m iSyi' W: M i S f*,ir- \m Mm mMkm ill„.„ XI E) R_AR.Y OF THE UNIVERSITY or ILLINOIS NATURAL HISTORY SURVEY. state of Illinois John Stelle, Governor Department of Registration and Education John J. Halllhan, Director PRELIMINARY REPORT OH AVAILABILITY AiJD USE OF V-ATERFOVL FOOD PLANTS IN THE ILLINOIS RIVLR VALLEY Frank C. Btllrosc, Jr. Karr:: G. Anderson Published hy Authority of tiie State of Illinois NATURAL L'l STORY SURVEY Theodore H. Prison, Chief Biological Notes No. 15 Urbana, Illinois Deocmbei*, 1940 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). 4 An index rating of 1.0 Indicates that the food plants so rated were used approximately in proportion to their abundance. An index rating greater 'than 1.0 indicates that the food was preferred and .sought by ducks; of less than 1.0, that the food was less popu- lar than- it was- abundant. . . ■ . POSSIBLE SOURCES OF ERKOR The index rating figure may or may not 'be a precise indi- cator of the relative value of a waterfowl food plant. Habits of '.".•atprfowl, plant differences and habitat characteristics are factors .tending to prevent a minutely exact rating figure. • ■ Ducks frequently feed in, more' tlian one lake in the same day.' The- ar'ea in which a duck is. killed may not be that in which it has filled its gizzard, and yet the mechanics of this study have made necessary the tacit assuitiptipn that tlq contents of each giz- zard were -gathered in - the area in which the duck was killed. ' •' ■ .Accurate mcasurem.ent of the difrerencos in food yields of the saftie species o.f plant under varying conditions has not been .possible in this- study. For example, sago pondv/eed is very erratic in seed production. Some beds produce no seed; ot}iers produce a large ^amount. In the case of several spt;cies, seeds were available to ducks in an area in which no plants v.erc seen; the seeds liad been dropped in the -mud by t^iC previous year's plants but had not sprouted to produce vegetation. Then, too, no accurate measurement has 'been possible of the effect of differences in water level on the availability to ducks of plant parts. Lovi/ v/atur, or no water, may preclude the use of certain food plants; y/ater of greater than usual depth may have the same efiect \¥ith rcspoct to other plants. The index rating in each case should be considered rela- tive rather than exact for the reason that no numerical values were recorded for abundance of certain plants, and these plants were dis- regarded in calculating tl,L.e per cent of _ abundance, of other plants, W'iereas all plants wt,re Included in calculating the per cent of use. Even though the possibility of error in Individual ducks, or Ln individual areas, is great, the authors believe that in those food plants in wl.lch the number of samples is large the errors tend to cancel each, other. Field observations confirm or only slightly modify the f indln' s presented .in table 1. Th^e index rating column seems sufficiently valid to justify its use in planting programs, at least for the- eight pl.ants with the highest percentage of use. Of the first eight, those with a low index rating should be avoided in m.ost planting programs. AREAS Ul'JBER INVESTIGATION Most of th'e duck gizzards collected in 1938 were from but 4 areas of the 20 that' were mapped. T.herefore, the per cent of 'abundance cf aquatic plants- on only thuse four areas has been con- sidered in this study. • These sample areas contained representatives of all important plants ' existing in the Illinois Ri'vur Valley, under three different types of v;ater levels. The four areas are as fellows: 1. Cuba Islan d , near the mouth of the Sangamon hiver. This area had senistabilized water levels; rice cut-^rass and marsh smartvifced formed the two raajor food plants. Duck gls-zards exajnined from this area totaled 289. 