Decision implementation and the double-loop process in adaptive management of horseshoe crab harvest in Delaware Bay
No abstract available.
Delaware Bay↗
Geology topics
James E. Lyons
Publications and source records attributed to James E. Lyons.
Resource allocation for coastal wetland management: Confronting uncertainty about sea level rise
Coastal wetlands are rich and diverse ecosystems with a wide variety of birdlife and other natural resources. Decision making for coastal wetland management is difficult given the complex nature of these ecological systems and the frequent need to meet multiple objectives for varied resources. Management challenges in the coastal zone are exacerbated by uncertainty about sea level rise and impacts on infrastructure, particularly the levees and structures which provide managers the ability to manipulate water levels in managed wetlands and create high quality habitat for birds and other wildlife. The most challenging decisions in coastal wetland management involve resource allocation for habitat manipulations and longer-term investments to maintain management control in wetlands that are increasingly compromised by sea level rise and increasing storm frequency and intensity associated with a changing climate. We used multi-criteria decision analysis to create a resource allocation framework for managed wetlands that identifies the most effective and efficient management strategies that are robust to uncertainty about sea level rise. The prototype framework includes a small number of managed wetlands, for which subject matter experts articulated potential management and restoration actions. The consequences of these actions were predicted using expert elicitation with the subject matter experts; furthermore, expert judgment was used to articulate expected outcomes with two hypotheses about the rate of sea level rise. We used a constrained optimization (integer linear programming) to find optimal resource allocation strategies given a range of budget constraints; we also used a Pareto efficiency analysis for a graphical solution to the problem if the exact budget constraint is not known. Finally, given the importance of preference weights in a multi-criteria decision analysis, we also evaluated sensitivity to objective weights. With this resource allocation framework, we showed how to identify optimal combinations of management and restoration actions to maximize benefits in terms of stated objectives. We show how multiple working hypotheses about sea level rise can be incorporated into decisions for coastal wetland management. Our resource allocation approach can be modified for a wide variety of natural resource management settings.
Book chapter↗
Introduction to resource allocation
With ongoing habitat loss and degradation, ever-increasing threats to biodiversity, and limited funding for conservation and management, nearly every natural resource manager routinely faces difficult resource allocation problems. Funding and capacity for natural resource management rarely meet the need, and informed resource allocations are increasingly important. These decision problems include not only habitat and species management but also a wide variety of administrative decisions. Ranking projects or plans by benefit-cost ratio is an intuitive, heuristic approach to resource allocation but may be inefficient. We present a general resource allocation framework in which these decision problems can be stated mathematically, making it relatively easy to find solutions using mathematical programming such as linear programming. amenable to Linear programming and other constrained optimization routines, which can be implemented in common software applications and used with a wide variety of decision problems, including project prioritization and portfolio decisions. Constrained optimization has advantages over intuitive benefit-cost ratios and can accommodate single and multiple objective problems. We also introduce the three case studies in this section illustrating a variety of resource allocation problems: the first case study shows how to select cost-effective management actions for discrete management units such as wetlands or grassland patches; the second, how to use a patch dynamics model to allocation allocate resources for a reserve network that protects habitat for multiple species of conservation concern; and the third, how to use stochastic simulation to determine allocation of resources in space and time for invasive species management.
Book chapter↗
Optimization of salt marsh management at the Rhode Island National Wildlife Refuge Complex through use of structured decision making
Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing salt marsh management decisions at the Rhode Island National Wildlife Refuge Complex. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of nine salt marsh management units within the refuge complex and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that would be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per salt marsh management unit, that would maximize total management benefits at different cost constraints at the refuge scale. Results indicated that, for the objectives and actions considered here, total management benefits may increase consistently up to approximately $ 150,000, but that further expenditures may yield diminishing return on investment. Management actions in optimal portfolios at total costs less than $ 150,000 included digging runnels (by hand or machine) on the marsh surface to improve drainage in eight management units, applying sediment to the marsh surface (thin layer deposition) in one management unit, constructing islands for use by tidal marsh obligate birds in two management units, and controlling Phragmites australis in one management unit. The management benefits were derived from expected improvements in the capacity for marsh elevation to keep pace with sea-level rise and increases in numbers of spiders (as an indicator of trophic health) and tidal marsh obligate birds. The prototype presented here provides a framework for decision making at the Rhode Island National Wildlife Refuge Complex that can be updated as new data and information become available. Insights from this process may also be useful to inform future habitat management planning at the refuge.
