. Distribution and abundance of winter populations of bald eagles in Illinois. Bald eagle. Illinois Natural History Survey Biological Notes No. 129. Fig. 1.—Immature bald eagle in night (Photo by David ). Fig. 2.—Adult bald eagle search- ing for prey (Photo by David L. Fischer). States during winter. The difficulty of coordinating a census over such a large area has resulted in counts that provide only an index to actual population levels. Nationwide bald eagle censuses have shown a dramatic increase since the late 1970s (Table 1). The increase is attributed partially to more effectiv
. Distribution and abundance of winter populations of bald eagles in Illinois. Bald eagle. Illinois Natural History Survey Biological Notes No. 129. Fig. 1.—Immature bald eagle in night (Photo by David ). Fig. 2.—Adult bald eagle search- ing for prey (Photo by David L. Fischer). States during winter. The difficulty of coordinating a census over such a large area has resulted in counts that provide only an index to actual population levels. Nationwide bald eagle censuses have shown a dramatic increase since the late 1970s (Table 1). The increase is attributed partially to more effective counts. Until 1976, counts were the result of incidental eagle sightings during a USFWS January waterfowl inventory. In 1979, the National Wildlife Federation (NWF) organized an annual midwinter bald eagle sur- vey. Thousands of persons are currently involved in the enumeration of bald eagles. Although variation in geographical coverage of the midwinter bald eagle surveys among years makes accurate counts difficult, bald eagles appeared to have reached their highest number of 13,825 in 1982 (Table 1). Millsap (1986) noted that a reasonable esti- mate of the midwinter population of bald eagles for the lower 48 states during the early 1980s was 14,000- 22,000 birds. A decline in numbers observed on the midwinter survey has occurred since 1982 (Table 1). Table 1.—Number of bald eagles in the contiguous United States during January, 1961-1986. Year Number Counted Reference 1961 Spruntand Ligas 1963 1962 3,807 Spruntand Ligas 1963 1963 Spruntand Ligas 1963 1971 2,490 USFWS unpublished'' 1972 2,668 USFWS unpublished = 1973 2,986 USFWS unpublished^ 1974 3,553 USFWS unpublished" 1975 3,580 USFWS unpublished'' 1976 4,478 USFWS unpublished = 1979 9,815 NWF (1985) 1980 13,046 NWF(1985) 1981 13,689 NWF(I985) 1982 13,825 NWF(1985) 1983 12,098 NWF(1985) 1984 11,819 NWF(1985) 1985 10,985 NWF (1985) 1986 8,318 NWF'' 'Stcenhof (1976). 'Personal communication. The 1985 e
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