These "front-line" environmental field workers typically are the ones who take the soil and water
samples, who count the plants and animals, and who use the herbicides and tractors. They are
the ones who
first notice when a single plant species is taking over, or when a duck species does not return the
next year;
they are the ones who report to the rest of us what's happening in the real world. Therefore, they
need to know
as much as possible about the wetlands they work in. These workers must know about the
conspicuous invaders
and the reclusive rarities, and also those "other plants" that are so important to the health and
functioning of
wetland ecosystems. They need to know about the grasses, sedges and rushes.
Grasses, sedges and rushes are often thought of, and frequently listed as "other
plants" by workers
in the "natural resource management" world. This is because grasses, sedges and rushes are
difficult to identify,
they don't get much press, and there are very many species.
Even professional managers of wetlands, mostly non-botanists, often cannot tell a rush from a
sedge
or a beneficial native grass from an unchecked invader. This is actually very understandable.
Nature managers
must focus on "invasions" by hundreds of new species and are less able to pay attention to the
"other plants".
Consider also the "common name problem": short things are "sedges" (whether they are or not);
tall things are "big
grasses."
We could have a problem here.
One reason why managers should pay close attention to the grasses, sedges
and rushes that
grow in
their marshes, lakes and rivers is that these plants are very important to the diets of many
waterfowl such as
ducks and geese. If the necessary grasses, sedges and rushes disappear from a wetland or lake or
river, so could
many of the kinds of birds and other animals that depend on them for food and shelter. Natural
resource
management personnel, especially field workers, must be able to recognize native and non-native
grasses,
sedges and rushes in order to control only the non-native invasive plants and to promote the
growth of these
native plants that wild animals depend on.
This article lists some of the published research about several of the specific grasses, sedges
and
rushes that are preferred foods of ducks, geese and other waterfowl. The research cited here was
identified in the
APIRS database of the University of Florida. Though this database is about
aquatic, wetland and
invasive plants, it naturally includes much information about the animals that use them.
For the birds
Actually, it's not just for the birds. Research shows that the wild grasses, sedges
and rushes of our
wetlands
are eaten and otherwise used by all kinds of animals including mammals as diverse as deer,
rabbits, moose,
cattle, alligators, beavers and boar. And, of course, birds.
Like other classes of animals, the birds include some species that are mostly vegetarian, some
that are mostly
carnivorous, and some that eat both plants and animals. Among the waterfowl, for example,
wetland plant matter is
very important to the diets of American widgeon, ring-necked ducks, redheads, gadwalls,
mallards, pintails, wood
ducks and canvasbacks; plant parts also are important to the diets of fulvous whistling ducks,
green- and blue-winged
teal, black ducks, spoonbill ducks, coots, moorhen, soras, Canada geese, snow geese, greylag
geese, sandhill cranes,
mourning doves, white-winged doves and other birds. Certain wetland grasses, sedges and rushes
are also important as
habitat and nesting materials. For example, American woodcocks have a special affinity for
switch cane habitat
(Arundinaria gigantea), and clapper rails prefer to nest in black needle rush
(Juncus
roemerianus) (46).
Management objectives
The literature shows that there are many issues that wetlands managers must deal with, such
as development,
pollution, recreational uses ("consumptive" uses such as hunting and "non-consumptive" uses
such as tourism),
and non-native species invasions. All of these challenges also affect the wetland's populations of
grasses,
sedges and rushes, and the animals that depend on them.
"The first step to accomplishing the goal of marsh management for wildlife is to conduct a
food habit study
to determine if the best plants are growing in the marshes," according to H.F. Percival. To help
answer this
question for a South Carolina wetland, researchers investigated the conditions necessary for the
growth of
important wildlife plants such as soil nutrition, soluble salts concentrations and water level
(40).
It is surprising how much wildlife food is produced in an acre of productive wetland. In a
1951 study by J.R.
