Adaptive Management of American Oystercatchers Within the National
Seashore System
Shiloh Schulte
Department of Zoology,
North Carolina State University, Box 7617,
Raleigh, NC 27695
Dissertation Committee:
Theodore R. Simons: Professor of Zoology and Forestry. USGS Cooperative Fish and Wildlife
Research Unit, North Carolina State University
Kenneth H. Pollock: Professor of Zoology, Biomathematics and Statistics. North Carolina State
University
Jaime A. Collazo: Professor of Zoology and Forestry. USGS Cooperative Fish and Wildlife
Research Unit, North Carolina State University
Stephen Brown: Director, Shorebird Research and Conservation, Manomet Center for
Conservation Sciences, Manomet, Massachusetts.
Background and Problem Description
Beachfront development along the Atlantic coast is widespread and expected to increase
significantly in the next decade, particularly in the southeastern states (Culliton et al. 1990).
Natural communities along the coast are at increasing risk from habitat fragmentation, human
recreational activity, and introduced predators. Beach nesting shorebirds are increasingly
confined to protected areas like the National Seashores, as human use and recreational pressures
on these lands grow with each passing year.
American Oystercatchers are large, conspicuous shorebirds that nest from Nova Scotia to
Mexico (Figure 1). The US Shorebird Conservation Plan lists eastern American Oystercatchers
Haematopus palliatus palliatus as a high priority species (Brown et al. 2001), in part because of
significant threats from heavy recreational use of coastal breeding habitats, and generally low
reproductive success. Because American Oystercatchers are restricted to a narrow band of
coastal habitat, they are particularly sensitive to human disturbance and habitat change (Nol
2000, Davis et al, 2001). Oystercatchers nest from April to August, which means they often
compete directly with humans for barrier beach habitat. As birds appear to be expanding their
range in the Northeast (Nol et al 2000) populations are simultaneously declining in Mid-Atlantic
core breeding areas (Mawhinney and Bennedict 1999, Davis et al. 2001). A recent (2002/3)
aerial survey of the species’ winter range in the United States resulted in a population estimate of
only 10971 +/-298 individuals, with 7500-8000 wintering on the Atlantic Coast (Brown et al.
2003). The small population size, low observed reproductive success, and restricted range,
highlight the need for a closer examination of Oystercatcher population dynamics. There is
currently no coordinated long-term monitoring effort underway to determine population trends
for the American Oystercatcher, and reliable estimates of key demographic parameters such as
juvenile and adult survivorship are lacking.
The network of National Seashores that extend from Cape Cod to Padre Island presents a
unique opportunity for coordinated research and management of the species across much of its
breeding and wintering range. Though widely separated, the Seashores share common habitat
characteristics and management issues. All nine National Seashores along the Atlantic and Gulf
coasts have identified issues related to shorebird management as important priorities in their
natural resource management plans. The dynamic barrier beaches that characterize these Parks
provide important shorebird nesting habitat, but they also draw large numbers of recreational
visitors, particularly during the summer months when the birds are nesting. Perhaps more
importantly, many predators of shorebird eggs and young (feral cats, raccoons, and foxes) thrive
in the presence of humans.
The goals of the National Park Service Biological Inventories Project include describing
the distribution and abundance of species of special concern and designing long-term monitoring
plans for these species. The American Oystercatcher is an ideal species to serve as the focus of a
large scale multi-park research and monitoring initiative for several reasons:
1) Oystercatchers breed on every National Seashore from Cape Cod to Padre Island.
2) They are sensitive to a variety of factors, including; human recreational use of beaches,
introduced predators, and shoreline erosion, which are all of management concern on
National Seashores.
3) They are conspicuous and long-lived, which facilitates detection and long-term
monitoring.
These factors combine to make American Oystercatchers excellent indicators of the health of
beachfront natural communities on National Seashores.
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This proposal seeks support for a study of the distribution, movement patterns, and
population dynamics of the American Oystercatcher to determine specific management concerns
and necessary actions for the protection of this species, and to incorporate American
Oystercatchers as a component of long-term natural resource monitoring within the National
Seashore system.
Objectives:
This study has two primary objectives. The first objective is to establish reliable
estimates of key demographic parameters, including reproductive success, and survival rates of
adults, sub-adults, and juveniles. These estimates will be used to construct a demographic model
and project population trends for eastern American Oystercatchers. Information is currently
lacking about adult and juvenile dispersal patterns and direct estimates of survival are lacking as
well. These data are essential to developing conservation strategies for the species. Four years
of color-banding adults and juveniles on Cape Lookout and Cape Hatteras have demonstrated
that long-term studies of adult and juvenile survival and movement are feasible. Information
gained from these studies will be critical to understanding the status and trends of Oystercatcher
populations over time, and for evaluating sustainable fecundity and survival rates in remaining
populations.
