Conservation Planning and Monitoring
Avian Habitat
Daniel J. Twedt
Charles R. Loesch
Abstract—Migratory bird conservation plans should not only develop population goals, they also should establish attainable objectives for optimizing avian habitats. Meeting population goals is of
paramount importance, but progress toward established habitat
objectives can generally be monitored more easily than can progress
toward population goals. Additionally, local or regional habitat
objectives can be attained regardless of perturbations to avian
populations that occur outside the geographic area covered by
conservation plans. Assessments of current avian habitats, obtained from remotely sensed data, and the historical distribution of
habitats should be used in establishing habitat objectives. Habitat
planning and monitoring are best conducted using a geographic
information system. Habitat objectives are assigned to three categories: maintaining existing habitat, restoring habitat, and creating
new or alternative habitat. Progress toward meeting habitat objectives can be monitored through geographic information systems by
incorporating georeferenced information on public lands, private
lands under conservation easements, corporate lands under prescribed management, habitat restoration areas, and private lands
under alternative management to enhance wildlife values. We
recommend that the area and distribution of habitats within the
area covered by conservation plans be reassessed from remotely
sensed imagery at intervals appropriate to detect predicted habitat
changes.
Arresting declining populations of Neotropical migratory
birds will, in many cases, require migratory bird conservation plans that include regional and local management
actions. Bird conservation plans developed for physiographic
areas or smaller local areas will likely focus on maintaining
or increasing populations of specific bird species (Mueller
and others, this proceedings). Progress toward population
goals set by these bird conservation plans, however, will be
difficult to evaluate. In some cases, established population
goals, especially those for migratory birds, may be unreachable by actions undertaken solely within the geographic
boundaries covered by the conservation plan. For example,
factors outside established boundaries may adversely impact some species. Even when population goals can be
In: Bonney, Rick; Pashley, David N.; Cooper, Robert J.; Niles, Larry,
eds. 2000. Strategies for bird conservation: The Partners in Flight planning process; Proceedings of the 3rd Partners in Flight Workshop; 1995
October 1-5; Cape May, NJ. Proceedings RMRS-P-16. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
Daniel J. Twedt, USGS Patuxent Wildlife Research Center, Mississippi
Valley Research Field Station, 2524 Frontage Road, Vicksburg, MS 39180.
Charles R. Loesch, Habitat and Population Team, U.S. Fish and Wildlife
Service, 1500 East Capitol Avenue, Bismarck, ND 58501.
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attained by conservation efforts within defined geographic
boundaries, assessing progress toward population goals
may be difficult. Monitoring bird populations and their
demographics over large geographic areas and over extended time periods can be a Herculean task in terms of
personnel and financial resources (Sherry and Holmes, this
proceedings).
Fortunately, many species of concern to managers are
closely linked to specific habitat types (Hamel 1992b; Hunter
and others 1993b). Often, behavioral and spatial relationships exist which allow quantifiable breeding bird populations to be associated with specified areas of designated
habitat types. We recommend that bird conservation plans
establish habitat objectives that enhance the likelihood of
achieving avian population goals. To be effective, habitat
objectives must be achievable regardless of external impacts
on bird populations. Once established, habitat objectives
provide benchmarks that usually can be measured, evaluated, and achieved more easily than population goals.
Determining Baseline Habitat
Data __________________________
After habitats critical to migratory bird species of concern
within a planning unit have been identified, the availability
of these habitats should be assessed. At landscape scales,
this assessment can be achieved through remote sensing
technologies such as satellite imagery. Remotely sensed
data can be obtained at scales from 1 km to less than 10 m
using panchromatic, multispectral, infrared, or radar sensors. Choice of scale and sensor often are dictated by cost and
the extent and location of desired coverage. Planners should
consult with experts in remote sensing or geographic information systems (GIS) to ascertain the advantages of different imaging systems.
Managers planning at local scales have additional options
for assessing avian habitats, including aerial photography
and videography. When available, archived and current
management records might provide accurate and detailed
descriptions of habitats. Finally, ground reconnaissance
should be used to delineate habitats or to verify habitat
assessments from other sources.
Whether at landscape or local scales, information about
avian habitats must be organized in a format that is conducive to planning and ultimately to monitoring. A GIS format
is appropriate because remotely sensed data are available
in digital form and can be imported directly. Additionally,
these digital data must represent habitat types that are
derived via computerized classification procedures. Other
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habitat data, such as photographs, management records,
and ground reconnaissance, can be entered into a GIS by
scanning or by digitizing maps.
For example, in the Mississippi Alluvial Valley, the extent
and distribution of bottomland hardwood forest (critical
habitat for avian species of concern in the Mississippi Valley
[Mueller and others, this proceedings]) were classified from
Thematic Mapper imagery (fig. 1). We suggest using this
type of data on avian habitats as baseline data from which
to establish habitat objectives. In many states, digital habitat data derived from Thematic Mapper imagery are currently or soon will be available for wildlife conservation
planning through statewide “Gap analysis” projects (Scott
and others 1993).
