&EPA
United States Environmental Office of Water EPA-822-R-02-023
Protection Agency Washington, DC 20460 March 2002
METHODS FOR EVALUATING WETLAND CONDITION
# 13 Biological Assessment
Methods for Birds
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United States Environmental Office of Water EPA-822-R-02-023
Protection Agency Washington, DC 20460 March 2002
METHODS FOR EVALUATING WETLAND CONDITION
# 13 Biological Assessment
Methods for Birds
Principal Contributor
Department of Fisheries and Wildlife, Oregon State University
Paul R. Adamus
Prepared jointly by:
The U.S. Environmental Protection Agency
Health and Ecological Criteria Division (Office of Science and Technology)
and
Wetlands Division (Office of Wetlands, Oceans, and Watersheds)
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NOTICE
The material in this document has been subjected to U.S. Environmental Protection Agency (EPA)
technical review and has been approved for publication as an EPA document. The information
contained herein is offered to the reader as a review of the "state of the science" concerning wetland
bioassessment and nutrient enrichment and is not intended to be prescriptive guidance or firm advice.
Mention of trade names, products or services does not convey, and should not be interpreted as
conveying official EPAapproval, endorsement, or recommendation.
APPROPRIATE CITATION
U.S. EPA. 2002. Methods for Evaluating Wetland Condition: Biological Assessment Methods
for Birds. Office of Water, U.S. Environmental Protection Agency, Washington, DC. EPA-822-R-
02-023.
This entire document can be downloaded from the following U.S. EPA websites:
http://www.epa.gov/ost/standards
http://www.epa.gov/owow/wetlands/bawwg
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CONTENTS
FOREWORD iv
LIST OF "METHODS FOR EVALUATING WETLAND
CONDITION" MODULES v
SUMMARY 1
PURPOSE 1
INTRODUCTION: WHY SURVEY BIRDS? 1
WHAT CAN A BIRD IBI (INDEX OF BIOLOGICAL INTEGRITY) TELL You? 1
WHAT DOES A BIRD IBI ESTIMATE? 2
STEPS IN DEVELOPING AN IBI FOR BIRDS 3
APPLYING A CALIBRATED BIRD IBI 7
WHAT TO MEASURE 7
FIELD SURVEY PROTOCOLS 7
RESEARCH NEEDS ll
REFERENCES 12
OTHER RELEVANT LITERATURE 15
LIST OF FIGURES
FIGURE 1: A STRATEGY FOR LOCATING BIRD POINT COUNTS AND AREA
COUNTS IN A DIVERSE WETLAND 1O
LIST OF TABLES
TABLE 1: CANDIDATE BIRD METRIC 5
in
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FOREWORD
In 1999, the U. S. Environmental Protection Agency (EPA) began work on this series of reports entitled
Methods for Evaluating Wetland Condition. The purpose of these reports is to help States and
Tribes develop methods to evaluate (1) the overall ecological condition of wetlands using biological
assessments and (2) nutrient enrichment of wetlands, which is one of the primary stressors damaging
wetlands in many parts of the country. This information is intended to serve as a starting point for States
and Tribes to eventually establish biological and nutrient water quality criteria specifically refined for
wetland waterbodies.
This purpose was to be accomplished by providing a series of "state of the science" modules concerning
wetland bioassessment as well as the nutrient enrichment of wetlands. The individual module format
was used instead of one large publication to facilitate the addition of other reports as wetland science
progresses and wetlands are further incorporated into water quality programs. Also, this modular
approach allows EPA to revise reports without having to reprint them all. A list of the inaugural set of
20 modules can be found at the end of this section.
