Managing Wetlands for Waterbirds: How
Managers Can Make a Difference in
Improving Habitat to Support a North
American Bird Conservation Plan
R. Michael Erwin
Murray K. Laubhan
John E. Cornely
Dana M. Bradshaw
Abstract—Wetlands are the most productive ecosystems in the
world, yet they have suffered more loss and degradation than any
other ecosystem. Not surprisingly, 50% (29 of 58) of all the bird
species in the United States (excluding Hawaii and territories) that
are listed either as federally threatened or endangered, or are on the
U.S. Fish and Wildlife Service 1995 List of Migratory Nongame
Birds of Management Concern, occupy wetland or aquatic habitats
even though many remaining wetlands across the North American
landscape already are managed primarily for waterbirds. Some of
these wetlands are administered by federal and state entities (e.g.,
national wildlife refuges, national and state parks, state wetland
management areas) or are maintained on private lands through
federally supported restoration and enhancement programs (e.g.,
Conservation Reserve Program, Wetland Reserve Program, Waterfowl Production Areas, and Partners for Wildlife). Private organizations, such as the National Audubon Society, The Nature Conservancy, and private hunting clubs also own wetland areas that are
managed specifically to benefit wildlife. If management philosophies are altered to consider the entire complex of wetlands, many
wetlands can provide benefits to a broad array of waterbirds, as
opposed to just one or a few species. However, challenges for natural
resource managers are in forming partnerships with owners-managers of wetlands where the objectives are not primarily wildlife
oriented. These owners or managers need to be included in wetland
training workshops in an attempt to educate them about wetland
values and secondary wildlife benefits that may be derived in
flooded agricultural lands, aquaculture ponds, altered coastal
marshes (mosquito control), and salt evaporation ponds. In some
cases, compensation for crop damages by wildlife may be a necessary part of any cooperative agreements. In the development of a
North American Bird Conservation Plan, we propose a four-step
approach and recommend that emphasis be placed on working with
Joint Ventures of the North American Waterfowl Management Plan
In: Bonney, Rick; Pashley, David N.; Cooper, Robert J.; Niles, Larry,
eds. 2000. Strategies for bird conservation: The Partners in Flight planning process; Proceedings of the 3rd Partners in Flight Workshop; 1995
October 1-5; Cape May, NJ. Proceedings RMRS-P-16. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
R. Michael Erwin, Biological Resources Division, USGS, Patuxent Wildlife Research Center-Charlottesville Office, Department of Environmental
Sciences, Clark Hall, University of Virginia, Charlottesville, VA 22903.
Murray K. Laubhan, Biological Resources Division, USGS, Midcontinent
Ecological Science Center, Fort Collins, CO 80525. John E. Cornely, U.S.
Fish and Wildlife Service, Region 6, P.O. Box 25486, Denver Federal Center,
Denver, CO 80225. Dana M. Bradshaw, Center for Conservation Biology,
College of William and Mary, Williamsburg, Virginia 23185.
82
to ensure that a diverse array of waterbird species will benefit.
Efforts also should be devoted to developing similar partnerships in
areas where important wetland resources exist but no Joint Ventures are planned.
Although wetlands are widely recognized as among the
most productive ecosystems globally, wetland loss continues
both in North America and throughout the world, owing
largely to a burgeoning human population and the concomitant conversion of natural wetlands for human uses. For
example, the Bay of Fundy is a critical habitat for shorebirds
during migration (Morrison and others 1994) but is threatened with both hydroelectric development and harvesting of
polychaete worms (major shorebird prey) for sport fishing
(P. Hicklin, Canadian Wildlife Service, personal communication). Similarly, James and western Hudson Bays are the
subjects of major water development planning, despite their
roles as major nesting and migration areas for geese and a
number of species of shorebirds. The prairie pothole region
of Saskatchewan and Manitoba are part of a Canadian
prairie habitat joint venture (JV) under the North American
Waterfowl Management Plan (NAWMP[USFWS 1986]). The
region has been recognized internationally as one of the
premier nesting grounds for many diving and dabbling
ducks, and it also provides habitat for endangered Piping
Plovers (Charadrius melodus). This area historically has
faced numerous conversions of potholes to croplands. The
western Canadian regions of most concern are the Fraser
River corridor and delta and the adjacent Vancouver Island
region. Development and growth is rapid in that region, and
intense logging occurs along the Fraser. The region is well
known for its wintering waterfowl and marine bird concentrations (Vermeer and Butler 1989). Similar examples are
numerous throughout most of North America. However,
during the past two decades, many federal, provincial, and
state programs have been initiated to provide economic
incentives for wetland conservation in an attempt to achieve
a “no net loss” of wetlands (The Conservation Foundation
1988). These earlier losses of wetlands, and recent changes
in the status of wetlands, have broad implications to wildlife.