Singleton of the east Texas gulf coast, researchers found that in a single acre, Scirpus
robustus produced an
average of about 300 lbs. (dry weight) of seeds per acre per year; Echinochloa
walteri produced about 800
lbs.
of seeds per acre, Cladium jamaicense and Polygonum hydropiperoides
each produced about
600 lbs. of
seeds per acre, Leersia oryzoides produced about 150 lbs. of seeds per acre,
Rhynchospora
corniculata
produced about 900 lbs. of seeds per acre, and each acre produced about 5 tons of plant corms
(44).
Among their other responsibilities, wetland resource managers must control non-native
invasive plants,
lest they take over a wetland and replace native wildlife food plants. For example, F.A. Johnson
noted that in
central Florida, the very invasive torpedograss (Panicum repens) can become "dense
enough to discourage
waterfowl use". However, managers need to realize that when they are herbiciding, burning,
chopping and
otherwise controlling undesirable plants, they may also be killing very important grasses, sedges
and rushes.
According to Reid et al., "herbicide use has reduced grasses in the field" (46). When managers
are controlling
those familiar invaders such as cat-tail (Typha), silk reed (Neyraudia
reynaudiana), elephant
grass (Pennisetum purpurea) and para
grass (Brachiaria mutica), they should take care that their herbicides and flames are
not also killing those
unfamiliar "other plants."
Food plants and birds
Birds are known to consume all parts of grasses, sedges and rushes, including tubers,
rhizomes, stems,
foliage, inflorescences and seeds. Therefore, work on the nutritional value and digestibility of
wild plant parts
has been conducted on Scirpus americanus, Spartina spp., Juncus
gerardi and
other grasses, sedges and
rushes. (26).
In one unmatched study of mallard duck diets from 1918, W.L. McAtee reported collecting
animals
in 22 states and finding that mallards are mostly vegetarian, with more than 90% of their food
being plant parts.
Sedges (Scirpus cubensis and Scirpus fluviatilis), and
Fimbristylis,
Cyperus and Cladium comprised about a
quarter of the mallard diet; with grasses (Zizania aquatica, Echinochloa, Panicum
and
Spartina) making up
another 13%. The remainder of the mallard diet consisted of "smartweeds, 10%; pondweeds 8%;
duckweeds
6%, coontail, 6%; wild celery 5%; sagittaria 5%; with the rest being acorns and berries"
(30).
While some species of ducks eat more animals than plants, and some eat more plants than
animals,
for others the ratio depends on the habitat, food availability, and seasonality.
Seasonality in bird diets has been documented for several waterfowl species. Some kinds of
ducks
eat more animals during breeding/nesting season, and the same ones might prefer plant seeds
during migration.
For example, blue-winged teal change their diets seasonally, from eating aquatic invertebrates
(such as gnats
and small snails) in the breeding season, to eating mostly plant seeds during fall and winter (33).
This may be
due to the fact that animal foods provide more protein, possiby needed for egg development, etc.,
while plant
seeds, rich in carbohydrates, provide more "quick energy" needed for flying.
In a study of gut contents of Wisconsin redhead ducks (Aythya americana),
researchers found 34
animal species and 30 plant species. Seeds predominated in pre-laying birds; Scirpus
seeds and
Potamogeton
tubers were the primary components of laying redheads (22).
Duck diets change not just seasonally, but also according to location and food availability.
For
example, a study found that canvasbacks in Louisiana ate lots of grasses, sedges and rushes (17),
but in
another study in Maryland they ate mostly widgeongrass (Ruppia spp.) and
Potamogeton
perfoliatus (41).
Redhead ducks are so-called "diving ducks", so one might presume that redheads eat only
underwater
plants and animals. However, a study in North Dakota found that as much as 30% of the redhead
duck diet was
plant material, most of which was Scirpus seeds (11%), and seeds from a variety of
other emergent plants
including Eleocharis and Echinochloa. In fact, overall, redhead ducks
ate more emersed plant
food than
submersed plant food (48).
Grasses sedges and rushes are important foods even to very aquatic birds, such as the
bottom-sifting
shoal-water spoonbill duck (Spatula clypeata). In one study, 16% of the spoonbill
diet was Scirpus,
Carex
and Cladium, 11% was Potamogeton and 8% was Panicum
spp. (31).