This series of reports is the product of a collaborative effort between EPAs Health and Ecological
Criteria Division of the Office of Science and Technology (OST) and the Wetlands Division of the
Office of Wetlands, Oceans and Watersheds (OWOW). The reports were initiated with the support
and oversight of Thomas J. Danielson (OWOW), Amanda K. Parker and Susan K. Jackson (OST),
and seen to completion by Douglas G. Hoskins (OWOW) and Ifeyinwa F. Davis (OST). EPArelied
heavily on the input, recommendations, and energy of three panels of experts, which unfortunately have
too many members to list individually:
• Biological Assessment of Wetlands Workgroup
• New England Biological Assessment of Wetlands Workgroup
• Wetlands Nutrient Criteria Workgroup
More information about biological and nutrient criteria is available at the following EPA website:
http ://www. epa. gov/ost/standards
More information about wetland biological assessments is available at the following EPA website:
htto ://www.epa. gov/owow/wetlands/bawwg
IV
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LIST OF "METHODS FOR EVALUATING WETLAND
CONDITION" MODULES
MODULE # MODULE TITLE
1 INTRODUCTION TO WETLAND BIOLOGICAL ASSESSMENT
2 INTRODUCTION TO WETLAND NUTRIENT ASSESSMENT
3 THE STATE OF WETLAND SCIENCE
4 STUDY DESIGN FOR MONITORING WETLANDS
5 ADMINISTRATIVE FRAMEWORK FOR THE IMPLEMENTATION OF A
WETLAND BIOASSESSMENT PROGRAM
6 DEVELOPING METRICS AND INDEXES OF BIOLOGICAL INTEGRITY
7 WETLANDS CLASSIFICATION
8 VOLUNTEERS AND WETLAND BIOMONITORING
9 DEVELOPING AN INVERTEBRATE INDEX OF BIOLOGICAL
INTEGRITY FOR WETLANDS
10 USING VEGETATION TO ASSESS ENVIRONMENTAL CONDITIONS
IN WETLANDS
11 USING ALGAE TO ASSESS ENVIRONMENTAL CONDITIONS IN
WETLANDS
12 USING AMPHIBIANS IN BlOASSESSMENTS OF WETLANDS
13 BIOLOGICAL ASSESSMENT METHODS FOR BIRDS
14 WETLAND BIOASSESSMENT CASE STUDIES
15 BIOASSESSMENT METHODS FOR FISH
16 VEGETATION-BASED INDICATORS OF WETLAND NUTRIENT
ENRICHMENT
17 LAND-USE CHARACTERIZATION FOR NUTRIENT AND SEDIMENT
RISK ASSESSMENT
18 BlOGEOCHEMICAL INDICATORS
19 NUTRIENT LOAD ESTIMATION
2O SUSTAINABLE NUTRIENT LOADING
v
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SUMMARY
are eager to help with surveys, sometimes on
a volunteer basis.
Birds potentially detect aspects of wetland
landscape condition that are not detected by the
other groups commonly used as indicators.
Moreover, birds are of high interest to a broad
sector of the public. When using birds as indi-
cators, one must pay particular attention to is-
sues of spatial scale. This requires an under-
standing of home range sizes of the bird species
being surveyed. The development of wetland
and riparian bird indices of biological integrity is
still in its infancy, but holds considerable
promise.
PURPOSE
This module is intended to suggest study de-
signs and data collection procedures that might
be used when constructing and testing a regional
index of biological integrity, using birds as indi-
cators.
INTRODUCTION:
WHY SURVEY BIRDS?
The public notices birds and often becomes
concerned when they die or disappear.
Birds can indicate the integrity (health or con-
dition) of a landscape in addition to the integ-
rity of individual wetlands. Assessing integ-
rity of landscapes (watersheds or other areas
many square miles in size) is vital to assessing
the cumulative effects of human activities.
Most birds are easy to survey: there is no need
to collect and analyze samples or struggle with
complex taxonomic keys.
A relatively large pool exists of interested data
collectors, many of whom are proficient at bird
identification or can be trained. They often
WHAT CAN A BIRD IBI
(INDEX OF BIOLOGICAL
INTEGRITY) TELL You?
7n contrast to chemical monitoring, a bird IBI
J. can tell you, simply and directly, the condition
of living systems at a site (an individual wetland)
or in a landscape of interest. Such knowledge
is more direct and more integrative than infor-
mation merely about a site's contamination sta-
tus. A well-conceived, adequately validated bird
IBI considers a whole host of natural and hu-
man environmental influences to indicate if a
landscape is currently supporting an integrated
and adaptive biological system. Such an index
is of practical use in several contexts:
• Protection Priorities, Cleanup Priorities, and
Section 305(b) Reporting: Are wetlands in
watershed "X" generally more degraded by
human alteration than those in watershed "Y"?
• Restoration Progress: Have efforts to restore
wetlands A, B, and D succeeded in establish-
ing representative bird communities?
• Trends: Over a multiyear period, are we main-
taining or improving the biological quality—
not just the quantity—of our region's wet-
lands?
Though not a panacea, IBIs do embody the con-
cept that biological condition, as represented by
bird species composition and species character-
istics, can reflect the relative degree of human
alteration. When used together with other assess-
ment tools, IBIs simplify and summarize complex
biological information so it can be understood and
used more readily by resource managers.
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The development of wetland and riparian bird
IBIs is, unfortunately, still in its infancy. Thus
information in this module is based mainly on a
healthy dose of ecological theory, monitoring ex-
perience, and just a few studies (notably
O'Connell et al. 1998, Rottenborn 1999, Rich-
ter and Azous 2001). In contrast to the few IBI-
oriented studies of birds, agencies have eagerly
supported the development and testing of re-
gional IBIs for fish and stream invertebrates for
over 15 years.
WHAT DOES A BIRD IBI
ESTIMATE?
