1

WETLANDS, Vol. 21, No. 1, March 2001, pp. 1–17

2001, The Society of Wetland Scientists

A LANDSCAPE APPROACH TO CONSERVING WETLAND BIRD HABITAT

IN THE PRAIRIE POTHOLE REGION OF EASTERN SOUTH DAKOTA1

David E. Naugle

College of Natural Resources

University of Wisconsin

Stevens Point, Wisconsin, USA 54481

Rex R. Johnson

North American Waterfowl and Wetlands Office

Patuxent Wildlife Research Center

Laurel, Maryland, USA 20708

Michael E. Estey

U.S. Fish and Wildlife Service

Habitat and Population Evaluation Team

Bismarck, North Dakota, USA 58501

Kenneth F. Higgins

South Dakota Cooperative Fish and Wildlife Research Unit

U.S. Geological Survey

South Dakota State University

Brookings, South Dakota, USA 57007

Abstract: Resource managers confronted with preserving ecosystems for prairie wetland birds in fragmented

landscapes require landscape studies that direct conservation efforts over broad geographic regions. We

investigated the role of local and landscape factors affecting habitat suitability by integrating remotely sensed

wetland and land-cover data with wetland bird habitat models. We linked habitat models with locations of

easement and fee-title wetlands to evaluate spatial location and extent of protected, suitable habitat. We also

simulated impacts of the loss of small wetlands on suitability of larger wetlands for mobile species that use

multiple wetlands. Lastly, we evaluated the efficacy of waterfowl habitat programs in preserving suitable

habitat for nongame wetland bird species to recommend strategies for maximizing regional landscape connectivity. Regional databases constructed for this study indicate that easement and fee-title tracts encompass

13.9% (1.2 million ha) of land area and protect 19.8% of the wetlands in eastern South Dakota, USA.

Proportion of protected wetlands is highest for semi-permanent (32.3%), intermediate for seasonal (25.6%),

and lowest for temporary wetlands (15.8%). A stratified, two-stage cluster sample was used to randomly

select 834 semi-permanent and seasonal wetlands that were surveyed for birds in 1995 and 1996. Logistic

analyses indicate that habitat suitability for some species (e.g., Virginia rail, pied-billed grebe) is related to

local vegetation conditions within wetlands, while suitability for others (e.g., northern pintail, black tern) is

related to landscape structure at larger scales. As a result, unfragmented prairie wetland landscapes (i.e.,

areas with wetland complexes embedded within upland grasslands) provide habitat for more species than

isolated wetlands in tillage fields. Models developed from survey wetlands were used to classify habitat

suitability for all semi-permanent and seasonal wetlands in eastern South Dakota. Small wetlands are critical

components of the surrounding landscape that influence habitat suitability of larger wetlands. Models used

to reclassify suitability of larger remaining wetlands after small wetlands (0.5 ha) were removed indicate

that species most vulnerable to loss of small wetlands are vagile species that exploit resources over broad

spatial scales. Number of wetlands suitable for northern pintails, a mobile species that uses multiple wetlands

within a season, decreased 20.7% when wetlands 0.5 ha were removed. Historic paradigms dictating

waterfowl habitat protection efforts also have conserved habitat for nongame bird species. Modern paradigms

that acknowledge the importance of small shallow wetlands to breeding waterfowl have shifted the focus of

protection towards preserving habitat for species that occupy more abundant seasonal wetlands. Cessation

of protection efforts would result in further fragmentation of regional wetland landscapes. We recommend

that wetlands be acquired not only to consolidate suitable habitat within protected core areas but also to

ensure that core areas coalesce to preserve connectivity among regional wetland landscapes.

Key Words: habitat fragmentation, landscapes, nongame, Prairie Pothole Region, small wetlands, South

Dakota, waterfowl, wetland birds, wetland protection

1 This manuscript was previously published in Volume 20, No. 4; however, a printer error resulted in failure to include color figures necessary

to illustrate results properly. The Editor-in-Chief made the decision to reprint the paper in this issue in its intended form.
2 WETLANDS, Volume 21, No. 1, 2001

Figure 1. Remotely sensed wetland and land cover data

and easement and fee-title tracts were combined with habitat

suitability models for 20 prairie wetland bird species in a

GIS to evaluate the location and extent of protected, suitable

wetland habitat.

INTRODUCTION

Local vegetation structure has long been known to

affect habitat use by prairie wetland birds (e.g., Weller

and Spatcher 1965, Kaminski and Prince 1981,1984,

Murkin et al. 1997), whereas more recent research has

indicated that landscape attributes also may influence

local species abundance and diversity (e.g., Pearson

1993, Koopowitz et al. 1994, Vos and Stumpel 1995).

In a little over a century, the Prairie Pothole Region

(PPR) of North America has been transformed from a

contiguous expanse of wetlands and grasslands into a

highly fragmented agricultural landscape. Wetland

ecosystems provide principal breeding and foraging

habitats for about one quarter of the regional avifauna,

most of which are nongame species. Resource managers confronted with preserving ecosystems for prairie wetland birds require large-scale studies that direct

wetland conservation over broad geographic regions to

complement what has been learned at local scales

(Flather and Sauer 1996, Haig et al. 1998). Managers

continue to extrapolate recommendations from local

studies to regional conservation planning because few

studies have taken a landscape approach to evaluation.

Recent advances in geographic information systems

(GIS) and remote sensing technologies now enable researchers to use sampling strategies that result in inferences over larger landscapes. Landscape-level research, which is lacking in wetland ecosystems, is used

in forested ecosystems to direct conservation efforts

and design reserve systems (e.g., Askins et al. 1987,

Robbins et al. 1989, Hansson and Angelstam 1991,

Pearson 1993, Flather and Sauer 1996). Pioneering research by Brown and Dinsmore (1986), involving 30

marshes in northwest Iowa, demonstrated that wetland

bird species richness was related to wetland area and

isolation. Although Johnson and Grier (1988) found

that waterfowl settling patterns were related to species

life history characteristics and regional wetland conditions, additional research is needed to identify how

prairie wetland birds relate to habitat variability across

local and landscape scales.

In this study, we investigated the role of local and

landscape attributes in predicting habitat suitability for

20 wetland bird species by integrating remotely sensed

wetland and land-cover data with models of habitat

suitability (Figure 1). Habitat models were linked with

locations of easement and fee-title lands to evaluate

location and extent of protected, suitable wetland habitat. We also simulated impacts of the loss of small

wetlands on suitability of larger wetlands for mobile

species that exploit wetland resources over broad spatial scales. Lastly, we evaluated the efficacy of waterfowl habitat programs in preserving suitable habitat for

nongame wetland bird species to recommend strategies

for maximizing regional landscape connectivity.

