VTechWorks Repository :: Browsing by Author "Catlin, Daniel H."

Browsing by Author "Catlin, Daniel H."

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Application of Bayesian robust design model to assess the impacts of a hurricane on shorebird demography
Gibson, Daniel; Riecke, Thomas V.; Keyes, Tim; Depkin, Chris; Fraser, James D.; Catlin, Daniel H. (Ecological Society of America, 2018-08)
The increasing use of Bayesian inference in population demography requires rapid advancements in modeling frameworks to approach the rigor and flexibility of the current suite of maximum-likelihood models. We developed an unbiased, Jolly-Seber robust design (JSRD) model that is both accessible and generalizable in a Bayesian hierarchical multistate framework. We integrated band and age-classification data to estimate site entry, temporary emigration, and apparent survival rates, as well as estimate age-class specific abundances. The complete model parameterization is provided in the Appendix S1, as well as tools for simulating capture histories and an assessment of model fit. We applied this model to determine whether these demographic processes in non-breeding population of American oystercatchers (Haematopus palliatus) were affected by a major hurricane event (Hurricane Matthew) in coastal Georgia. The JSRD model was demonstrably unbiased at relatively small sample sizes, and the majority of parameters were identifiable in the fully saturated model parameterization. In the model application, we found that Hurricane Matthew temporarily altered local population abundances of American oystercatchers through increased movements of individuals into and out of the observable population, but mortality rates were largely unaffected. Together, our results suggest that American oystercatchers were largely able to avoid the immediate demographic consequences (i.e., reduced survival) of Hurricane Matthew. Integrating age and band ratios from survey data allowed for more descriptive and potentially less biased estimates of age-specific abundance, relative to estimates generated solely from either mark-resight or survey data.
Assessing the Effects of Sea-Level Rise on Piping Plover (Charadrius Melodus) Nesting Habitat, and the Ecology of a Key Mammalian Shorebird Predator, on Assateague Island
Gieder, Katherina Dominique (Virginia Tech, 2015-09-02)
The piping plover (Charadrius melodus) is a federally-listed shorebird that nests on barrier islands along the U.S. Atlantic Coast and is highly vulnerable to habitat change and predation. We have addressed these two threats by 1) developing and implementing a linked model system that predicts future change to piping plover habitat resulting from sea-level rise and beach management efforts by joining dynamic models of sea-level rise, shoreline change, island geomorphology and piping plover nest habitat suitability, and 2) quantifying occupancy and movement of the red fox (Vulpes vulpes), a key shorebird predator at Assateague Island, Maryland and Virginia. We constructed and tested a model that links changes in geomorphological characteristics to piping plover nesting habitat suitability. We then linked this model to larger scale shoreline change resulting from sea level rise and storms. Using this linked model to forecast future sea-level rise and beach management efforts, we found that modest sea-level rise rates (3 mm and 4.1 mm/yr; similar to current rates) may increase suitable piping plover nesting habitat area in 50-100 years and some beach management strategies (beach nourishment and artificial dune modifications) also influence habitat availability. Our development and implementation of this tool to predict change in piping plover habitat suitability provides a vital starting point for predicting how plover nesting habitat will change in a context of planned human modifications intended to address climate change-related threats. Our findings regarding red fox occupancy and movement complement the use of this model for planning future management actions by providing vital information on the effects of certain predator management activities and habitat use of a key mammalian predator, the red fox, for shorebirds along the U.S. Atlantic Coast. Overall, we found that 1) red fox occupancy was strongly tied to eastern cottontail (Sylvilagus floridanus) trap success, increasing sharply with increased eastern cottontail trap success, 2) red fox occupancy did not change in response to an intensive eradication program, and 3) red foxes in our study area generally moved little between camera stations spaced 300 m from each other, but may move large distances (> 6km) at times, likely to occupy new territory available after lethal control efforts. Our findings have important ramifications for the sustainability of long-term predator removal programs and our understanding of future habitat change on the red fox. For example how vegetation changes affect eastern cottontails, how resulting fluctuations in eastern cottontails affect red fox occupancy, and how consequential changes in red fox occupancy affect plover breeding productivity. Our predictive model combined with these predator findings will allow wildlife managers to better plan and implement effective management actions for piping plovers in response to the multiple stressors of SLR-induced habitat change and predation.