2. Crane Lake and a marsh adjacent to it, in the vicinity of Snicarte. The lake had fluctuating water levels in 1938; tlie marsh semistable v.ater levels. Duck gizzards examined from this area totaled 293. 3. Lake Chautauqua and Clear Lake , which lie adjacent to each other, north of havana. The former had a stable v»-ater level, with an abiondance of coontail, longleaf and sago pondweeds and marsh smartweed. The latter had fluctuating water levels and a paucity of duck food plants. While all the duck gizzards were collected at Clear Lake, field observations indicated tr.at the ducks obtained most of the natural food from Lake Chautauqua. Gizzards exam.ined from this area totaled 358. 4. Duck Island , a s"..ort distance fron Lake Chautauqua and CJ-ear Lake, had semistabilized water levels. Coontail, marsh sm.art- weed and duck potato v;ere the nost important native duck food plants.. .Duck.- gizzards examined from tx.is area totaled 207. V.ATERFOV.L FOODS ON FOUR AREAS In table 1 are listed the 20 aquatic plants that occurred in greatest abundance in the four areas considered as a whole. Of these, onlj^ eight were used extensivel;r for food by waterfowl. This table presents -a^comparison between ..abundance and use of waterfowl food plants, virit} an index rating of their value for the study areas considered as a vvhole. In order to illustrate the effect of environmental condi- tions, v;hicli alter the value of duck food plants in different types of habitat, the abundance, use and index ratings of duck food plants sumirarized in table 1 are presented for each of the four sample areas in tables 2, 3, 4 and 5. Table 1. - Per cent of r-.se, per cent of abundance and index rating of aquatic plants in four areas of the Illinois 2xvk.r Valley, IbvjO, Plant Per Cent of Use Per Cent Index of. Abundance li.ating Rice cut-,':rass ( Leersi a oryzo^des ) 2C.45 Coontail ( Cerato pliyll u-M dpue^rs;^:!^;:^) • ■ 22.72 Nut:3ra3ses ( C yperu s spp. ) 11.70 Marsli srnartweed ( Polyponu.a I .u^-ler-bgrjjii ) S.61 Loneleaf '-'ondweed ( Potanofeton aji.iericanus ) 5.35 Buttonbusli ( Cephalantlius occidentalis ) Teal grass ( Eragrostis hypnoides ) V/ater herap ( Acn^da tuberculata ) Sr.iar tweeds (Polyigonu'i spp. ) -;.--;- Duck potato ( Sag itta ria latif olia) Sago pondweed ( Pota:"ior:eton pecti r iatu s ) .li.ierican lotus ( rel^ai.ibo lutea) Giant burreed ( Sparganiu^n eurycarpujg ) River bulrush ( S cirp-gs f luvi ati lis ) '..Lite waterlily ( C astalia tuberosa ) Marsli cord [,i-ass ( S partina I'licliau.xiana ) Gpike rushes ( Sleocliari s spp.) Pickerelweed ( Pontederia cordata ) Bushy pond'/eed ( I'a jas guadalupsn s i s ) liud plantain ( He teranthera dub in ) Other native foods (total of 50) 3.49 5.16 2.17 1.55 1.40 0.39 . 55 0.50 0.21 0.15 0.05 0.00 0.00 0.00 0.75 39.00 14.20 1.33 trace high 14.43 0.G5 15.48 0.43 abundant l0V7 trace medium trace nediui-.i trace nediui'n 7.14 0.20 O.Cl 0.10 23.50 0.01 trace low 9.97 0.03 0.30 0.26 0.70 0.21 1.04 0.05 0.40 vevj low trace very lov/ trace ver"-" low -;;-;. Other than jiuPxlenoergi: -;;-,;--;d,"o figure given because of difficulty of r.easurey.ient Table -2. - Per cent of use, p'ef e'en f'' of aB^ondarice and index rating of aquatic plants at Cuba Island, 1938. Per Cent Per Cent Index Plan t -^_ of- Use - of Abundance Rating Rice cut-grass ( Leersia oryzoides ) Nutgrasses ( C^'perus spp.) Marsh smartweed ( Polygonum Muhlenbergii )- Teal grass ( Eragrostis hypnoides ) Ccontail ( Cera t ophyl lun dernersuiti ) I'Jater hemp , ( Aonid a tubercular r.) Luttonbush ( C ephal an thug occidentalis ) Snartweeds ( Polygonum spp. )■'"•' Longleaf pondweed ( Potamogeton americanus ) 0.67 Sago pondweed (Pot amogeton ye ctinatu s) Duck potato ( Sagittaria latlfolia ) River bulrush ( Scirpus fluviatilis ) Spike rushes ( Eleocharis spp. ) American lotus ( Ilelumbo lutea ) ?!arsh cord grass ( Spartin a richau xi ana ) Other native foods (total of 28) 53.76 3.04 17.68 16.65 trace high 8.92 48.70 1.83 6.53 trace high 5.39 0.15 22.60 3.11 0.00-:: high £.83 ab 'and ant low 1.92 trace high 0.67 0.60 1.12 0.10 trace low 0.10 trace low 0.09 trace low 0.05 trace low ,0.00 42.31 very low 0.00 5.20 ■'•'ery low 1.88 -•;,-",-;'. 'None recorded for the area. '"Other tPian Muhlenter-li. 'No figure given because of difficulty of measurement. 8 Table 5 - Per cent o.f use,, per cent of abundance and index rating of aquatio plants at Crane Lake and adjacent marsh, 1938. Plant per Cent of Use Per Cent of Abundance Index Rating; Coontail ( Cerat'ophyllum demersum ) -"■■* 18.79 Rice cut-grass ( Leersia c'ryzoides ) 17.42 Nutgrasses ( Gyperus spp.) ' 12.35 Marsh smartv;eed ( Polygonum Muhlenbergii ) 8.66 Buttbnbush ( Ceplialanthus oocidentalis ) 8.55 Water hemp ( Achida tuberculata ) 4.03 Smartweeds ( Polygonum spp.)-::--;:- 2.35 3ago pondweed ( Potamogeton pectinatus ) 2.02 Ar-ierlcan lotus ( Melumbo lutea ) ■ ■ ■ 1.51 "I'Jiite waterlily ( Castalla ' tuberosa ) 1.17 Longleaf pondweed ( Potamogeton america nus ) o«98 Teal grass ( Eragrostis hypnoides ) 0.88 River bulrush ( Scirpus f luviatilis ) 0.37 Giant burreed ( Spargan ium eurycarpum ) 0.27 Spike rushes ( Eleocharis spp.) 0.14 Marsh cord grass ( Spartina Mlchauxiana ) 0.02 Duck potato ( Sagittaria latifolia ) 0.01 Other native foods (total of 34) " 20.43 1.40 • 3.50 0.00-:;- 2.80 abiindant 0.00-;:- . 00-::- 1.60 72.90 6.10 0.10 0.00-;:- 9.10 0.00-::- 0.00-;:- 1.00 1.50 13.42 4.98 high 3.09 medium medium medium 1.26 0.02 0.19 9.80 medium 0.04 low low 0.02 0.006 None recorded for the area. Other than Muhlenbergii . llo figure given because of difficulty of measurement Table 4. - Per cent of .use, per cent of abundance and Index rat- ing of aquatic plants at Lake Chautauqua and Clear Lake, 1958. Plant Per Cent Per Cent Index of Use of Abundance Rating Coontail (Ceratopliylluin demersum) 23.74 Lon£leaf pondweed ( PotaiTiOgeton americanus )16. 14 Marsh smartwoed ( Pol;^ gonuin M ulilenbergii ) 14.21 Iv-itgrasses ( Gyperus spp. ) 12.80 Duck potato ( Sagittar ia la tlfolia ) 6.59 Buttonbush ( Ceplialanthus occldenta lis ) 5.80 Sago pondweed ( Pota mo geton p ectinatus ) 5.03 Rice cut-grass (Lee rsia oryzoides ) 2.54 oiTiartweeds ( Polygonum spp . )•::--:;• ■ 1.53 River bulrush (Scl rpus fluviatilis) 1.27 uiant burreed ( Sparganium eurycarpum) ' 0.95 '.Vater hemp ( Acnida tuberculata ) 0.07 3pike rush ( Eleocharls spp.) 0.04 liushy pondweed ( ITaias guadalupensis ) 0.01 '^t: er native foods (total of 54) 15.63 27.91 52.01 9.40 trace 2.01 abundant 20.55 0.00-;;- trace 5.62 trace 0.00-;;- 2.50 trace 0.85 0.50 1.51 mediujn 5.18 low 0.15 high high 0.23 medium low 0.02 low "l\[one recorded for tLe area '""""Other than M'ii:Llenbergii . No figure given because of difficulty of measurement. 