Forsythe National Wildlife Refuge Research Articles

A Decision Support Tool to Guide the Use of Nest Exclosures for Piping Plover Conservation

ABSTRACTWire cages (exclosures) that exclude nest predators are regularly used for management of federally threatened and endangered populations of piping plovers (Charadrius melodus) and similar species. However, recent evidence that apparent nest abandonment related to exclosure use is indicative of adult mortality has led to concern about the technique. We developed a decision support tool named PiperEx that uses site‐specific nest‐fate data to inform a stochastic population projection model to predict population growth rate at the site level with and without exclosure use. Underlying PiperEx is a Bayesian logistic‐exposure multinomial nest fate model, with informative priors based on analysis of 1,312 piping plover nests monitored throughout the U.S. Atlantic Coast in 2015 and 2016. We used simulated nest fate data sets and real nest data from 3 management areas from 2013 to 2018 to test tool performance. Based on simulations, the probability of making the correct decision increased with sample size, exceeding 80% with 20 nests. Decisions recommended by the tool were robust to variation in demographic parameters. Using real data, the decision for a given year only matched the decision for the immediately previous year 16% to 67% of the time, whereas data pooled across years predicted the best decision for a particular year up to 100% of the time for a given area. We used a case study of Edwin B. Forsythe National Wildlife Refuge to demonstrate that the optimal decision is sensitive to how a site was defined. We recommend that data for PiperEx be collected on an annual basis, and data for the previous 5 or 6 years be pooled for making a decision at the start of the season. Further development of the tool should focus on its use to make regional recommendations, and use of multiple years of data to improve the capability of the tool to make robust site‐specific recommendations. © 2020 The Wildlife Society.

Does Invasive Common Reed in Coastal Salt Marshes Affect Dabbling Duck Food Availability?

AbstractCommon reed, Phragmites australis, a nonnative perennial grass, is considered a nuisance species to land managers and wildlife biologists. Common reed thrives in areas with reduced soil salinities, increased nitrogen availability, and anthropogenic shoreline development. The expansion of nonnative common reed into tidal wetlands of North America detrimentally affects native wildlife by altering resource utilization, modifying trophic structures, and changing disturbance regimes. Thus, it also has the potential to drastically affect dabbling duck (Family Anatidae, SubFamily Anatinae, Tribe Anatini) energetic carrying capacity in salt marsh ecosystems. We assessed whether invaded monocultures of common reed in dabbling duck habitat could alter the availability of invertebrate and seed foods for the mallard Anas platyrhynchos, American black duck Anas rubripes, green-winged teal Anas crecca, northern shoveler Spatula clypeata, and northern pintail Anas acuta as compared with wetland type (mudflat, low marsh, high marsh, and impoundments). We compared food and energy availability in > 90% common reed monocultures with noncommon reed-invaded salt marshes in five study areas in Edwin B. Forsythe National Wildlife Refuge, New Jersey, 2015–2016. To estimate wetland-specific food energy supply, we collected sediment core samples, fixed them with formalin, and washed, dried, sorted, and weighed them for seeds and invertebrates. We multiplied biomass (g) by true metabolizable energy values to estimate species-specific dabbling duck food energy availability. We further estimated wetland-specific energetic carrying capacity (duck energy days) on the basis of known species-specific energetic demands. We determined that duck energy days/ha were greater for dabbling ducks in wetlands invaded with common reed because they contained more consumable seed energy and less consumable invertebrate energy. However, future research should explore how accessible these foods are when common reed grass is dense. To aid in restoration efforts once common reed is removed by control efforts, our results indicate that a robust seed bank exists in the soil strata, thus increasing salt-marsh seed biodiversity.

A geospatially resolved wetland vulnerability index: Synthesis of physical drivers.

