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State of Illinois
John Stelle, Governor

Department of Registration and Education
John J. Hallihan, Director

PRELIMINARY REPORT ON
AVAILABILITY AND USE OF WATERFOV.L FOOD PLANTS ~
IN THE ILLINOIS RIVLR VALLEY

Krank C. Belirose, Jr.
Harry G. Anderson

Rueesiieoe bya hubhorikby Om Ghe TSisabe on smileinoedss

NATURAL EISTORY SURVEY
Pheodore HH. FPrisom,. Chier

Biological Notes No. 15 Urbana, Mlanous December,

1940

= stant fi 3. Ss
nent rad ae Denes uu,

eibec babi ia: spel tite 7220 OF fo “ign faa
Le abe) ad eta ol scial,

PHO1laA YRASIN: sa
crue SU Sel) a guar aaenth 4
cn tebe i nil

PRELIMINARY REPORT ON
- AVAILABILITY AND USE OF WATERFOWL FOOD PLANTS
IN THE ILLINOIS RIVER VALLEY

Frank C. Bellrose, Jr., and Harry G. Anderson”

Because studies conducted in the past on duck food habits
have covered extensive rather than localized areas, the abundance
of aquatic plants and their use by waterfowl have never before been
correlated to secure an index rating: of yalue.for these plants.

The, Ll Linows) 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¢ inches to the mile were available and duck giz-
zards were obtainable in quantity from. hunting clubs.

in L958, 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,
Seb up Under terms of the Federal Aid an’ 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
abundanee, the decision was 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 junior 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 case being obtained by a planimeter used on vegetation maps
made by the senior author,

Because of the impossibility of obtaining accurate figures,
no measurement was 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 Teéhnician, I1li-
nois Natural History Survey; Harry G. Anderson, Junior Biologist,
Illinois Natural Eistory Survey, State Department of Conservation
and U. S. Fish and Wildlife Service (Federal Aid Program).

-— oO

1

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
waterfowl, plant differences and habitat characteristics are factors
tending £0 eeewent a minutely eae rating et Bue

; Ducks frequently feed in more. than one lake in the same
Gay. The!.area 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 assumption that the contents of each giz-
zard | were ‘ \eni tie neds in.the area in wnich the duck was killed.

_ Accurate measurement of he Cidimerences — food yields of
the ‘same species ef plant under varying conditions has not. been

possible in this study. For exemple, sago pondweed is very erratic
in seed production. Some beads produce. no seeds; others produce a
large samount.. In thé ..case of several species,) seeds were available

FO aguceks im an arca in which mo plants were seen; tne sceds hadepers
(Gropped: in, the-mud, bythe previous, year's. plants but had not
sprouted - to: produce vegetation. hen, TOO, No, accurate |measumemenr
has been possible of the effect of differences in water level om the
availability -to.- ducks of plant parts. Low water, Or no water, may
precitide, the: use,of certain food plants; water of, greater, than Lswall
depth may have the same effect with respect to» other plants.

the index rating in each case should be considered wee
Give 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 the per cent of abundance of other plants,
Whereas. ali plants were imeduded. in: calculating the, per) centyoLimser

Even though) the possibility of error an) individual Gdiekess
or in, individual areas, is great, the authors believe that in those
food) plants, in which) the number; of samples'is large the errorss pend
to cancel each, others, Ficeld,observations confirm or only) slightdy

modify the findings presented in table 1. |The index rating) columm
seems sufficiently valid to justify its use in planting programs, cr
leases Ors thie caghte plants with theyhignest percentagesois use. 0m
the+Tirst. eight, those, with a low index rating should be avoidedyim
most planting programs.

AS UNDER INVESTIGATION

Most.of the duck gizzards ‘collected in 1938.were from but
A areas. OF te ZO Lnat, were mappedw..Pacretore, theyper cenbeos
‘abundance of aquatic cr heme only these four areas has been con-
sidered in this study. - These sample areas contained representatives
of all important iene existing in. the Illinois River Valley, under
lie Chhewsigsiais wes) Oat Weseic Tevels. :

The four areas are as follows:

1. Cuba Island, near the mouth of the Sangamon River.
This area had senistabilized water levels; rice cut-grass and marsh
smartweed formed the two major food plants. Duck gizzards examined
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: the
marsh semistable water levels. Duck gizzards examined from this
area totaled 293.

&. Lake Chautauqua and Clear Lake, which lie adjacent to
each other, north of Lavana. The former had a stable water level,
with an abundance 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
Glear Lake, field observations indicated that the ducks obtained
most of the natural food from Lake Cliautauqua. Gizzards examined
from this area totaled 3558.