STUDY AREA

The study area encompassed eastern South Dakota,

USA from the Minnesota border west to the Missouri

River. We divided the region into 3 domains, Prairie

Coteau (28.7%), Central Lowlands (44.3%), and Missouri Coteau (27.0%), based on similarity of wetland

characteristics (Figure 2). The Prairie Coteau is characterized by an abundance of semi-permanent and permanent wetlands. The Central Lowlands, a low relief

landscape, has an abundance of seasonal and temporary wetlands. The Missouri Coteau has numerous sea-
Naugle et al., WETLAND BIRD HABITAT 3

Figure 2. A delineation of the 3 domains (Missouri Coteau,

Central Lowlands, Prairie Coteau) defined for surveying

wetlands in eastern South Dakota. Domains are modifications of 6 major physiographic regions that were previously

delineated using soil characteristics (Johnson et al. 1995).

Shaded area in the lower left corner depicts the full extent

of the Prairie Pothole Region in the USA.

sonal wetlands in the northeast and fluviatile wetlands

throughout the south and west. Johnson and Higgins

(1997) provide a comprehensive characterization of

wetland habitats in eastern South Dakota.

Variable wet-dry cycles (Winter 1989) in the PPR

make wetland conditions inherently unpredictable.

Wet hydrologic conditions in the study area kept seasonal and semi-permanent wetlands inundated

throughout the breeding season. Remaining native upland vegetation throughout eastern South Dakota is

tall-grass/mixed-grass prairie (Westin and Malo 1978).

Abundance of native and non-native grasslands (e.g.,

Conservation Reserve Program [CRP] fields) varies regionally. Native sod is most abundant in the Missouri

Coteau and in northerly portions of the Prairie Coteau.

Farming is intensive in the remainder of the Prairie

Coteau and throughout the Central Lowlands where

small grains and row crops have replaced native upland vegetation.

METHODS

Creation of GIS Data Layers

Wetland Coverages. We used National Wetlands Inventory (NWI) maps and converted wetlands to wetland basins using techniques described by Cowardin

et al. (1995) and Johnson and Higgins (1997). Polygons defining adjacent wetlands were combined to delineate contiguous wetland basins. Basins were classified as temporary, seasonal, semi-permanent, or permanent by the water regime of the most permanent

wetland they contained. Polygons labeled as excavated

semi-permanent wetlands were reclassified according

to the most permanent water regime of the surrounding

natural wetland to ensure that our findings would reflect wetland bird habitat use of natural depressions.

Isolated excavated and impounded semi-permanent

wetlands were excluded from analyses. Linear wetlands (e.g., drainage ditches) were eliminated from the

GIS to minimize bias in estimated wetland density

(Johnson et al. 1999). We compared log-transformed

densities of temporary, seasonal, semi-permanent, and

permanent wetlands among 3 physiographic domains

(Figure 2) using analysis-of-variance. Multiple comparisons were performed using Tukey’s pairwise mean

comparisons.

Easement and Fee-title Tracts. We manually transferred map boundaries for waterfowl production areas,

perpetual wetland easements, national wildlife refuges

acquired by the U.S. Fish and Wildlife Service

(USFWS) (1:21,120 scale), and game production areas

acquired by South Dakota Department of Game, Fish

and Parks (1:63,360 scale) before 30 September 1994

to copies of NWI maps (1:24,000 scale) (Estey 1998).

We then digitized tract boundaries to create wetland

protection coverages encompassing eastern South Dakota.

Land-Cover Data. Landsat Thematic Mapper imagery from 8 scenes covering eastern South Dakota were

used to classify uplands into tilled and untilled vegetation classes. Untilled lands were permanent pastures,

CRP grasslands, and alfalfa. We used imagery newer

than 1990 (April and May 1991 and 1992 scenes) to

ensure that changes in CRP enrollment were incorporated into land-use classifications. Trees, which constituted 1% of area in eastern South Dakota, were

not distinguished from untilled herbaceous grassland

cover types. Crops and annually fallowed areas were

considered tilled lands. Naugle et al. (1999) provide

descriptions of methods used to process imagery and

assess accuracy of classifications. Overall, per-pixel

classification accuracy for the map was 97%.

Wetland Selection Process

A grid comprised of 3,800 25.9-km2 cells was overlayed onto wetlands. A cell size of 25.9 km2 was
4 WETLANDS, Volume 21, No. 1, 2001

Figure 3. Four landscape types used to characterize the

wetland complex surrounding surveyed wetlands. Solid

polygons depict semi-permanent wetlands while hatched

polygons are seasonal wetlands. Each cell is 25.9 km2 in

area.

selected to maximize between-cell variability (Stoms

1992) and minimize bias associated with estimating

number of wetlands using quadrats (Johnson and Higgins 1998). The center of wetlands was used to assign

them to a single cell. Wetland area encompassed within a cell was used to estimate total wetland area. Median values of the frequency distributions for wetland

densities (110 wetlands) and areas (124 ha) per cell

were used to classify cells within domains into 4 Landscape Types (Figure 3): Landscape Type a cells were

low in wetland density and area, Type b cells were

high in density and low in area, Type c cells were low

in density and high in area, and Type d cells were high

in density and in area. We randomly selected 216 cells

allocated equally across landscape types within domains in 1995 and 1996 (Figure 4). In 1996, 7 more

cells of Landscape Type a were randomly selected

from each domain to ensure an adequate sample of

semi-permanent wetlands. Alternate wetlands replaced

those that were dry, farmed, burned, or mowed.

Bird Surveys

Two seasonal and 2 semi-permanent wetlands were

randomly selected within each cell. After obtaining

permission to access wetlands on private lands, we surveyed 416 semi-permanent and 418 seasonal wetlands

from 5 May to 10 July in 1995 and 1996. Surveys

were conducted when birds were most active (sunrise

to 1000 hr and 1800 hr to sunset [Verner and Ritter

1986]). Surveys were not conducted during rainy or

windy ( 24 km/h) days. Before entering a wetland,

open water was observed from a vantage point, and

all birds seen or heard were recorded. Next, we visited

a set of predetermined points where tape-recorded calls

of Virginia rail (Rallus limicola Vieillot), sora (Porzana carolina L.), least bittern (Ixobrychus exilis Gmelin), and American bittern (Botaurus lentiginosus

Rackett) were played to elicit responses from these

secretive species (Johnson and Dinsmore 1986, Gibbs

and Melvin 1993, 1997). Number of points in a wetland varied with wetland area: 1 point in wetlands 

0.5 ha; 2 points in wetlands 0.5–5 ha; 3 points in 5–

10 ha wetlands; and 4 points in wetlands 10 ha

(VanRees-Siewert and Dinsmore 1996, Naugle et al.