Assessing wetland vulnerability to chronic and episodic physical drivers is fundamental for establishing restoration priorities. We synthesized multiple data sets from E.B. Forsythe National Wildlife Refuge, New Jersey, to establish a wetland vulnerability metric that integrates a range of physical processes, anthropogenic impact and physical/biophysical features. The geospatial data are based on aerial imagery, remote sensing, regulatory information, and hydrodynamic modeling; and include elevation, tidal range, unvegetated to vegetated marsh ratio (UVVR), shoreline erosion, potential exposure to contaminants, residence time, marsh condition change, change in salinity, salinity exposure and sediment concentration. First, we delineated the wetland complex into individual marsh units based on surface contours, and then defined a wetland vulnerability index that combined contributions from all parameters. We applied principal component and cluster analyses to explore the interrelations between the data layers, and separate regions that exhibited common characteristics. Our analysis shows that the spatial variation of vulnerability in this domain cannot be explained satisfactorily by a smaller subset of the variables. The most influential factor on the vulnerability index was the combined effect of elevation, tide range, residence time, and UVVR. Tide range and residence time had the highest correlation, and similar bay-wide spatial variation. Some variables (e.g., shoreline erosion) had no significant correlation with the rest of the variables. The aggregated index based on the complete dataset allows us to assess the overall state of a given marsh unit and quickly locate the most vulnerable units in a larger marsh complex. The application of geospatially complete datasets and consideration of chronic and episodic physical drivers represents an advance over traditional point-based methods for wetland assessment.

Estimating Waterfowl Carrying Capacity at Local Scales: A Case Study From Edwin B. Forsythe National Wildlife Refuge, New Jersey1

Abstract The management of wintering North American waterfowl is based on the premise that the amount of foraging habitat can limit populations. To estimate carrying capacity of winter habitats, managers use bioenergetic models to quantify energy (food) availability and energy demand, and use results as planning tools to meet regional conservation objectives. Regional models provide only coarse estimates of carrying capacity because habitat area, habitat energy values, and temporal trends in population-level demand are difficult to quantify precisely at large scales. We took advantage of detailed data previously collected on wintering waterfowl at Edwin B. Forsythe National Wildlife Refuge and surrounding marsh, New Jersey, and created a well-constrained local model of carrying capacity. We used 1,223 core samples collected between 2006 and 2015 to estimate food availability. We used species-specific 24-h time–activity data collected between 2011 and 2013 to estimate daily energy expenditure, morphometrically corrected for site- and day-specific thermoregulatory costs. To estimate population-level energy demand, we used standardized monthly ground surveys (2005–2014) to create a migration curve, and proportionally scaled that to fit aerial survey data (2005–2014). Crucially, we also explicitly incorporated estimates of variance in all of these parameters and conducted a sensitivity analysis to diagnose the most important sources of variation in the model. Our results from an outlier-removed, a strict depletion model indicated that at estimated mean levels of supply (923 million kcal) and cumulative demand (3.4 billion kcal), refuge food resources were depleted before November. However, a constant-supply model that represented tidal replenishment of resources indicated that just enough energy was present to sustain peak winter populations. Variation in model output appeared to be driven primarily by uncertainty in population abundance during peak periods of use, emphasizing a new management focus on studying migration chronologies of waterfowl. This model allows for relative assessment of biases and uncertainties in carrying-capacity modeling, and serves as a framework identifying critical science needs to improve local and regional waterfowl management planning.

