. Distribution and abundance of winter populations of bald eagles in Illinois. Bald eagle. 8 22 e 20 3 17 I IS 29 12 26 9 23 9 23 6 20 SEPT OCT NOV DEC JAN FEB MAR APR DATE Fig. '.tM iiiiiiibfr of bald eagles counted per inveiuoi y in ihe Lower Mississippi River Region. 1972-l9<S(i. occurred from late October to mid-November, some- what later than in the more northern reaches of the Mississippi River. Spring departures, however, were usually similar in most years to those in other regions of the Mississippi River, although from 1983 to 1985 eagles were present until late April, or 2 t
. Distribution and abundance of winter populations of bald eagles in Illinois. Bald eagle. 8 22 e 20 3 17 I IS 29 12 26 9 23 9 23 6 20 SEPT OCT NOV DEC JAN FEB MAR APR DATE Fig. '.tM iiiiiiibfr of bald eagles counted per inveiuoi y in ihe Lower Mississippi River Region. 1972-l9<S(i. occurred from late October to mid-November, some- what later than in the more northern reaches of the Mississippi River. Spring departures, however, were usually similar in most years to those in other regions of the Mississippi River, although from 1983 to 1985 eagles were present until late April, or 2 to 3 weeks later than in other regions. Peak population counts occurred between 4 Janu- ary and 18 February in this region. The highest number of bald eagles observed on one day was 262 on 6 February 1979. Immature birds ranged between 0 and 1009^ of the eagles seen on individual inven- tories and averaged for all inventories. The mean number of eagles per inventory for areas within this region is shown in Figuie 17. Num- bers of bald eagles were higher in the downstream portion of this reach (Appendix). Few eagles were seen between St. Louis and Kimmswick, Missouri, but numbers steadily increased to the area from Cajie Girardeau, Missouri, to Cairo, Illinois, where the high- est numbers were seen. This stretch of the river is also adjacent to some of the major winter areas for Canada geese (Branta canadensis) in southern Illinois. The average density of bald eagles in the Lower Mississippi River Region was 1 bird per ri\er mile. 10,00 Fig. 17.—Mean niniiljer ol bald eagles counted per inventory at census areas within the Lower Mississippi River Region, 1972-1986. or per square mile of wetland habitat. These density values of bald eagles were the lowest of all the Mississippi Ri\er regions. Upper Illinois River Region. The L^pper Illinois River Region stretches from Morris, Illinois, to near Spring Valley, Illinois (Fig. 6). Most portions of this region were sur
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