BALD EAGLE FORAGING PERCH DISTRIBUTION AT LOCK AND DAM 19,
MISSISSIPPI RIVER.  

Brian P. Kraskiewicz and Thomas C. Dunstan.   Department of
Biological Sciences, Western Illinois University, Macomb, IL
61455.  

Bald Eagle foraging perch site locations along the shores of the
Mississippi River near Lock and Dam 19, (River Mile (RM) 358 to
RM 364.5) were identified during 70 censuses from 21 November
1998 to 27 March 1999.  Adult and immature eagles were counted
and perch sites located twice weekly via one-hour long roadside
censuses along the Illinois shore upstream and across the Keokuk,
IA - Hamilton, IL automobile bridge and downstream along the Iowa
shore.  The winter eagle population increased in January to a
season peak count of 432 birds on 14 January 1999 after which the
population declined but peaked again at 359 eagles on 24 January
1999.  The population decreased in February to 39 eagles on the
21st, but increased to 107 eagles on the 26th, before dwindling
to less than 10 birds at the close of the field season on 27
March 1999.  The perch locations of foraging eagles was
influenced by the presence or absence of river ice cover, with
more expansive shoreline distribution during open water periods
of winter.  During greatest ice conditions eagles gathered about
open water created by the activity of the old (est. 1913) lock
and dam and the hydroelectric plant, and included adequate perch
trees in the Illinois owned Montebello Park and adjacent natural
and artificial perches, and the IL Chapter of the Nature
Conservancy's island night roost and day perch areas.  The
dispersion of perched eagles was clumped (not random or uniform)
along the shores, and directly related to the presence of large
cottonwood and silver maple trees.  Eagle foraging perch use was
significanly greater on the Illinois shore than on the Iowa or
Missouri shores.    

Keywords:  bald eagle, foraging, perch site, Mississippi River