Short-Term Resilience of New Jersey Tidal Marshes to Hurricane Sandy

Hurricane Sandy made landfall in the USA on October 29, 2012 and had devastating impacts on human-dominated landscapes in the mid-Atlantic and New England states, but its effects on tidal marsh habitats remain largely undescribed. We evaluated the short-term resilience (a resistance to change or a rapid return to pre-storm conditions) of tidal marshes on Edwin B. Forsythe National Wildlife Refuge, New Jersey by comparing vegetation cover/composition, meadow vole (Microtus pennsylvanicus) relative abundance, and predation rates on artificial bird nests, from three to six months pre-hurricane with seven to 11 months post-hurricane. These three metrics show a high degree of resilience to Hurricane Sandy. Vegetation cover/composition remained similar pre- and post-hurricane, except for five site-specific changes. Although meadow voles were significantly less abundant following the hurricane, we detected a rapid increase from June to July 2013, indicating resiliency via rapid recovery in the population. We also did not observe widespread changes in nest predation rates on artificial nests. Our findings indicate that management actions intended to recover vegetation, small mammals, and nest predators following a large hurricane disturbance may be of less importance than long-term strategies to avoid gradual changes that can reduce ecosystem resilience.

Factors that influence vital rates of Seaside and Saltmarsh sparrows in coastal New Jersey, USA.

As saltmarsh habitat continues to disappear, understanding the factors that influence saltmarsh breeding bird population dynamics is an important step for the conservation of these declining species. Using five years (2011 - 2015) of demographic data, we evaluated and compared Seaside (Ammodramus maritimus) and Saltmarsh (A. caudacutus) sparrow apparent adult survival and nest survival at the Edwin B. Forsythe National Wildlife Refuge, New Jersey, USA. We determined the effect of site management history (unditched vs. ditched marsh) on adult and nest survival to aid in prioritizing future management or restoration actions. Seaside Sparrow apparent adult survival (61.6%, 95% CI: 52.5 - 70.0%) averaged >1.5 times greater than Saltmarsh Sparrow apparent adult survival (39.9%, 95% CI: 34.0 - 46.2%). Nest survival and predation and flooding rates did not differ between species, and predation was the primary cause of failure for both species. Apparent adult survival and nest survival did not differ between unditched and ditched marshes for either species, indicating that marsh ditching history may not affect breeding habitat quality for these species. With predation as the primary cause of nest failure for both species in New Jersey, we suggest that future research should focus on identification of predator communities in salt marshes and the potential for implementing predator-control programs to limit population declines.

Notice: The authors have discovered an error in raw data analyzed in this paper. This article has been retracted. The corrected article is published online early as Ringelman KM, Williams CK, Castelli PM, Sieges ML, Longenecker RA, Nichols TC, Earsom AD. 2018. Estimating waterfowl carrying capacity at local scales: A case study from Edwin B. Forsythe National Wildlife Refuge, New

Abstract The management of wintering North American waterfowl is based on the premise that the amount of foraging habitat can limit populations. To estimate carrying capacity of winter habitats, managers use bioenergetic models to quantify energy (food) availability and energy demand, and use results as planning tools to meet regional conservation objectives. Regional models provide only coarse estimates of carrying capacity because habitat area, habitat energy values, and temporal trends in population-level demand are difficult to quantify precisely at large scales. We took advantage of detailed data previously collected on wintering waterfowl at Edwin B. Forsythe National Wildlife Refuge and surrounding marsh, New Jersey, USA, and created a well-constrained local model of carrying capacity. We used 1,223 core samples collected between 2006 and 2015 to estimate available food. We used species-specific 24-h time-activity data collected between 2011 and 2013 to estimate daily energy expenditure, morphometrically corrected for site- and day-specific thermoregulatory costs. To estimate population-level energy demand, we used standardized monthly ground-surveys (2005–2014) to create a migration curve, and proportionally scaled that to fit aerial survey data (2005–2014). Crucially, we also explicitly incorporated estimates of variance in all of these parameters and conducted a sensitivity analysis to diagnose the most important sources of variation in the model. Our results indicated that at estimated mean levels of supply (2.34 × 109 kcal) and cumulative demand (3.4 × 109 kcal), refuge resources were depleted before the end of the wintering season. However, at one standard error greater in supply and one standard error less in demand, 1.33 × 109 kcal remained on the landscape at the end of winter. Variation in model output appeared to be driven primarily by uncertainty in food abundance in high marsh habitats. This model allows for relative assessment of biases and uncertainties in carrying capacity modeling, and serves as a framework identifying critical science needs to improve local and regional waterfowl management planning.