Collectively, birds are sensitive both directly
and indirectly to a variety of environmental
influences (Adamus and Brandt 1990):
• Vegetation extent, pattern, and structure, es-
pecially woody and robust herbaceous veg-
etation (Finch 1991)
• Water extent, depth, duration, and seasonal
frequency (Wakeley and Roberts 1994)
• Salinity (Halse et al. 1993)
• Water quality, i.e., nutrient loads, anoxia, wa-
ter clarity, acidity, contaminants, sedimenta-
tion (Hoyer and Canfield 1994, Rushton et al.
1994, Savardetal. 1994)
• Disturbance by traffic, persistent human visi-
tation, and associated predatory animals (Craig
and Barclay 1992, Reijnen et al. 1995, Miller
et al. 1998)
It is not always possible to establish with cer-
tainty which of the above (or other) environmen-
tal influences is causing a bird IBI to have a low
value. A bird IBI usually cannot prove cause-
effect connections. However, once general im-
pairment has been established using an IBI, more
intensive studies may be desired to diagnose spe-
cific causes. Moreover, in many situations it is
not necessary to define specific causes of im-
pairment. Birds are valuable as an indicator pre-
cisely because they are integrators of the cumu-
lative effects of multiple environmental influences
in a landscape. For example, based on
regionwide surveys, one study (O'Connell et al.
1998) quantified regional landscape integrity in
avian terms as follows:
Among other distinct characteristics, a
significantly greater percentage of the
species observed at these [highest qual-
ity] sites are insectivorous, forage in de-
caying tree bark, and migrate from dis-
tant wintering grounds, than those ob-
served at other sites. This partial profile
tells us these habitats support upper lev-
els of the food chain, trees in advancing
stages of age and decay, and songbird
species with continental range. As such,
these habitats exhibit important func-
tional, structural, and compositional el-
ements of biological diversity. At the
other end of the spectrum, 27% of the
survey sites exhibited low ecological in-
tegrity. A significantly greater percent-
age of species observed at these sites are
omnivorous, non-native, reproduce mul-
tiple times per season, and parasitize or
prey on the nests of other birds. This is a
classic profile of opportunistic behavior,
and is observed in both plant and animal
species when habitats are disturbed by
human or other events.
Blue-winged Teal
2
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Because many bird species are long-lived and
migrate annually between continents, it is likely
that the status of some species in a particular
area may be influenced as much or more by the
conditions in their wintering or summering ar-
eas as by the conditions in the study area (Finch
and Stangel 1993). However, this factor's ef-
fect on a bird IBI may be lessened by surveying
a sufficient number of sites throughout a region
during IBI development.
The boundaries of the "landscape" whose con-
dition is being represented by a bird IBI will de-
pend on characteristics of the particular bird spe-
cies that are present (Hansen and Urban 1992).
For example, bird IBI values for a site inhabited
mostly by particular small, strongly wetland-de-
pendent birds that wander little during the breed-
ing season (e.g., rails, some sparrows) may re-
flect more the condition of the particular site than
the condition of surrounding uplands,that is, the
broader landscape. The opposite is true for sites
inhabited mostly by particular large birds that
wander greatly (e.g., raptors, shorebirds, water-
fowl). Thus, in most instances, a bird IBI should
be segregated into components that reflect these
two (or more) scales. Alternatively, the IBI
should use data only from species that charac-
terize a particular scale, so that the area (or spe-
cies group) whose integrity the IBI is represent-
ing is clear to users.
STEPS IN DEVELOPING AN
IBI FOR BIRDS
7 Within an ecoregion (a region of gener
ally similar physiography, land use, and
climate) decide on what basis you will
group (classify) wetlands into types (classes).
Wetlands may be classified based on vegetation,
water regime, or a host of other factors. Choose
the factor(s) that best account for the naturally
occurring, within-class variability in bird species
composition. To accomplish this, consider us-
ing the classification of Cowardin et al. (1979,
as used on National Wetland Inventory maps),
Brinson (1993, the hydrogeomorphic or HGM
classification), or others described in the Classi-
fication module. Then focus your sampling on
one class, for example, flow-through riverine
wetlands dominated by woody vegetation. The
more narrowly you define your target class, the
more likely you are to find effective bird metrics
(because you have constrained natural variabil-
ity). However, the utility of the resulting metrics
will be limited because they address only that
one class.
2 Identify at least 10 sites of that class that
seem potentially to be the most altered1 by
humans, 10 that seem the least altered, and
10 with a potentially intermediate condition
(these numbers are arbitrary and it is not essen-
tial that they be equal or that 30 sites be selected).
Eliminate from further consideration sites that
cannot be accessed because of ownership restric-
tions or hazards. In some situations it may be
possible to predict fairly precisely the number of
sites that need to be surveyed by using prior es-
timates of spatial and temporal variability from
1 The criteria for prejudging which sites are least or
most altered necessarily will be subjective, and it
may be helpful to prepare and apply a standardized,
semiquantitative checklist for systematically evaluat-
ing potential impacts at all candidate sites (e.g.,
Bryce et al. 1999). The inventory of alterations
should include indicators of human disturbance
thought most likely to have an impact on birds, for
example, densities of houses and roads, proximity to
houses and roads, percent of land that is
nonvegetated or mowed lawn; and habitat patch
area, perimeter-area ratio, width, and connectivity to
similar patches (Robinson et al. 1995, Miller et al.
1997, Germaine et al. 1998, Helzer and Jelinski
1999). See the Developing Metrics and Indexes of
Biological Integrity module for further information
on characterizing alteration.
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similar wetland types in the same region. For
some wetland bird metrics, such variance esti-
mates are compiled in Adamus and Brandt 1990
(Tables 15 and 16 of that report) and Adamus
1996 (Appendix N of that report). Visit the se-
lected sites to confirm the accuracy of the eco-
logical classification and apparent alteration.
Alternatively, you may select fewer sites but col-
lect data both during prealteration and
postalteration years (e.g., Richter and Azous
2001). Occasionally, it may be feasible to ana-
lyze existing databases to identify assemblages
of species that are most sensitive to particular
types of alterations (e.g., Burdick et al. 1989).
For example, if you are aware that economic,
legal, or policy factors resulted in a surge in
wetland drainage, wetland restoration, land-
clearing, or construction in a particular county
between 1985 and 1990, you might determine if
Breeding Bird Surveys (BBS) or Christmas Bird
Counts (CBC) were conducted in the county be-
fore, during, and after that period (this determi-
nation can be made by visiting for the BBS
data or for the CBC data). If so, you may be able to
download the data and look for trends in indi-
vidual species and species groups, being careful
also to examine the possibility that apparent
trends might be the result of interannual changes
in the level of precipitation, the observers in-
volved, the survey date, or other factors (Sauer
and Droege 1990). From such a review, you
may be able to characterize species as "adapt-
ers," "exploiters," or "avoiders" (Blair 1996) and
then use these designations as bird metrics in a
multimetric index to be tested at other sites.
3
Conduct equal-effort surveys of birds,
applying the same methods to all chosen
sites (see Field Survey Protocols, below).
A During at least one site visit, estimate the
//extent and condition of structural attributes,
i both within and around the wetland, that
potentially constitute habitat for most expected
species (Morrison et al. 1998). If unsure, con-
sult with local birders and ornithologists. At-
tributes likely to be particularly important are
the acreages of standing open water (permanent
as opposed to seasonal); woody vegetation (ri-
parian as opposed to upland and various age
classes), cropland, and unmanaged fields; prox-
imity to similar wetlands and other natural habi-
tats; the cumulative length of roads, ditches, and
streams; presence offish; and the number of resi-
dences and vegetation strata (layers) (Craig and
Beal 1992, Lovvorn and Baldwin 1996, Weller
1999). These features should be assessed both
within the site and, if possible, through aerial
imagery in concentric zones at various distances
from the site, up to perhaps 1 mile away. Distri-
bution of surface water should be assessed dur-
ing both wet and dry seasons whenever possible.
Suggestions for assessing many habitat features
is provided by Bookhout (1994).
5 From the collected data, identify species
and groups of species whose attributes
(e.g., presence, abundance, frequency) are
clearly skewed towards the most—or least—al-
tered sites, or identify the years with most and
least alteration. Do not rely too heavily on sta-
tistical correlation; more important is the pres-
ence or absence of particular species or groups
exclusively at either the least or most altered sites.
Also important is the proportional distribution
of abundances of species at these sites (i.e., bird
community "evenness"). When only one or a
few species dominate a site numerically, it some-
times indicates broader degradation of the site's
ecological systems. Such a diagnosis depends
on the particular species and habitat type. See
the Developing Metrics and Indexes of Biologi-
cal Integrity module for further information on
interpreting data.
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TABLE 1: CANDIDATE BIRD METRIC
ATTRIBUTE
Frequency of occurrence of species that are Insectivorous aerial foragers
Percent of species that are long-distance (e.g., Neotropical) migrants
Proportional abundance (%) of blackbirds and starlings
Ratio of juvenile to adult-plumaged diurnal raptors
Cumulative frequency of occurrence of all regionally rare species
Number of species that typically feed on submersed aquatic vegetation
Proportional abundance (%) of the three most common species
Frequency of occurrence of reputedly egg-predating or parasitizing species
(e.g., corvids, cowblrds, marsh wren) (Rogers et al. 1997)
Number of found species that have shown statistically significant declines In the region
according to BBS data
Percent of found species that also are regularly present on >90% of the BBS routes In
the same region ("core" species, Collins and Glenn 1997)
Percent of the expected species (based on geographic range, wetland type, vegetated
area, and other variables) that were found (e.g., "Avian Richness Evaluation Method"
of Adamus 1995, "Index of Avian Integrity" of Schroeder 1996)
Genetic diversity among found species, as assumed from their phylogenetlc
relationships ("functional Integrity," von Euler 1999)
HYPOTHESIZED RELATIONSHIP
TO ENVIRONMENTAL
DEGRADATION
decrease
decrease
Increase
decrease
decrease
decrease
Increase
Increase
decrease
Increase
decrease
decrease
f Try creating "metrics" by pooling data
A"\from groups of species. Define the groups
v-^based on similar life history, home range
size, or other behavioral or demographic char-
acteristics (Croonquist and Brooks 1991,
Mulyani and DuBowy 1993, Bournaud 1994,
Weller 1995, Wiens et al. 1996). Metrics are
attributes shown empirically to change in value
along a gradient of human disturbance. Examples
might include those shown in Table 1 (these are
not comprehensive and most have not been vali-
dated). Analysis of data from mainly upland land-
scapes suggests that resident species may be less
affected than migrants by habitat structure as
measured at a landscape scale (Flather and Sauer
1996).
Be sure that candidate metrics do not, as a whole,
imply that sites are in better ecological condition
only because they are wetter, or have closed
canopies. Some wetland bird species are
naturally adapted to dryer sites or sites with no
trees or no vegetation at all, as in the case of
many shorebirds (Rottenborn 1996). Prolonged
duration of inundation, or invasion by trees or
even low emergents, actually may signal
degradation of their associated wetland class.
Thus metrics that express only species richness
without accounting for the characteristics of the
component species, and thus which may reflect
only the area of habitat at a site and its natural
structural complexity rather than ecological deg-
radation (Findlay and Houlihan 1997, Warkentin
and Reed 2000), may yield information that is
less useful (Meiklejohn and Hughes 1999,
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Whitaker and Montevecchi 1999). Moreover, a
variety of wetland types, regardless of their
internal heterogeneity, is essential to supporting
biodiversity at regional scales (Leonard 1994,
Haig et al. 1998, Warnock et al. 1998).
7Using data plots and statistical analysis,
/erify that the alteration category, rather
;han a wetland habitat feature such as acre-
age or seasonal duration of standing water, was
associated strongly with the apparent affinity of
some birds for most or least altered sites or years.
If the alteration category is associated with spe-
cies affinity, proceed to step 9. If not, go to step
8. This verification step is unnecessary if previ-
ously it was demonstrated that the correlated
habitat feature's condition is governed entirely
by human alteration. Ideally, it is best to exam-
ine the relationship of bird metrics to alteration
category and habitat structure over a multiyear
period (Gibbs et al. 1991, Wilson et al. 1998).
Many good sources are available for planning
and conducting a statistical analysis of data, for
example, Verner et al. (1986), Ramsey and
Schafer (1997), and Nur et al. (1999).
If your extensive review of data plots and
statistical analysis results shows that no
species or grouping of species has a con-
sistent tendency to occur at the most or least
altered sites, it may be because prolonged al-
teration has eliminated all sensitive species from
the local landscape (Freemark and Merriam
1986). Or, it may be that human factors have
not yet begun to affect local bird communities.
Either possibility is impossible to prove. You will
need to survey additional least-altered sites (if
the first situation seems more likely) or additional
most-altered sites (in the second situation). To
identify these sites, you may need to expand the
study region or broaden the wetland class you
are examining and then repeat steps 6 through
8. You also will need to survey additional sites
if the spatial distribution of all species and group-
ings seems related more to particular habitat fea-
tures than to an alteration regime unrelated to
these features. An appropriate classification of
sites prior to sampling can avoid this situation.
Alternatively, you may consider dividing the
wetland class into habitat subclasses and cali-
brating separate IBIs for each (e.g., for shallow
and deep wetlands). This, too, would require
surveys at additional sites, so it is best to antici-
pate and address such factors during the study
design phase, before beginning the surveys.
Propose a simple mathematical formula
and try several ways of combining the
metricsinto one or more "multimetric indi-
ces," after first standardizing each metric with
respect to its numeric range. A multimetric in-
dex might consist, for example, of the sum of
individual metrics such as (a) the number of spe-
cies that are long-distance migrants and (b) the
percent of total abundance consisting of aerial
foraging species, divided by (c) the frequency of
the European Starling. It is not necessary for
the individual metrics to be logically or mecha-
nistically interrelated as in classical ecological
models, but alone they should have a relation-
ship to human disturbance of wetlands that is
supported at least by ecological theory and ide-
ally by experimental data. Separate multimetric
indices may be warranted for different measure-
ment scales (site versus landscape) and differ-
ent seasons, depending on the particular regional
avifauna. Iterative experimentation and adapta-
tion are important in identifying the most sensi-
tive and consistently accurate indices. The best
multimetric index will be one that responds most
sensitively to the human disturbance gradient,
independent of habitat conditions that are unre-
lated to alteration. A multimetric index that
comprises at least six bird metrics, each measur-
ing a unique type of avian response to human
alteration, is most likely to show adequate sen-
sitivity in future applications.