Rhode Island↗
Optimization of salt marsh management at the Chincoteague National Wildlife Refuge, Virginia, through use of structured decision making
Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing salt marsh management decisions at the Chincoteague National Wildlife Refuge in Virginia. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of 12 salt marsh management units within the refuge and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that would be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per salt marsh management unit, that would maximize total management benefits at different cost constraints at the refuge scale. Results indicated that, for the objectives and actions considered here, total management benefits may increase consistently up to approximately $ 2.5 million, but that further expenditures may yield diminishing return on investment. For multiple salt marsh management units, a scenario incorporating managing grazing practices within the marsh was selected to maximize benefits while constraining total costs for the refuge at less than $ 2.5 million. Thin-layer deposition was predicted to increase the total management benefit substantially, but at considerable total costs ( $ 2.5 million to $ 83 million). The prototype presented here provides a framework for decision making at the Chincoteague National Wildlife Refuge that can be updated as new data and information become available. Insights from this process may also be useful to inform future habitat management planning at the refuge.
Virginia↗
Spatial integration of biological and social objectives to identify priority landscapes for waterfowl habitat conservation
Waterfowl population management and habitat conservation compose one of the oldest and most successful adaptive management frameworks in the world. Since its inception, the North American Waterfowl Management Plan (NAWMP) has emphasized strategically targeted conservation investments in regions that most affect waterfowl population dynamics. By 2012, regional conservation had progressively become more science-based and strategic: many migratory bird partnerships had initiated or completed projects on mapping and modeling waterfowl distribution and abundances using geospatial techniques. However, when developing a map depicting and titled “Areas of Greatest Continental Significance to North American Ducks, Geese, and Swans” for the 2012 NAWMP Revision, waterfowl professionals articulated the need for improved decision frameworks and use of consistent datasets for refining large-scale spatial products depicting priority areas for waterfowl and people. This report describes a framework for developing a spatial value model to support the identification of North American geographies of importance to waterfowl during the breeding and non-breeding periods and to resource users who could potentially support (financially and (or) politically) waterfowl habitat conservation. Objectives used to identify priority geographies were determined through a collaborative process of the NAWMP Science Support Team, Priority Landscapes Committee (PLC), and other experts in the fields of waterfowl biology and ecology, environmental science, and human dimensions. ArcGIS Desktop was used as the platform for managing, analyzing, combining and displaying the spatial data as well as producing new data through spatial analysis functions. Thirty-eight spatial layers were developed, and several composite spatially explicit products (maps of North America) were produced based on PLC recommendations. The composite products have extensive similarities to the 2012 NAWMP map depicting areas of greatest continental significance to North American waterfowl. There are also some differences, especially in regions of the high Arctic and in Mexico. These differences between spatial value model maps and the 2012 NAWMP output likely arose from inclusion of social objectives, reduced dependence on expert opinion to generate abundance estimates, lack of population surveys in some regions and availability of expanded survey data in other regions, and use of model-based waterfowl population estimates for some unsurveyed areas. The structured decision-making framework application in this study is discussed, and the appropriate use of the products and their limitations are outlined. Additionally, options for future improvements are presented by identifying gaps in data collection, waterfowl-habitat association assumptions, and uncertainties related to social objectives. These spatial products are intended for use by national, regional, and province/state level wildlife professionals to aid their decisions in targeting waterfowl habitat conservation.