Establishing Habitat
Objectives _____________________
The area and distribution of habitat objectives can be
established from a direct assessment of hypothesized habitat needs (Mueller and others, this proceedings) or indirectly
based on the needs of previously identified population goals
(Loesch and others 1994; Loesch and others, this proceedings). Regardless of how established, habitat objectives can
be categorized as: Maintaining existing habitats, restoring
former habitats, or creating new or alternative habitats. All
categories should be considered when formulating habitat
objectives.
For example, to ensure continuation of extant habitats,
management plans may suggest maintaining current habitat conditions (e.g., uneven-aged timber harvest) or they
may compensate for habitat change by replacing existing
habitat with habitat at other sites (e.g., even-aged, rotational timber harvest). Even maintaining existing habitats
may be a significant challenge in areas where urban encroachment is fragmenting existing avian habitats.
Before restoring habitat, examining the historical distribution of habitats is useful. Although remotely sensed data
are available for only about the past 30 years, cartographic
data may be obtained for much earlier periods. Historical
land surveys, topographic maps, or aerial photographs might
reveal dramatic changes in avian habitats compared to
current conditions. When conservation plans include restoring former habitats, historical information can be an important guide to developing logical and achievable restoration
objectives. Other factors also may indicate where restoring
habitat is practical. For example, soil type often determines
what plant communities will thrive, thereby defining avian
habitats. Similarly, water-control projects (i.e., dams and
levees) have altered the hydrology of many ecosystems to the
extent that restoration of historical habitats is not feasible.
Thus, inclusion of soil type and hydrologic data in a GIS will
provide important ancillary information for identifying areas for habitat restoration.
In areas where maintaining and restoring endemic avian
habitat are not feasible, creating new habitat, establishing
alternative habitat, or implementing management practices that promote avian use of existing habitats may be
practical solutions. For example, in the Mississippi Alluvial
Valley, replacing conventional row crops with short-rotation
agroforestry provides breeding, migration, and wintering
habitat for migratory forest birds while continuing to provide income for landowners. Another alternative incorporates water-control structures within existing agricultural
fields to retain water on harvested croplands, thereby providing foraging habitat for wintering waterfowl without
restricting farm operations during the growing season.
Monitoring Progress Toward Habitat
Objectives _____________________
Figure 1—Distribution of forested habitat within the Mississippi “Delta,”
that portion of the Mississippi Alluvial Valley between Vicksburg, MS,
and Memphis, TN, circa 1992, circa 1976, and circa 1957.
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After habitat objectives have been established, data added
to the GIS will aid in monitoring progress toward these
objectives. On a landscape scale, for example, the areas of
public land ownership (e.g., national wildlife refuges, state
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wildlife management areas, national forests, state parks,
etc.) and management (e.g., natural areas, wildlife management, multipurpose management, etc.) can be incorporated
into the GIS (fig 2). Similarly, private lands enrolled in
conservation easements (e.g., Ducks Unlimited), in government programs (e.g., Conservation Reserve or Wetland
Reserve), or maintained for long-term economic return (e.g.,
corporate timber holdings and private grazing land) can be
added to the GIS (fig. 3). The area and location of these
dedicated conservation lands, in relation to habitat objectives, directly affects our ability to maintain existing avian
habitats. Additionally, these lands provide opportunities to
restore former habitats and can serve as areas to focus
habitat restoration.
Projects to restore habitats often are part of larger conservation efforts; therefore managers should ensure that the
areas influenced by their restoration project are accurately
delineated on georeferenced maps or geocoded (e.g., by
Figure 2—Location of public lands within the Mississippi “Delta,” that
portion of the Mississippi Alluvial Valley between Vicksburg, MS, and
Memphis, TN.
Figure 3—Lands enrolled in the Wetland Reserve Program and private
lands under cooperative agreements (e.g., Mississippi Partners projects)
to manage wildlife within the Mississippi “Delta,” that portion of the
Mississippi Alluvial Valley between Vicksburg, MS, and Memphis, TN.
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Figure 4—Four forest classes derived from 1992 Thematic Mapper
imagery of the northern portion of Tensas River National Wildlife
Refuge, LA. Black line depicts refuge boundary.
global positioning systems). When private landowners restore habitat, they should be encouraged or assisted in
geocoding the area impacted, and these data should be
incorporated into the habitat-monitoring database. When
alternate land management or conservation enhancements
are developed, such as installation of water-control structures, the lands affected should also be incorporated into the
GIS (fig. 3).
On a local scale, similar data can be incorporated into
migratory bird conservation plans for wildlife management
areas or other management units (fig. 4). Habitat objectives
within the management unit can be established in concert
with habitat objectives set at a landscape scale and restored
or modified habitat can be added to the GIS (fig. 5).
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Figure 5—Areas of reforestation, areas of timber harvest, and areas
of unmanaged forest on the northern portion of Tensas River National
Wildlife Refuge, LA.
Identification of public and private managed lands, inclusion of restoration areas, and identification of areas under
alternative management may be sufficient to monitor
progress toward achieving migratory bird habitat objectives at local scales. However, to monitor progress toward
habitat objectives at landscape scales, we recommend using
remote sensing to periodically update habitat data.
Acknowledgments _____________
We thank S. E. Mott, C. K. Baxter, and K. J. Reinecke for
stimulating discussions in formulating this paper. J. Sauer,
B. Varin, and D. Rassa provided editorial reviews.
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