The most important "staging area" for migrating greater snow geese (Chen
caerulescens) is a
3750-ha
Scirpus americanus marsh, where rhizomes, shoots and stems make up about half
their entire diet during
the
several weeks of both migration seasons (5).
Coots (Fulica atra) also are major wetland plant consumers. In one study on a
Polish lake,
two-thirds
of the coot diet was plant parts and one-third was animals. Even though coots spend much of
their time s
wimming and diving, the second-most important plant in the coot diet was Phragmites
australis (after the
bottom-growing Chara spp) (8).
Grow more grasses, sedges and rushes
In 1917, McAtee called for more dealers to grow and offer plants and seeds of various species
of
bur-reeds, pondweeds, cord grasses, bulrushes, saw grass, and sedges in order to supply wildlife
managers
who wanted to grow the right plants for birds (29).
In this booklet, McAtee tells managers how to propagate Zizania aquatica
because wild rice,
"in every stage of its growth is eaten by one or another of the North American ducks and geese,
and
practically all ducks feed on its ripened grain." It is "the staple fall food of many ducks in the
numerous
rice marshes of eastern U.S." This booklet also explains how to propagate chufas (Cyperus
esculentus)
and wild millet (Echinochloa crus-galli) (29).
Information abounds
Natural resource managers, including those workers who maintain and protect wetlands, lakes
and rivers, should remember the importance of the "other plants" in their charge. Managers
should learn
about the grasses, sedges and rushes, and promote these and other plants that are essential to so
many
species of birds and other animals.
GRASSES, SEDGES AND RUSHES USED BY WATERFOWL --CITED
RESEARCH
ARTICLES
The following is a list of some of the feeding studies of water birds taken from the
APIRS database:
Arundinaria gigantea stands -- a preferred habitat of American
woodcock (Straw et al,
(46))
Brachiaria extensa seeds -- a major part of the diet of fulvous
whistling ducks in
Louisiana ricefields. (20)
Carex spp. -- common snipe habitat (Arnold, (46))
Cladium jamaicense seeds -- very important to wintering gadwalls
in Louisiana (39); a
major food of ducks in SE Texas (44); a major food of
mallards in the US (30)
Cyperus spp. -- a major part of the diet of fulvous whistling ducks
in Louisiana (20);
tubers are a major part of canvasback diet in Mississippi
River Delta (17)
Distichlis spp. -- a food of sandhill cranes (46); among favorite
food of gadwalls in Utah
(13); eaten by mourning doves (46)
Echinochloa spp. -- eaten by mourning doves (46)
Eleocharis spp. -- a favorite food of gadwalls in Utah (13), and of
ruddy ducks (48)
Fimbristylis spp. -- a major food of mallard ducks (30)
Juncus roemerianus -- favored clapper rail nesting habitat
(Eddleman and Conway,
(46))
Leersia spp. -- a major part of diet in 3-year study of redhead
ducks in Wisconsin.
(22)
Panicum spp. -- preferred food of mourning doves and
white-winged doves (46); a
major food of mallard ducks (30)
Paspalum distichum -- used by greylag and barheaded geese
(36)
Phalaris arundinacea -- a major food of ring-necked ducks in
Minnesota (16)
Phragmites communis -- a major plant food of coots in Poland
(8)
Rhynchospora spp. -- a major food of fulvous whistling ducks in
Louisiana (20)
Scirpus spp. -- a major component of the diet of ruddy ducks (48)
and common moorhen
(Griej, (46)), soras (Melvin and Gibbs, (46)), seeds
very important to overwintering gadwalls in Louisiana, to redheads in Wisconsin (22); a major
food of spoonbill ducks
(31)
Setaria spp. -- preferred food of mourning doves and
white-winged doves in
southwestern U.S. (46)
Zizania aquatica -- "eaten by practically all ducks" (29); a favorite
food of soras in upper
midwest U.S. (Melvin and Gibbs, (46)); a major
food of mallard ducks in U.S. (30); a major food of black ducks and wood ducks (29)
BIBLIOGRAPHY
The following publications were identified by a search of the APIRS (aquatic,
wetland and invasive
plant) database, searching for
information about the food preferences and consumption rates of waterfowl.
