Up geA se Dt BONG Bil ih al 31 
THE ILLINOIS AMERICAN BOTTOMS: 
SUMMER BIRDING AREA OF ILLINOIS 
by G. MICHAEL FLEIG 
Curator of Birds, Brookfield Zoo 
For a period of over five years (1961-1966), from the 15th of April to the 
3lst of August, I conducted extensive observations of the avifauna of the 
Illinois American bottom. This study area extends southward in Illinois 
from the Jefferson Barracks Bridge (Bypass 50) to Chester where the 
bluff joins the river, the eastern boundary being the bluff, the western 
the Mississippi River. The area is rich bottomland sparsely populated and 
extensively farmed. A levee one-half to one mile from the river prevents 
extensive flooding. 
The study area is unique in that many birds of the southern swamp- 
lands are summer residents here. They include: the Mississippi Kite, Fish 
Crow, Black Vulture, White Ibis, Hooded Warbler, Cattle Egret, Snowy 
Egret, Common Egret, Black-crowned Night Heron, Yellow-crowned Night 
Heron, and Common Gallinule. Some casual visitants are Wood Stork, 
Glossy Ibis, Purple Gallinule, and White Pelican. 
The limiting factor influencing the birds’ arrival, departure, and term 
of residency is the availability of open water in swamps, marshlands, or 
mud flats. In years when water was available, but scarce, in the study 
area (but a severe drought in evidence in the southeastern United States), 
the bird population in the Heron rookeries grew and species heretofore 
unknown from this area appeared either in the early summer or during 
the post-breeding dispersal. In 1965 when water was abundant in the 
study area and also in the southeastern United States, populations were 
at a relative low. 
It would be well to collate observational data with meteorological 
data of this area and that of the southeastern United States to learn the 
effects of drought on the distribution and population dispersal of those 
species which depend on water for their breeding cycle and survival. Also 
an attempt to collate annual fluctuations of Herons in a rookery with 
meteorological data. The Fults Island rookery contains anywhere from 
a few hundred to a thousand breeding birds, namely Little Blue Herons 
(Florida c. caerulea), Black-crowned Night Herons; Common Egrets; and 
a few pair of Snowy Egrets and Great Blue Herons (Ardea herodias). 
Cattle Egrets nested in only one year, although they are seen commonly 
and probably nest nearby. Hooded Warblers were common in 1962 but were 
rare and irregular in other years. Black Vultures were found uncommonly 
only in 1962. The nesting colony of Mississippi Kites is their northernmost 
range extension in the Mississippi Valley. 
A swamp area of particular interest contains many plants characteris- 
tic of southern swamps, for example, Hibiscus sp., Cephalanthus sp., 