4. Duek Island, a suort distance from Lake Chautauqua and
Clear Lake, had semistabilized water levels. Coontail, marsh: smart-
weed and duck potato were tlhe most important native duck food plants.
Duck-gizzards examined from this area totaled 207.

WATERFOWL FOODS ON FOUR AREAS

im Gable i are listed the 20 aquatic plants that ocemered
im. greatest abundance in. the four areas considered as a whole. Of
imese, Only eight were used extensively for food by waterfowl. This
table presents-a-comparison between-abunaance and use of waterfowl
food plants, with an index ratings of tl.eir value for the study areas
considered as a whole.

im order to pilustrate tie. eftechrof lenvaronmental’ condi
tions, Which alter the value of duck food ,lants in different types
of habitat, the abundance, use and index ratings of duck food plants
summarized in table 1 are presented for each of the four sample areas

i tables 2, ©, 4 and ‘5.

6"
Table 1. = Per cent of use, per cent of abundance and index
rating of aquatic plants in four areas of the Illinois River Valley,

1938,

= op To. nae »ber,Centy aapber Cent Tndeuaam

Plant of Use oF “Boundance | having

Rice cut-grass (Leersia oryzoides) 20.46 0.75 59.00
Coontail (Ceratopiyllum demersum +. 22.72 14,20 1.63
Nutgrasses (Cyperus snp.) dle trace high
Marsh smartweed (Polygonua Muhlenbergii ) 9.61 re 0.66
Longleaf nondweed (Potamoceton americanus) 5.95 15.48 0.435
Buttonbush (Cephalanthus occidentalis) 5.49 abundant low
Teal grass (Eragrostis hynnoides) Senko trace medium
Water hemp (Acnida tuberculata) Bole trace nediun
Smartweeds (Polygonum spp.) i* WG SS) trace mediuia
Duck potato (Sasittaria latifolia) Hy dk BO Pe Le On ZO
Sago pondweed (Potamoreton vectinatus ) Oo 3S Smne Ope
American lotus (KRelwabo lutea) | On 56 28.30 ©, Ou
Giant burreed (Sparganiun evrycarpum) ORB) trace Low
River bulrush (Scirous fluviatilis) Os50 O97 OnGs
vhite waterlily (Castalia tuberosa) Geral O50 Ono
Marsh cord grass (Sp rtina Michauxiana) OR ILS OS We Oo Ail
Spake rusnes (Hleotharis s Dp.) 0.05 1,04 0.05
Pickerelweead (Pontederia corcata) 0.00 0.40 very low
busny pondvreed (Najas suadaluvensis) 0.00 trace very low
liud plantain (Heteranthera dubia) O.00 trace very Low
Other native foods (total of 50) 7.40 Seoese

—— eee

bier than Muhblenpersii.

Dono pEsgume (oLSeH PeCause Ol Cilficulty oP measurenient

Table-2. - Per cent of use, pér cént of abundance and index
rating of aquatic plants at Cuba Island, 1958.

san ; ; Plant cree _of Use of Abundance Rating
Rice cut-grass (Leersia oryzoides) “tne AS elF6 0904 suited 768
BE eresses: (Cyperus SPP. ) seek 16. eee : trace high
ech smartweed (Polygonum einen cia 8, 92 48.70 1,465
Teal grass (Eragrostis hypnoides) : 6.53 trace high
Ccontail (Ceratophyllum demersum) ~ 5.39 0.15 22.60
Water hemp ,(Aonida tuberculata) Sis 0.00% high
Buttonbush (Gephalanthus ocesidentalis) . 2 eOd abundant low
Smartweeds (Polygonum spp. ) #4 teat bee trace high
Longleaf pondweed (Pecement es americanus) 0.67 0.60 Lad2
Sago pondweed ({Potamozeton pectinatus) Ow EO trace low
Duck potato (Sagittaria latifolia) (@PeKe) trace low
——_ bulrush (Scirpus Sim aey te) _ 0.09 trace low
Spike rushes i oe er re 0..05 trace low
American totus (Nelumibo lutea) a egy a 42.31 very low
Marsh on grass (Spartina Michauxiana) 0.00 | 5.20 very, low

Other native foods (total of 28) 1.89

“Nene recorded for the area.

*““Other than Muhlenbergii.

“““No figure given because of difficulty of measurement.

Table 3 - Per cent of use, .per cent of abundance and index rating
of aquatic plants at Crane Lake and adjacent marsh, 1938.