Open-File Report↗
Effects of individual misidentification on estimates of survival in long-term mark–resight studies
All ecological measurements are subject to error; the effects of missed detection (false negatives) are well known, but the effects of mistaken detection (false positives) are less understood. Long-term capture–recapture datasets provide valuable ecological insights and baselines for conservation and management, but where such studies rely on noninvasive re-encounters, such as field-readable color bands, there is the potential to accumulate detection errors as the length of the study and number of tags deployed increases. We investigated the prevalence and effects of misreads in a 10-yr dataset of Red Knots ( Calidris canutus rufa ) marked with field-readable leg flags in Delaware, USA. We quantified the effects of misreads on survival estimation via a simulation study and evaluated whether removal of individuals only reported once in a year (potential misreads) influenced survival estimation from both simulated datasets and our case study data. We found overall apparent error rates of 0.31% (minimum) to 6.6% (maximum). Observer-specific error rates and the variation among observers both decreased with the number of flags an observer recorded. Our simulation study showed that misreads lead to spurious negative trends in survival over time, particularly for long-term studies. Removing all records in which a flag was only recorded once in a sampling occasion reduced bias and eliminated spurious negative trends in survival but also reduced precision in survival estimates. Without data filtering, we found a slight decrease in Red Knot annual survival probability from 2008 to 2018 (β = −0.043 ± 0.03), but removing all single-observation records resulted in no apparent trend (β = −0.0074 ± 0.02). Spurious trends in demographic rates could influence inference about population trajectories and resultant conservation decision-making. Data filtering could eliminate errors, but researchers should carefully consider the tradeoff between precision obtained by larger sample sizes and potential bias due to misreads in their data.
Delaware↗
Why strategic bird monitoring plan for the Gulf of Mexico?
No abstract available.
Alabama, Florida, Louisiana, Mississippi, Texas↗
Optimization of salt marsh management at the Bombay Hook National Wildlife Refuge, Delaware, through use of structured decision making
Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing salt marsh management decisions at the Bombay Hook National Wildlife Refuge in Delaware. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of eight salt marsh management units within the refuge and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that would be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per salt marsh management unit, that would maximize total management benefits at different cost constraints at the refuge scale. Results indicated that for the objectives and actions considered here, total management benefits would increase consistently up to approximately \$300,000, but that further expenditures would yield diminishing return on investment. Management actions selected within optimal portfolios at total costs less than \$300,000 included hydrologic restoration, recontouring adjacent uplands to facilitate marsh migration, and burning the marsh. The prototype presented here provides a framework for decision making at the Bombay Hook National Wildlife Refuge that can be updated as new data and information become available. Insights from this process may also be useful to inform future habitat management planning at the refuge.
Delaware↗
Monitoring the social benefits of ecological restoration
Ecological restoration has traditionally been evaluated by monitoring the recovery of ecosystem conditions, such as species diversity and abundance, physical form, and water quality, whereas monitoring the social benefits of restoration is uncommon. Current monitoring frameworks do not track who benefits from restoration or by how much. In this study, we investigate how ecological restoration could be monitored to provide indications of progress in terms of social conditions. We provide suggestions for measuring several categories of benefit indicators, including access, beneficiaries, and quality of benefit, using information compiled from natural and social science literature. We also demonstrate how to evaluate ecological and social benefit indicators over time at a site or landscape scale using multi-criteria analysis. We use flood protection and recreation as example benefits to monitor.
Restoration Ecology↗
Accounting for surveyor effort in large-scale monitoring programs
Accounting for errors in wildlife surveys is necessary for reliable status assessments and quantification of uncertainty in estimates of population size. We apply a hierarchical log-linear Poisson regression model that accounts for multiple sources of variability in count data collected for the Integrated Waterbird Management and Monitoring Program during 2010–2014. In some large-scale monitoring programs (e.g., Christmas Bird Count) there are diminishing returns in numbers counted as survey effort increases; therefore, we also explore the need to account for variable survey duration as a proxy for effort. In general, we found a high degree of concordance between counts and effort-adjusted estimates of relative abundance from the Integrated Waterbird Management and Monitoring Program ( x̄ difference = 0.02%; 0.25% SD). We suggest that the model-based adjustments were small because there is only a weak asymptotic relationship with effort and count. Whereas effort adjustments are reasonable and effective when applied to count data from plots of standardized area, such adjustments may not be necessary when the area of sample units is not standardized and surveyor effort increases with number of birds present. That is, large units require more effort only when there are many birds present. The general framework we implemented to evaluate effects of varying survey effort applies to a wide variety of wildlife monitoring efforts.