The second objective is to use the baseline population projection data to assess and
prioritize management objectives for the species. A network of Oystercatcher monitoring
programs will be established on National Seashores along the Atlantic and Gulf Coasts. These
programs will build on eight years of research conducted at Cape Hatteras and Cape Lookout
National Seashores by Dr. Ted Simons and his students in the cooperative Fish and Wildlife
Research Unit at North Carolina State University. Ultimately, these Oystercatcher monitoring
programs will become part of long-term natural resource monitoring at each National Seashore.
Collectively, they will contribute substantially to the management and conservation of the
species in the Eastern United States.
This proposal is ambitious in scope, but entirely feasible to implement. My advisor, Dr.
Ted Simons, is the former Director of the Cooperative Park Studies Unit at NC State and he has
worked extensively with National Seashores over the past 20 years. He is currently a member of
the USGS Cooperative Fish and Wildlife Research Unit and has studied Oystercatcher
population dynamics on Cape Hatteras and Cape Lookout for eight years. Dr. Simons currently
has funding for four years of Oystercatcher research in North Carolina. With the Canon National
Parks Science Scholars Grant I could expand the spatial and temporal scale of this work to meet
the objectives of this proposal. While working at the Manomet Center for Conservation Sciences
I helped design and conduct a series of extensive aerial surveys covering the entire winter range
of the eastern American Oystercatcher in the United States. Later, I designed and implemented
the American Oystercatcher monitoring plan at Monomoy National Wildlife Refuge, which
included nest and chick monitoring, banding, and radio telemetry. Research permits have
already been obtained for Cape Hatteras and Cape Lookout National Seashores and the resource
managers at Cape Cod, Fire Island, Cape Hatteras, Cape Lookout, Assateague Island, and Gulf
Islands National Seashores have all expressed strong interest in this proposal. I have already
begun a dialogue with resource management staff regarding ways in which Oystercatcher
monitoring protocols could be integrated with existing long-term monitoring programs. With the
combined skill set and interest level of the principals involved, I submit that this project is not
only important and feasible, but that now is precisely the time to implement it.
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Research Methods and Data Analysis
Study Areas:
Complete breeding surveys and productivity monitoring will take place at Cape Cod, Fire
Island, Assateague Island, Cape Hatteras, Cape Lookout, Cumberland Island, Canaveral, Gulf
Islands and Padre Island National Seashores (Figure 1). The majority of the banding and radio
telemetry work will occur on Cape Hatteras and Cape Lookout National Seashores which
comprise over 160km of barrier island habitat and support a population of approximately 90
breeding pairs of Oystercatchers.
Productivity Monitoring:
Field Technicians will be hired to conduct Oystercatcher breeding surveys and monitor
Oystercatcher nests and young at participating National Seashores. Technicians will be trained
in nest searching techniques including watching for behavioral cues from the birds that facilitate
nest detection. Although Oystercatchers do not usually employ “broken-wing” distraction
displays like many smaller shorebirds, they do exhibit easily identifiable behaviors such as false
incubating and alarm calling as one approaches the nest area. Once in the nest area, nest scrapes
will be located by following Oystercatcher tracks or by systematic searching in marsh habitat.
Technicians will observe minimal site disturbance practices including using natural features as
nest markers, never walking directly to a nest and spending minimal time in the nest area. Once
located, nests will be monitored every 2-4 days until hatching or nest failure.
If a nest fails, the observer will attempt to determine the cause by searching the nest area
for predator tracks or signs of human activity that may have caused the failure. In addition, we
may employ “washover cups” to determine if the nest was lost due to a high water event.
Washover cups are small covered containers with holes punctured in the sides. These containers
are placed in the ground near the nest and parallel to the water. If a flood event reaches the
height of the nest during the incubation period the cup will fill with salt water. The status of
each nest will be recorded on each visit and will be used to calculate a Mayfield estimate of daily
survival (Mayfield 1975).
If a nest hatches, the status and number of young will be recorded every 2-4 days until
fledging or loss of the chicks. Observers will opportunistically record any information on causes
of chick mortality, but due to difficulties in following oystercatcher chicks and determining when
and why they disappear, estimates of daily chick survival rates and causes of mortality will be
determined primarily through radio telemetry and banding work at Cape Hatteras and Cape
Lookout National Seashores.