10 Table 5. - Per cent of use, per dent of abundance and Index rat- ing of dquatic plants at ruck Island, 1938. Plant Codntall ( Ceratophyllum d erne r sum ) Lorlgleaf pondweed ( Pota mo'geto n ainericanus) 14.14 Marsh smar tweed ( Pol^-goraiiii I .Iul^len - ergii) Duck potato ( Sag it t ar la lat lfol ia) Rice cut-grass (Le ersia cry z o ides ) Giant burreed ( Sparganiura euryca rx^u m) Marsh cord grass ( Spartina Micliauxiana ) American lotus ( Helumbo lutea ) 5m.ar tweeds ( Polygonum spp'. ) -:;--:;- Buttonbush ( C'eph alanthus b cciden t all's ) River bulrush ( Scirpus f luviatilis ) Sago pondv/eed' ( Po tamogetoh pectinat us ) V.'hite waterlily ( Castalia tube rosa) Other native foods (total' of 39) Per Cent Per Cent Index of Use of Abundan ce Rating 56. 56 6.50 10.24 3) 14.14 trace high 8.77 15.60 0.56 2 .04 17.00 ■ 0.12 1.28 ■ 0.00-;;- high 0.79 trace raedi-'um 0.71 ■ 0.00-:;- low 0.51 42.60 0.01 0.43 . 00-;;- medium 0.41 comriion low . £0 18.10 0.01 0.18 • trace medium ■ 0.00 0.20 very low 3.98 ."..-"--", Hone recorded for the area Other than Miol - 1 e nb e r g i i No figure given because of difiiculty of Tieasureiient 11 VALUE OF POOD. PLANTS STUDIED , The value as v;aterfowl food of" the most abundant aquatic plants in the Illinois River Valley in 1938' is discussed below, plant by plant. Statements . are based upon data obtained in the four . study areas' nentioned above. RICE CUT-GRASS, L eersla oryzoide s Sv;. , in 1938 v^as appar- ently the best native duck food lolant in tile Illinois River re;rion with an index' rating of 39.00 for the four study areas considered as a vvhole. At Cuba Island, wliere an excellent bed occurred, it rated second to coontail. lerhaps there coontail v.as more abundant than recorded.- In early., svttmier, many coont.ail plants were noticed at Cuba Island in a large bed of marsh smartweed, but, when the vegeta- tion was mapped in August, the v;ater was so low that it was virtu- ally impossible to worl: a boat into the bed and ascertain t}ie extent of the coontail. At Crane Lake, rice cut-grass was second to long- leaf pondweed in index -rating. There only a small portion of the rice cut-grass bed was available to the ducks because the birds could not feed en the rootstocks of the m.any plants t].at were not flooded. COONTAIL', Cer atop hyll^jm demers^ju n L. , was slightly below rice cut-grass in actual use, but, since ft was much more a.bundant, its index rating for the f.^ur study ai-eas considered as a whole was only 1.68. ' This species grew almost exclusively in areas with stable .or semistable water levels. Of the four areas studied, the best, for demonstrating the value of coontail was -Duck Island, where this species was first in value, v^ith an index rating of 10.24. In t}ie Clear Lake region, coontail had a lower index rating than duck potato or marsh smartv^reed. NUTGRASSES, Cyperus erythrorhizos Muhl . , Cyperus s trigosus L. , and Cyperus esculentus L. , forr,ied 11.73 per cent of all native duck foods in the- gizzards examined; yet in 1938 these species oc- curred only as sm.all" patches in a few }. laces in the four' areas from which gizzards wore' oollocted. How was it lossible for ducks to ob- tain such a large volume of food from t]'.ose small-seeded spe'cies? In 1938- a large per cent of the waterfowl on the study areas fed on mud flats as well as in shallow laku water. No plants were seen growing on' the mud f lats--exposed areas of the shallDv; lake basins. In the two preceding years, 1936 and 1937, " because the water had receded early in the summer, nutgrasses (as' well as sm_art- weeds, v;ater hemp and teal grass) formed luxuriant beds on tlie mud flats. The conjecture was made that large quantities of seed dropped by the 1936 and 1937 crops of these plants furnished food for ducks in 1938. . • To substantiate or disprove this conjecture, several mud samples were collected froi.i barren mud flats in September, 1940, three ;^'ears after moist soil plants had grown on these areas. These sam^-lcs, collected from. IS square .feet of- surface, yielded 2,500 seeds of Cyperus erythrorhizos • and 2,000 seeds of C. strigosus . The above evidence, we believe, lends strong support to tie statement that Cyp erus seeds fo-und in duck stomachs in 1938 were from 1936 and 1937 croiTs^"" 12 TEAL GRASS, Eragrostis h ypnoldes (Lain.j BSP. , V.ATER liEMP' or FIGVi^'EED, Acnida tuberculata Moq.', and SMARTw'EEDS, I^ lyr'^'i'iu^ ^ s::^.. ■ tT^E.or" cliT.z'.'