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ll


SECTION 4

SAMPLING METHODS

Data on bird distributions, water depths, and vegetation-structure
characteristics were collected in 59 sampling plots between 22 May and 2 June
1975 in the wetland adjacent to the cooling lake (Figure 1). The plots were
circular with a radius of 20 m and an area of one-eighth ha. They were cen-
tered on stakes that mark the corners of an existing 50-m by 50-m grid pat-
tern that covers that section of the wetland.

Bird populations were observed once in each area for a 12-min period.
All observations were conducted during the 3 h following sunrise. Data were
collected on the number of individuals of each species present, the sex of
each individual, and their activity.

Data on seven water-depth and vegetation-structure characteristics were
collected in each sample plot: percentage of cover, average water depth,
average water-depth deviation, stem density, percentage of graminoid stems,
percentage of dead stems, and effective height.

To determine percentage of cover a 10-m line intercept, divided in 100
lengths (10 cm each), was randomly run through each bird-sampling plot.
The number of lengths that intercepted open water and the number that inter-
cepted vegetation were recorded, and a value for percentage of cover was
calculated.

A water-depth measurement was taken at 0.5-m intervals along the same
line intercept, and the mean of the resulting 20 measurements was calculated.

The standard deviation of the water-depth measurements was calculated
to acquire a rough estimate of the evenness of the bottom substrate.

To measure stem density five circles, each with an area of 0.5 m?, were
randomly located within each bird-sampling plot. The total number of plant
stems located within each circle was counted, and the five values were
averaged.

In the same circles the number of plant stems that were of graminoid
structure and the number that were of broad-leaved structure were counted.
The percentage of all stems that were of graminoid structure was calculated.

The number of dead stems and the number of live stems in each circle
were counted, and the percentage of dead stems was calculated.


Ww YS RM L
n Lo dee ——w Average water depth
WwW Ys RM L
~<L a abet ——— Percentage cover
wy s RM L _» Percentage graminoid
stems
L
w Y s R M i—~- Percentage dead
stems
Ys Mw oR L Stem density

Figure 5. Relative positions of specific means and the overall mean for
habitat features along which bird-distribution patterns were
significint. M is the overall mean, W is the yellow warbler,
Y is the common yellowthroat, S is the swamp sparrow, R is the
red-winged blackbird, and L is the long-billed marsh wren.
Arrows point towards larger values.

blackbird was present in most of the sample plots, no predictions about its
distribution can be made, and it is left out of the analysis. Predictions
about frequency changes can be made for the other species, whose distri-
butions are centered toward an extreme of the habitat variable. Their
frequency in the wetland is negatively correlated with the deviation of
their specific mean from the overall mean. A shift in the overall mean of a
variable toward a specific mean should increase the habitat used by that
species, and its frequency should increase {Shugart and Patten 1972, Anderson
and Shugart 1974). A shift in the overall mean of a variable away from the
specific mean should decrease the habitat usable by that species, and it
should become less frequent (Figure 7).

The groundwater hydrology modeling of the Columbia site has shown an
increase in groundwater flow into the wetland (Andrews and Anderson 1978).
The increased ground-water flow is raising the surface water levels in the
wetland. The overall mean of the average water depth is shifting towards the

15


FOREWORD

The U.S. Environmental Protection Agency (EPA) was designed to coordinate
our country's efforts toward protecting and improving the environment. This
extremely complex task requires continuous research in a multitude of scien-
tific and technical areas. Such research is necessary to monitor changes in
the environment, to discover relationships within that environment, to
determine heaith standards, and to eliminate potentially hazardous effects.

One project, which the EPA is supporting through its Environmental
Research Laboratory in Duluth, Minnesota, is the study "The Impacts of Coal-
Fired Power Plants on the Environment.'"' This interdisciplinary study, centered
mainly around the Columbia Generating Station near Portage, Wis., involves
investigators and experiments from many academic departments at the Univer-
sity of Wisconsin and is being carried out by the Environmental Monitoring
and Data Acquisition Group of the Institute for Environmental Studies at
the University of Wisconsin-Madison. Several utilities and State agencies
are cooperating in the study: Wisconsin Power and Light Company, Madison Gas
and Electric Company, Wisconsin Public Service Corporation, Wisconsin Public
Service Commission, and Wisconsin Department of Natural Resources.