1999). We visited each point for 8 minutes and began

3 minutes of taped calling during the third minute. We

walked the perimeter of each wetland after walking

through the emergent vegetation zone to ensure that

all species present were detected. Naugle et al. (1999)

contains an accuracy assessment of methods used in

this study. Bird species were classified as present if we

observed adults, active nests, or young.

Local Vegetation Variables

Percent vegetated wetland area was estimated into

the following class intervals using a modification of

the Daubenmire scale (Bailey and Poulton 1968):

1) 1%, 2) 1–5%, 3) 6–25%, 4) 26–50%, 5) 51–75%,

6) 76–95%, and 7) 95%. Pattern of emergent vegetation was recorded using the 4 cover-type classifications of Stewart and Kantrud (1971). Grazing intensity

within wetlands was visually estimated as light, moderate, or heavy. Wetlands were lightly grazed when

there was little or no evidence that cattle had been

present within the wetland, whereas emergent vegetation in moderately grazed wetlands showed signs of

trampling and consumption. Emergent vegetation in

heavily grazed wetlands was severely impacted by the

presence of cattle. Grazing intensity was estimated on

natural shorelines by visual inspection of residual vegetation and current year’s growth. Shorelines ranged

from idled (i.e., 1%) to heavily grazed (i.e., 95%).

Percent of the wetland perimeter occupied by woody

vegetation (i.e., willow [Salix spp.] and cottonwood

[Populus deltoides Marsh]) was recorded into class in-
Naugle et al., WETLAND BIRD HABITAT 5

Figure 4. Distribution of 25.9 km2 cells used to evaluate

prairie wetland bird use of semi-permanent and seasonal

wetlands in the Missouri Coteau, Central Lowlands, and

Prairie Coteau domains of eastern South Dakota.

Table 1. Description of local and landscape variables used to

evaluate habitat suitability for 20 wetland bird species in eastern

South Dakota. Acronyms in text are shown in parentheses.

Local variables quantified within or immediately adjacent to the

wetland

Percent vegetated wetland area (COVER)a

Index to grazing intensity on shorelines adjacent to wetlands

(GRAZE)a

Proportion of wetland perimeter encompassed by trees (TREES)a

Variable indicating whether dominant hydrophytes are thick- or

thin-stemmed (STEM)a

Number of dominant hydrophytes comprising 10% of vegetated wetland area (NUMB)a

Wetland area (AREA)

Wetland perimetera

Cover type classificationb

Index to grazing intensity within wetlands

Landscape attributes quantified within 25.9 km2 cells surrounding surveyed wetlands

Grassland area (GRASS)a

Total temporary wetland area (TEMP)a

Total seasonal wetland areas (SEAS)a

Total semi-permanent wetland area (SEMI)a

Total permanent wetland area (PERM)a

Number of temporary wetlands

Number of seasonal wetlands

Number of semi-permanent wetlands

Number of permanent wetlands

a Variable included in analyses.

b Cover type classifications (Stewart and Kantrud 1971) describe the distribution of emergent vegetation within wetlands. tervals. Land use adjacent to surveyed wetlands was

recorded as tilled or untilled. Class-interval mid-points

were used to analyze categorical data.

Number of dominant emergent vegetation types

comprising 10% of the vegetated wetland area was

recorded as an index to wetland vegetation heterogeneity. Emergent cover also was used to categorize wetlands into 2 classes of nesting substrates for wetland

birds. Class 1 substrates were dominated by thickstemmed emergent vegetation types (e.g., cattail [Typha spp.]) that were capable of supporting the weight

of a bird nest. Class 2 substrates were dominated by

thin-stemmed emergent vegetation types (e.g., spike

rush [Eleocharis spp.] and sedges [Cyperaceae])

whose weaker stems are less capable of supporting a

nest.

Landscape Variables

Landscape variables calculated using the wetland

GIS were total wetland area and density for each of 4

water regimes (temporary, seasonal, semi-permanent,

permanent [Stewart and Kantrud 1971]) (Table 1).

Data were log-transformed to approximate normality.

Area (ha) and shoreline length (m) of the wetland surveyed also were estimated using the wetland GIS. We

used land-cover data to estimate area of untilled upland within 25.9-km2 cells. Proportion of untilled area

was defined as the sum of untilled area divided by the

sum of non-wetland area. Percentage data were squareroot transformed to approximate normality. Eleven local and landscape variables were used in analyses (see

Table 1) after others were eliminated to reduce collinearity.

Logistic Regression Habitat Analyses

Forward stepwise logistic regression analyses (Cox

1970, Wilkinson 1997) were used to evaluate relationships between local and landscape variables and the

probability of individual bird species occurrences.

McFadden’s Rho-squared statistic, which was used to

evaluate model fit, is a transformation of the likelihood

ratio statistic intended to mimic R2 values in logistic

regression. Rho-squared values normally are lower

than R2 values. Rho-squared values  0.20 imply good

model fit (Hensher and Johnson 1981). Variables entering the stepwise procedure at P 0.15 were retained when P 0.01. Bird occurrences in seasonal
6 WETLANDS, Volume 21, No. 1, 2001

Table 2. Number and area (ha) of wetlands by water regime in the Missouri Coteau, Central Lowlands, and Prairie Coteau domains

(modified from Johnson and Higgins 1997).

Domain

Water Regime

Missouri Coteau

No. Hectares %a

Central Lowlands

No. Hectares %

Prairie Coteau

No. Hectares %

Temporary

Seasonal

Semi-permanentb

Permanent

Total

95,459

81,001

18,443

421

195,324

28,299

59,843

67,477

19,960

175,579

1.2

2.6

2.9

0.6

7.3

328,464

167,925

29,504

452

526,345

100,106

120,523

116,100

38,399

375,128

2.5

3.1

2.9

1.0

9.5

93,232

84,020

25,689

607

203,548

29,333

43,000

106,421

57,066

235,820

1.2

1.7

4.3

2.3

9.5

a Percent of total domain area.

b Includes natural, excavated, and impounded semi-permanent wetlands.

and semi-permanent wetlands were analyzed separately.

Identifying Suitable Wetlands Using Landscape

Variables

We selected 4 wetland-obligate bird species for further study (mallard [Anas platyrhynchos L.], northern

pintail [Anas acuta L.], black tern [Chlidonias niger

L.], and eared grebe [Podiceps nigricollis L.]) that differed in their sensitivity to landscape-level variation.