Carrying capacity of wintering American black ducks in forested wetlands

ABSTRACTWintering populations of American black ducks (Anas rubripes) have declined throughout their range since the 1950s. Conservation for wintering black ducks is based largely on bioenergetic models of carrying capacity, and managers seek to provide wetlands with sufficient food energy to support target populations. Although the significance of salt marsh to wintering black ducks along the Atlantic Coast is well documented, forested wetlands are also used by wintering black ducks, and yet their foraging value and energetic potential is unknown. Therefore, quantifying the energetic value of forested wetlands is important for accurately estimating the carrying capacity of black ducks. We collected soil core samples from forested wetlands on Prime Hook National Wildlife Refuge, Milton, Delaware in 2014 (n = 46) and Edwin B. Forsythe National Wildlife Refuge, Galloway, New Jersey, USA in 2015 (n = 41) to estimate food biomass and quantify the energetic capacity of forested wetlands representative of the mid‐Atlantic region. We estimated the mean energetic value of forested wetlands as 84,667 ± 21,822 kcal/ha. Considering all forested wetlands that are potentially available to black ducks along the mid‐Atlantic Coast, we estimated that forested wetlands within a 24.1‐km distance from the coast provide between 103,696,524–192,678,224 duck‐use days supporting 489,135–908,860 black ducks over the 212 days of winter. Forested wetlands may be an important foraging resource for wintering black ducks, and our estimates of energetic value will help to refine bioenergetic models for black ducks in the Atlantic Flyway. © 2017 The Wildlife Society.

Diamondback terrapins as indicator species of persistent organic pollutants: Using Barnegat Bay, New Jersey as a case study

The diamondback terrapin’s ( Malaclemys terrapin) wide geographic distribution, long life span, occurrence in a variety of habitats within the saltmarsh ecosystem, predatory foraging behavior, and high site fidelity make it a useful indicator species for contaminant monitoring in estuarine ecosystems. In this study fat biopsies and plasma samples were collected from males and females from two sites within Barnegat Bay, New Jersey, as well as tissues from a gravid female and blue mussels ( Mytilus edulis), which are terrapin prey. Samples were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, and methyl-triclosan. Terrapins from the northern site, Spizzle Creek, closest to influences from industrial areas, had higher POP concentrations for both tissues than terrapins from the less impacted Forsythe National Wildlife Refuge. Sex differences were observed with males having higher contaminant concentrations in fat and females in plasma. PCB patterns in terrapin fat and plasma were comparable to other wildlife. An atypical PBDE pattern was observed, dominated by PBDEs 153 and 100 instead of PBDEs 47 and 99, which has been documented in only a few other turtle species. The typical PBDE patterns measured in mussels, terrapin prey, suggests that the terrapin may efficiently biotransform or eliminate PBDE 47 and possibly PBDE 99. Plasma contaminant concentrations significantly and positively correlated with those in fat. This study addresses several aspects of using the terrapin as an indicator species for POP monitoring: site and sex differences, tissue sampling choices, maternal transfer, and biomagnification.

Status of organic pollutants in surface sediments of Barnegat Bay-Little Egg Harbor Estuary, New Jersey, USA

Numerous surveys have demonstrated that diffuse pollution from urban-residential run-off and industrial discharges can adversely impact salt marsh and tidal creek sediment quality (Barrett & McBrien, 2006; Fox et al., 2001; Iannuzzi et al., 1995; Long et al., 1995; Sanger et al., 2004; White et al., 2005). The impact of shipping activities, including major discharge of fuel oil onto salt marshes, has also been reported (White et al., 2005). However, few studies have assessed organic pollution accumulating in salt marshes with watersheds that are mainly comprised of forests and wetlands but which have major residential areas located off-shore of the mainland. The salt marshes of Barnegat Bay-Little Egg Harbor Estuary, southeast New Jersey represent one such geographical setting (Fig .1). The shallow (17 m), narrow (3-9 mile) bay is separated from the Atlantic Ocean by a back barrier island complex (Long Beach Island) which is heavily developed and a major area of tourism (Fig. 1). The salt marshes are protected and managed as part of the Edwin B. Forsythe National Wildlife Refuge, this comprises 186 km of wetlands and 145 km of salt marshes and has a mixed pattern of watershed land use such as forestry (45.9 %), wetlands (25.2 %), urban/residential (19.5 %) and agricultural (6.6 %).