Pre-fledging juvenile survival rates and causes of mortality are very difficult to determine
for precocial shorebird chicks. Chicks often leave the nest bowl within a few hours of hatching,
after which they are cryptic and highly mobile. If a chick is lost to predators, exposure, or other
factors it is usually impossible to determine the chick’s state. Because much of the reduction in
annual productivity occurs at this stage several recent studies have stressed the need for a better
understanding of the factors affecting chick mortality (Davis et al. 2001, McGowan, 2004).
This information is necessary for the formulation of appropriate management strategies to reduce
chick mortality rates and will be important in the development of a demographic model.
Radio transmitters produced by Holohil Systems Ltd (model LB-2N 0. 4g) will be
attached to chicks shortly after they leave the nest and become mobile (1-3 days after hatch).
The transmitters are designed to be glued to the chick’s back feathers and will be camouflaged
appropriately. Marked chicks will be re-located every 2-4 days through the pre-fledging period.
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If a chick dies or disappears before fledging, the transmitter will be located to determine the
cause of mortality. Surviving chicks will be recaptured and color-banded shortly before fledging
(26-30 days). Due to the high cost of telemetry both in time and money, this portion of the study
will be confined to Oystercatcher chicks on Cape Hatteras and Cape Lookout National Seashores
and nearby dredge spoil islands.
Mark-Re-sight
Estimates of adult and sub-adult survival and recruitment rates will be obtained through a
cooperative mark-recapture study. Color-banding efforts began in 1999 on Cape Lookout and in
2002 on Cape Hatteras National Seashore. Since then, 89 adult and juvenile oystercatchers have
been banded on both Seashores. The South Carolina Department of Natural Resources began
winter banding of Oystercatchers in 2002 using cannon nets and now has over 200 birds banded.
Dozens more have been banded during recent efforts in Georgia, Virginia, and Massachusetts.
The goal of this widespread banding effort is to establish a color-banded population to study
dispersal patterns and determine survival rates for each age class.
Over the past five years a broad collective, grass-roots effort has evolved among
researchers working with American Oystercatchers to promote data sharing and standardization
of methods. In 2004, with the cooperation of researchers in state and private organizations, a
central database of all color-banded Oystercatchers was compiled at North Carolina State
University (NCSU), including the date and location of every known re-sighting (Figure 2).
Observers report re-sightings of banded birds through a website set up for this purpose. This
database will be updated after each field season to include new banded birds from each location.
The color-banding effort on Cape Hatteras and Cape Lookout National Seashores will be
expanded over the next three years. Breeding adult birds will be captured using a decoy and
noose-carpet technique developed at NCSU (McGowan and Simons, in press) and used
successfully in North Carolina, Massachusetts, Georgia and South Carolina. This trapping
method is based on the bal-chatri raptor trap (Bub 1991) and relies on the aggressive territoriality
of the American Oystercatcher. A remote-control decoy and call playback device surrounded by
concealed noose carpets is set up within an Oystercatcher territory. When the pair arrives to
display to the decoy their feet become entangled in the nooses. This method eliminates
disturbance at the nest site and is much more effective then more conventional trapping methods
such as walk-in or bow traps (McGowan and Simons, in press).
Adults and juveniles will be individually marked with color-bands inscribed with alphanumeric codes in accordance with a banding scheme recently adopted by all researchers working
with American Oystercatchers. Under the scheme, each state was assigned a color and a
sequence of 625 individual 2-digit codes to be used on all Oystercatchers banded in the state.
Captured birds will be sexed and assigned to an age class using morphological measurements
(Nol and Humphrey 1994).
Systematic re-sighting efforts will be divided into breeding and non-breeding components
to obtain bi-annual survival rates for adults and sub-adults. Breeding season re-sighting efforts
will coincide with complete annual breeding pair surveys on the Seashores (May-June). All
breeding and non-breeding adults and sub-adults will be checked for color-bands by trained field
technicians. The non-breeding season re-sighting period will be November-February and will
focus on the Oystercatcher population in the southeastern states, the heart of the wintering range
(Brown et al. 2003). Winter re-sighting will be a cooperative effort between researchers in
North Carolina, South Carolina, and Georgia. In 2002 and 2003 the South Carolina and Georgia
Departments of Natural Resources conducted comprehensive re-sighting surveys in their
respective states. In 2004 we will initiate winter re-sighting surveys in North Carolina based on
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wintering flock locations identified in a 2002-2003 aerial survey (Brown et al. 2003) and
coordinate closely with efforts in South Carolina and Georgia. These comprehensive,
coordinated re-sighting surveys will ensure equal detection probabilities for banded
Oystercatchers in the Southeast wintering population.