We hypothesized that our species-specific approach to

evaluating habitat suitability would reveal contrasting

perspectives of landscape structure among bird species

(Pearson et al. 1996). Forward stepwise discriminant

function analyses (Wilkinson 1997) was used to classify wetland suitability. Preliminary evaluations indicated that discriminant analyses provided correct classification rates that were 10% higher than those from

logistic analyses. Only landscape variables encoded in

the GIS were included in analyses so that functions

could be used to classify suitability of all semi-permanent and seasonal wetlands  0.20 ha in eastern

South Dakota. Jackknife classification rates (Wilkinson 1997) were used as one method of cross-validating

our ability to predict potential wetland bird habitat. We

also cross-validated our predictive capability using

bird survey information collected in 1997 from 75

semi-permanent wetlands on the Prairie Coteau domain that were not used in model construction.

We classified wetlands in the GIS as suitable or unsuitable according to the largest value of the classification functions for each of the selected species. We

calculated the number of suitable wetlands within

25.9-km2 cells using the GIS. The easement and feetitle lands coverage was overlayed on wetlands to estimate proportion of suitable wetlands under federal or

state protection. We classified wetlands as protected

when they were 90% encompassed by an easement

or fee-title tract.

Effect of Removing Small Wetlands from the

Landscape

Two simulations were conducted to evaluate the potential effect of loss of small wetlands on suitability

of larger remaining wetlands. In the first simulation,

only unprotected wetlands 0.50 ha were removed,

whereas in the second simulation, all wetlands 0.50

ha, regardless of protected status, were removed. Data

from the remaining wetland area in cells were used to

reclassify wetland suitability for species (northern pintail, black tern) whose presence was related to the total

wetland area in the landscape. We calculated the percent decline in number of suitable wetlands within size

categories for each simulation.

RESULTS

Characteristics of Eastern South Dakota Wetlands

Summary data indicate that 932,795 wetlands comprised 861,462 ha or 9.4% of eastern South Dakota.

Of this number, 925,217 (99.2%) comprising 786,527

ha occurred within the 3 study domains (Table 2). Natural semi-permanent wetlands comprised 31.5% of all

semi-permanent wetlands. An additional 50.7% were

shallower wetlands containing dugouts or other excavations imparting a semi-permanent water regime, and

15.1% were impoundments. Median area of all wetlands was 0.16 ha. Median sizes were 0.92 ha for semipermanent and 0.20 ha for seasonal wetlands.

Number of temporary (F  581.67, df  2, 3245,

P 0.001), seasonal (F  29.25, df  2, 3245, P 

0.001), semi-permanent (F  116.98, df  2, 3245, P

0.001), and permanent (F  19.77, df  2, 3245,

P 0.001) wetlands differed among domains (Table

2). Number of temporary (P 0.001) and seasonal (P

0.001) wetlands was greater in the Central Lowlands

than in the Prairie Coteau and Missouri Coteau, where

numbers were similar (P  0.20). Number of semipermanent and permanent wetlands was greater in the
Naugle et al., WETLAND BIRD HABITAT 7

Figure 5. Distribution of easement and fee-title tracts encompassing protected wetlands in the Missouri Coteau, Central Lowlands, and Prairie Coteau domains of eastern South

Dakota.

Prairie Coteau than in other domains (P 0.002).

Number of semi-permanent wetlands was greater in

the Central Lowlands than in the Missouri Coteau (P

0.001); however, number of permanent wetlands

was greater in the Missouri Coteau than in the Central

Lowlands (P  0.002).

Distribution and Abundance of Protected Tracts

We identified 14,840 easement and fee-title tracts

encompassing 13.9% (1,271,085 ha) of eastern South

Dakota (Figure 5). Easement and fee-title tracts protected 19.8% (158,139) of all wetlands in eastern

South Dakota (Table 3). Protected wetlands comprised

22.0% (127,324 ha) of temporary, seasonal, and semipermanent wetland area (Table 3). Easements encompassed 1,138,648 ha and protected 141,242 ha of wetland (Table 4). Federal and state fee-title tracts encompassed 132,440 ha of wetland and upland habitat (Table 4).

Proportion of protected wetlands differed among

temporary (15.8%), seasonal (25.6%), and semi-permanent (32.3%) water regimes (2  6.083, df  2, P

 0.048) (Table 3). Among domains, proportion of

protected wetlands of all water regimes was greatest

in the Missouri Coteau and least in the Central Lowlands (2  6.091, df  2, P  0.048) (Table 3). A

greater proportion of protected wetlands had semi-permanent water regimes in the Prairie Coteau than in the

Missouri Coteau, where a greater proportion had temporary and seasonal regimes (2  7.674, df  2, P 

0.022). Proportion of protected wetlands by water regime in the Central Lowlands was similar to proportions in the Missouri Coteau (2  1.559, df  2, P

 0.459) and Prairie Coteau (2  2.421, df  2, P

 0.298) (Table 3). Size structure of protected wetlands by water regime was representative of the size

structure of the wetland universe (Figure 6). The greatest number of unprotected wetlands had temporary and

seasonal water regimes and were 0.50 ha (Figure 7).

Bird-Habitat Relationships

We surveyed larger areas of larger wetlands to obtain a complete census of the bird community. We

expected larger wetlands to contain more species than

smaller wetlands because larger wetlands provide

more surface area in which birds may randomly settle

during migration. Although bird use of wetlands in this

study is a direct reflection of current bird distribution

and abundance, we do not interpret AREA relationships (e.g., a species area-sensitivity) because bird use

of small wetlands may fluctuate in response to changes

in species settling patterns and regional population sizes. AREA was allowed to step into models to account

for variation explained by area of the surveyed wetland. With AREA included in models, percent vegetated wetland area (COVER) was the most common

variable related to species’ occurrences in semi-permanent and seasonal wetlands (Tables 5 and 6). For

those species where percent vegetated wetland area

was a predictor of occurrence, presence of waterfowl

species was negative, whereas presence of nongame

species was positive to COVER (Tables 5 and 6). Total wetland (SEMI or SEAS) and/or total grassland

habitat (GRASS) within cells was positively related to

the occurrence of 9 bird species.

Classifying Wetland Suitability Using Landscape

Attributes

Using the discriminant functions, we identified

semi-permanent (SEMI) and seasonal (SEAS) wetland

area and grassland habitat (GRASS) within cells as

useful in classifying habitat suitability for selected species (i.e., mallard, northern pintail, black tern, eared

grebe; Table 7) (P 0.005 for each function). All

model coefficients were positive, indicating that species were positively associated with total wetland and

grassland habitat area in the surrounding landscape.

Classification rates indicated that discriminant functions correctly classified 75–88% of unsuitable semipermanent and 79–81% of unsuitable seasonal wet-
8 WETLANDS, Volume 21, No. 1, 2001

Table 3. Number and area of protected wetlands by water regime within the Missouri Coteau, Central Lowlands and Prairie Coteau

domains of eastern South Dakota.