6
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APPLYING A CALIBRATED
BIRD IBI
ace a bird IBI has been developed, or an ex
sting bird IBI has been calibrated for local
conditions, you will apply it during routine site
assessments by conducting bird surveys at a prob-
ability sample of sites (e.g., a statistically ran-
dom selection of accessible sites) whose degree
of alteration is unknown. The surveys should be
conducted using the same methods used when
developing the bird IBI, and it may be possible
at this point to conserve effort by focusing on a
narrower range of species or species groups—
those found during IBI development to be most
reliable as indicators. Then organize the collected
data according to the metrics in the bird IBI, and
compare the site's values for these metrics with
the range of regional values embodied in the bird
IBI previously developed from multisite or
multiyear data.
WHAT TO MEASURE
• Abundance of each species and number of spe-
cies—appropriate for reconnaissance-level
surveys (one-time visit)
• Frequency of occurrence, by species and sea-
son—if additional resources are available for
more frequent surveys
• Duration of wetland use by individual birds—
feasible only if professional biologists can dis-
tinctively band or otherwise mark individual
birds, but potentially the most diagnostic at-
tribute
• Behavior of individual birds (e.g., feeding,
resting)—feasible only where nearly all indi-
viduals can be viewed
Many other features of bird populations can be
indicative of wetland degradation, but they are
not described here because their requirements
for specialized equipment, skills, or time makes
them unsuitable for use in routine regional-scale
monitoring programs.
FIELD SURVEY
PROTOCOLS
fTr he following are recommendations based
J. partly on accepted bird survey protocols
from nonwetland habitats, for example, Ralph et
al. (1993, 1995), Bibby et al. (1992), as well as
some techniques applied specifically to wetlands
(Ribic et al. 1999, Weller 1999). They have been
tempered to reflect what we have learned so far
from surveying wetland birds. These protocols
will not apply equally well in all situations and
will likely evolve as we learn more.
Birds in wetlands are best inventoried using area
searches or point counts.
Area searches (also called "direct counts,"
Weller 1999) are appropriate for the parts of
wetlands where visibility is unobstructed, such
as open water areas, mudflats, and short-grass
flats (e.g., Igl and Johnson 1997). Species
are counted based on visual, not auditory, iden-
tification.
Point counts can include all habitats within a
site and are especially appropriate where vis-
ibility is partly obstructed by trees, shrubs, and/
or tall grasses. Species that are seen or heard
are counted.
Area searches involve using a spotting scope
or binoculars to scan the open area from one or
more fixed points, generally viewpoints with the
best visibility of the site and whose fields of vi-
sion do not overlap. Occasionally, area searches
will involve canvassing an area by boat, aircraft,
or by walking. Birds should be identified and
7
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counted until all individuals within the field of
view have been tallied. The time required to
complete the count should be recorded and the
exact size (hectares) of the scanned area should
be measured (e.g., from aerial photographs or
field sketches). These estimates of area searched
and time spent should be used as covariates in
the statistical analysis, or less desirably, used to
derive variables such as "birds per minutes
searching" and "birds per hectares scanned." To
facilitate later data interpretation, the search area
(and associated data collection) may be subdi-
vided into individual habitat types. Area searches
may be used in wetlands of any size wherever
views are unobstructed. They are not effective
for surveying most songbirds, which constitute
the majority of species in many wetlands.
Point counts also involve tallying birds from
fixed points, but require the observer to identify
all species by sound as well as sight. Standard
protocols for terrestrial point counts specify that
birds be tallied for 5 minutes at each point (some
biologists prefer 10 minutes). Usually, no two
points should be closer than 200 m to each other
(Ralph et al. 1995). Thus the number of points
allocated to any wetland will depend on wetland
size. This requirement also implies that, if the
objective is to sample only the wetlands and not
the adjoining uplands, ideally, the wetlands must
be no less than 8 acres in size (if perfectly round;
much larger if not) in order to situate points more
than 100 m from the wetland-upland edge.
Some researchers also recommend that observ-
ers estimate distance to each identified bird re-
gardless of wetland size (Emlen 1971), or at least
differentiate between individuals detected within
25, 50, or 100 m and those farther away (Hodges
and Krementz 1996). This step may be particu-
larly important if an IBI is to include abundance
(density) metrics or if the species that are being
surveyed differ greatly with regard to their abil-
ity to be detected.
