (Figure 6), the abundance of this species in these regions was lower 
than in any other except the North Plains. Rough-legged Hawk abundance 
did not vary significantly from period to period in either region. The number 
of days with significant snow cover was relatively stable in the East Great 
Lakes but decreased slightly in the West Great Lakes in the second 14-year 
period. Human population in the counties associated with the CBC circles 
grew slowly (10%) in the East Great Lakes and declined (-1%) in the West 
Great Lakes. 
East and Atlantic Coast Regions 
The Red-tailed Hawk’s abundance in the East region increased mark- 
edly; numbers in the last 14-year period were more than double those of 
the first period (Figure 7). In the Atlantic Coast region, it was relatively low 
(51 birds/ 100 party hours) and increased much less dramatically. In both 
Period 
Figure 6. 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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