Domain Water Regime

Protected

Number % Area %

Unprotected

Number Area

Missouri Coteau Temporary

Seasonal

Semi-permanent

21604

27738

1053

24.6

36.0

27.4

11417

22358

7870

23.3

36.4

31.4

66068

49315

2792

37481

39105

8245

Central Lowlands Temporary

Seasonal

Semi-permanent

44956

25694

2014

14.5

19.4

23.0

19066

22639

9920

14.2

20.5

22.2

265558

106603

6740

115446

87663

34793

Prairie Coteau Temporary

Seasonal

Semi-permanent

9988

18849

6243

11.4

25.7

38.5

4501

6719

22826

11.5

18.7

29.3

77307

54411

9988

34549

29098

55197

Domains combined Temporary

Seasonal

Semi-permanent

76548

72281

9310

15.8

25.6

32.3

34984

51716

40624

15.7

24.9

27.5

408933

210329

19520

187476

155866

98235

Table 4. Land area (ha) and percent (%) of total land area within easement and fee-title tracts in the Missouri Coteau, Central Lowlands

and Prairie Coteau domains of eastern South Dakota. Fee-title tracts include federal and state-owned property. Percent (%) total wetland

area indicates proportion of wetland area protected from drainage on easement tracts.

Domain

Fee-title Tracts

Land Area

(ha)

Protected

% Total

Land Area

Easement Tracts

Land Area

(ha)

Protected

% Total

Land Area

Wetland

Area (ha)

Protected

% Total

Wetland

Area

Missouri Coteau

Central Lowlands

Prairie Coteau

28351

44628

59461

1.2

1.0

1.2

416452

468270

253926

19.1

11.8

12.6

43887

59675

37680

36.6

21.8

27.7

lands that were used in model construction (Table 7).

Calculations from a sample of 75 semi-permanent wetlands that were not used to construct discriminant

functions indicated that, except for mallards, classification rates from the test data set were as high as apparent and jackknifed rates for unoccupied wetlands

(Table 7).

Discriminant functions were used in the GIS to classify habitat suitability of 24,083 semi-permanent and

159,524 seasonal wetlands in eastern South Dakota

that were 0.2 ha. Proportion of seasonal wetlands 

10 ha that provided suitable habitat for mallards and

northern pintails was greater than that of semi-permanent wetlands of the same size (Table 8). Number

of wetlands classified as suitable habitat for mallards,

northern pintails, black terns, and eared grebes was

summarized within 25.9-km2 cells into 4 classes: 1) 0,

2) 1–2, 3) 3–9, 4) 9 suitable wetlands (Figure 8).

Results indicated that suitable mallard habitat was

abundant and widespread throughout all domains (Figure 8). Although northern pintail habitat also was

widespread, extent of the most abundant habitat was

more restricted in all domains. Among wetlands suitable for mallards, 51.7% of semi-permanent and

74.8% of seasonal wetlands also were suitable for

northern pintails. Suitable habitat for black terns,

which only nested in semi-permanent wetlands, was

most abundant in the northern Prairie Coteau and an

isolated portion of the northeastern Missouri Coteau.

Eared grebe habitat was primarily confined to northern

reaches of the Prairie Coteau. Semi-permanent wetlands that were suitable for mallards also provided

habitat for nongame species with more restrictive habitat requirements. Among semi-permanent wetlands

suitable for mallards, 92.6% also were suitable for

black terns, and 27.0% were suitable for eared grebes.

Effect of Removing Small Wetlands from the

Landscape

Proportion of wetlands  0.5 ha that were classified

as suitable habitat decreased when smaller wetlands

were removed from the surrounding landscape (Table

9). For example, removal of all small wetlands (0.5

ha), regardless of their protection status, resulted in an

overall 20.7% decrease in number of wetlands  0.5
Naugle et al., WETLAND BIRD HABITAT 9

Figure 6. Percentage of temporary, seasonal, and semi-permanent wetlands that are protected within easement and feetitle tracts in eastern South Dakota. Solid bars represent %

of the total number of wetlands and shaded bars are total

number of protected wetlands within size classes. Size classes (ha) are 1) 0–0.2, 2) 0.3–0.5, 3) 0.6–1.0, 4) 1.1–2.0,

5) 2.1–5.0, and 6) 5.0.

Figure 7. Number of unprotected temporary, seasonal, and

semi-permanent wetlands in eastern South Dakota. Size classes (ha) are 1) 0–0.2, 2) 0.3–0.5, 3) 0.6–1.0, 4) 1.1–2.0,

5) 2.1–5.0, and 6) 5.0.

ha that had been previously classified as suitable habitat for northern pintails. Decreases in number of suitable wetlands were highest in smaller size classes (Table 9). Removal of only unprotected small wetlands

resulted in a 70.4% decrease in previously suitable

1.0–2.0 ha wetlands compared to a decrease of 80.2%

when all small wetlands were removed. Protection of

wetlands 0.5 ha has preserved the suitability of 9.8%

of 1.0–2.0 ha wetlands (Table 9).

DISCUSSION

Scale-dependent Perspectives of Habitat Suitability

Landscapes differ in their potential to provide habitat for wetland birds because species have contrasting

life histories that influence the way that each interacts

with the landscape. Habitat suitability for some species

(e.g., Virginia rail, marsh wren [Cistothorus palustris

Wilson]) is related to local vegetative attributes within

wetlands, while others (e.g., northern pintail, black

tern) relate to landscape attributes at larger spatial

scales. Prairie landscapes containing wetland complexes that are embedded within upland grasslands likely

provide habitat for more species than depauperate wetland landscapes that have been impacted by agricultural tillage.

High classification rates for habitats in which black

terns, northern pintails, and eared grebes were absent

indicated that landscape characteristics (i.e., attributes

of the wetland complex and surrounding upland matrix) provide a coarse filter for assessing habitat suitability at a landscape scale. Identification of landscape

characteristics related to habitat suitability is critical

because a wetland embedded within an unsuitable

landscape may not provide habitat despite favorable

local vegetative conditions. Lower classification rates

for occupied wetlands indicated that suitability also is

dependent on local factors in wetlands located within

a favorable landscape context (only landscape characteristics available in the GIS were used in models).

For example, black terns vacated wetlands occupied in
10 WETLANDS, Volume 21, No. 1, 2001

Table 5. Habitat models using stepwise logistic regression analyses for 20 bird species in semi-permanent wetlands. Habitat variables

entered regressions at P  0.15 and were retained in the model when P  0.01. Variables are listed in order of entry into equations.