Points may be located along a transect (e.g.,
Dickson 1978,Niemi andHanowski 1984). With
transects, birds detected while the observer was
walking or canoeing between points usually are
recorded as well. There is no technical or statis-
tical advantage to using transects rather than
point counts and area counts alone, and there
are significant disadvantages. Using transects
reduces the flexibility needed to situate points in
the full range of hydrologic zones and vegeta-
tion strata within a wetland. Although some
transect protocols allow for including individual
birds observed between points, such observations
must be analyzed separately from observations
made at the points, because of the possibility of
double-counting of individuals located closer
together than the required 200 m separation dis-
tance.
Data from area searches and point counts
should not be combined. Also, the need to situ-
ate point counts no closer than 100 m from the
wetland-upland edge is a significant constraint.
Researchers who use point counts in smaller
wetlands sometimes include upland habitats as
well (Smith 1998). Or they attempt to distinguish
birds heard from within a wetland from those
heard only from the adjoining upland and ana-
lyze just the within-wetland data. Surveys of
small wetlands also are likely to result in encoun-
ters with few species: the usual tendency is for
avian richness to increase with patch size. Low
richness in wetlands that are very small or that
have very simple vegetation structure can dis-
tort some of the candidate metrics, for example,
calculating the percentage of bird species that
are nonnative, when only two species are
present. To mitigate this problem, during the
data analysis phase it may sometimes be appro-
priate to analyze data only from sites that meet
minimum thresholds for number of species and/
or individuals.
8
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Regardless of the methods chosen, all sites
should be visited within a few-day period (no
more than 1 week). Otherwise, changing weather
and migration can make the data almost impos-
sible to interpret correctly. If an IBI will be used
later to monitor interannual changes in wetlands,
it is preferable to use multiple years of field data
to calibrate the IBI initially.
can be accomplished by strategically placing points
between adjoining vegetation strata (Figure 1).
However, if quantitative metrics (e.g., relative
abundance) will be used later in multimetric indi-
ces, then random or systematic location of sam-
pling or observation points within zones may be
justified and a much larger number of samples will
be necessitated.
Unless you intend to survey the same micro-
habitat (e.g., herbaceous plants in permanently
inundated areas) in every wetland, point counts
and area searches should be used in a comple-
mentary manner to survey each of the following
zones if they are present, accessible, and survey
points can be separated by at least 200 m: (1)
permanently inundated areas, (2) seasonally in-
undated areas, (3) areas saturated but seldom
inundated. Secondarily, point counts should be
located collectively so that they are within (or
no more than 100 m from) each of the following
vegetation strata (cover types), if present within
a site:
• Herbaceous plant communities (aquatic or ter-
restrial) not under a woody canopy, if not al-
ready covered by an area search.
• Herbaceous plant communities (aquatic or ter-
restrial) under a woody canopy
• Shrub/vine stands not under a tree canopy if
not already covered by an area search.
• Shrub/vine stands under a tree canopy
• Open-canopy stands of trees (both deciduous
and coniferous)
• Closed-canopy stands of trees (both decidu-
ous and coniferous)
For purposes of IBI development, within these
three zones and six strata, points usually should
not be located randomly, but rather in a manner
that the investigator anticipates will yield cumu-
latively the most species. Often, this objective
When comparing sites (separate wetlands), data
from the sites should represent equal effort. For
example, it is inappropriate to make compari-
sons using seven survey points from a large site
but only two survey points from a smaller site,
or five visits to one site but only two to another
during the same month. In such situations, com-
pare the sites based on a single point or date cho-
sen randomly from those at each site, or include
a log of the area as a covariate in the statistical
analysis. Alternatively, you might select from
each wetland the point or date you found to have
the highest counts of birds, or a point believed
to be of exactly the same habitat type in all the
surveyed sites. Such practices are not recom-
TTfc
Black Rail by Thomas J. Danielson
9
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FIGURE 1: A STRATEGY FOR LOCATING BIRD POINT COUNTS AND AREA
COUNTS IN A DIVERSE WETLAND.
Point counts (PI, P2, P3) must be located no closer than 200 m from each other, and preferably at least 100 m from the wetland-
upland edge, so point counts cannot be used effectively unless the wetland is at least 8 acres (if round, much more if narrow). They
should lie within (preferably) or within 100 m of each of the major hydrologic zones (H = permanently inundated; B = seasonally/
semipermanently inundated; C = saturated only) and each of the major vegetation strata (FO = forest; SS = shrub/scrub; Em =
emergent). Point counts are primarily intended to survey passerine species.