In this paper we review the status of wetlands as habitats
for waterbirds (defined as waterfowl, colonial waterbirds,
shorebirds, and rails and allies). We focus on species whose
USDA Forest Service Proceedings RMRS-P-16. 2000
status is of concern either regionally or nationally, and on
current wetland management practices that are detrimental to wetland birds. We identify gaps in our knowledge of
ecological principles for managing habitats for waterbirds,
and conclude with recommendations for improving wetland management to enhance waterbird populations.
Status of Species and Associated
Wetlands ______________________
We consulted two recent publications to identify the major
waterbird species of concern in North America: The 1994 list
of endangered and threatened wildlife and plants (USFWS
1994b) and the 1995 List of Migratory Nongame Birds of
Management Concern (Office of Migratory Bird Management [OMBM] 1995). These lists indicate that more than
50% of birds of concern in the U.S. are associated with either
wetlands or aquatic habitats (table 1) (Canada and Mexico
do not have formal endangered species listings). The federal
endangered and threatened list includes 16 of 35 species (not
including Hawaii or trust territories) that are wetland or
aquatic-dependent, while the comparable figures from the
OMBM list are 14 of 23 species.
The habitats used by these species suggest that the majority are associated with freshwater (interior) marshes or
coastal beaches and/or islands. These are habitats that have
been among the most affected by humans, either by direct
disturbance (beaches) or indirectly by agricultural conversions (freshwater marshes). In addition, interior marshes and
coastal areas often are intensively managed, suggesting that
current habitat management practices should be evaluated
relative to providing benefits to a diversity of species. For
example, many of the major wetland complexes listed for the
U.S. already are included under JVs in the NAWMP (table 2).
However, the Atlantic Coast Habitat Joint Venture focuses on
American Black Ducks (Anas rubripes). Separate (but unequal) programs are directed at restoration of the endangered
Piping Plover, and at monitoring certain declining colonial
waterbird species in the mid-Atlantic barrier region.
During the past decade, however, the scope of habitats and
avian species being considered has been increasing. For
example, discussions are under way (C. Hunter, USFWS,
personal communication) to form a JV for part of the extensive
Table 1—List of wetland/aquatic bird species of concern in the United States.
Common name
Federal threatened/endangered b
California Brown Pelican
Wood Stork
Spectacled Eider
Everglade Snail Kite
Bald Eagle
Light-footed Clapper Rail
Yuma Clapper Rail
Whooping Crane
Mississippi Sandhill Crane
Western Snowy Plover
Piping Plover
(Interior) Least Tern
California Least Tern
Roseate Tern
Marbled Murrelet
Cape Sable Seaside Sparrow
Scientific name
Pelecanus occidentalis
Mycteria americana
Somateria fischeri
Rostrhamus sociabilis plumbeus
Haliaeetus leucocephalus
Rallus longirostris levipes
Rallus longirostris yumanensis
Grus americana
Grus canadensis pulla
Charadrius alexandrinus nivosus
Charadrius melodus
Sterna antillarum athalassos
Sterna antillarum browni
Sterna dougallii dougallii
Brachyramphus marmoratus marmoratus
Ammodramus maritimus mirabilis
Habitat
Wetland
Aquatica
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
c
USFWS List
Common Loon
American Bittern
Least Bittern
Reddish Egret
White-faced Ibis
Trumpeter Swan
Northern Harrier
Red-shouldered Hawk
Black Rail
Snowy Plover
Bristle-thighed Curlew
Black Tern
Cerulean Warbler
Seaside Sparrow
Gavia immer
Botaurus lentiginosus
Ixobrychus exilis
Egretta rufescens
Plegadis chihi
Cygnus buccinator
Circus cyaneus
Buteo lineatus
Laterallus jamaicensis
Charadrius alexandrinus
Numenius tahitiensis
Chlidonias niger
Dendroica cerulea
Ammodramus maritimus
X
X
X
X
X
X
X
X
X
X
X
X
X
X
a
"Aquatic” refers to primary use of lake, river, and/or marine habitats.