Species Habitat Model

Number of

Occurrences

McFadden’s

Rho-squared

Dabbling Ducks

Mallard

Blue-winged Teal

Gadwall

Northern Pintail

Northern Shoveler

 COVER  AREA

 COVER  AREA

AREA  GRASS

AREA  SEAS

AREA  TREES

198

246

146

76

92

0.20

0.18

0.16

0.15

0.13

Diving Ducksa

Redhead

Lesser Scaup

Ruddy Duck

AREA  SEMI  GRASS

 COVER  AREA

AREA

82

50

68

0.20

0.20

0.18

Nongame Birdsa

Eared Grebe

Black Tern

American Bittern

Wilson’s Phalarope

Marsh Wren

Pied-billed Grebe

AREA  STEM

AREA  SEMI  GRASS

COVER  AREA

AREA  STEM  NUMB  GRASS

COVER  AREA  STEM

AREA

18

106

34

58

119

120

0.41

0.24

0.21

0.21

0.20

0.19

Common Yellowthroat

American Coot

Yellow-headed Blackbird

Sora

Virginia Rail

Red-winged Blackbird

COVER  AREA  SEMI  STEM

AREA  STEM

COVER  AREA  STEM

COVER  GRAZE  SEMI  NUMB

COVER  AREA  STEM

 TREES  STEM

150

206

250

179

89

358

0.17

0.17

0.17

0.13

0.13

0.06

a Scientific names of species in table that are not provided in text: Redhead (Aythya americana Eyton), Lesser Scaup (Aythya affinis Eyton), Ruddy Duck

(Oxyura jamaicensis Gmelin), Pied-billed Grebe (Podilymbus podiceps L.), Common Yellowthroat (Geothlypis trichas L.), American Coot (Fulica americana Gmelin), Yellow-headed Blackbird (Xanthocephalus xanthocephalus Bonaparte), Red-winged Blackbird (Agelaius phoeniceus L.).

Table 6. Habitat models using stepwise logistic regression analyses for 14 bird species in seasonal wetlands. Habitat variables entered

regressions at P  0.15 and were retained in the model when P  0.01. Variables are listed in order of entry into equations.

Speciesa Habitat Model

Number of

Occurrences

McFadden’s

Rho-squared

Dabbling Ducks

Mallard

Blue-winged Teal

Gadwall

Northern Pintail

Northern Shoveler

 COVER  AREA

AREA  COVER  SEMI  SEAS

AREA  GRASS

AREA  STEM

AREA  COVER

132

206

95

57

56

0.11

0.23

0.07

0.14

0.16

Nongame Birds

Wilson’s Phalarope

Marsh Wren

Pied-billed Grebe

Common Yellowthroat

American Coot

Yellow-headed Blackbird

Sora

Virginia Rail

Red-winged Blackbird

AREA  STEM

STEM  COVER  GRAZE  AREA

AREA

STEM  COVER  GRAZE

AREA  SEAS

AREA  STEM

COVER

STEM  COVER

STEM  COVER  TREES

51

50

28

87

81

102

142

38

365

0.13

0.19

0.11

0.14

0.07

0.18

0.08

0.09

0.13

a Diving ducks, eared grebe, black tern, and American bittern were excluded from analyses due to their minimal use of seasonal wetlands.
Naugle et al., WETLAND BIRD HABITAT 11

Table 7. Coefficients of variables used in discriminant functions to classify suitability of semi-permanent wetlands as habitat for 4 species

that differ in their sensitivity to landscape structure.

Classification Function

Coefficients by Species Constant

Wetland

Area

Semipermanent

Area

(25.9 km2

)

Seasonal

Wetland

Area

(25.9 km2

)

Grassland

Index

Classification Rate (%)

Apparent

Jackknifed True

Semi-permanent wetlands

Mallard

unsuitable

suitable

14.575

17.540

1.291

2.325

38.367

40.505

82

63

80

63

45

76

Northern Pintail

unsuitable

suitable

18.911

23.275

1.128

2.087

8.804

9.455

75

61

75

61

95

33

Black Tern

unsuitable

suitable

16.490

23.403

1.862

2.888

0.854

1.127

39.670

45.528

76

78

76

78

100

22

Semi-permanent wetlands

Eared Grebe

unsuitable

suitable

1.765

7.442

1.538

3.860

88

94

88

94

100

0

Seasonal wetlands

Mallard

unsuitable

suitable

1.230

2.138

1.949

3.198

79

48

79

48

Northern Pintail

unsuitable

suitable

1.356

2.908

2.190

4.004

81

58

81

58

Table 8. Proportion of the number of wetlands classified as suitable habitat. Variables used in discriminant functions to classify suitability

are in Table 7.

Wetland Size (ha)

0.2–0.5 0.5–1.0 1.0–2.0 2.0–5.0 5.0–10.0 10.0

Semi-permanent wetlands

Total # of wetlands

Black Tern

Mallard

Northern Pintail

Eared Grebe

4034

38.0

4157

39.4

4660

43.9

11.9

1.7

5638

56.8

60.1

23.9

2720

80.7

89.9

76.2

2874

97.0

100.0

98.7

94.5

Seasonal wetlands

Total # of wetlands

Mallard

Northern Pintail

63835 42735 30049

88.2

49.9

17653

100.0

41.8

3832

100.0

37.1

1420

100.0

34.2

previous years when height and density of emergent

vegetation no longer provided adequate nesting sites

(Naugle et al. 2000).

Preserving Long-term Avian Habitat Suitability

In the PPR, an ecosystem with inherently unpredictable hydrologic cycles, wetland bird settling patterns are largely dictated by wetland conditions and

the number of ponded wetlands. Pulses in wetland bird

production typically occur during wet hydrologic conditions when seasonal wetlands remain inundated

throughout the breeding season (e.g., Kantrud and

Stewart 1977, 1984). Unfortunately, peaks in waterfowl production during ideal hydrologic conditions

when dry years are followed by series of wet years

(i.e., 3 or more) have occurred rarely in the past 50

years (Higgins et al. 1992). Thus, for the future of
12 WETLANDS, Volume 21, No. 1, 2001

Table 9. Declines in previously suitable semi-permanent wetlands that were reclassified as unsuitable using discriminant functions (Table

7) after small wetlands were removed from the landscape. Habitat suitability for species whose occurrence was related to surrounding

wetland area was reclassified once after only unprotected wetlands 0.50 ha were removed, and again after all wetlands 0.50 ha,

regardless of their protection status, were removed.