1) Amat, J.A. 1995. Effects of wintering greylag geese Anser anser on their
Scirpus food plants.
Ecography 18:155-163.
2) Belanger, L; J.-F. Giroux and J. Bedard. 1990. Effects of goose grazing on
the quality of Scirpus
americanus rhizomes.
Can. J. Zool. 68:1012-1014.
3) Belanger, L. and J. Bedard. 1994. Foraging ecology of greater snow geese,
Chen caerulescense
atlantica, in different Scirpus
marsh plant communities. Can. Field-Naturl. 108(3):271-281.
4) Belanger, L. and J. Bedard. 1994. Role of ice scouring and goose grubbing
in marsh plant
dynamics. J. Ecol. 82:437-445.
5) Belanger, L. and D. Lehoux. 1994. Use of a tidal saltmarsh and coastal
impoundments by
sympatric breeding and staging American
black ducks, Anas rubripes, and mallards, A. platyrhynchos. Can. Field-Naturl.
108(3):311-317.
6) Beltzer, A.H. and J.J. Neiff. Bird distribution in the Parana River
floodplain. Relationship with
hydrological regime and vegetation.
Ambiente Subtropical 2:77-102. In Spanish; English summary.
7) Bogiatto, R.J. 1990. Fall and winter food habits of American coots in the
northern Sacramento
Valley, California.
Calif. Fish Game 76(4):211-215.
8) Borowiec, E. 1975. Food of the coot (Fulica atra L.) in different
phenological periods. Pol. Arch.
Hydrobiol. 22(2):157-166.
9) Connelly, D.P. and D.L. Chesemore. 1980. Food habits of pintails, Anas
acuta, wintering on
seasonally flooded wetlands in the
northern San Joaquin Valley, California. Calif. Fish Game 66(4):233-237.
10) Euliss, N.H. and S.W. Harris. 1987. Feeding ecology of northern pintails
and green-winged teal
wintering in California.
J. Wildl. Manage. 51(4):724-732.
11) Gadallah, F.L. and R.L. Jefferies. 1995. Comparison of the nutrient
contents of the principal
forage plants utilized by lesser
snow geese on summer breeding grounds. J. Appl. Ecol. 32(2):263-275.
12) Gadallah, F.L. and R.L. Jefferies. 1995. Forage quality in brood rearing
areas of the lesser snow
goose and the growth of
captive goslings. J. Appl. Ecol. 32(2):276-287.
13) Gates, J.M. 1957. Autumn food habits of the gadwall in northern Utah.
Utah Acad. Proc.
34:69-71.
14) Hartman, F.E. 1963. Estuarine wintering habitat for black ducks. J.
Wildl. Manage.
27(3):339-347.
15) Hocutt, G.E. and R.W. Dimmick. 1971. Summer food habits of juvenile
wood ducks in east
Tennessee.
J. Wildl. Manage. 35(2):286-292.
16) Hohman, W.L. 1985. Feeding ecology of ring-necked ducks in
northwestern Minnesota. J.
Wildl. Manage. 49(3):546-557.
17) Hohman, W.L.; D.W. Woolington and J.H. Devries. 1990. Food habits of
wintering canvasbacks
in Louisiana.
Can. J. Zool. 68(12):2605-2609.
18) Hohman, W.L.; C.D. Ankney; and D.L. Roster. 1992. Body condition,
food habits, and molt
status of late-wintering ruddy
ducks in California. Southwestern Naturalist 37(3):268-273.
19) Hohman, W.L. and C.D. Ankney. 1994. Body size and condition, age,
plumage quality, and
foods of prenesting male cinnamon
teal in relation to pair status. Can. J. Zool. 72:2172-2176.