During the next year reports from this study will be published as a
series within the EPA Ecological Research Series. These reports will include
topics related to chemical constituents, chemical transport mechanisms,
biological effects, social and economic effects, and integration and synthesis.

One pronounced effect of the Columbia Generating Station is an increase
in the water levels and water temperatures in a wetland adjoining the site.
This report examines the importance to five passerine bird species of
specific habitat variables and, on the basis of that examination, predicts
how changes in the wetland’ are likely to affect bird populations and distri-
butions.

J. David Yount

Acting Director

Environmental Research Laboratory-Duluth
Duluth, Minnesota

iii


measured in all sample plots. The five specific means, one for each bird
species, were then compared to the overall mean for each variable. The
deviation_(D) of each specific mean from the overall mean was calculated by:
D = |X - S|, where X is the overall mean and S is the specific mean,

The frequency of each species was regressed on the species' deviation
value (Figure 4). A significant linear correlation (p < 0.05) for this
regression occurred with four habitat variables: average water depth, per-
centage cover, percentage graminoid stems, and percentage dead stems. The
correlation coefficient was negative in each case; in other words, the further
a specific mean deviated from the overall mean, the less frequent the species
was, No significant linear correlations occurred for three variables: water-
depth deviation, stem density, and effective height. In these cases deviation
of the specific mean from the overall mean cannot be used to predict the
frequency of the species.

The relative locations of the specific means with respect to the overall
means reveal an interesting pattern (Figure 5). The red-winged blackbird's
specific mean is always near the overall mean, probably because the red-wing
was found in a high percentage of the sample plots. The long-billed marsh
wrer.'s specific mean is always located on one extreme of the gradients,
while the means of the other three species are found at the other end of
the gradients.

RELATION BETWEEN WATER DEPTH AND HABITAT VARIABLES

Previous sections have shown the relationships between species distri-
butions and the values of the habitat variables. The following analysis will
examine relationships between the habitat variables to determine whether or
not they are independent. The variables will be compared to average water-
depth values, because one major effect of the cooling lake on the wetland
is an alteration of water levels.

The values for each variable were regressed on the values of average
water depth (Figure 6). Except for effective height, all variables resulted
in a statistically significant linear correlation with average water depth,
and the slopes of the regression lines are significantly different from zero.

These correlations, however, are not always very strong. The x? value,
which represents the percentage of the variation of the dependent variable
that is accounted for by the independent variable, is often low, and in no
case exceeds 60%.

The significant linear correlations between the variables and the water-
depth values can be taken to mean that a change in the values of water depth
can predict changes in the other variables.

In some cases a curvilinear relationship would fit the data better than

a linear one. A curvilinear function would predict the same direction of
change as the linear one, but would predict a different magnitude of that

12


of percentage of dead stems shifts the overall mean towards the specific mean
of the marsh wren and away from the specific means of the swamp sparrow,
common yellowthroat, and yellow warbler. These shifts also predict an increase
in frequency of the marsh wren and decreased frequencies of the swamp sparrow,
common yellowthroat, and yellow warbler.

The results of these analyses are four sets of identical predictions con-
cerning frequency changes of four wetland passerine species (Table 2).

18


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change. Since the goal of this analysis is the prediction of direction,
not of magnitude, the linear function provides adequate approximations of
the relationships among the variables.

PREDICTIONS OF FREQUENCY CHANGE

The foregoing analyses can be connected to make a set of predictions
concerning changes in frequencies of the bird species resulting from an
increase in overall water levels in the wetland. Since the red-winged

14


which indicates that marsh wrens apparently make no preferential use of any
particular range of this variable. In the second pattern the distribution
of the values of stem density in the sample plots with marsh wrens is dif-
ferent from the distribution of the values in sample plots lacking marsh
wrens (Figure 3). Marsh wrens were found more often in areas with low stem-
density values and were infrequently found in areas with higher values.

Statistical tests were performed to determine significant differences
between the "present" and "absent" distributions. These tests compared the
means of the two distributions, with the null hypothesis stating that they
were equal (Table 1).

For the red-winged blackbird the only significant difference between the
present and absent values was along the percentage graminoid-stems variable.
The red-wing was found in almost all the sample plots, so these analyses are
not very conclusive.