Semipermanent Wetland Area (ha)

0.2–0.5 0.5–1.0 1.0–2.0 2.0–5.0 5.0–10.0 10.0

Total number of wetlands 4034 4157 4660 5638 2720 2874

Number of suitable wetlands before small

wetland removal

Northern Pintail

Black Tern

0

1533

3

1638

81

2045

1345

3200

2073

2196

2838

2787

Number of suitable wetlands after removal

of unprotected wetlands 0.5 ha

Northern Pintail

Black Tern

0

1365

0

1552

24

1924

828

3043

1753

2139

2767

2775

% loss in number of suitable wetlands after

removal of unprotected wetlands 0.5

ha

Northern Pintail

Black Tern

0

11.0

100.0

5.3

70.4

5.9

38.4

4.9

15.4

2.6

2.5

0.4

Number of suitable wetlands after removal

of wetlands 0.5 ha

Northern Pintail

Black Tern

0

0

0

1550

16

1921

714

3041

1578

2139

2720

2783

% Loss in number of suitable wetlands after removal of all wetlands 0.5 ha

Northern Pintail

Black Tern

0

100.0

100.0

5.4

80.2

6.1

46.9

5.0

23.9

2.6

4.2

0.4

wetland bird production, as many wetlands as possible

should be protected to maintain the pulse potential of

wetland landscapes.

Numerous species in this study (e.g., Wilson’s phalarope [Steganopus tricolor Vieillot], black tern, gadwall [Anas strepera L.]) were more likely to inhabit

wetlands within landscapes where 50% of the upland

matrix was tilled. Average proportion of grasslands

within cells was 10.4% higher near semi-permanent

wetlands in which dabbling duck species richness was

at a maximum compared to wetlands that were devoid

of dabbling ducks. Greenwood et al. (1995) reported

that dabbling duck nest success was correlated positively with the proportion of grassland in their study

sites in southern Canada. Recent advances in the field

of landscape ecology (Turner 1989, Turner and Gardner 1991, Forman 1995, Bissonette 1997) indicate that

the matrix (e.g., adjacent uplands) often influences

landscape function by altering within-patch (e.g., wetland) dynamics. In northern prairie ecosystems, pesticide and fertilizer runoff and siltation from agricultural

lands alter wetland vegetation composition (Kantrud

1986, Freeland et al. 1999) and reduce invertebrate

abundance (Novak 1992, Dunn and Agro 1995). We

used grassland abundance in this study as a surrogate

measure reflecting the negative impacts of agricultural

activities on wetland habitats. Findings from Beintema

(1997), which indicate that agricultural tillage decreases diversity of invertebrate forage available to wetland

avifauna, reinforce our contention that human-induced

modifications in upland habitats are related to processes within wetland complexes. Management designed to increase habitat suitability for waterfowl and

nongame species should include continued establishment and maintenance of grassland cover. Future research concerning the role of grasslands should address the influences of grassland patch size, grassland

structure within patches, and configuration of multiple

grassland patches on wetland bird use and productivity

(i.e., source/sink dynamics) (e.g., van Horne 1983,

Pulliam 1988).

The Value of Small Wetlands

Resource specialists acknowledge the current lack

of empirical evidence needed to rebut opponents who
Naugle et al., WETLAND BIRD HABITAT 13

Figure 8. Distribution of the number of suitable semi-permanent and seasonal wetlands for A) mallards, B) northern pintails,

C) black terns, and D) eared grebes in eastern South Dakota. Wetland area and various landscape-level attributes were used

in discriminant functions to classify wetland suitability for species A-D that differed in their sensitivity to landscape variation.

Colors indicate the number of suitable wetlands within 25.9 km2 cells.
14 WETLANDS, Volume 21, No. 1, 2001

Table 10. Percentage of suitable wetlands protected within easement and fee-title tracts. Wetlands were classified as suitable using

discriminant functions (Table 7) for selected species.

Wetland Area (ha)

0.2–0.5 0.5–1.0 1.0–2.0 2.0–5.0 5.0–10.0 10.0

Semi-permanent Wetlands

Total # of wetlands

Black Tern

Mallard

Northern Pintail

Eared Grebe

4034

51.9

4157

50.7

4660

49.2

50.5

34.6

5638

43.1

40.6

41.8

2720

38.8

35.8

37.1

2874

34.6

34.0

34.2

33.9

Seasonal Wetlands

Total # of wetlands

Mallard

Northern Pintail

63835 42735 30049

28.0

27.9

17653

28.1

28.1

3832

25.1

25.1

1420

17.8

17.8

question the value of small wetlands (Gibbs 1993,

Haig et al. 1998, Semlitsch and Bodie 1998). A heightened awareness of the value of small wetlands is critical in the PPR because most unprotected wetlands are

small (Figure 7). We previously estimated that the deregulation of small wetlands (0.4 ha) in agricultural

fields could result in drainage of up to 49% of the

remaining wetlands in eastern South Dakota (Johnson

et al. 1996). Opponents viewing wetlands as individual, disjunct patches quickly devalue the importance

of small wetlands as suitable habitat because a single

large wetland typically contains more species than one

of a smaller size. When viewed as components of a

larger landscape, however, small wetlands are critical

landscape elements that influence the suitability of

larger wetlands.

Discriminant functions that were used to reclassify

the suitability of larger remaining wetlands after small

wetlands (0.5 ha) had been removed from the landscape indicated that species most vulnerable to the loss

of small wetlands are vagile species that exploit resources over broader spatial scales. Using the same

wetland sites surveyed for this study, Naugle et al.

(1999) found that black terns occupied wetlands located in high-density wetland landscapes (landscape

type d; Figure 3) more frequently than those in low

wetland density landscapes (landscape type a) where

potential food sources are spread over large distances.

In this study, decreases in the number of previously

suitable wetlands were greatest in smaller size classes

(0.5–5.0 ha; Table 9) because black terns become increasingly dependent on characteristics of the surrounding landscape as wetland size decreases. Similarly, number of wetlands suitable for northern pintails,

a vagile species that uses multiple wetlands within a

season, decreased 20.7% when small wetlands were

removed from the landscape. Suitability of larger wetlands probably decreased when small wetlands were

removed because northern pintails breed near small,

shallow temporary and seasonal wetlands before moving their broods to larger, more permanent wetland

habitats.

To further quantify the importance of small wetlands, we also used discriminant functions to reclassify

wetland habitat suitability after only unprotected small

wetlands, rather than all small wetlands regardless of

their protection status, were removed from the surrounding landscape. The 9.8% increase in proportion

of suitable 1–2 ha wetlands when protected small wetlands remained intact further attests to the importance

of small wetlands to northern pintails. Perhaps more

importantly, these results also indicate that, despite

similarities in proportions of protected wetlands across

size classes (Figure 6), the greatest number of unprotected wetlands are still those that are the smallest

(Figure 7).