Per Cent © Per Cent Index

Plant Se et Se of Abundance Rating
Geontaii (Geratophyllum demersum) ~~" -1870™ 1.40 13.42
Rice cut-grass (Leersia oryzoides) 17,42°" —taReeo 4,98
Nutgrasses (Cyperus spp.) Pe BCE 12755: 0.00% | high
Marsh smartweed (Polygonum Muhlenbergii)* 8.66 Brio S09
Buttonbush (Cephalanthus occidentalis) 8.55 abundant medium
Water hemp (Acnida tuberculata) 4.03 0.00% medium
Smartweeds (Polygonum spp.) ro) amen 0. 00+ medium
Sago pondweed (Potamogeton pectinatus) Oe Ts 60 1.26
American lotus (Nelumbo lutea) nae 1g Suk 72.90 0.02
White waterlily (Castalia tuberosa) Mee dli7/ 6.10 0.19
Longleaf pondweed (Potamogeton americanus) 0.98 sate 9.80
Teal grass (Eragrostis hypnoides) 0.88 5OmOOss medium
River bulrush (Scirpus fluviatilis) Omir 9.10 0.04
Giant burreed (Sparganium eurycarpum) Ome 7 iO OOse low
Spike rushes (Eleocharis spp.) 0.14 0.00% low
Marsh cord grass (Spartina Michauxiana) 0.02 IOG) 0.02
Duck potato (Sagittaria latifolia) Oo Ok Ibs 910) 0.006
Other native foods (total of 34) "20.48

“None recorded for the area.
“Other than Muhlenbergii.

Are figure fuyen Wecause of Gitilteulty of measurement.

Table 4. = Per cent of..use,

ee

a et

Per (Cent
of Abundance Rating

Pei Cenc
_ ees Seo oe LOR MUSE
Coontail (Ceratophyllwn demersum) Bow lS

Longleaf pondweed (Potamogeton americanus)16.14

Marsh smartweed (Polygonum Muhlenbergit) i 2a
Nutgrasses (Cyperus spp.) Le. BO
Duck potato (Sagittaria latifolia) 6.09
Buttonbush (Cephalanthus oc occidentalis) 5.80
Sago pondweed (Potamoseton pectinatus ) 02035
Rice cut-grass (Leersia oryzoides) 2.4
Smartweeds (Polygonum spp. )* 1.58
River bulrush (Scirpus fluviatilis) deener7
Giant burreed (Sparganium eury ycarpum) 0.95
Water hemp (Acnida tuberculata) Ono
Spike rush (Hleocharis spp. ) 0.04
Bushy pondweed (Najas guadalupensis) 0.01
Guber native foods (total. of $4) Lo wOS

“None recorded for the area.

“Other than Muhlenbergii.

ng of aquatic plants at Lake Chautauqua and Clear Lake,

re oeyit

9.40

trace

ra OM

abundant

20.55

©. OO

““"No figure given because of difficulty of measurement.

per cent of abundance and index rat-
1938.

0.85

high
0.28
medium
low
0.02

low

Index

LO

Table 5. - Per cerit of use,
ing of dquatic plants at Duck Island, 1908.

Coéntail (Ceratophyllum demersum)

Lorgleaf pondweed (Potamogeton americanus) 14.14

,

Marsh smartwéed (Polygonum Mulilenbergii)
ee —————— Ta,

Duck potato (Sagittaria latifolia)

Rice cut-grass (Leersia oryzoides)

Giant burreed (Sparganium eurycarpum)
Marsh cord grass (Spartina Michauxiana)
American lotus (Nelumbo lutea)
Smartweeds (Polygonum Sppe ) 3%

Bubtonbush (Gephalanthus occidentalis)
Rayer bulrush (Scirpus fluviatilis)

Sago pondweed’ (Potamoseton pectinatus)
White waterlily (Castalia tuberosa)

Other native foods (total of 39)

Oe

None recoracea for tl:e area

tl.er than Muhlenbergii
Se eee

SnSeS4
er er)

¢ 8. rae.

2.04

42.60
0.00%

common

18.10
trace

0.20

No figure given because of difficulty of measurement

per dent of abundance arid index rat-

"Per Gent Per Cent imeem
of Use of Abundance Rating

56.56

10.24
high
0.56
Ome
high
medium
low
0.01
medium
low
0.01
medium

very low

oe edeS OF FOOD. PLANTS STUDIED

‘The value as ‘waterfowl food of" “the ose “abundant aquatic
plants’ in-the.illinois River Valley in’:1958 is discussed below,
pliant by plant. Statements.are. based upon da ata obtained in the four
. study areas’ mentioned above.