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Figure 2. Distribution of effective height values in sample plots where long-
billed marsh wrens were present and where they were absent.

The long-billed marsh wren, swamp sparrow, and common yellowthroat had
significant differences between the means for five habitat variables: average
water depth, percentage cover, percentage graminoid stems, percentage dead
stems, and stem density. The yellow warbler, the most infrequent species

9


SECTION 1

INTRODUCTION

The Columbia Generating Station, a new coal-fired electric generating
station, is located on the Wisconsin River 4 miles south of Portage, Wis. It
consists of two 527-MW generating units, one in operation since April 1975
and the second since May 1978, Waste heat from this facility is dissipated
to the air by using a 2-km? (490-acre) cooling lake and two wet cooling towers.
The cooling lake was built in a large riparian wetland of sedge meadow,
shallow marsh, shrub carr, and flood-plain forest. Studies have been conducted
on the effects of the cooling lake on the local ground-water regime and the
effects of the altered ground-water regime on vegetation in the wetland
adjacent to the cooling lake (Andrews and Anderson 1978).

Prior to construction of the cooling lake, the wetland was a discharge
area of the local ground-water system. The operation of the cooling lake has
greatly modified ground-water-flow patterns in this wetland area (Andrews
and Anderson 1978). Discharge rates have increased by a factor of 6, and
in addition the seasonal temperature profile of the discharging water has been
altered. The altered ground-water-flow rates and seasonal temperature
patterns have had severe effects on the wetland vegetation, in part because
of the altered seasonal phenology of the plants (Bedford 1977). A rapid
thinning of sensitive perennials is occurring, and annuals and more tolerant
perennials are invading the area.

In the early part of the research program a simple model was constructed
to predict the impact of the generating station on the breeding birds found
in the wetland. The work previously cited indicates large modifications in
both biotic and abiotic components of the nesting habitat of these birds.

This investigation uses correlations between water depths, components of
vegetation structure, and distributions of breeding birds to predict frequency
changes in the nesting birds given the condition of increased water levels.

At the beginning of the nesting season a bird must choose an area suit-
able for nesting. Any place it attempts to settle will be a complex matrix
of environmental factors, both biotic and abiotic. Each species has a range
of tolerance, over which it can survive and successfully reproduce, for each
environmental factor. When all individual tolerances are plotted together in
a space representing the whole environmental range, with each factor on a
separate axis, an n-dimensional hypervolume results (Hutchinson 1957). This
hypervolume is a graphic representation of the areas suitable for that species.


Weller, M.W., and C.S. Spatcher. 1965. Role of habitat in the distribution
and abundance of marsh birds. JIowa Agric. Home Econ. Exp. Sta.,
Rep. 43. 31 p.

Willson, M.F. 1966. Breeding biology of the yellow-headed blackbird.
Ecol. Monogr. 36:51-77.

24


BIRD DISTRIBUTIONS AND HABITAT STRUCTURE

The distributions of birds within the wetland have been described with
respect to a number of features of the wetland, including water regime and
vegetation structure. These features have been shown to be related to the
distributions of the birds. An emphasis was placed on investigating bird
distributions with respect to the water regime and vegetation structure rather
than plant-species composition. Human taxonomic methods are designed to
differentiate separate genetic units. A bird, however, is not concerned
whether two plants are the same species or different; what matters is how those
plants contribute to the environment. From the point of view of nesting birds,
two genetically distinct species of plants can contribute identically to the
environment. Birds and human taxonomists do not classify for the same purposes.

An alteration of the composition of plant species of the wetland resulting
from the altered water regime will affect bird populations by altering the
physical structure of their environment. Why birds choose the particular
parts of the environment that they do is not yet known. The structure of the
vegetation can affect the availability of song perches, nest sites, foraging
sites, and escape cover. The physical structure of the vegetation also affects
the type of food resources present.

PREDICTION OF BIRD CHANGES

The ultimate goal of this study is to predict some of the effects of the
power plant on bird populations. This report covers only a portion of the
total effect of the Columbia Generating Station.