United States Fish and Wildlife Service (1994).
Office of Migratory Bird Management (1995).
b
c
USDA Forest Service Proceedings RMRS-P-16. 2000
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Table 2—Primary wetland regions for waterbird conservation in North America.
Country
Complex
Canada
Bay of Fundy
James Bay-W. Hudson Bay
Prairie potholes (S. Saskatchewan, Manitoba)
Fraser River corridor-delta
Vancouver Island region
United States
Atlantic coastal barriers
Forested wetland of the southeast-lower Mississippi River
Prairie potholes/Rainwater Basins
Riparian corridors-Intermountain west
Copper River delta, Alaska
Yukon River delta, Alaska
Playa Lakes Region (Texas, Oklahoma, S. Colorado)
West coast estuaries
Agricultural valleys-West
Mexico
Ensenada del Pabellon and Boca de la Barra
Marismas Nacionales
Usumacinta-Grijalva delta
Laguna de Terminos
Rio Lagartosa
Rio de Celestuna
a
Sian Ka’an
Laguna Babicoraa
a
Designated as a Faunal Reserve or international Man and Biosphere Reserve
(UNESCO).
forested wetlands in the southeastern U.S. from Virginia to
Florida where forested wetland loss has resulted in marked
declines of wintering waterfowl and certain songbirds such as
the Swainson’s Warbler (Lymnothlypis swainsonii). The lower
Mississippi River supports a very active JV that includes
waterfowl, shorebirds, and Neotropical migrants. In the interior, agriculture has been modified to be more “friendly” to
wetland birds in several JV areas: The Playa Lake region of
Texas and southern Colorado, the Prairie Potholes of the
Dakotas and Montana, and the Rainwater Basins in Nebraska. The Playas are important waterfowl wintering habitat, while the latter two areas are critical for breeding and
migrating waterfowl and shorebirds.
Farther west, the riparian corridors of the arid intermountain west and the large agricultural valleys (e.g., Central,
Sacramento, and San Luis in California, and Willamette in
Oregon) represent important wintering and migration habitat for waterfowl and shorebirds, respectively. Metal contamination (selenium and boron) of irrigation drainwater in
the agricultural basins of the West has stirred major controversies concerning whether wetlands in wildlife refuges
should become sumps. Along the west coast, the few estuaries with remaining wetlands (San Francisco Bay, San Diego
Bay, Puget Sound, Fraser River delta and corridor) require
constant vigilance to protect against further loss and degradation. Recently, the USFWS named Puget Sound as a
national estuary program.
In Alaska, numerous wetlands abound both on the coast
and on interior wildlife refuges and parks; most of these
are under no immediate threats. The major exception is
the Arctic National Wildlife Refuge, which some U.S.
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congressmen refer to as the Alaska Oil Reserve. Special
mention also should be made of the Copper River delta,
which is critical to enormous numbers of migrating shorebirds in spring and fall (Gill and others 1995). It also is
important to many species of geese and ducks.
In Mexico, a number of important wetland areas for
waterbirds, especially waterfowl, have been identified under the NAWMP. To date, however, none has been designated as a JV area (USFWS 1995). Several, however, have
been designated by UNESCO as Man and Biosphere Reserves or as Faunal Reserves by Mexico (Baldassarre and
others 1989) (table 2). Of hemispheric importance is the
Usumacinta-Grijalva delta region, which exceeds the size
and significance of the present-day Everglades region in
Florida (Ogden and others 1988). It is threatened by conversion to agricultural uses and dam construction. The northern coastal lagoons of Rio Lagartos and Rio Celestun are
important to the rare Greater Flamingo (Phoenicopterus
ruber) and are major wintering areas for several species of
waterfowl migrants from the U.S.