Journal of Fish and Wildlife Management↗
Flooding tolerance of Sagittaria latifolia and Sagittaria rigida under controlled laboratory conditions
Pool‐scale growing‐season water‐level reductions (drawdowns) have been implemented on the Upper Mississippi River in an effort to improve fish and wildlife habitat. Aquatic vegetation is a key habitat component, with perennial emergent species, such as Sagittaria latifolia and Sagittaria rigida , especially important. River managers have assumed the need for continuous drawdown during the growing season with limited reflooding and used this guidance in assessing the potential for an ecologically successful drawdown. However, information on the effects of growing‐season flooding episodes on survival and growth of Sagittaria is limited. To assess the flooding tolerance of S. latifolia and S. rigida , we evaluated multiple levels of timing, duration, and depth on survival and productivity of plants. Plants were produced from S. latifolia and S. rigida seeds and S. latifolia tubers; all were reared under moist‐soil or shallow‐flooded rearing conditions. Mortality of plants was low (2%) among plants from large tubers, low (7%) among seedlings (and largely associated with early flooding treatments), and modest (11%) among plants from small tubers (with no clear effects of inundation). Flooding treatments generally had a positive effect on biomass production from seedlings, particularly when treatments occurred early, were relatively shallow, and were short in duration. There were no clear effects of depth, duration, or timing components of flooding treatments on plant biomass arising from tubers. This experiment indicates that S. latifolia and S. rigida are relatively tolerant of flooding events during the growing season and may actually benefit from some level of inundation.
River Research and Applications↗
Integrated wetland management for waterfowl and shorebirds at Mattamuskeet National Wildlife Refuge, North Carolina
Mattamuskeet National Wildlife Refuge (MNWR) offers a mix of open water, marsh, forest, and cropland habitats on 20,307 hectares in coastal North Carolina. In 1934, Federal legislation (Executive Order 6924) established MNWR to benefit wintering waterfowl and other migratory bird species. On an annual basis, the refuge staff decide how to manage 14 impoundments to benefit not only waterfowl during the nonbreeding season, but also shorebirds during fall and spring migration. In making these decisions, the challenge is to select a portfolio, or collection, of management actions for the impoundments that optimizes use by the three groups of birds while respecting budget constraints. In this study, a decision support tool was developed for these annual management decisions. Within the decision framework, there are three different management objectives: shorebird-use days during fall and spring migrations, and waterfowl-use days during the nonbreeding season. Sixteen potential management actions were identified for impoundments; each action represents a combination of hydroperiod and vegetation manipulation. Example hydroperiods include semi-permanent and seasonal drawdowns, and vegetation manipulations include mechanical-chemical treatment, burning, disking, and no action. Expert elicitation was used to build a Bayesian Belief Network (BBN) model that predicts shorebird- and waterfowl-use days for each potential management action. The BBN was parameterized for a representative impoundment, MI-9, and predictions were re-scaled for this impoundment to predict outcomes at other impoundments on the basis of size. Parameter estimates in the BBN model can be updated using observations from ongoing monitoring that is part of the Integrated Waterbird Management and Monitoring (IWMM) program. The optimal portfolio of management actions depends on the importance, that is, weights, assigned to the three objectives, as well as the budget. Five scenarios with a variety of objective weights and budgets were developed. Given the large number of possible portfolios (16 14 ), a heuristic genetic algorithm was used to identify a management action portfolio that maximized use-day objectives while respecting budget constraints. The genetic algorithm identified a portfolio of management actions for each of the five scenarios, enabling refuge staff to explore the sensitivity of their management decisions to objective weights and budget constraints. The decision framework developed here provides a transparent, defensible, and testable foundation for decision making at MNWR. The BBN model explicitly structures and parameterizes a mental model previously used by an expert to assign management actions to the impoundments. With ongoing IWMM monitoring, predictions from the model can be tested, and model parameters updated, to reflect empirical observations. This framework is intended to be a living document that can be updated to reflect changes in the decision context (for example, new objectives or constraints, or new models to compete with the current BBN model). Rather than a mandate to refuge staff, this framework is intended to be a decision support tool; tool outputs can become part of the deliberations of refuge staff when making difficult management decisions for multiple objectives.