Conserving Habitat for Nongame Wetland Birds

Using Waterfowl Paradigms

Advances in waterfowl and wetland research continually shape and change our current understanding

of what constitutes suitable wetland bird habitat. Resource managers operating under prevailing habitat

paradigms dictate policy and guidelines for wetlands

preservation. Initial paradigms (circa 1960s) dictated

that waterfowl managers acquire large semi-permanent

wetlands to provide pair and brood-rearing habitat.

Our results indicate that acquisition of large semi-permanent wetlands for breeding waterfowl also have resulted in preservation of wetland habitats for many

nongame bird species. Results from this study further

indicate that efforts intended to protect wetland habitat

for waterfowl have protected 45% of suitable wetlands

for nesting and foraging black terns (Table 10).

More recent recognition of the value of smaller, sea-
Naugle et al., WETLAND BIRD HABITAT 15

sonal wetlands for waterfowl pairs during pre-laying

and laying periods resulted in a paradigm shift (circa

1980s) that redirected protection efforts towards high

density landscapes dominated by complexes of semipermanent and seasonal wetlands. This second paradigm shift initiated preservation of the more extensive

suitable habitat for nongame species that relate to surrounding landscape structure (e.g., northern pintail and

black tern on the northeastern Missouri Coteau; Figure

8). Occupancy rates that were an average of 15% higher in seasonal wetlands compared to semi-permanent

wetlands for northern pintails, blue-winged teal [Anas

discors L.], and northern shoveler [Anas clypeata L.]

indicate that small seasonal wetlands provide extensive

breeding habitat for dabbling ducks. Small seasonal

wetlands, which are  6 times as abundant as semipermanent wetlands in eastern South Dakota, also provide habitat for species like Wilson’s phalaropes and

Virginia rails. Wilson’s phalaropes and Virginia rails

in this study were most abundant in small seasonal

wetlands that met their nesting and foraging requirements (Johnson and Dinsmore 1986, Colwell and Jehl

1994). In retrospect, shifting habitat paradigms among

resource managers have resulted in preservation of

suitable habitat for nongame species that use large

semi-permanent wetlands and are now preserving habitat for species that occupy the far more abundant seasonal wetlands.

Strategies for Future Habitat Preservation

Easement and fee-title lands in eastern South Dakota

protect 34–52% of semi-permanent and 18–28% of

seasonal wetlands suitable for a representative group

of species (black tern, mallard, northern pintail, and

eared grebe; Table 10) whose habitat needs differ

markedly across local and landscape scales (Tables 5

and 6). Cessation of protection efforts would ultimately result in further fragmentation of the regional wetland landscape after drainage and expansion of tillage

agriculture. Current distribution of protected tracts

(Figure 5) most closely mimics distribution of landscapes with large numbers of wetlands that are suitable

for northern pintails (Figure 8), a species that reached

all-time population lows in the 1980s and is a species

of special concern to waterfowl managers (Hestbeck

1996). Protection of additional wetlands will increase

connectivity of protected tracts and reduce the potential extent of fragmentation. The largest gap in distribution of protected tracts exists in the middle Central

Lowlands domain of eastern South Dakota (Figure 5).

Wetlands in the Central Lowlands are among those at

greatest risk of drainage because 84% are small, unprotected temporary and seasonal wetlands (Table 3;

Figure 7) located within agricultural fields (Johnson et

al. 1996). Our results indicate that 9 species of nongame wetland birds (Table 6) nest in and around small

seasonal wetlands. Wetland acquisitions in the Central

Lowlands would preserve landscapes where seasonal

wetland densities commonly exceed 180 wetlands/

25.9-km2 (Johnson and Higgins 1997) and would link

the Prairie Coteau and Missouri Coteau into a more

highly connected, regional wetland complex (Figure

5).

Importance of Temporary Wetlands

Bird surveys were not conducted in temporary wetlands, the most abundant wetland type in all domains,

because the brief duration of ponding in spring precludes breeding by wetland bird species in most years.

Readers should not devalue the importance of temporary wetlands, however, because these wetlands are

integral components of wetland landscapes. The importance of temporary wetlands as pair habitat for early nesting duck species (e.g., mallard and northern pintail) (Drewien 1968, Dzubin 1969, Krapu 1974, Duebbert et al. 1983) is well known. Temporary wetlands

in agricultural landscapes also provide foraging habitat

for migrating waterfowl (LaGrange and Dinsmore

1989) and shorebirds (Skagen and Knopf 1994). Migrating pectoral sandpipers (Calidris melanotos Vieillot) reduced energetic costs by foraging in landscapes

containing multiple closely spaced temporary wetlands

(Farmer and Parent 1997). Additional landscape studies are necessary to gain a comprehensive understanding of the spatial and temporal dynamics of temporary

wetlands.

ACKNOWLEDGMENTS

Primary project funding was provided by Federal

Aid to Wildlife Restoration (W-107-R, Job No. 8) via

the South Dakota Cooperative Fish and Wildlife Research Unit, in cooperation with South Dakota Department of Game, Fish and Parks, U.S. Geological

Survey, South Dakota State University, U.S. Fish and

Wildlife Service, and the Wildlife Management Institute. We thank C. A. Lively, Coordinator of the Prairie

Pothole Joint Venture, North American Waterfowl

Management Plan, for funding to cover publication

and distribution costs. This study benefited greatly

from conversations with C. R. Madsen and C. R. Elliott of the USFWS. J. R. Sauer, F. A. Johnson, C. S.

Robbins, G. R. Guntenspergen, J. A. Dubovsky, J. A.

Royle, M. R. Koneff, and J. S. Wortham provided

helpful comments on an earlier draft. USFWS Division

of Realty Office in Denver, CO, USFWS Wetland Acquisition Offices in Huron and Aberdeen, SD, and

South Dakota Department of Game, Fish and Parks
16 WETLANDS, Volume 21, No. 1, 2001

provided invaluable technical assistance. We thank M.

J. Kjellsen for help in interpreting National Wetland

Inventory data and in acquiring digital wetland protection information. We also thank L. D. Flake and Z.

W. Wicks III for comments during conceptual phases

of this project. R. E. Reynolds and D. Cohan developed techniques used in GIS wetland basin construction. J. A. Jenks and D. M. Dateo (South Dakota State

University) and J. E. Vogelmann (EROS Data Center,

U. S. Geological Survey) provided technical support

and computer facilities during production of the digital

land use cover. Land-cover was produced as part of

the South Dakota GAP Analysis Project funded by

U.S. Geological Survey-Biological Resources Division. F. R. Quamen, K. K. Bakker, S. A. Stolz, J. W.

Bauer, B. L. Kopplin, and M. S. Wilsdon assisted with

field work.

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