THE AUDUBOs BULLETIS® 
Published Quarterly by the 
meetieie Ove Ss xy UD U BON Sr Gta ely: 
Roosevelt Road and Lake Shore Drive, Chicago 5, IIl. 
Number 124 December, 1962 
Wintering Bald Eagles In Northwestern Illinois 
By William E. Southern 
DURING THE LAST few years the Bald Eagle, Haliaeetus leucocephalus, 
has attracted the attention of ornithologists and conservationists. Studies 
have been undertaken to determine whether or not the species is actually 
decreasing in numter. If it is, the data accumulated would be used in de- 
termining management and conservation practices to prevent extinction 
of the birds. 
Between November 27, 1961, and April 1, 1962, I conducted the first 
phase of a study of the winter eagle population at the Savanna Army 
Depot (Carroll and Jo Daviess Counties). The objectives of the study were 
to (a) live-trap, color-mark, and determine the movements of Bald Eagles 
during the winter and early spring; (b) census the eagle population within 
the 14-mile study area as often as possible during the winter; (c) record 
feeding, roosting and other behavior patterns; and (d) obtain data on 
weights, measurements, plumage characteristics, and internal and exter- 
nal parasites. A report on these phases of the project has been accepted 
for publication in The Wilson Bulletin. 
Probably few Illinois residents are aware of the eagle concentrations 
at various locations along the Mississippi and other major rivers of the 
state, Still fewer persons, I am sure, have witnessed many of these magnifi- 
cent birds feeding or loafing at such localities. The Savanna population 
consisted of 16 eagles on December 9; increased to a peak population of 
262 on February 2; and gradually decreased to one immature on March 
30 and none by April 1. This appeared to be the largest concentration of 
eagles reported anywhere in the Midwest. 
In this paper I will attempt to present a pictorial view of the Savanna 
area and its eagle population in addition to brief notes about the birds 
and their habits. During the winter we saw up to 130 adult eagles near 
a single open hole along the Mississippi. Everyone should experience such 
a sight; it is indeed a thrill. 
The Savanna Army Depot is closed to the public, but there are sev- 
eral other areas in the state that have sizeable eagle populations (refer to 
the Christmas Census Reports in The Audubon Bulletin). The best time 
to visit these areas is probably during late January, February, or early 
March. There is usually a fluctuation in the number of birds to be seen 
on a single day or on successive days; however, we were always sure of 
seeing a number of eagles during the above dates. 
The study was supported by a grant from the Frank M, Chapman 
Memorial Fund (American Museum of Natural History). Field assistance 
was given by James Tate, Jr., and Alfred Bjelland. Major Ira Meyers ar- 
ranged for us to conduct our study on the U. S. Army Savanna Depot. 
Many other persons aided the project in various ways. 
[1] 