Population Modeling
A series of demographic models will be constructed to achieve the following goals: (1) project
population trajectory over time, (2) determine the sensitivity of the population growth rate to
each parameter and determine parameter values necessary to prevent population decline, and (3)
identify spatial variation in demographic rates among Oystercatcher populations. The models
will be parameterized with survival and stage transition estimates obtained through the
cooperative mark-recapture effort and estimates of fecundity from over 1000 nesting attempts
monitored in North Carolina, Massachusetts and Virginia from 1999-2003 (Simons unpubl.
data).
I will construct a preliminary stage-based model with the following demographic
parameters: fecundity, juvenile survival, subadult survival without transition, subadult survival
with transition to adult, and adult survival. Subadult survival is divided into two components
because subadults may survive from year i to year i + 1 without establishing a breeding territory
and transitioning to the adult stage. Survival estimates will be generated using program MARK
(White and Burnham 1999). Four alternative models will be compared using a Jolly-Seber
reduced parameter model for open populations (Jolly 1965, Seber 1965) to test whether survival
(φ) and re-sighting (ρ) probabilities are constant or vary over time (φtρt, φtρ, φρt, φρ).
Model complexity will increase as movement and spatial variation in demographic rates
are incorporated. I will use a multistate 3-sample mark-resight model to estimate movement
probabilities between sub-populations for birds in each stage. Sub-populations will be defined
by state boundaries. This model will be parameterized with spatial transition and sighting
probabilities defined as:
i,j,k = probability that a bird alive and present in state j during year i survives and is
present in state k during year i + 1
Pi,j = Probability that a bird present in region j during year i is sighted during that period.
Hestbeck and Nichols (1991) used a similar approach to estimate between-region movement of
individually marked Canada Geese wintering in the Atlantic states.
I recognize there are many challenges involved in estimating demographic parameters
and developing population models. Estimating true survival and transition rates is problematic
because mortality is confounded with emigration unless the study area encompasses the entire
range of habitats and locations where a banded bird could be. Oystercatchers often use remote
areas that are difficult to access, particularly in the winter (Brown at al. , 2003). Oystercatchers
are also migratory in the northern part of their range, which means the population is only stable
enough to survey during mid-summer and mid-winter.
Despite these complications I believe there is a good chance of success. Oystercatchers
are confined to a narrow band of coastal habitat throughout the year, which greatly reduces the
required search area. The distribution of wintering flocks is well understood thanks to a
comprehensive 2002-2003 aerial survey by the Manomet Center for Conservation Sciences
(Brown et al. 2003), and consistent re-sighting efforts by the South Carolina and Georgia
Departments of Natural Resources show that state-wide ground surveys are possible. This
information will allow us to implement a cost-effective sampling plan that reduces bias and
makes the best use of survey time.
It is important to remember that this three-year study is not intended to result in a
5
complete understanding of all aspects of Oystercatcher population dynamics. My goal is to
make the best use of the data available to move us toward a better understanding of this complex
species, and to provide good information on which to base long term monitoring and
management.
Expected Results and Products
When searching for answers to ecological questions it is vital to study the system in
question at an appropriate scale. In Large Scale Ecology and Conservation Biology, Robert May
suggests there is an “increasing need for ecologists in general and conservation biologists in
particular, to deal with larger spatial scales than most of us are used to, or happy with”.
American Oystercatchers are highly mobile, long-lived, and occur along both the Atlantic and
Gulf Coasts. By including nine National Seashores in this multi-Park effort I believe this study
of Oystercatcher population dynamics will take place at a scale that is appropriate to the
questions asked.
A series of spatially explicit demographic models will be constructed to project
Oystercatcher population trajectories and identify minimum survival and fecundity rates needed
to prevent population decline. Modeling local differences in demographic rates and movement
probabilities will permit an examination of source-sink dynamics in eastern American
Oystercatcher populations. Sub-populations will be classified as sources or sinks based on
whether local fecundity is high enough to offset mortality without immigration (Pulliam 1988).