Atlantic Flyway Disturbance Project Phase 2: Biological Data Collection Report
Gibson, Daniel; Hunt, Kelsi L.; Catlin, Daniel H. (2021)
Human disturbance is a significant threat facing shorebirds throughout the annual cycle, and threats to shorebird habitats may be exacerbated by increased human use (e.g., beach recreationists, off-leash dogs), reducing the amount of coastal habitat that is functionally available to shorebirds. We worked with partners across the Atlantic flyway to develop a standardized protocol for data collection to evaluate the effects of human disturbance on six Atlantic Flyway Shorebird Initiative (AFSI) focal species (American Oystercatchers [AMOY; Haematopus palliates], Piping Plovers [PIPL; Charadrius melodus], Red Knots [REKN; Calidris canutus], Sanderling [SAND; Calidris Alba], Semipalmated Sandpipers [SESA; Calidris pusilla], and Wilson’s Plovers [WIPL; Charadrius wilsonia]).
Biology and conservation of the endangered Bahama Swallow (Tachycineta cyaneoviridis)
Wilson, Maya (Virginia Tech, 2020-01-02)
In order to prevent species extinctions, conservation strategies need to incorporate the identification and mitigation of the root causes of population decline with an assessment of vulnerability to genetic and stochastic factors affecting small populations. Species or populations with small ranges, such as those on islands, are particularly vulnerable to extinction, and deficient knowledge of these species often impedes conservation efforts. The Bahama Swallow (Tachycineta cyaneoviridis) is an endangered secondary cavity-nester that only breeds on three islands in the northern Bahamas: Abaco, Grand Bahama, and Andros. I investigated questions related to population size and distribution, genetic diversity and population structure, breeding biology, and ecological interactions of the swallow, with the goal of informing the conservation and management of the species. Using several population survey methods on Abaco, I found that swallow site occupancy and density is higher in southern Abaco, especially near roads and pine snags. Future research should prioritize identifying the causes of variable and low population densities in parts of the swallow's range. I used microsatellite markers and morphometrics to assess differences between populations on Abaco and Andros. We found a lack of genetic differentiation (G'ST = 0.03) between populations, but differences in morphology suggest that gene flow might be low enough to enable traits under selection to diverge. By locating and monitoring nests, I found that swallows rely on woodpecker-excavated cavities in pine snags and utility poles, and that swallows nesting in pine snags had higher fledging success (92%) than those nesting in utility poles (50-62%). Using a cavity nest-web approach, I assessed how swallows interact with cavity-nesting birds and resources on Abaco. Hairy Woodpeckers (Dryobates villosus) primarily excavated pine snags, while West Indian Woodpeckers (Melanerpes superciliaris) excavated utility poles in non-pine habitat. Only swallows and La Sagra's Flycatchers (Myiarchus sagrae) used nest sites in the pine forest. Swallows in non-pine habitat face competition for cavities with American Kestrels (Falco sparverius), and non-native House Sparrows (Passer domesticus) and European Starlings (Sturnus vulgaris). These results highlight the importance of pine forest and the Hairy Woodpecker for the persistence of the swallow.
Body Condition Indices Predict Reproductive Success but Not Survival in a Sedentary, Tropical Bird
Milenkaya, Olga; Catlin, Daniel H.; Legge, Sarah; Walters, Jeffrey R. (PLOS, 2015-08-25)
Body condition may predict individual fitness because those in better condition have more resources to allocate towards improving their fitness. However, the hypothesis that condition indices are meaningful proxies for fitness has been questioned. Here, we ask if intraspecific variation in condition indices predicts annual reproductive success and survival. We monitored a population of Neochmia phaeton (crimson finch), a sedentary, tropical passerine, for reproductive success and survival over four breeding seasons, and sampled them for commonly used condition indices: mass adjusted for body size, muscle and fat scores, packed cell volume, hemoglobin concentration, total plasma protein, and heterophil to lymphocyte ratio. Our study population is well suited for this research because individuals forage in common areas and do not hold territories such that variation in condition between individuals is not confounded by differences in habitat quality. Furthermore, we controlled for factors that are known to impact condition indices in our study population (e.g., breeding stage) such that we assessed individual condition relative to others in the same context. Condition indices that reflect energy reserves predicted both the probability of an individual fledging young and the number of young produced that survived to independence, but only during some years. Those that were relatively heavy for their body size produced about three times more independent young compared to light individuals. That energy reserves are a meaningful predictor of reproductive success in a sedentary passerine supports the idea that energy reserves are at least sometimes predictors of fitness. However, hematological indices failed to predict reproductive success and none of the indices predicted survival. Therefore, some but not all condition indices may be informative, but because we found that most indices did not predict any component of fitness, we question the ubiquitous interpretation of condition indices as surrogates for individual quality and fitness.