Since the impact occurs by way of a number of intermediate steps, predic-
tion of changes in wetland bird populations that result from the altered water
regime is not easy. The changing water levels affect birds primarily because
of the effects of these changes on other aspects of the environment. The re-
lationships between water levels, vegetation, and invertebrates are statistical
and are poorly understood. The distribution of birds across vegetation gra-
dients is also statistical, The final analysis between water levels and bird
populations is therefore a combination of several poorly understood relation-
ships. As one adds more statistical links to a chain, the relationships
between the endpoints become less determinable.

Despite these difficulties several predictions could be made concerning
changes in bird-species frequencies. Each prediction is based on an over-
simplification of the ecological system, and by itself each prediction is
suspect. When a number of these individual predictions are similar, however,
more confidence is justified as to future distributions in the study area.
Many relationships among water level, vegetation, and birds all suggest the
same changes in bird populations resulting from the increased water levels:
long-billed marsh wrens should become more frequent in the area, and the swamp
sparrow, common yellowthroat, and yellow warbler should become less frequent.

21


Foreword... . ee ee ee
Abstract... . .
Figures and Tables .
Acknowledgment .
1. Introduction .......
2. Conclusions .
3. Recommendations . oe
4, Sampling Methods ...
5. Results .
Distributions | along “habitat “variables
Frequency relationships . .
Relation between water depth and habitat variables .
Predictions of frequency change we
6. Discussion .. hone

CONTENTS

Bird distributions and habitat structure .
Prediction of bird changes .
Applications .....

References . 1. 6. ee ee ee ee

iii
iv
vi
vii


ABSTRACT

The distribution of breeding passerines (songbirds) was investigated in
a wetland in southern Wisconsin to develop a model for use in predicting
changes in bird frequencies resulting from environmental alterations. The
wetland is adjacent to the cooling lake of a coal-fired electric generating
station. The water levels in the wetland are being altered by the cooling
lake's effect on the local ground-water system. The model uses information
on distributions of bird species along gradients of water depth and vege-
tation-structure characteristics and information on the relationships between
the characteristics to predict changes in bird species’ frequencies resulting
from increased water levels. The predictions are qualitative, in that they
predict only the direction of the change, not its magnitude. The resulting
predictions are: (1) the long-billed marsh wren should increase in frequency;
and (2) the swamp sparrow, common yellowthroat, and yellow warbler should
decrease in frequency. No prediction could be made concerning the frequency
of the red-winged blackbird.

This report was prepared with the cooperation of faculty and graduate
students in the Department of Zoology at the University of Wisconsin-Madison.
Most of the funding for the research reported here was provided by the U.S.
Environmental Protection Agency; funds also were granted by the University
of Wisconsin-Madison, Wisconsin Power and Light Company, Madison Gas and
Electric Company, Wisconsin Public Service Corporation, and the Wisconsin
Public Service Commission. This report is submitted toward fulfillment of
Grant No. R803971 by the Environmental Monitoring and Data Acquisition Group,
Institute for Environmental Studies, University of Wisconsin-Madison, under
the partial sponsorship of the U.S. Environmental Protection Agency. The
report covers the period May 1975 to December 1977, and work was completed
as of December 1978.

iv


in the wetland, had significant differences for only three variables: average
water depth, percentage cover, and percentage graminoid stems.

No species showed a significant distribution pattern on the water-depth-
deviation variable. Only the swamp sparrow had a significant difference
between means on the effective height variable.

FREQUENCY RELATIONSHIPS

The values of a habitat variable in the sample plots that contained a
species were averaged, which resulted in a specific mean for that variable.
The overall mean for a variable was calculated by averaging the values

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billed marsh wrens were present and where they were absent.

10


ACKNOWLEDGMENTS

Barbara Bedford and Stephen Brick assisted me in the collection of the
field data. I greatly appreciate their help and encouragement and humbly
apologize for forcing them to awaken so often in what seemed the middle of
the night to collect the data.

Philip Page assisted me in the preparation of the manuscript and Steve
Horn prepared many of the figures.

M.F, Willson, C.M. Weise, and T.C. Moermond reviewed the manuscript.
I thank them for their comments.

Finally, I thank Daniel Willard for his constant help and encouragement
in overseeing this research.

vii


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SECTION 2

CONCLUSIONS

Five habitat variables--percentage of cover, water-depth deviation,
percentage of graminoid stems, percentage of dead stems, and stem density--
have significant linear correlations with average water-depth values. A
sixth variabic, effective height, does not.

‘Distributions of passerines are correlated with five habitat variables:
Average water depth, percentage of cover, percentage of dead stems, percentage
of graminoid stems, and stem density. They are not correlated with water-
depth deviation or effective height.

A passerine's frequency is related to its distribution along a habitat
variable.

The altered water regime predicts a series of vegetation changes, which
in turn generate predictions for changes in frequencies of the passerines.
The long-billed marsh wren should increase; the swamp sparrow, common yellow-
throat, and yellow warbler should decrease. No prediction could be made
concerning the red-winged blackbird.

The analyses concern the frequency of occurrence of a species, but not
their density. A more complete approach would measure densities or some
form of reproductive success; however, the field methods used in this study
do not allow these forms of analysis.


Hutchinson's hypervolume model can be used to predict the effects of
environmental alterations on bird species by comparing the hypervolume of the
total area in question with the subset of that hypervolume that is used by
a species (Shugart and Patten 1972, Anderson and Shugart 1974).

If a species' hypervolume is identical to the total hypervolume, that
species should occur throughout the area. If a species’ hypervolume does not
lie anywhere within the total hypervolume, that species should not be present
at all. Neither of these two cases is of any great value to the present
analysis. The more common situation is that part of a species' hypervolume
occupies a portion of the total hypervolume. Habitat alterations that shift
the total hypervolume in the direction of the species' hypervolume should
increase the suitable habitat for that species, and the species should become
more abundant. Likewise, a shift away from the species’ hypervolume should
decrease the available suitable habitat, and the species should become less
abundant. These two notions in a simplified form are the basis of the anal-
yses that follow.


REFERENCES

Anderson, S.H., and H.H. Shugart, Jr. 1974. Habitat selection of breeding
birds in an east Tennessee deciduous forest. Ecology 55:828-837.

Andrews, C.B., and M.P. Anderson. 1978. Impact of a power plant on the ground
water system of a wetland. Ground Water 16:105-111.

Bedford, B.L. 1977. Changes in wetland vegetation associated with leakage
from the cooling lake of a coal-fired power plant. M.S. Thesis.
Univ. Wisconsin-Madison, Madison, Wis. 39 p.

Beecher, W.J. 1942. Nesting birds and the vegetative substrate. Chicago
Ornithal. Soc., Chicago, I1l. 69 p.

Hutchinson, G.E. 1957. Concluding remarks. Cold Spring Harbor Symp. Quant.
Biol. 22:415-427.

Millar, J.B. 1973. Vegetation changes in shallow marsh wetlands under improv-
ing moisture regime. Can. J. Bot. 51:1443-1457.

Shugart, H.H., Jr., and B.C. Patten. 1972. Niche quantification and the
concept of niche pattern, p. 283-327. In B.C. Patten [ed.] Systems
analysis and simulation in ecology. Vol. II. Academic Press, New York.

Stewart, R.E., and H.A. Kantrud. 1972. Vegetation of prairie potholes,
North Dakota, in relation to quality of water and other environmental
factors. U.S. Geol. Surv. Prof. Pap. 585-D, Washington, D.C. 36 p.

Verner, J. 1964. Evolution of polygamy in the long-billed marsh wren.
Evolution 18:252-261.

Voights, D.K. 1976. Aquatic invertebrate abundance in relation to changing
marsh vegetation. Am. Midl. Nat, 95:313-322.

Walker, B.H., and R.T. Coupland. 1968. An analysis of vegetation-environment
relationships in Saskatchewan sloughs. Can. J. Bot. 46:509-522.

Walker, B.H., and C.F. Wehrhahn. 1971. Relationships between derived
vegetation gradients and measured environmental variables in Saskatchewan
wetlands. Ecology 52:85-95.

Weller, M.W., and L.H. Fredrickson. 1973. Avian ecology of a managed
glacial marsh. Living Bird 12:269-291.