.'vyil^x-i.'.r'.j-i) f?.c:-i^";: tiie nutgrasses, were very scarce in the'lTrinois"^RTv"er~regTon' in 1938, because of unfavorable water lev- els.- Yet tl.'ey formed, respectively, 3.16, 2.17 and 1.63 per cent of the native food plants taken from the 1,147 duck stomachs examined. Vve believe that miany seeds of these moist soil plants were deposited in 1936 and 1937, when the plants were abundant, and that waterfowl feeding on the barren mud .flats in 1938 picked up the seeds. A ■sm.all sample of mud collected from barren mud flats in 1940 yielded 550 seeds cl v/ater hemp. ' , - MARSI-I SMARTWEED, P olygon!^ MulxlenbergJi (I.Ieisn. ) \cats., rated higher than longleaf pondweed, but below coontail, for the four areas as a whole; its index rating was 0.66, about one-third that of coontail. This smartv\feed rarely produces seed when growing on dry soil. In 1938, seed was produced by all beds in the areas considered.. Marsh smartweed was of more value in the Crane Lake area, where a greater scarcity." of natural foods existed, than in .the other ' areas. LONGLEAF POKDV.'EED, Pota moge ton am.ericanus C. & S.", liad an index rating for the four areas of O.'liT, indicating that it v/as about two-thirds as valuable as -marsh smartweed. This pondweed was •scarce in the Cuba Island, Crane Lake and Duck Island areas. At Lake Chautauqua, where it ranked fourth in preference, it was the most abundant species, due to stabilized water levels there." In the Crane' Lake region, it rated as th'e second best duck food plant. The high p'ercentage of longleaf pondweed recorded, for the gizzards col- lected "at Duc.k Island was evidently due to the f.act that many of the ducks killed there had previously fed in nearby Lake Chautauqua. GIANT BURREED, Sparganium eurycarpu m Engelm. , had an ex- tensive' distribution, but- its occurrence-was limited to small, scat- tered p.atches. 'Ae believe' that it forined about 1.0 per cent of 'the vegetation. This would indicate that burreed was not preferred to longleaf pondweed b.ut was .a better, food than white vi/aterlily or duck potato. BUTTONBUSK, Cephalanthus occidentalis L. , was approximately as abundant in the Illinois River region in 1933 as was river bul- rush. It was, hovvever, seldom within the mapping area, occurring for tlie most part inside the sliore line.. Seeds of the buttonbush amounted to- 3.49 per cent of the native plant foods fo'uhd in the duck gizzards examined. This figure probably entitles it to be ranked in 1938 as a better, duck food than wlxite waterlily or duck potato. It should be noted that in the stomachs taken from Duck Island and Cuba Island, where natural foods abounded, little buttonbush seed was found. However, in the gizzards taken from Crane' Lake, where there was a dearth of good, natural food, buttonbusli seed amounted to 8.55 per cent of the native plant food's. WHITE VvATERLILY, C astalia tuberosa (Paine) Greene, had an index rating for the four areas of 0.26, almost half that of long- leaf pondweed. ' -However, we are hesitant to believe that this water- lily is as valuable as indicated. Its limited distribution and tlie hlghcontent of a few gizzards may have distorted its value. In the Crane Lake region, where the most extensive area of wLiite waterlily occurred and other natural foods were scarce, the index ratirgwas 0. 