Building a Comprehensive Understanding of Disturbance Mitigation in Migrating Shorebirds
Mengak, Lara Frances (Virginia Tech, 2019-01-17)
Human disturbance is a serious threat facing shorebirds, and reducing disturbance presents a significant conservation challenge. It requires an understanding of the complex factors that influence both shorebird biology and human behavior related to shorebirds and coastal environments. This thesis used information from ecological and social science fields, along with the applied knowledge of conservation practitioners to build a more holistic understanding of human-shorebird interactions, specifically related to human disturbance of migrating shorebirds. Further, this research provides practical solutions for better managing these interactions. To accomplish this, we used the Delphi technique, an iterative group communication process, to bring scientists and managers together to develop a shared definition of "human disturbance to shorebirds" and a list of priority disturbance categories that affect migratory shorebirds. Next, we collated and synthesized literature on human disturbance during migration and drivers of human behavior related to disturbance or potential management actions. Then, through manager interviews, we examined how shorebird management decisions are made during migration and explored how managers balance the needs of shorebirds and public use of their sites. The disturbance definition and priority disturbance categories, literature synthesis, and manager interviews were used to create a best practices guidance document for reducing human disturbance to migratory shorebirds in the Northeastern U.S. Finally, we conducted a survey of beachgoers to evaluate a shorebird conservation outreach campaign and examined the factors that influence pro-shorebird behavior change. This research demonstrates how integrating social and ecological information and expert opinion can inform conservation and management.
Contrasting long-term population trends of beach-nesting shorebirds under shared environmental pressures
Kwon, Eunbi; Robinson, Samantha G.; Weithman, Chelsea E.; Catlin, Daniel H.; Karpanty, Sarah M.; Altman, Jon; Simons, Theodore R.; Fraser, James D. (Elsevier, 2021-08-01)
Identifying the drivers of long-term population change is a key goal of ecological studies. It is complicated by extrinsic and intrinsic factors that may covary with time and/or operate on a time lag. For migratory shorebirds that breed on the barrier islands of eastern North America, populations may be limited by the anthropogenic, climatic, biological environments they encounter throughout the annual cycle. Using three-decades (1989–2017) of breeding monitoring data collected by the National Park Service at two national seashores in North Carolina (Hatteras and Lookout), we examined the potential drivers of nesting piping plover (Charadrius melodus) and American oystercatcher (Haematopus palliates) populations. Hatteras had five times more annual visitors than Lookout, and our modelling revealed a strong negative relationship between the population size of breeding plovers and human activity and a positive relationship with protection efforts aimed at reducing disturbance. Breeding and wintering climatic conditions, population productivity, and nesting habitat availability showed only weak effects. Thus, a decade-long decline in plover numbers at both seashores starting in the mid-90s reversed as the parks' visitor counts decreased and stricter protections from potential disturbance were implemented. However, the two sympatric populations of oystercatchers showed the opposite population trends from each other at the neighboring seashores, increasing only on Lookout after a hurricane improved habitat and subsequently the reproductive output. Our study suggests a strong relationship between the anthropogenic environment and the population trend of a threatened species and, simultaneously, the important role of stochastic events in shaping populations of long-lived shorebird species.