Wetland Practices Unfavorable to
Waterbird Conservation __________
In this section, we highlight some current practices
occurring in wetlands that adversely affect either the
quality or quantity of wetland habitat available to
waterbirds (table 3). The principal areas affected also are
indentified. Where possible, we make recommendations for
improvement.
USDA Forest Service Proceedings RMRS-P-16. 2000
Table 3—Wetland practices unfavorable to waterbirds and wetland conservation in North America.
Issue
All
wetlands
1. Federal-state wetland policy
2. Contaminants
3. Human disturbance
4. Timber harvest
5. Grazing
6. Drainage-agriculture
7. Exotic species
8. Single-species (or group) management
Barrier
beaches
Coastal
marshes
x
x
x
x
Riparian
wetlands
Playaspotholes
x
x
x
x (geese)
x
x (cattle)
x
x
x
Current Practices
Navigation and Flood Control—The hydrology of many
rivers has been severely modified. In many cases, peak
discharges have been reduced and low flows have been
increased, resulting in more stable hydroperiods among
seasons and years. Although moderation of flows improves
efficiency of hydroelectric power generation, provides more
reliable navigation, and reduces the threat of floods, many
habitats important for avian species have been destroyed or
their value severely decreased. However, recent attempts to
coordinate water discharges to facilitate reestablishment of
riparian wetland types and regeneration of woody riparian
species have met with some success. Additional effort should
be directed toward cooperation among responsible agencies
and individuals with respect to alternative methods of river
management.
Human Disturbances Along Beaches and Islands in
the Coastal Barrier Regions—Increases in population
and recreational demands by boaters continue, especially in
the Atlantic and Gulf coasts of the U.S. In the Yucatan region
of Mexico, resort development and ecotourism continue to
grow. Increasing access to formerly remote mangrove islands by personal watercraft (e.g., Jet Skis) represents an
increasing threat to nesting herons, spoonbills, storks, pelicans, and cormorants in Florida, Texas, Mexico, and other
tropical coastal resort areas (Erwin and others 1995; Rodgers
and Smith 1995). These threats call for additional regulatory actions regarding land access as well as environmental
education, especially for boaters who may be oblivious to
bird conservation needs.
Mosquito Control in Coastal Marshes—Historically,
coastal marshes were diked to stabilize water levels, thereby
reducing the magnitude of mosquito problems. Current
mosquito control in most coastal areas combines use of
organophosphate pesticides as adulticides with some form of
marsh management. The latter often involves use of heavy
equipment to create high-marsh ponds and canals that allow
fish to access mosquito breeding areas (Meredith and
Stachecki 1985). Although this practice may be ecologically
superior to using dikes and chemical pesticides, in many
areas the net benefit to waterbirds and other wildlife may be
marginal at best (Erwin and others 1994). Because few
natural coastal marshes remain along the east and Gulf
coasts of the U.S., marsh manipulations should be restricted
to those areas that already have been severely altered by
humans, and where mosquitoes are a major nuisance.
USDA Forest Service Proceedings RMRS-P-16. 2000
Palustrine
forests
Timber Harvesting on Private Lands—Especially in
Canada and the southeastern U.S., timber harvesting in
palustrine forested regions has resulted in large losses of
wetlands for wildlife (Erwin 1996). In addition, many remaining forested wetlands have been fragmented—or natural
hydrologic regimes have been disrupted—by road construction for timber harvesting. Conservation organizations need
to develop partnerships with private organizations and corporations to determine market-compatible methods of extraction that are more “friendly” to wildlife. This effort also will
require more education of “corporate America” (as well as
corporate Mexico and Canada) about the values of biodiversity.
Single-Species Management in Forested Wetlands—
Wildlife management in forested wetlands of the Mississippi River corridor and throughout much of the south and
northeastern U.S. has concentrated on “greentree reservoirs” where the primary focus has been to produce Wood
Ducks (Aix sponsa) (Fredrickson and others 1990). The
Wood Duck has been a major “target species” for both state
and federal refuge lands. Although “woodies” have become
increasingly important to waterfowl hunters as other species have declined over the past decade, managing for one
species is usually accomplished at the expense of many
others in the ecosystem. Within a complex of impoundments,
managers should seek to diversify water management schedules to maintain current forest composition and structure as
well as to promote natural regeneration.