19. 13 MARSH CORD -QHASS, apart ina . Mi ckauxi na Hitchc. , usually considered only a fair duck 'food, had -an" index rating for the four areas of 0.21. We "believe this rating ^ to' he too high; seeds of this species occurred in only two gizzards, vd-.ich v^'ere completely filled with tlLen. ihe sampling is too. small to. give a valid index rating. DUCE POTATO, Sagittaria latifclia V.illd. , is regarded by many hunters along the Illinois River as a good duck food plant; yet the index rating of 0.20 for the four areas studied indicates that it was one of the least valuable of the plants in 1958. r.iost tubers of this plant examined in the field were too larg'e for ducks to con- sijme; consequently, most of the food from this plant found zards consisted of seeds. The, high index rating, 2.18, for the Clear Lake region was due in part to a n'jmbcr of gizzards containing tubers. SAGO POKDVvELD, F otatr.ogeton j^ ectinatus L. , a highly rated duck food, had an index rating of 0.10 for the four areas. It abounded at Lake Chautauqua, forming one-fifth of the vegetation. In other regions it was scarce. For the Clear Lake and Chautauqua region, this species had an index rating of 0.15. In the 1., 147 giz- zards examined, no foliage or tubers of tuis plant v>^ere found--only seeds. Seed production of tl.'is ;.^ondwoed in the Illinois River Val- ley was very low in 1938, a situation that may account for the fact tl'.at tills plant, usually considered an excellent source of duck food, rated as one of the poorest in ti.-is region for the year. SPIKE RUSHES, Eleocharis spp., seemed to be cf slight value as duck food in the areas studied in 1938. They had an index rating of but 0.05 and were very limited in tlioir distribution. At Clear Lake a fairly large bod of Eleoel aris palustris (L.) R. & S. occurred. Its index rating cf 0.02 indicates that it had little value as a duck food. RIVER BULRUSH, S cirpus fluviatilis (Torr. ) Gray, -a coarse, dominant marsh plant, covered large areas in the Illinois River Valley in 1938, as in most other years. Lespite its abundance, only 0.30 per cent of the natural food found in the duck gizzards col- lected from the four areas was from this species. The indi^x rating for the four areas was 0.03, indicating tiiat tiiis species is one of tlie least valuable of the duck food plants. The slight value of this plant is due in part to the small quantity of seed it usually produces. Only occasionally does a rlvcr bulrush bed produce seed \n quantity. In 1938, at Lake Chautauqua, \.hen the bulrush beds pi'oduced an abundance of seed, the index rating of t}.is plant for th.e area was 0.23, almost half that of longleaf pondwecd. General- ly this bulrush is a weed species, competing for space with more valuable food plants. ALIERICAi': LOTUS, N elximbo lute a (Vvilld. ) Pers., was in 1958 the most ab"'andant plant in the Illinois River Valley. It represented 28.3 per cent of the aquatic vegetation in tP.e areas considered in tills paper. Yet the hard, nutlike seeds v.ere so seldom taken by ducks that they totaled only 0.58 ].er cent by volume of the native duck foods in the stomachs examined. Its index rating cf 0.01 indi- cates that it is one of the poorest of the waterfowl food plants. Since it, like river bulrush, often crov«ds out more desirable plants, we must consider it a ;veed in a v.'aterfowl liabitat. 'I **.<' > * n«^ ' i )iU' n;i;:fr/M5< lihi r > t } -ft! iVcK ii.'-j ?i .ii*i$u.r m IhH' f, 5, s^?;>^^ Hr*: