United States
Environmental Protection
Agency
Office of Research and
Development
Washington, DC 20460
EPA/620/R-00/003
June 2000
www.epa.gov
MAIA Project Summary
Birds Indicate Ecological Condition
of the Mid-Atlantic Highlands
General Information on the Mid-Atlantic Integrated Assessment can be found through the World Wide Web at
http://www.epa.gov/maia. The research supporting this document was funded by the U.S. EPA Office of Research
and Development under Interagency Agreement Number DW14936411-01-2 with the U.S. Fish and Wildlife Service. It
has been subjected to EPA's peer and administrative review. The management recommendations were developed by
EPA Region 3. The full research report, The Bird Community Index: A Tool for Assessing Biotic Integrity in the
Mid-Atlantic Highlands, Report Number 98-4, the Perm State Cooperative Wetlands Center, can be obtained at
www.wetlands.cas.psu.edu.
The Mid-Atlantic Integrated Assessment
(MAIA) is an interagency, multi disciplinary research,
monitoring and assessment program to develop
high-quality scientific information on the region's
natural resources: current condition, stressors, trends,
and vulnerabilities. MAIA results and information are
intended to satisfy a broad group of stakeholders'
needs, convey important information relevant to their
assessment questions and issues, and be useful in
making management decisions.
OVERVIEW
During the spring breeding season, more than a
hundred songbird species conduct a birds-eye
assessment of the Mid-Atlantic highlands to determine
suitable habitat for mating and raising young.
Ecolillcai Condition
Land Cover
Figure 1. Relationship between birds, land cover, and
ecological condition.
Different bird species require different habitats for
food, shelter and breeding. Some species need
extensive areas of dense forest. Others prefer fringe
areas with a mix of trees, shrubs, grasses, and farm-
land. Still others are adapted to more developed
urban and suburban landscapes. This brochure
explains that the types of birds found in an area are an
indication of its ecological condition; it also demon-
strates the linkages between bird communities and
land use/land cover. (See the graphic on the back
cover as an example of the types of birds indicative of
various ecological conditions and the types of land
cover they represent.)
The types of birds found in an area indicate the
ecological condition of that area. Bird communi-
ties and ecological condition are also linked to
land cover. As the land cover of an area
changes, so do the types of birds in that area
(See Figure 1).
The quality of our environment affects our health,
our economy, and the future of our children.
Environmental scientists have long suspected that
ecological condition is linked to changing land-
use patterns brought on by increasing population
and economic development.
The U. S. Environmental Protection Agency and
the Penn State Cooperative Wetlands Center
have found associations among songbirds, where
they live, and environmental health or condition in
the Mid-Atlantic highlands area (65,000 square
miles; see Figure 2).
We can now measure how the distribution of
various birds changes as land use is altered.
This association allows birds to be used in
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199fi Sites
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Figure 2. The songbird study surveyed 126 sites that were
randomly distributed across the highlands (65,000 sq. mi.).
conjunction with other indicators to estimate ecological
condition.
The presence or absence of particular birds across the
study area indicates that:
16% of the highlands is in excellent ecological
condition;
another 27 % is in good condition;
36% is in fair ecological condition; and
a total of 21 % (5% urban and 16% rural) is in
poor condition.
It was also found within the 200-acre survey sites that
ecological condition was closely associated with theamount
and age of forest and other land-cover. For example:
Sites in good or excellent ecological condition
were usually associated with an average of 87%
forest cover.
Sites in excellent condition had a taller and more
closed tree canopy (a mature forest) than sites in
good condition.
Sites in poor ecological condition were usually
associated with less than 28% forest cover.
Sites in poor ecological condition were also
observed when agricultural/non-woody-plant
cover exceeded 61%, or urban/residential cover
exceeded 29%.
Most of the Mid-Atlantic highlands is
forested. A forest is an area thickly
covered with trees and distinguished by
the types of trees and plants, their
density, and the soil type. Forests are
also divided into vertical layers: the
canopy, the shrub layer, and the forest
floor. Clearing forests not only removes
the trees, but also the crucial habitat
needed by non-woody plants, insects,
birds, and other wildlife in each forest
layer. Forest clearing also degrades
aquatic systems and water quality by
increasing erosion and light penetration.
In the absence of human activity, the
geology, climate, rainfall, and frequency
of natural disturbances in the Mid-
Atlantic highlands support naturally-
occurring forests. Therefore, mature
forests represent the highest ecological
condition potentially attainable in the
region. Human activity creates habitats such as lawns,
agricultural fields, forest edges, and forests with only a
few species of trees. These areas represent a lower
ecological condition than a mature forest.