23


APPLICATIONS

Current interest in the environmental effects of man's actions is intense.
In many instances Federal and State laws require that these effects be examin-
ed and discussed during the planning stages of projects. Although methods of
analysis for many forms of environmental effects are well established, methods
of analyzing and predicting effects on bird populations are still poorly
developed. Examination of environmental assessments reveals two general forms
of analysis with respect to bird populations, First, the text refers the
reader to an appendix that describes observations of birds on the project site,
often no more than a list of species. Second, a tabulation is given of the
number of acres of different habitat types that would be eliminated by the
project. Along with a list of the densities of birds inhabiting each habitat
type, this tabulation is used to predict the total number of birds lost
through destruction of habitat. The question of the effects on bird popula-
tions in areas that the proposed project would alter but not destroy is seldom
addressed. Many projects affect bird habitats to an extent less than total
destruction. The current study is an attempt to analyze such a situation.

At the Columbia site the water regime of a wetland next to a generating
station has been altered. A set of relationships between the water regime
and vegetation structure was investigated. These relationships were combined
to generate predictions of frequency changes in bird svecies that wouldresult
from the altered water regime. The form of analysis used in this study
should be applicable to other locations where a project is altering the physi-
cal features of an area in a known way. In such situations the effects of
those alterations on bird populations can often be predicted, if such pre-
dictions are considered desirable. Such predictions can increase the
thoroughness of the environmental assessment procedure.

22


FIGURES

Number

1 Columbia Generating Station and location of wetland study
site adjacent to the cooling lake .

2 Distribution of effective height values in sample plots where
long-billed marsh wrens were present and where they were
absent 6 wee ee

3 Distribution of stem-density values in sample plots where
long-billed marsh wrens were present and where they were
absent

4 Regression of frequency (number of occurrences) of five
passerines in the deviation of specific means from overall
mean for the water-regime and vegetation-structure variables

5 Relative positions of specific means and the overall mean for
habitat features along which bird-distribution patterns
were significant

6 Regression of the values of each habitat variable on average
water-depth values oe

7 Loss of available suitable breeding areas (cross hatched) as
environment shifts away from that used by a species .

TABLES

Number
1 Results of Mann-Whitney U-Statistic When Comparing Mean of
"Present" Values and Mean of "Absent" Values of Five Bird
Species and Seven Habitat Variables .

2 Predictions of Frequency Changes for Four Passerine Species
Based on an Increase in Water Levels in the Marsh .

vi

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10

13

15

16

17

Page

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19


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Average water depth (cm) z Percentage graminoid stems
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° 8
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5 .
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z 4 8 12 16 3 30 60 90 120
Percentage cover Percentage dead stems

Figure 4. Regression of frequency (number of occurrences) of five passerines
on the deviation of specific means from overall mean for the water-
regime and vegetation-structure variables. (continued)

13


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19


DISCLAIMER

This report has been reviewed by the Environmental Research Laboratory-
Duluth, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or recommen-
dation for use.

di


$ |
Columbia t |
Generating F
. Station

Cooling

Lake

Figure 1. Columbia Generating Station and location of wetland study site

adjacent to the cooling lake. Insert shows location of generating
station.


SECTION 5

RESULTS

This paper examines the distribution patterns along gradients of water
depth and vegetation-structure variables of five wetland passerine species:
the red-winged blackbird, long-billed marsh wren, swamp sparrow, common
yellowthroat, and yellow warbler. These species compose the vast majority of
the birds observed in the sampling plots. Although the sampling technique
was well suited for conspicuous birds, such as singing passerines, it did
not adequately sample many inconspicuous species, such as rails and bitterns.
The distribution patterns of the less conspicuous species are relevant to
the problem at hand, but analysis of the data collected on them could be
very misleading.

The bird-distribution analyses are divided into four sections. First,
the bird distributions were compared to gradients of habitat variables, to
determine if the birds were using only portions of the available habitat,
at least portions that could be characterized by the water regime and vege-
tation structure. Second, the frequencies of occurrence of the bird species
were analyzed with respect to their distributions along habitat gradients.
Third, the correlations between average water depth and the other habitat
variables were determined. Fourth, the previous analyses were combined to
generate predictions on frequency changes in the birds that would result from
the increasing water levels in the wetland.

DISTRIBUTIONS ALONG HABITAT VARIABLES

The values of a particular variable for all sample plots in which a
particular bird species was present were compared with the values of that
variable in all the sample plots in which the bird species was not found.
This comparison was done both graphically and with the Mann-Whitney U-test.
The tests showed if a bird species was found in areas that represent only
a portion of the total range of a habitat feature. The null hypothesis for
the Mann-Whitney test was that the mean value of the habitat variable in the
areas where a species was found was equal to the mean value in the areas
where the species was not found.