20) Hohman, W.L.; T.M. Stark and J.L. Moore. 1996. Food availability and
feeding preferences of
breeding fulvous
whistling-ducks in Louisiana ricefields. Wilson Bull. 108(1):137-150.
21) Hudec, K. 1973. The food of the greylag goose, Anser anser, in southern
Moravia,
Czechoslovakia.
Zool. Listy 22(1):41-58. In German.
22) Kenow, K.P. and D.H. Rusch. 1996. Food habits of redheads at the
Horicon Marsh, Wisconsin.
J. Field Ornithol. 67(4):649-659.
23) Kerekes, J.J. editor. 1994. Aquatic Birds in the Trophic Web of Lakes.
Developments in
Hydrobiology.
Proceeding of a Symposium... Kluwer Academic Publishers, Dordrecht, The Netherlands. 524
pp.
24) Knapton, R.W. and K. Pauls. 1994. Fall food habits of American wigeon
at Long Point, Lake
Erie, Ontario.
J. Great Lakes Res. 20(1):271-276.
25) Krapu, G.L. 1974. Foods of breeding pintails in North Dakota. J. Wildl.
Manage.
38(3):408-417.
26) Krapu, G.L. and K.J. Reinecke. 1992. Foraging ecology and nutrition.
IN: Ecology and
Management of Breeding
Waterfowl, B.D.J. Batt, et al., editors, Univ. Minnesota Press, Minneapolis, pp. 1-29.
27) Lemly, A.D. 1994. Irrigated agriculture and freshwater wetlands: a
struggle for coexistence in
the western United States.
Wetlands Ecol. Manage. 3(1):3-15.
28) McAtee, W.L. 1915. Eleven important wild-duck foods. Bull. U.S. Dept.
Agric. No. 205,
Washington, D.C. 25 pp.
29) McAtee, W.L. 1917. Propagation of wild-duck foods. Bull. U.S. Dept.
Agric. No. 465,
Washington, D.C. 40 pp.
30) McAtee, W.L. 1918. Food habits of the mallard ducks of the United
States. Bull. U.S. Dept.
Agric., No. 720, Washington, D.C. 36 pp.
31) McAtee, W.L. 1922. Notes on food habits of the shoveller or spoonbill
duck (Spatula clypeata).
Auk 39(3):380-386.
32) McAtee, W.L. 1925. Notes on drift, vegetable balls, and aquatic insects as
a food product of
inland waters. Ecology 6(3):288-302.
33) Manley, S.W.; W.L. Hohman; J.L. Moore; and D. Richard. 1992. Food
preferences of
spring-migrating blue-winged teal in southwestern
Louisiana. Proc. Annu. Conf. Southeast. Assoc. Fish Wildl. Agenices 46:46-56.
34) Mendall, H.L. 1949. Food habits in relation to black duck management in
Maine. J. Wildl.
Manage. 13(1):64-101.
35) Middleton, B.A. 1992. Seed herbivory by nilgai, feral cattle, and wild
boar in the Keoladeo
National Park, India. Biotropica 24(4):538-543.
36) Middleton, B.A. 1994. Management of monsoonal wetlands for greylag
(Anser anser L.) and
barheaded geese (Anser indicus L.)
in the Keoladeo National Park, India. Internat. J. Ecol. Environ. Sci. 20:163-171.
37) Nummi, P. 1989. Simulated effects of the beaver on vegetation,
invertebrates and ducks. Ann.
Zool. Fennici 26:43-52.
38) Patten, B.C. editor. 1990. Wetlands and Shallow Continental Water
Bodies. Volume 1. Natural
and Human Relationships.
SPB Academic Publishing, 759 pp.
39) Paulus, S.L. 1982. Feeding ecology of gadwalls in Louisiana in winter.
J. Wildl. Manage.
46(1):71-79.
40) Percival, F.H.; L.G. Webb and N.R. Page. 1970. Some ecological
conditions under which
selected waterfowl food plants grow in
South Carolina. Proc. SE Assoc. Game & Fish Comm. 24:121-126.