Grazing in Riparian Zones Along Western Rivers—
Exclosures or other methods of preventing livestock access
to free-flowing rivers of the arid west are essential to ensuring stream water quality and to resisting further invasions
of exotic plants. This problem is critical in the western U.S.
(Naiman and others 1995) and especially western Mexico.
Water Rights of Wildlife—In the western U.S. and
prairie regions of Canada, water rights among state, provincial, and local interests are politically charged. Wetland
managers need to argue that wetland wildlife also has a
“share” in this essential commodity, and that refuges should
not simply become shunts for receiving irrigation drainwater
that will adversely affect water quality. Concentrations of
metals (e.g., selenium) in drainwater in vast regions of the
arid western U.S., from California across Nevada to Wyoming, have compromised the wildlife quality of many refuge
wetlands and other non-federal impounded wetlands
(Ohlendorf and others 1986).
85
Protecting Small Pothole Complexes in the Prairie
Regions—In Canada and the U.S., valuable gains have
been made to set aside marginal agricultural lands for
wildlife. Further efforts are needed to insure that large
complexes of these small wetlands are maintained to conserve the diversity of habitat needed by nesting waterfowl,
shorebirds, rails, and grebes. Farmers must have continued
financial incentives (e.g., the Conservation Reserve Program under the Food Act of 1985) to maintain the successes
achieved to date. The lessons learned in Canada and the U.S.
need to be applied in Mexico, where farmers presently have
few economic incentives to save wetlands.
Runoff and Sedimentation—In the Playa Lakes region
in Oklahoma, west Texas, and southeastern Colorado, water
quality suffers in many areas due to feedlot manure runoff
and sedimentation into the lakes from livestock areas. More
effective buffering is needed. Cotton crops are ecologically
dangerous because of the intensive pesticides they require,
and because of soil erosion resulting from lands left barren
much of the year. Alternative land uses are advised.
Pesticides—Modern organophosphate pesticide applications, although not as toxic as organochlorines (Grue and
others 1983), are still problematic throughout most agricultural areas in North America. In the Rainwater Basins of
Nebraska, in addition to heavy pesticide applications, a
number of exotic plants also have invaded. More biological
control of pest species is strongly encouraged. Water quality
in these small basins has suffered.
Major Gaps in Our Knowledge to
Effectively Manage Wetlands for
Wildlife ________________________
We identify below some major gaps in our understanding
of wetland wildlife and its habitat needs, how wetlands
function as quality wildlife habitat, and how to more effectively integrate and communicate our knowledge to managers and the public.
Major Gaps in Knowledge
Integration of Wetlands Within the Landscape Matrix—Often, studies of habitats have focused only on the
individual habitat type: Wetlands, grasslands, forest type,
and so forth. Further, information regarding differential use
of wetland types by wetland-dependent species is lacking.
Little attempt has been made to determine how the juxtaposition of various wetland or habitat types affects their
respective uses by wildlife. Research is required to determine how local (e.g., wetland complex) and regional (e.g.,
flyway) landscape processes affect patterns of use.
Regional and National Monitoring of Populations—
Wintering locations of most waterfowl have been identified
as part of the regular inventory of states and USFWS flyway
councils. The major shorebird concentration areas have
been identified by the Western Hemisphere Shorebird Reserve Network (WHSRN, Myers and others 1987), now part
of the larger Wetlands for the Americas Program. Although
86
songbirds are well monitored by the annual roadside Breeding Bird Survey, wetland species are much less covered
because of lack of road access to most wetland areas. The
International Shorebird Survey is undergoing a review (B.
Harrington, personal communication) and a colonial
waterbird national database is under development within
the Biological Resources Division of the U.S. Geological
Survey (BRD) since the National Audubon Society database
was terminated in the late 1980s. A marsh bird (rails,
bitterns, grebes) survey has been under discussion within
BRD (S. Droege, USGS, personal communication) because of
the dearth of information on this group of birds, some of
which are hunted annually. Currently much less information is available on either migration concentration areas or
on important wintering sites of colonial waterbirds, rails,
and bitterns. All of these major groups are lacking in comprehensive survey coverage to allow for national assessments of trends in populations.