Potential environmental contaminant risks to avian species at important bird areas in the Northeastern United States

Environmental contaminants can have profound effects on birds, acting from the molecular through population levels of biological organization. An analysis of potential contaminant threats was undertaken at 52 Important Bird Areas (IBAs) within the northeastern Atlantic coast drainage. Using geographic information system methodology, data layers describing or integrating contamination (impaired waters, fish or wildlife consumption advisories, toxic release inventory sites, and estimates of pesticide use) were overlaid on buffered IBA boundaries, and the relative threat at each site was ranked. Some species of birds residing at Jefferson National Forrest (NF), Stewart B. McKinney National Wildlife Refuge (NWR), Great Dismal Swamp NWR, Blue Ridge Parkway, Shenandoah National Park (NP), Adirondack Park, Edwin B. Forsythe NWR, George Washington NF, Green Mountain NF, Long Island Piping Plover Beaches, and Merrymeeting Bay may be threatened by environmental contaminants. These sites exhibited moderate to high percentages of impaired waters and had fish consumption advisories related to mercury and polychlorinated biphenyls, and were located in counties with substantial pesticide use. Endangered, threatened, and Watch List bird species are present at these sites. The Contaminant Exposure and Effects-Terrestrial Vertebrates database was searched within buffered IBA boundaries, and for a moderate number of sites there was concordance between the perceived risk and contaminant exposure. Several of the IBAs with apparently substantial contaminant threats had no avian ecotoxicological data (e.g., George Washington NF, Shenandoah NP). Based upon this screening level risk assessment, contaminant biomonitoring of birds is warranted at such sites, and data generated from these efforts could foster natural resource management activities.

Changes in lagoonal marsh morphology at selected Northeastern Atlantic coast sites of significance to migratory waterbirds

Five lagoonal salt marsh areas, ranging from 220 ha to 3,670 ha, were selected from Cape Cod, Massachusetts to the southern DelMarVa peninsula, Virginia, USA to examine the degree to which Spartina marsh area and microhabitats had changed from the early or mid- 1900s to recent periods. We chose areas based on their importance to migratory bird populations, agency concerns about marsh loss and sea-level rise, and availability of historic imagery. We georeferenced and processed aerial photographs from a variety of sources ranging from 1932 to 1994. Of particular interest were changes in total salt marsh area, tidal creeks, tidal flats, tidal and non-tidal ponds, and open water habitats. Nauset Marsh, within Cape Cod National Seashore, experienced an annual marsh loss of 0.40% (19% from 1947 to 1994) with most loss attributed to sand overwash and conversion to open water. At Forsythe National Wildlife Refuge in southern New Jersey, annual loss was 0.27% (17% from 1932 to 1995), with nearly equal attribution of loss to open water and tidal pond expansion. At Curlew Bay, Virginia, annual loss was 0.20% (9% from 1949 to 1994) and almost entirely due to perimeter erosion to open water. At Gull Marsh, Virginia, a site chosen because of known erosional losses, we recorded the highest annual loss rate, 0.67% per annum, again almost entirely due to erosional, perimeter loss. In contrast, at the southernmost site, Mockhorn Island Wildlife Management Area, Virginia, there was a net gain of 0.09% per annum (4% from 1949 to 1994), with tidal flats becoming increasingly vegetated. Habitat implications for waterbirds are considerable; salt marsh specialists such as laughing gulls (Larus atricilla), Forster’s terns (Sterna forsteri), black rail, (Laterallus jamaicensis), seaside sparrow (Ammodramus maritimus), and saltmarsh sharp-tailed sparrow (Ammodramus caudacutus) are particularly at risk if these trends continue, and all but the laughing gull are species of concern to state and federal managers.