41) Perry, M.C. and F.M. Uhler. 1988. Food habits and distribution of
wintering canvasbacks,
Aythya valisineria, on Chesapeake Bay.
Estuaries 11(1):57-67.
42) Ringelman, J.K. 1990. Managing agricultural foods for waterfowl. Fish
Wildlife Leaflet
133.4.3. Waterfowl Management Handbook,
Fish Wildlife Serv., U.S. Dept. Interior, Washington, D.C. 4 pp.
43) Ringelman, J.K. 1992. Ecology of montane wetlands. Fish Wildlife
Leaflet 133.3.6. Waterfowl
Management Handbook, Fish Widlife
Serv., U.S. Dept. Interior, Washington, D.C. 7 pp.
44) Singleton, J.R. 1951. Production and utilization of waterfowl food plants
on the east Texas gulf
coast. J. Wildl. Manage. 15(1):46-56.
45) Sjoberg, K.; K. Danell. 1981. Food availability and utilization by ducks
of a shallow
brackish-water bay in the northern Bothnian Bay.
Ann. Zool. Fennici 18:253-261.
46) Tacha, T.C. and C.E. Braun, editors. 1994. Migratory Shore and Upland
Game Bird
Management in North America. International
Association of Fish and Wildlife Agencies, Washington, D.C. 223 pp.
47) Verhoeven, J.T.A. 1980. The ecology of Ruppia-dominated communities
in western Europe.
III. Aspects of production, consumption
and decomposition. Aquat. Bot. 8:209-253.
48) Woodin, M.C.; G.A. Swanson. 1989. Foods and dietary strategies of
prairie-nesting ruddy
ducks and redheads. Condor 91:280-297.
49) Weller, M.W. 1994. Freshwater Marshes. Ecology and Wildlife
Management. U Minnesota
Press, Minneapolis, 3rd ed. 155 pp.
Although the APIRS database collects literature on aquatic, wetland and
invasive plants,
this necessarily includes peripheral subjects such as animals which use these plants for food,
habitat, nesting, etc. For example, the database contains over 1,000 references with the
following
keywords: (duck or ducks or birds or waterfowl or avian or geese or goose).
(NOTE: if you use duck$, you will retrieve a few hundred duckweed articles
that don't necessarily
pertain to
ducks.) If you combine this search with (food$ or feed$ or diet$ or consum$ or graz$ or
herbiv$),
you will retrieve over 300 references. With (habitat or host plant$ or nest$ or breed$) - over 680
references.
With ((primary production) or productivity) - over 180 references that might report on the
effects of
herbivory on productivity, or the effects of productivity on bird habitat, foods, etc.
Carex subspathacea -- a favorite food of geese (11)
Echinochloa crus-galli -- a preferred food of pintail ducks in
California (9), (10); a
preferred food of green-winged teal (10); a major food of
mallard ducks in the US (30)
Echinochloa walteri -- a major food of ducks in SE Texas
(44)
Eleocharis cellulosa -- a major food plant of ducks in Texas
(44)
Eleocharis equisetoides and E.
quadrangulata --
important foods to overwintering waterfowl in South Carolina (40)
Eleocharis parvula -- leaves eaten by wintering gadwalls in
Louisiana (39); a major food
plant of ducks in Texas (44)
Eleocharis quadrangulata -- a major food of ducks in Texas
(44)
Scirpus acutus -- among favorite foods of gadwalls in Utah
(13)
Scirpus americanus -- rhizomes and seeds a major part of diet in
canvasbacks in the
Mississippi River Delta (17)
Scirpus cubensis -- a major food of mallard ducks in US (30)
Scirpus fluviatilis -- a major food of mallard ducks in US
(30)
Scirpus littoralis and Scirpus
maritimus -- tubers eaten by
wintering greylag geese in Spain (1)
Scirpus robustus and Scirpus
validus -- important foods
to overwintering birds in South Carolina. (40)
Scirpus subterminalis and Scirpus
torreyi -- constituted
30% of the fall food diet of black ducks in Maine (34)