Two patterns were evident in the graphic representations of distri-
butions along habitat gradients. The first pattern is illustrated by the
distribution of the long-billed marsh wren along the effective height vari-
able (Figure 2). The distribution of the sample plots with marsh wrens is
almost identical to the distribution of the sample plots lacking marsh wrens,


EPA-60073-80-020
January 1980

PREDICTING EFFECTS OF AN ELECTRIC GENERATING STATION
ON WETLAND PASSERINE BIRDS

Wisconsin Power Plant Impact Study

by

Michael John Jaeger
Institute for Environmental Studies
University of Wisconsin-Madison
Madison, Wisconsin 53706

Grant R803971

Project Officer

Gary E. Glass
Environmental Research Laboratory-Duluth
Duluth, Minnesota

This study was conducted in cooperation with

Wisconsin Power and Light Company,
Madison Gas and Electric Company,
Wisconsin Public Service Corporation,
Wisconsin Public Service Commission,
and Wisconsin Department of Natural Resources

ENVIRONMENTAL RESEARCH LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804



Figure 7. Loss of available suitable breeding areas (cross hatched) as
environment shifts away from that used by a species. Horizontal
dimension is an environmental factor gradient, vertical dimension
is a frequency of that given factor value.

long-billed marsh wren's specific mean and away from the means of the swamp
sparrow, common yellowthroat, and yellow warbler. The increase in water
levels thus predicts an increase in frequency of the marsh wren and decreases
in frequencies of the other three species.

Values of percentage cover are negatively correlated with values of
average water depth. An increase in water depth thus predicts a decrease
in percentage cover values in the wetland. A decrease in percentage cover
shifts the overall mean for percentage cover towards the specific mean of
the marsh wren and away from the specific means of the swamp sparrow, common
yellowthroat, and yellow warbler. These shifts predict an increase in long-
billed marsh wrens and decreased frequencies of the other three species.

Values of percentage of graminoid stems are positively correlated with
values of average water depth. An increase in water depths thus predicts
an increase in values of percentage of graminoid stems in the wetland, An
increase in values of percentage of graminoid stems shifts the overall mean
towards the specific mean of the marsh wren and away from the means of
the other three species, This shift also predicts increased frequencies of
marsh wrens and decreased frequencies of the others.

Values of percentage of dead stems are positively correlated with values
of average water depth. An increase in water levels thus predicts an increase
in values of percentage of dead stems in the wetland. An increase in values

17


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, US Environmental
Protection Agency. have been grouped into nine series These nine broad cate-
gories were established to facilitate further development anc application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The nine series are

Environmental Health Effects Research

Environmental Protection Technology

Ecological Research

Environmental Monitoring

Socioeconomic Environmental Studies

Scientific and Technical Assessment Reports (STAR)
Interagency Energy-Environment Research and Development
“Special” Reports

Q Miscellaneous Reports

ONRORwWR +

This report has been assigned to the ECOLOGICAL RESEARCH series This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials Problems are assessed for their long- and short-term influ-
ences Investigations include formation. transport, and pathway studies to deter-
mine the fate of pollutants and their effects This work provides the technical basis
for setting standards to minimize undesirable changes tn living organisms in the
aquatic, terrestrial. and atmospheric environments

This documents available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

T. REPORT NO. 2. [3. RECIPIENT'S ACCESSION NO.
EPA-600/3-80-020
4. TITLE ANO SUBTITLE 5. REPORT DATE

January 1980 issuing date

Predicting Effects of an Electric Generating Station
on Wetland Passerine Birds: Wisconsin Power Plant

Impact Stud
7 AUTHOR(S) ls. PERFORMING ORGANIZATION REPORT NO.

6. PERFORMING ORGANIZATION CODE

Michael John Jaeger

Ig. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.