RICE CUT-GRA ‘Leersia oryzoides Sw., in 1938 was appar-
ently the best:.native anek food plant ‘in tlie Illinois River PESUOmn,
with an index rating of 59.00 for’ the four: study areas considered as
a whole. At Cuba Island, where an excellent bed OCcurved=] Tt) raced.
second to coontail. Perhaps there coontail was more abundant than
recorded.-: In early simmer, many coontail plants were noticed at
Cuba Island in a large bed of marsh smartweed, but, when tlie vezeta-
tion was mapped in August, the water was so low that it was virtu-
ally impossible to work .a boat. into the bed-and ascertain the extent
of the coontail.. At Crane Lake, rice cut-grass was second ‘to long-
leaf pondweed in index:rating. There only a4 ‘small portion of the
rice cut-grass bed was available to the ducks because the birds
could not feed on the rootstocks of the many plants that were not
flooded,

COONTAIL, Cératophyllum Gemersum L., was slightly below
Tice Cuy=erass in actual use, but, since it was much more abundant,
its index ‘rating .for the four study areas considered as a whole Was
Hii Poo. thes species, srew almost exclusively in areas with
.Sstable or semistable water levels. Of the four areas studied, the
best for demonstrating the value of coontail was Duck Island, * where
Giis species was’ first in’ value, with an index rating of 10. BA. In
the Clear Lake region, coontail had a lower index rating than duck
potato or marsh smartweed.

NUTGRASSES, Cyperus erythrorhizos Muhl., Cyperus strigosus
i eno oyperus Sseulentus L., formed TI 7S per cent of all native
G@uck foods in the gizzards examined; yet in 1938 these species oc-
curred: only as small patches in a few places in the four areas from
which gizzards were collected. How was it possible for ducks to ob-
tain such a large volume of food from these small-seeded species?

in 1936: a large’ per cent of the waterfowl on the study
areas fed on. mud Bese as well as in shallow lake water. Wo plants
were seen growing on the mud flats--exposed areas of the shallow
lake basins. In the two preceding years, 1956 and 1937, because ‘the
water kad receded early in the summer, nutgrasses (as’ well as smart-
weeds, water hemp and téal grass) formed luxuriant beds on the mud
flats. ~The coni¢ceture: was: nriade that large quantities of seed
dropped by- the 1926 and. 1937 crors of these plants furnished food
for ducks in heey :

To substantiate or disprove. this conjecture, several mud
samples were collected from barren'mud flats in September, 1940,
barPee Wears albor moist sold plants iad crown on these areagien Lhe
Bemove st Colteerea, trom.16 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 supp pan to tke statement
hat. Cyperus scecs found in duck stomachs in 1958 were from 1956 and
1937 crops.

12

TEAL GRASS, Eragrostis hypnoides (yams) BSP., WATER fe

or PIGWEED, Acnida tuberculata Moq-., and nd SMARTWEEDS, Pokypo sous" SUL
{ycher’ emi uh ben Ome wad) pesca the nutgrasses, were very Scarce ‘in
the Iiiinois River Yégion in 1938, because of unfavorable water lev-
els. Yet they formed, respectively, 5.463, 0em47 sand 1.60 jpem Cenmimmos
the mative food plants taken trom whe i. 147 duck stomachs examined.
We believe that many seeds of these motst soil plants were deposited
in 1936 and 1937, when the plants were abundant, and that waterfowl
feeding on the barren mud. flats. in J968-p,icked up the seeds. A
‘small sample Qn mud scol lected from barren mud flatis,in 1940 “yVemeed

550 seeds cf water hemp.

MARSH SMARTWEED, Polygonum Tei ulenor eel (Meisn.) Wats.,
mated higher than longleaf pondweed, but below coontail, for the
Hour Areas as & whole} its index rating was 0.66, about one-third
Baas of coomeall. This smartweed rarely produces seed when growing
On dry soil. ‘In 1958, seed was. produced by all beds iim the apene
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 PONDWEED, go eieule lee americanus C. & S., had@am
inigek rating stor tlie four areas of 0.4 io, indicating that it was
about two-thirds as valuable as-marsh smartweed. This pondweed was
‘scarce in the Cuba Island, Crane Lake and Duck Island areas. At
hake Chautauqua, where it ranked fourth in preierence, it was the
Most abundant species, due) to, stabilized jwwaber Mevels there. 5 tana
Grane Make region, it rated as the second, best, duck food. plant ayaa.
heh percentase of longleaf pondweed recorded) fom the gizzards yeok=
lected at Duck Island was evidently due to the fact that many of the
ducks killed there had previously fed in néarby Lake Chautauqua.