Spatially explicit demographic modeling has significant advantages over simple abundance
estimates as it allows us to identify the relative contribution of each region to the growth or
decline of the overall population (Pulliam 1988, Sherry and Holmes 1995). This work will lay
the foundation for understanding on a sufficiently large scale, the dynamic, spatially variable
processes of reproduction, dispersal, movement, and survival in the American Oystercatcher
population
This research is expected to produce quantitative estimates of the abundance, distribution,
reproductive success, survival, and population trend of American Oystercatchers breeding on the
National Seashores. The study will establish standard protocols for monitoring Oystercatcher
nesting success which will provide the basis for incorporating Oystercatcher population
monitoring as a component of long-term natural resource monitoring on the National Seashores.
The intended users of project results and products are the resource management staff of
the National Seashores and the Regional and Network Coordinators for the National Park
Service Biological Inventory and Monitoring Project, as well as other State and private natural
resource managers who have an interest in the conservation of shorebird populations.
The project results will allow managers to:
 Produce accurate distribution maps and population estimates of American
Oystercatchers breeding at each National Seashore on the Atlantic and Gulf coasts.
 Assess how human-related disturbance and introduced predators are affecting the
distribution, abundance, productivity, and persistence of Oystercatcher populations.
 Estimate the importance of the National Seashore system in supporting continental
populations of American Oystercatchers.
 Integrate American Oystercatcher population monitoring into the long-term natural
resource monitoring programs on the National Seashores.
 Meet the goals of the Biological Inventory Project for the Gulf Coast, Southeast
Coast, and Northeast Coastal and Barrier I&M Networks.
6
Adaptive Management
Environmental and social conditions in coastal regions are constantly changing. The
natural process of beach migration, the sea level rise predicted by many scientists (Titus, 1990),
and an increasing human presence (Culliton et al 1990) are examples of factors that affect natural
resources in the Parks and can introduce uncertainty into the process of natural resource
managment. Adaptive management is an iterative process of hypothesis driven design,
implementation, and evaluation of alternative management practices. An adaptive management
strategy reduces uncertainty about the effects of management actions and can effectively identify
the optimal course of action to achieve a stated long-term objective (Johnson and Case, 2000).
Adaptive management holds great promise for conserving natural resources as the Parks
come under increasing pressure from many sources. Adaptive management of American
Oystercatchers on the National Seashores could serve as a model for a broader adoption of this
concept within the National Park System. This study will lay the groundwork for an adaptive
management strategy for American Oystercatchers on the National Seashores. Critical values for
survival and fecundity determined through demographic modeling will be used to set
management goals and objectives, while the integrated resource monitoring program will assess
the effects of management actions. For example, the NPS could set an objective of maintaining
or increasing current Oystercatcher populations on the National Seashores. A specific
management goal would be to maintain an annual fecundity (number of chicks fledged per pair)
equal to or exceeding the critical level identified in this study through demographic modeling.
Hypotheses about the effects of specific management actions on fledging rates would be
generated and the actions implemented in such a way as to permit testing of the hypotheses. For
instance, the hypothesis that meso-carnivore trapping prior to the nesting season increases
Oystercatcher fecundity could be examined by randomly assigning nesting areas to trapping or
control treatments. The effect of the management action on fecundity would be evaluated using
Oystercatcher productivity monitoring protocols developed during this study and the null
hypothesis accepted or rejected based on differences in fecundity in control and treatment
groups. This process could be used to quantify the effects of off road vehicle traffic, shoreline
erosion, and other management issues. This adaptive management approach is an iterative
process through which management actions are constantly evaluated and adjusted to more
efficiently address explicit management objectives.
Schedule for completion of Research:
 Summer 2004 – Expand banding program at Cape Hatteras and Cape Lookout National
Seashores. Continue comprehensive nest monitoring program in cooperation with both
Seashores. Begin radio-telemetry study of juveniles and sub-adults to determine
survivorship and causes of mortality. Begin preliminary surveys at other seashores
 Summer 2005 – Hire Field Techs for Fire Island, Cape Cod, Cape Hatteras, etc.
Establish standardized protocols for all seashores. Conduct complete AMOY breeding
survey and monitor all nests at these sites for success rates and causes of failure. Begin
second year of survivorship study with the radio/gps-telemetry work.
 Fall/Spring 2005-2006 – Begin building preliminary demographic model using survival
rates from the telemetry work and re-sighting database.
 Summer 2006 – Expand monitoring program to other seashores/recreation areas. Adjust
standardized protocols as appropriate at each seashore.
 Fall/Spring 2006-2007 – Complete demographic model and population viability analysis
for the eastern American Oystercatcher. Produce a report that summarizes monitoring
efforts and provides detailed management recommendations for each National Seashore.
7
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