Institute for Environmental Studies 1BA820

+ - - A 11. CONTRACT/GRANT NO.
University of Wisconsin-Madison

Madison, Wisconsin 53706 R803971

12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED

Environmental Research Laboratory - Duluth, MN
Office of Research and Development

U.S. Environmental Protection Agency

Duluth, MN 55804

14, SPONSORING AGENCY CODE
EPA/600/03

15. SUPPLEMENTARY NOTES

16. ABSTRACT

The distribution of breeding passerines (songbirds) was investigated in a wetland
in southern Wisconsin to develop a model for use in predicting changes in bird
frequencies resulting from environmental alterations. The wetland is adjacent to
the cooling lake of a coal-fired electric generating station. The water levels in
the wetland are being altered by the cooling lake's effect on the local ground-water
system. The model uses information on distributions of bird species along
gradients of water depth and vegetation-structure characteristics and information on
the relationships between the characteristics to predict changes in bird species’
frequencies resulting from increased water levels. The predictions are qualitative,
in that they predict only the direction of the change, not its magnitude. The
resulting predictions are: (1) the long~billed marsh wren should increase in
frequency; and (2) the swamp sparrow, common yellowthroat, and yellow warbler should
decrease in frequency. No prediction could be made concerning the frequency of the
red-winged blackbird.

h 7. KEY WORDS AND DOCUMENT ANALYSIS
a DESCRIPTORS Ib. IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Birds Song birds 43 F,E
Electric power generation and Wisconsin power plant 48 B,G
transmission lines study 68 A,B,D,E
Ponds Construction impacts
Populations of a cooling lake
18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 31. NO, OF PAGES
unclassified
Release to public 20. SECURITY CLASS (This page) 22. PRICE
unclassified
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE

25 18 USS GOVERNMENT PRINTING OFFICE 1990-657-146/5576


SECTION 6

DISCUSSION

The study of the distributions and abundances of nesting birds is complex.
A species is a genetic unit that has evolved the ability to locate its members
in places that allow successful reproduction. To reproduce successfully a
bird must accomplish a number of tasks: for example, feed itself, associate
with a mate, find shelter from adverse conditions, escape predators, build a
suitable nest, adequately feed its young. Many envircnmental features con-
tribute to each of these factors. The study of how various environmental
features contribute to the successful reproduction of a bird is difficult
for a number of reasons: no factor is completely independent of others; the
study on one factor in isolation can be misleading; the interactions of many
factors are poorly understood, if at all; and no two individual birds have
identical requirements and tolerances.

Earlier studies have suggested three major influences on the distribution
and abundance of breeding marsh birds. Beecher (1942) found that the structure
of the vegetation, not the plant species, was the major determinant of marsh-
bird distribution. Weller and his associates (Weller and Spatcher 1965,

Weller and Fredrickson 1973) argue that distributions are determined primarily
by vegetation structure, water depth, and their interactions. The availability
of suitable food, generally invertebrates with aquatic life stages, has also
been suggested as being important (Verner 1964, Willson 1966).

The difficulty in understanding how these three major factors, water
regime, vegetation, and availability of food, affect -reeding-bird distribu-
tions is compounded by their interactions. The water regime is an important
determinant in the distribution of plant species (Walker and Coupland 1968,
Walker and Wehrhahn 1971, Stewart and Kantrud 1972, Millar 1973). The plant-
species composition of the wetland, in part determined by the water regime,
influences the structural characteristics of the vegetation. Finally, the
plant-species composition and the vegetation structure all influence the
distribution and abundance of aquatic invertebrates, although these relation-
ships are still not well understood (Voigts 1976). Thus, the three important
features of the marsh bird's environment form a complex, interacting unit.

The interaction of the environmental features, and the poor understanding
thereof, make it difficult to understand the habitat requirements of marsh
birds. The relationships investigated in this report represent a simplifica-
tion of the true relationships between the birds and their environment and
between the various aspects of the environment.

20


SECTION 3

RECOMMENDATIONS

Since the wetland is still in a state of transition, the breeding pas-
serines should be surveyed again when the water regime and the vegetation
have reached a new equilibrium to determine if the predicted changes in bird
populations have occurred.

This form of analysis could be applied to other situations when a know-
ledge of the qualitative changes in frequencies of bird species is desired.

This first-order model should be expanded to allow quantitative pre-
dictions of changes in frequencies and abundances.

Caution should be exerted when building cooling lakes near wetland
areas so that valuable bird-breeding areas are not significantly degraded.


To determine the effective height of the vegetation, a wooded stake,
marked off in decimeters, was placed at the center of each circle. The
height to which the vegetation covered each stake when viewed from approxi-
mately 1 m was recorded and these values were averaged.