Obviously, the entire Mid-Atlantic highlands cannot be
returned to its highest ecological condition. This would
require destruction of many human amenities and, in
some cases, take hundreds of years to accomplish.
However, areas can be identified that are moving
toward a lower level of ecological condition. See the
APPLICATIONS section on page 7 for what can
be done to lessen the impact of this decline.
ECOLOGICAL INDICATORS
Our understanding of how living things interact and
how these interactions contribute to healthy surround-
ings is limited. To better understand these interactions
and improve efforts to protect the environment, we
need to measure characteristics which reflect the
condition of ecological resources and the impacts
which adversely affect them. These characteristics
are called ecological indicators.
BIRDS ARE SENSITIVE ECOLOGICAL
INDICATORS
Birds exhibit numerous traits that make them good
ecological indicators at regional and national scales.
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INDICATORS:
An indicator is a sign that relays a
complex message in a simplified and
useful manner.
An ecological indicator is a measure that
describes the condition of an ecosystem or
one of its critical components.
Example - The presence of trout in a stream
indicates cool, well-oxygenated water, with
lots of aquatic life; therefore, the presence
1^ or absence of trout is an indicator of
stream condition.
J
They are everywhere, and different species vary in
their sensitivity to physical, chemical, and biological
threats. Each species also exhibits life history traits
(e.g., ground nester - nests on the ground; temperate
migrant- migrates south of the Mid-Atlantic high-
lands, but within North America; omnivore - feeds
on both animal and plant material) that link to multiple
environmental characteristics. Recording bird species
within a designated area is relatively easy and inex-
pensive; birds have strong public appeal; bird species
are well known; there are many trained field observ-
ers available; and no laboratory analysis is required.
Additionally, survey methods harm neither birds nor
the survey sites, and long-term records and ongoing
programs are available to provide or augment data.
Because of the unique role of every bird species in its
habitat, the composition of the birds in an area is a
multi-faceted indicator of ecological condition.
EPA's EMAP develops indicators and
other research tools to track status
and trends in the condition of the
nation's ecological resources. These
resources include estuaries, wetlands,
inland lakes and streams, forests, and
mixed landscapes.
The authors of this study have analyzed and combined
information on the variety of species of birds present
in the Mid-Atlantic highlands area to create a regional
indicator of ecological condition. This indicator was
developed and tested here as part of EPA's Environ-
mental Monitoring and Assessment Program
(EMAP).
It is important to recognize that both the highest
ecological condition and the bird species that indicate
that condition may differ in other regions. Therefore,
the bird based ecological indicator for the Mid-
Atlantic highlands is intended for use solely in this
study area. It is anticipated that a similar indicator
can be developed for almost any region, based on the
region's birdlife.
PROCEDURE
In the early 1990s, 34 sites in central Pennsylvania
were selected and ranked according to their degree
of ecological decline or degradation (human distur-
bance gradient). The degree of degradation was
based on an intensive study of soil type; amount of
soil deposited by erosion; plant, amphibian, and
wildlife communities; and where each site fits into the
general landscape pattern. Sites were ranked from
nearly pristine to severely degraded.
Next, an independent ranking of these sites using only
bird species data was developed. Birds were sur-
veyed at each of the sites, thus determining the bird
composition (community) at each site. The bird
community at each site is comprised of multiple life
history groups (species that require similar habitat,
food, nest location, or other elements for survival) that
also reflect condition. The separate rankings of the
sites based on the original human disturbance gradient
and the bird communities were compared. This
comparison satisfactorily demonstrated that ecological
condition, as indicated by the bird community, closely
matched the ecological condition determined previ-
ously by other physical and biological characteristics
of each survey site.
Sixteen specific groups of bird species, such as omni-
vores, bark probers, residents, migrants, shrub nesters,
etc., were ultimately selected as representative of the
mostly forested Mid-Atlantic highlands area (Table 1).
Of the 16 groups, nine were "specialists" and seven
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were "generalists"; for example, insectivores are
specialists and omnivores are generalists. Placement of
specific bird species within each group was based on a
review of scientific publications. Species may be
assigned to several groups as well as to both specialist
and generalist groups simultaneously. In general, a high
proportion of birds with specialized requirements
indicates healthy natural habitat that provides ecological
benefits at local and larger scales.
Birds and vegetation were surveyed across the entire
Mid-Atlantic highlands within sites sufficiently large
(200 acres) to represent most of the habitat elements
that are required by breeding birds. Use of EPA's
EMAP survey design guaranteed that data from the
126 sample sites were representative of the entire
highlands area.
MAJOR FINDINGS
ECOLOGICAL CONDITION IS LINKED TO
BIRD COMMUNITY ATTRIBUTES
Five levels of ecological condition (Figure 3) were
clearly distinguishable across the study region from
the types of birds found at each site. Examples of
these birds are listed on page 6 and in the figure on
the back cover.
Highland areas in excellent condition are dominated
by birds that, among other traits:
eat insects exclusively,
seek food on the ground and in tree bark,
reproduce only once per year, and
migrate from distant wintering grounds.
Such characteristics tell us that these areas also support
upper levels of the food chain, structurally complex
habitat, relative protection from non-native predators
and competitors, and continental-scale lifecycles. In the
Mid-Atlantic highlands, an extensive mature hardwood
or mixed-hardwood forest provides the maximum
amount of these ecological features and benefits.
Many of the same bird species occur in areas of good
ecological condition. However, they do not dominate
the community as fully, while other species appear that
are less specialized, for example, in what and where they
eat. The bird community in these areas still reflects forest
habitat, but it is not as physically or biologically complex.
Kxcelknl
Poor urban
51
Poor rural /
Figure 3. The bird community indicator classified
the highlands area into five categories of ecological
condition.
These distinctions in the bird data were supported by
vegetation measurements: Areas in excellent condition
support a taller (~80 feet) and more closed (-61%)
tree canopy than areas in good condition (~65-foot
canopy height and -47% canopy closure). The
forests are no bigger at the sites in excellent condition,
but the trees are.
The bird community in areas of fair ecological condition
indicates a significant decline in the provision of protec-
tive ground cover as well as upper-canopy feeding and
nesting habitats. At the same time, non-native species
begin to appear, signaling aggressive competition with
native birds for food and shelter. With increasing shrub
and grassland species, this community signals a shift from
the native ecosystem to a mix of forest and the intro-
duced habitats of agricultural and residential areas.
Analysis separated areas of poor condition into two
classes rural and urban based on the distinct
bird groups observed in each landscape type. In both
cases, highland areas in poor ecological condition
have birds that:
are non-native
do not have specialized diets
reproduce multiple times per season
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
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habitats are simplified or otherwise disturbed by
human or other events. Habitats supporting these
bird groups are generally not sustainable. They are
maintained by intensive vegetation control, the
addition of nutrients, and other manipulations. These
activities halt the process of plant succession, disrupt
the natural food chain, and render these areas
inhospitable to many native species.
BIRD COMMUNITIES ARE LINKED TO
LANDSCAPE PATTERN
The term "landscape" refers to the spatial pattern or
structure of a land area and the repeating patterns
associated with dominant land uses. The relative
proportion of forest, agriculture and urban land cover
contained in an area also defines a landscape as does
the interrelationship between them. TheMAIA
landscape ranges from wilderness areas to major
cities, yet the patterns and processes of human and
natural activity within the landscape are interconnected
in many different ways and at many different scales.
The five categories of ecological condition as defined
by the bird communities were highly related to the
configuration of land cover in the 200-acre sites.
Figure 4 provides examples of these landscape pat-
terns, which were characterized from aerial photography.
"Excellent ecological condition" conveys the sense of an
undisturbed, self-sustaining natural area. In the Mid-
Atlantic highlands, most undisturbed areas develop into
mature forest communities. Therefore, it is not surprising
that this study finds ecological condition, as indicated by
bird composition, to be positively correlated with
percent forest cover and measures of mature forest
vegetation. What may be surprising is that less than
one-fifth of the Mid-Atlantic highlands remains in
excellent condition, and that labels of fair to poor
describe more than half of the region.
This study begins to define the critical thresholds of land-
cover change where shifts in ecological condition take
place. At the 200-acre scale, both good and excellent
ecological condition were associated with an
average of 87% forest cover. Poor ecological
condition was observed when agricultural/non-
woody-plant cover exceeded 61%, or urban/
residential cover exceeded 29%.
One interpretation of these results is to consider areas in
good ecological condition as desirable by society, and to
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Figure 4. Ecological condition, as indicated by
songbird communities, is highly correlated
with land-cover composition.
manage them so as to maintain current land cover.
Longer rotation sequences in forested areas of good
condition could create more areas with the potential to
support excellent condition. Many of the areas in poor
condition are also justified by societal requirements for
agricultural and urban land uses. Community planning
efforts may focus instead on those marginal landscapes in
fair condition, guiding development such that they are not
transformed beyond critical land-cover thresholds into
areas of poor ecological condition.
The results further demonstrate that bird community
composition is related to land-cover pattern at spatial
scales of at least 200 acres. To mitigate the spread of
poor-integrity environments, planners and managers
must consider the landscape-scale consequences of
localized land-cover transformations. Similarly, a
landscape framework should drive restoration activi-
ties to increase the percentage of the region in good
to excellent ecological condition.
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BIRD COMMUNITIES
The following species belong to Mid-Atlantic bird
communities shown to indicate levels of ecological
condition at the landscape scale. While a full com-
munity profile is necessary to apply the bird commu-
nity indicator, these examples illustrate the use of bird
characteristics to determine ecological condition.
The black-and-white warbler is an insectivore, a
neotropical migrant, a forest ground nester, and an
interior forest obligate (must have interior forest to
survive). If this species and other interior forest
obligates, such as ovenbirds, scarlet tanagers, and
worm-eating warblers, comprise more than 35% of
the species in your bird community, it is likely an area
of excellent or good ecological condition.
Black-and-White Warbler
The grasshopper sparrow is an omnivore, a short-
distance migrant, a double-brooded species, and an
open-ground nester.
Grasshopper Sparrow
You may be in an area of fair ecological condition
for the Mid-Atlantic highlands, if grassland species
such as this are found in mixed communities with
Tufted Titmouse
forest generalists, such as the tufted titmouse.
These areas contain fewer omnivores, nest predators,
residents, and exotics; and significantly more upper-
canopy foragers, single-brooded species, and forest-
ground nesters than areas of low ecological condition.
The European starling is an omnivore, a year-round
resident, a non-native (exotic) species, and a nest
predator (preys on eggs or young of other birds). If
this species and other nest predators such as the
American crow or the blue jay, or nest parasites
(lays its eggs in other birds' nests), such as the
brown-headed cowbird, comprise more than 15% of
the species in your bird community, it is likely an area
of poor ecological condition.
European Starling
(Refer to the graphic on the back cover as an ex-
ample of the types of birds indicative of various
ecological conditions and the types of land cover they
represent.)
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TABLE 1: SUMMARY OF THE LIFE HISTORY BIRD GROUPS* USED IN THE STUDY
LIFEfflSTORYBIRD GROUPS*
Omnivore (eats both animals
and plants)
Bark Prober
Ground Gleaner
Upper-Canopy Forager
Lower-Canopy Forager
Nest Predator/Brood Parasite
Exotic (introduced species)
Resident
Temperate Migrant
Single-Brooded
Canopy Nester
Shrub Nester
Open-Ground Nester
Forest-Ground Nester
Forest Generalist
Interior Forest Obligate (must
have interior forest to survive)
CATEGORY
Trophic (Diet)
Insectivore Foraging Behavior
Insectivore Foraging Behavior
Insectivore Foraging Behavior
Insectivore Foraging Behavior
Population Limiting
Origin
Migratory
Migratory
Number of Broods
Nest Placement
Nest Placement
Nest Placement
Nest Placement
Primary Habitat
Primary Habitat
SPECIALIST
X
X
X
X
X
X
X
X
X
GENERALIST
X
X
X
X
X
X
X
* These groups of species have similar life history traits; that is, they require similar habitat, food, or other elements for survival.
APPLICATIONS
Public and private agencies, organizations, and
individuals can help improve ecological conditions in
the Mid-Atlantic region in the following ways:
Protect and maintain exi sting forests that are in
good or excellent condition.
Restore areas in fair condition (e.g. marginally
productive agricultural land).
Guide development away from areas in good and
excellent condition. Work to avoid further degra-
dation of areas in fair condition.
Focus development in areas that show poor
ecological condition.
The land uses in the Mid-Atlantic and how they are
distributed across the area affect the quality of the
natural environment (see An Ecological Assessment
of the United States Mid-Atlantic Region -A
Landscape Atlas, EPA/600/R-97/130, November,
1997).
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Birds in the Mid-Atlantic Highlands as Indicators of Ecological Condition
Ecological Condition
Fair Poor Rurul Poenr I rbon
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For More Information, Please Contact
Timothy O'Connell/RobertBrooks TomDeMoss LauraJackson
Pennsylvania State University U.S. Environmental Protection Agency U.S. Environmental Protection Agency
Region 3 Office of Research and Development
Environmental Science Center Research Triangle Park, NC 27711
Ft. Meade, MD 20755-5350
demoss.tom@epa.gov
Cooperative Wetlands Center
University Park, PA 16802-4703
tjol 1 l@psu.edu / rpb2@psu.edu
j ackson. laura@epa. gov
Funded by the U.S. Environmental Protection Agency
&EPA
I'tnu State
Cooperative
Wetlands Center
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