North Carolina↗
Post-breeding migration and connectivity of red knots in the Western Atlantic
Red knots ( Calidris canutus rufa ) have 3 distinct nonbreeding regions: 1 in the southeastern United States and Caribbean, another on the northeast coast of Brazil in the Maranhão region, and a third along the Patagonian coasts of Chile and Argentina. Effective conservation and recovery of this threatened long-distance migrant will require knowledge of population structure, migration ecology, and abundance and distribution throughout the annual cycle. We conducted a stopover population and biogeographic assessment of knots at the Altamaha River Delta, Georgia, an important stopover area in the southeastern United States. We estimated stopover population size and stopover duration during post-breeding migration in 2011 at the Altamaha study area using mark-resight data, and we inferred nonbreeding regions for this stopover population using stable isotope ratios of carbon and nitrogen in feathers, and observations (sightings and captures) during boreal winter from across the hemisphere. With an integrated Bayesian analysis of all these data, we also estimated the number of birds in the southeastern United States and northern Brazil during boreal winter. For mark-resight analyses in Georgia, we made observations of marked individuals during 14 weeks from early August to early November 2011 and detected 814 individually marked birds. We used the Jolly-Seber mark-recapture model and estimated the southbound passage population at approximately 23,400 red knots. In ongoing studies elsewhere, isotope samples were collected from 175 (21%) of the 814 birds detected in our study, and ≥1 sighting or capture record during boreal winter was located in data repositories for 659 birds (81%). Isotopic signatures and boreal winter records indicate that the majority (82–96%) of the birds that stopped at the Altamaha Delta spend the boreal winter in the northern part of the nonbreeding range (southeast USA, Caribbean, and northern Brazil). Knots migrating to the southeastern United States, Caribbean, or Brazil remained on the Altamaha Delta for 42 days, whereas birds migrating to Tierra del Fuego remained only 21 days. Combining our estimate of the Altamaha stopover population size (23,400 birds) and the estimated proportion in the northern nonbreeding region (82–96%), we derived a minimum estimate of the number of knots in the southeastern United States, Caribbean, and northern South America during the boreal winter: approximately 20,800 knots, of which approximately 10,400 knots occupy the southeastern United States and 5,400 occupy Brazil. Our results provide additional evidence that coastal Georgia is an important migration area for red knots, and provide information about population structure and migratory connectivity that will be valuable for conservation planning.
Georgia↗
Balancing habitat delivery for breeding marsh birds and nonbreeding waterfowl: An integrated waterbird management and monitoring approach at Clarence Cannon National Wildlife Refuge, Missouri
The Clarence Cannon National Wildlife Refuge (CCNWR) in the Mississippi River flood plain of eastern Missouri provides high quality emergent marsh and moist-soil habitat benefitting both nesting marsh birds and migrating waterfowl. Staff of CCNWR manipulate water levels and vegetation in the 17 units of the CCNWR to provide conditions favorable to these two important guilds. Although both guilds include focal species at multiple planning levels and complement objectives to provide a diversity of wetland community types and water regimes, additional decision support is needed for choosing how much emergent marsh and moist-soil habitat should be provided through annual management actions. To develop decision guidance for balanced delivery of high-energy waterfowl habitat and breeding marsh bird habitat, two measureable management objectives were identified: nonbreeding Anas Linnaeus (dabbling duck) use-days and Rallus elegans (king rail) occupancy of managed units. Three different composite management actions were identified to achieve these objectives. Each composite management action is a unique combination of growing season water regime and soil disturbance. The three composite management actions are intense moist-soil management (moist-soil), intermediate moist-soil (intermediate), and perennial management, which idles soils disturbance (perennial). The two management objectives and three management options were used in a multi-criteria decision analysis to indicate resource allocations and inform annual decision making. Outcomes of the composite management actions were predicted in two ways and multi-criteria decision analysis was used with each set of predictions. First, outcomes were predicted using expert-elicitation techniques and a panel of subject matter experts. Second, empirical data from the Integrated Waterbird Management and Monitoring Initiative collected between 2010 and 2013 were used; where data were lacking, expert judgment was used. Also, a Bayesian decision model was developed that can be updated with monitoring data in an adaptive management framework. Optimal resource allocations were identified in the form of portfolios of composite management actions for the 17 units in the framework. A constrained optimization (linear programming) was used to maximize an objective function that was based on the sum of dabbling duck and king rail utility. The constraints, which included management costs and a minimum energetic carrying capacity (total moist-soil acres), were applied to balance habitat delivery for dabbling ducks and king rails. Also, the framework was constrained in some cases to apply certain management actions of interest to certain management units; these constraints allowed for a variety of hypothetical Habitat Management Plans, including one based on output from a hydrogeomorphic study of the refuge. The decision analysis thus created numerous refuge-wide scenarios, each representing a unique mix of options (one for each of 17 units) and associated benefits (i.e., outcomes with respect to two management objectives). Prepared in collaboration with the U.S. Fish and Wildlife Service, the decision framework presented here is designed as a decision-aiding tool for CCNWR managers who ultimately make difficult decisions each year with multiple objectives, multiple management units, and the complexity of natural systems. The framework also provides a way to document hypotheses about how the managed system functions. Furthermore, the framework identifies specific monitoring needs and illustrates precisely how monitoring data will be used for decision-aiding and adaptive management.