Fragmentation Effects—Although the effects of forest
fragmentation have been well studied for upland bird species (see Askins and others 1990 for a review), much less
information is available on the effects of wetland fragmentation. Research is required to investigate how changing
sizes and patterns of distinct wetlands (e.g., potholes) affect
their use by a variety of wetland birds. In addition, the
fragmentation of expansive areas of marshes (e.g., by mosquito control excavation) may adversely affect their use as
breeding habitat for some species (Burger and others 1979;
Erwin and others 1994).
Large-Scale Experimentation in Wetland Management—Seldom are well-controlled experiments performed
in wetlands. Impoundment water management, pesticide
applications, Phragmites control, mosquito ditching, and
marsh burning all are examples of activities for which
controlled and replicated experimentation is needed to critically evaluate different management practices in wetlands.
These approaches should follow an adaptive resource management strategy (Walters 1986; Conroy, this proceedings).
Training of Professionals—Many private, state, provincial, and federal biologists and managers involved in
either the conservation or regulation of wetlands possess
only a basic understanding of wetland ecology. More advanced training is required to understand the ecological
processes in wetlands and to understand the significance of
wetland complexes over a larger landscape. Geographic
information systems are becoming vital tools for managers
to learn the basics of ecosystem and landscape management.
Public Relations Concerning Wetlands—For the public to appreciate attempts to conserve wetlands, much more
emphasis must be placed on teaching the values of wetlands
to the citizenry of Canada, the U.S., and Mexico (Conservation Foundation 1988). Especially considering the anticipated demands for fresh water (water consumption in the
U.S. has doubled since the 1940s and may double again in
the next 20 years [Naiman and others 1995]), the public
must develop an appreciation of wetlands for the many
ecological, recreation, aesthetic, and public service values
that they hold. Teaching of wetland ecology should be included in public school curricula, and should be part of the
outreach effort of every scientist and landscape manager.
USDA Forest Service Proceedings RMRS-P-16. 2000
Recommendations ______________
Our general recommendations to improve wetland management for a wide array of waterbird species are:
• The current JVs in the U.S. under NAWMP should be
expanded to include more non-waterfowl avian species.
The Canadian prairie habitat JV and the Lower Mississippi Valley JV have significant shorebird components.
They also could be expanded to include colonial
waterbirds, rails, and bitterns. A single-species or
focal-group approach will achieve only limited success.
• New JVs and other partnerships should be established
in regions with no current JVs; this includes all of
Mexico, parts of eastern Canada, and the southeastern
U.S., although the forested wetlands of the southeastern coastal plain are receiving attention (C. Hunter,
USFWS, personal communication).
• Criteria should be developed for reaching resource goals
for JVs. Are population goals feasible to set? Are habitat
area goals sufficient? How are quality criteria set?
• Inventories should be supported to determine waterbird
status in critical wetlands, especially for little-studied
species. Concentration hotspots for colonial waterbirds
or rails could result in designations similar to those
used by WHSRN (i.e., sites of international, hemispheric importance).
USDA Forest Service Proceedings RMRS-P-16. 2000
• Training workshops for wetland biologists and managers
should be expanded and should include the private sector.
Aquaculturists, rice farmers, hunting preserve managers, large ranch owners, and leaders of ecotourism enterprises should be included in the educational process.
• Assistance in ecological planning for wetland construction or alteration needs to be institutionalized. As part of
a permitting process, regulatory personnel in state,
provincial, and federal governments should require that
a private permit holder consult with professional wetland scientists (certified by the Society of Wetland Managers) before embarking on large-scale wetland projects
such as construction of reservoirs, aquaculture facilities,
or irrigation systems. For example, if catfish ponds in the
south had been constructed as small (half-acre) ponds,
then bird exclosures would have been easier to construct
to preclude cormorant and heron damage. This information could have been provided by a professional who is
knowledgeable about waterbird biology.
Acknowledgments ______________
We thank Marcia Wilson and Bentley Wigley for advice in
the development of this paper. Useful comments were provided
by M. Haramis, D. Pashley, M. C. Perry, and D. Sparling.
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