PRELIMINARY REPORT ON 

 ■ AVAILAblLITY AND USE OF WATERFOV.'L FOOD PLANTS 

 IN THE ILLINOIS RIVER VALLEY 



Frank C. Bellrose, Jr., and Harry G. Anderson'"" 



B<^cause studies conducted in the past on duck food habits 

 have covered extensive rather than localized areas, the ab^ondance 

 of" aquatic plants and their use by waterfowl have never before been 

 correlated to secure an Index rating of value for these plants. 



The IlllnoLs River was selected for the Investigation out- 

 lined below because it offered exceptional opportunities for inten- 

 sive studies of duck foods. Vegetation of lakes was easy to map, 

 base maps scaled 5-4- inches to the mile were available and duck giz- 

 zards were obtainable in quantity from 11;^ ting clubs. 



In 1938, the senior author Inaugurated the study by map- 

 ping the vegetation communities of over 20 lakes and by collecting 

 waterfowl gizzards from hunting clubs. On June 1, 1939, the junior 

 author was employed to undertake Pittman-Robertson Project No. 2-R, 

 set up under terms of the Federal Aid in Wildlife Restoration Act, 

 to determine the contents of waterfowl gizzards collected in 1938 

 and to collect and examine gizzards in 1939' and 1940. 



Since the value of a plant is believed to change with its 

 abundance, the decision v/as made to conduct the study for two or 

 more years. This paper is a preliminary report on data obtained in 

 1938, Because of changes in water levels favorable to certain spe- 

 cies, later studies may add other species to the list of desirable 

 plants Included in this paper. 



INDEX RATING OF WATERFOWL FOODS 



The index rating of the utilization of waterfowl food 

 plants was -obtained by dividing the per cent of use by the per cent 

 of abundance. Per cent of use data were based upon volumetric meas- 

 urement by the j-onior author of the contents of 1,147 waterfowl giz- 

 zards collected in four areas. Per cent of abundance data were based 

 upon area in acres of various vegetation communities, the area in 

 each "^ase being obtained by a planimeter used on vegetation maps 

 made by the senior autlxor. 



Because of the impossibility of obtaining accurate figures, 

 no measurement v;as made of the abundance of certain plants, and these 

 plants were disregarded in calculating the per cent of abundance of 

 other plants. 



"Frank C. Bellrose, Jr.," Assistant Game Technician, Illi- 

 nois Natural History Survey; Earry G. Anderson, Jionior Biologist, 

 Illinois Natural History Sxirvey, State Department of Conservation 

 and U. S. Fish and Wildlife Service (Federal Aid Program). 