Missouri↗
Quantifying the relative contribution of an ecological reserve to conservation objectives
Evaluating the role public lands play in meeting conservation goals is an essential step in good governance. We present a tool for comparing the regional contribution of each of a suite of wildlife management units to conservation goals. We use weighted summation ( simple additive weighting ) to compute a Unit Contribution Index ( UCI ) based on species richness, population abundance, and a conservation score based on IUCN Red List classified threat levels. We evaluate UCI for a subset of the 729 participating wetlands of the Integrated Waterbird Management and Monitoring (IWMM) Program across U.S. Fish and Wildlife Service Regions 3 (Midwest USA), 4 (Southeast USA), and 5 (Northeast USA). We found that the median across-Region UCI for Region 5 was greater than Regions 3 and 4, while Region 4 had the greatest within-Region UCI median. This index is a powerful tool for wildlife managers to evaluate the performance of units within the conservation estate.
Global Ecology and Conservation↗
Population trends and distribution of Common Murre Uria aalge colonies in Washington, 1996-2015
Periodic assessments of population trends and changes in spatial distribution are valuable for managing marine birds and their breeding habitats, particularly when evaluating long-term response to threats such as oil spills, predation pressure, and changing ocean conditions. We evaluated recent trends in abundance and distribution of the Common Murre Uria aalge within Copalis, Quillayute Needles, and Flattery Rocks National Wildlife Refuges, which include all murre colonies in Washington except one, off-refuge, on Tatoosh Island. In 1996-2001 and 2010-2015, aerial photographic surveys were conducted during the incubation phase (mid-June through mid-July) each year. Using images from film (1996-2001) and digital (2010-2015) cameras that included all parts of each colony, we manually counted murres. We estimated population trend as annual percent change in whole-colony counts using an overdispersed Poisson regression model. Overall, numbers of murres counted at breeding colonies in Washington increased by 8.8% per year (95% CI 3.0%-14.9%) during 1996–2015. The overall statewide increase was driven by an increase at colonies in northern Washington of approximately 11% per year (95% CI 4.5%-17.8%). Despite an increasing trend, abundance remains lower than levels in the late 1970s, and the spatial distribution has changed. Colonies in southern Washington - where murres were historically the most abundant - are no longer active, or only minimally so, whereas colonies in the north - which were rarely active in the early 1970s - are now the largest. There was high variability in spatial distribution among years, a pattern that indicates a need for coordinated monitoring and movement studies throughout the California Current System to understand dispersal and colonization. Our results indicate that future management of refuge islands could protect both current and historic colony locations, given the patterns of colony dynamics and the uncertainty about long-term effects of a changing ocean ecosystem and predation pressure on the status of murres.
Washington↗
Bayesian analysis of Jolly-Seber type models
We propose the use of finite mixtures of continuous distributions in modelling the process by which new individuals, that arrive in groups, become part of a wildlife population. We demonstrate this approach using a data set of migrating semipalmated sandpipers ( Calidris pussila ) for which we extend existing stopover models to allow for individuals to have different behaviour in terms of their stopover duration at the site. We demonstrate the use of reversible jump MCMC methods to derive posterior distributions for the model parameters and the models, simultaneously. The algorithm moves between models with different numbers of arrival groups as well as between models with different numbers of behavioural groups. The approach is shown to provide new ecological insights about the stopover behaviour of semipalmated sandpipers but is generally applicable to any population in which animals arrive in groups and potentially exhibit heterogeneity in terms of one or more other processes.
Environmental and Ecological Statistics↗