_ GIANT BURREED, Sparganium eurycarpum Engelm., had an ex-
tensive: distribution, but: its occurrence’ was limited to small, scaj—
tered patches. We believe that it formed about 1.0-per tent of the
VESCEAclOnNe. Lhis would indicate, that burrecd was nov, prefernecdwuce
longleaf pondweed but was a better food than white waterlily or duck
potato.

BUTTONBEUSH, Cephalanthus occidentalis L., was approximately
as abundant in the Illinois River region in 1938 as was river bul-
rush.: It was, however, seldom within the mapping area, occurring for
Ehe mos par inside tne shore line... Seeds of the but tonbush
amounted to 35.49 per cent of the native plant foods found in the duck
gizzards examined. This figure probably entitles it to be ranked in
fos, as a beter, duck food, than, white. waterlily or duck potatows wile
should be noted, that in the stomachs, taken from Duck’ Island ahd 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, buttonbush seed amounted CO! Geo
per Gens of the native plant foods.

WHITE WATERLILY, Castalia tuberosa (Paine) Greene, had an
WMGex VAtIMe.,tOr the tour 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 -andy ule
high conten: Of a few gizzards may have distorted its valter.. Umemme
Crane Lake region, where the most extensive area of whité waterlily
occurred and other natural foods were scarce, the index ratingwas 0.19.

per.

13

MARSH CORD ‘GHKASS,. Spartina: Michauxina Hitché., usually
considered only a fair duck‘food, had ‘an“index rating for the four
areas of 0.21. Vie“believe this rating!to“be tod“high; seeds of this
species occurred in only two gizzards, which were completely filled
with them. ‘The sampling is..too. small:to give a valid index rating.

DUCK POTATO, Sagittaria latifolia Willd., is regarded by
many hunters along the Illinois River as a geod 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 ,lants in 1938.- Most tubers
of this plant examinéd in the field were’ too large for ducks to con-
sume; consequently, most of the food from this plant found in giz-
zards consisted of seeds. The high index rating, 3.18, for the
Clear Lake region was due in part to a number of gizzards containing
tubers.

SAGO POUDWELD, Potamogeton pectinatus L., a highly rated
eucle Food; had an index rating of 0.10 tor the four areas; Tt
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 this plant were found--only
seeds. Seed production of this pondweed in the Illinois River Val-
ley was very low in 1928, a situation that may account for the fact
that this plant, usually considered an excellent source of duck food,
rated as ‘one of’ the’ poorest in tiris region for the “year.

SPIKE RUSHES, Eleocharis spp., seemed to be of slight
value “as duck folod in the areas ‘studied’ in 1938. They had am index
Pps sot DUG O.O00 end were very Limited in their distributions VAG
Clear Lake a fairly large bed of Eleocharis -palustris (L) R. & S.
occurred. Dts index rating of -0.0d ‘indicates that it had Ii ttle
value as a duck food.

RIVER BULRUSH, Scirpus fluviatilis (Torr.) Gray, -a coarse,
dominant marsh plant, covered large areas in the Illinois River
Valley in 1958, as in most other years. Despite its abundance, only
0.50 per cent of the natural food found in the duck gizzards col-
tected from the four areas was from this’ species. “The “Index rating
form che four areas was 0.05, indicating that this species 1s one of
bie Eeast valuable of the duck food plants. 4TThe slight value of
this plant is due in part to the small quantity of seed it usually
EEoduces.) Omiy occasionally Gocs a miver puilrusis bed produce isced
in quantity. In 1938, at Lake Chautauqua, When the bulrush beds
produced an abundance of seed, the index rating of this plant for
tue area was 0.25, almost Lalf that of longleaf pondwecd. General-—
iy teis bulrush is a weed species, Competing for space with more
valuable food plants.

AMERICAN LOTUS, Nelumbo lutea (Willd.) Pers., was in 1938
the most abundant plant in the Tllinois River Valley. It represented
26.0 per cen, of the aquatic vegetation in the areas considered in
this paper. Yet the hard, nutlike seeds were so seldom taken by
Gucks that they totaled only 0.58.per cent by volume of the native
duck foods in the stomachs examined. Its index rating of 0.01 indi-
CoLcsubean hs one Of the poorest of tac waterfowl food plants.

it, like river bulrush, often crowds out more desirable plants;
we must consider it a weed in a waterfowl habitat.

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