Winter Survival of Female American Black Ducks on the Atlantic Coast

We used radio telemetry to monitor the winter survival and cause-specific mortality of 227 female American black ducks (Anas rubripes) captured in New Jersey and Virginia, 1983-85. Mean survival rate for 19 December-15 February was 0.65. Survival from hunting and nonhunting risk was 0.84 and 0.78, respectively. Causes of nonhunting mortality included predation and emaciation (winter stress). After-hatchyear (AHY) ducks had a higher probability of survival than hatch-year (HY) ducks (0.73 vs. 0.60); most of this difference was related to survival from nonhunting risk. After-hatch-year ducks with body masses > median had a higher survival probability (0.85) than AHY ducks with < median body masses (0.61) because of differential survival from hunting risk. Hatch-year ducks had lower body mass than AHY ducks, but among HY ducks body mass was not related to survival. There were no consistent patterns in survivorship in relation to mean daily temperature, although the timing of the onset of low temperatures and storms may have influenced movement patterns. Our estimated survival rates are consistent with estimates from other studies of seasonal and annual survival. It may be possible to manage habitats for population segments at high risk (HY and low body mass birds), and increase black duck survivorship. J. WILDL. MANAGE. 53(1):99-109 Populations of American black ducks have declined from the 1950's to present (Barske 1968, Grandy 1983, Feierabend 1984). Reasons for the decline are unknown but may be related to specific causes of mortality such as hunting (Blandin 1982, Krementz et al. 1988), predation (Ringelman and Longcore 1983), competition from and hybridization with mallards (Anas platyrhynchos) (Johnsgard 1961, 1967), and habitat losses (Barske 1968). Winter is a critical time for black ducks, because of high energetic demands (Albright 1981, Reinecke et al. 1982). Reinecke et al. (1982) demonstrated that immature females achieved adult structural size, but were lighter in weight and had smaller nutrient reserves than did adults during their first winter. Other studies have corroborated a link between age, body condition, and probability of survival. Hepp et al. (1986) reported that the probability of being shot by hunters for mallards in poor condition was higher than for those in better condition. Haramis et al. (1986) reported a direct relationship between the body mass of canvasbacks (Aythya valisineria) in early winter and probability of surviving the winter. Although immature black ducks are more vulnerable to hunting (Schierbaum and Foley 1957, Krementz et al. 1988), and have lower annual survival rates than do adults (Blandin 1982, Krementz et al. 1987), whether age-specific mortality persists through winter, or occurs primarily during the postfledging period and early hunting season is unknown. Managers need estimates of winter survival rates and identification of mortality sources to understand black duck population dynamics and assist in the management of black duck populations. Our objectives were to estimate survival rates of black ducks during winter, examine specific components of mortality, specifically hunting versus nonhunting mortality, and examine variation in survival rates during winter in relation to age, body condition, time, geographic location, and weather conditions. We appreciate the assistance of E. L. Derleth, N. Dietz, B. Dirks, B. L. Estel, S. Holzman, A. G. Larochelle, J. M. Morton, H. H. Obrecht III, S. R. Perin, N. Phelps, H. G. Russell, M. A. Spoden, J. M. Walsh, and G. Wright in the collection of field data. We also thank F. Ferrigno, New Jersey Fish and Game, G. L. Inman and D. L. Beall of Forsythe National Wildlife Refuge, and D. Holland of Chincoteague National 'Present address: Georgia Cooperative Fish and Wildlife Research Unit, School of Forest Resources, University of Georgia, Athens, GA 30602.