Area counts (Al, A2) should be located at the best vantage points for surveying birds on all bodies of open water (W-H) as well as
in permanently inundated stands of emergent vegetation within the site. Area counts are intended to survey only the most visible
waterbirds (e.g., ducks, herons, shorebirds). Area counts need not be a specific distance apart, so long as observers avoid overlap-
ping the visual count areas. Area counts may be located next to point counts or in adjoining uplands. Abiding by these constraints
and considering physical access, observers should attempt to survey as many point counts and area counts as can be fit into a
wetland site.
mended for use when statistical confidence is
needed from monitoring a probability sample of
wetlands, but they may be acceptable in some
situations involving IBI development and
testing.
If possible, sites in a multiwetland survey should
be visited all on the same day, or on consecutive
days, unless severe weather conditions intervene.
Concentrated visits are necessary because, es-
pecially during migration, the numbers and spe-
cies composition of bird communities shift on a
daily or even hourly basis. At the very least,
date and time of day (in standardized units)
should be included as covariates in statistical
analyses. Additionally, sites that are accessed all
on the same day should be revisited in a different
sequence on each successive visit.
Ideally, all sites could be visited monthly for an
entire year and separate IBIs calibrated for each
season. However, at a minimum, all sites should
10
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be surveyed at least twice per season, with at
least 2 weeks elapsed between visits. If data can
be collected during only one season, the breed-
ing season (generally May-July) generally is a
good time, because dispersal movements of most
species are minimal then (Morrison et al. 1998).
By detecting species at the same point during
repeat visits, probable breeding often can be in-
ferred (Vickeryetal. 1992). The same observer
should inventory all sites, at least during each
survey period. If multiple observers must be used
(as often is the case when volunteer birders are
assisting), pretesting must verify that their skill
levels, especially with regard to auditory-only
recognition and identification of a wide range of
expected species, are equivalent. If not, new
observers should be recruited, or at the very least,
"observer" should be included as a variable in
any statistical analysis.
Species detection (especially of most songbirds)
is greatest during early morning hours so sur-
veys should focus on the 4 hours beginning at
sunrise. Night-time coverage may be warranted
not only for typically nocturnal species such as
owls but also for waterfowl and wading birds,
which use different wetland types for roosting
and for feeding, especially during the hunting
season (Anderson and Smith 1999). Secretive
species (e.g., rails, some passerines) can be sur-
veyed effectively by broadcasting tape-recorded
calls of the secretive species. A protocol for
doing so is described by Ribic et al. (1999). Also,
during winter and other nonbreeding seasons,
you can induce many species that otherwise do
not vocalize then to reveal themselves by play-
ing tapes of small owl, chickadee, and nuthatch
calls (in alternating sequence). Counts during
the hunting season (generally September-Janu-
ary) should be avoided or, if necessary, some es-
timation should be made of hunting intensity at
each site.
If three points per wetland are surveyed, ap-
proximately 100 easily accessible wetlands in a
local area or small watershed can be visited three
times in a typical field season. Only a fraction of
this number of wetlands need be visited to ini-
tially develop and calibrate a regional IBI for a
single wetland class.
Least Bittern by Thomas J. Danielson
RESEARCH NEEDS
The IBIs that have been developed using fish,
algae, and aquatic invertebrates have benefited
from field testing in several regions of the world.
Similarly, the development of operational IBIs
using birds will require commitments to fund
studies in several types of wetland landscapes.
Such studies should examine spatial changes in
bird communities across multiple wetlands that
span gradients of identifiable human disturbance,
as well as interannual changes in altered and un-
altered wetland landscapes. The aim of the stud-
ies should be to establish which avian groups and
attributes are most regionally suitable as indica-
tors, and at which scales, because of their abil-
ity to sensitively distinguish anthropogenic from
natural background conditions.
1 1
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OTHER RELEVANT
LITERATURE
(A SELECTED LIST)
OTHER LITERATURE ON BIRD
COMMUNITIES AS INDICATORS OF
HUMAN ALTERATION
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NATURALLY OCCURRING WETLANDS
OR RIPARIAN AREAS
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SELECTED STUDIES OF BIRD
COMMUNITIES IN MULTIPLE RESTORED
OR CONSTRUCTED WETLANDS
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2000. Dipteran standing stock biomass and effects
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Darveau M, Beauchesne P, Belanger L, Huot J, LaRue
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Hoffman RH. 1979. Waterfowl utilization of ponds
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Lagrange TG, Dinsmore JJ. 1989. Plant and animal
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Machtans CS, Villard MA, Harmon SJ. 1996. Use of
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OTHER LITERATURE ON WETLAND
BIRD SURVEYS, DATA ANALYSIS
METHODS, AND CONSERVATION
Connors PG. 1986. Marsh and Shorebirds. In:
Cooperrider AY, Boyd RJ, Stuart HR (eds). Inventory
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Long Point Bird Observatory. 1997. World Wide Web
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U.S. Environmental Protection Agency. 2000. EPA
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U.S. Geological Survey, Biological Services Division,
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