Direct and indirect effects of nesting density on survival and breeding propensity of an endangered shorebird
Catlin, Daniel H.; Gibson, Daniel; Hunt, Kelsi L.; Friedrich, Meryl J.; Weithman, Chelsea E.; Karpanty, Sarah M.; Fraser, James D. (ESA, 2019-04-08)
Density-dependent regulation is a fundamental part of ecological theory and a significant driver of animal demography often through complex feedback loops. We investigated the relationship between flood- and demographically induced fluctuations in density and the breeding propensity and survival of a pioneer species, the piping plover (plover, Charadrius melodus).We captured and marked adult and hatchling plovers on the Gavins Point Reach of the Missouri River in South Dakota and Nebraska, USA, from 2005 to 2014. In 2010 and 2011, historically high water levels and flooding inundated much of the plover’s sandbar nesting habitat on theMissouri River.We developed a Bayesian formulation of a multievent model, or a multistate survival model with state uncertainty to estimate breeding propensity simultaneously with survival. Although plovers are conspicuous, their breeding status can be difficult to establish with certainty, which necessitated the use of uncertain states.With this model, we investigated the effect of sex, habitat availability, river flow, and density (birds/ha nesting habitat) on survival of hatch year and breeding and non-breeding adult plovers. In addition, we estimated the transition rates for these age classes between breeding and nonbreeding states. Non-breeding adults (ɸAHY, n = 0.58 ± 0.06) had lower survival rates than breeding adults (ɸAHY, b = 0.80 ± 0.04), and both breeding survival and breeding propensity decreased with increasing nesting density. Not only did survival and breeding propensity decrease directly at higher nest densities, but survival also was indirectly impacted by increasing the proportion of non-breeding birds with relatively low survival. Thus, plovers were regulated through a complex set of feedback loops, acting as densities increased. Our findings underscore the intricacy of density-dependent regulation and suggest that detailed demographic studies are needed to fully understand these effects.
Disturbance and Environmental Effects on Staging Roseate Tern Parent-Offspring Interactions and Hatch Year Survival at Cape Cod National Seashore
Davis, Kayla L. (Virginia Tech, 2017-01-31)
The study that I detail in the following thesis is a component of a three-part collaborative project to provide the U. S. National Park Service and Cape Cod National Seashore (CCNS) with data needed to inform management decisions for protection of the endangered northwest Atlantic Roseate Tern (ROST) during fall pre-migratory staging. This study was designed to address objectives related to hatch-year (HY) ROST behavior and survival in response to human and non-human activities and environmental variables at CCNS. Behavioral data showed that disturbance, specifically human and non-human activities, were related to increased HY ROST locomotion (flying and walking). We also found that environmental variables, including day of season and time of day were related to increased locomotion. Flock-level HY ROST begging behavior was decreased in the presence of human disturbance, but we did not see the same effect at the individual level. We found no evidence that the observed behavioral effect of disturbance resulted in decreased residency, recruitment, or staging duration of HY ROST at CCNS. Our work demonstrates that disturbance events around staging flocks have behavioral consequences, but it is unknown whether HY ROST behavioral responses to disturbances are great enough to impact survival after departure from CCNS. A conservative and proactive management strategy to minimize the potential for negative carryover effects on survival should limit ROST exposure to disturbance, particularly human activities, by exclosing staging sites between mid-July–mid-September to encompass the period of time when the highest number of ROST use CCNS.
Effects of climate change and anthropogenic modification on a disturbance-dependent species in a large riverine system
Zeigler, Sara L.; Catlin, Daniel H.; Brown, Mary Bomberger; Fraser, James D.; Dinan, Lauren R.; Hunt, Kelsi L.; Jorgensen, Joel G.; Karpanty, Sarah M. (Ecological Society of America, 2017-01)
Humans have altered nearly every natural disturbance regime on the planet through climate and land-use change, and in many instances, these processes may have interacting effects. For example, projected shifts in temperature and precipitation will likely influence disturbance regimes already affected by anthropogenic fire suppression or river impoundments. Understanding how disturbance-dependent species respond to complex and interacting environmental changes is important for conservation efforts. Using field-based demographic and movement rates, we conducted a metapopulation viability analysis for piping plovers (Charadrius melodus), a threatened disturbance-dependent species, along the Missouri and Platte rivers in the Great Plains of North America. Our aim was to better understand current and projected future metapopulation dynamics given that natural disturbances (flooding or high-flow events) have been greatly reduced by river impoundments and that climate change could further alter the disturbance regime. Although metapopulation abundance has been substantially reduced under the current suppressed disturbance regime (high-flow return interval similar to 20 yr), it could grow if the frequency of high-flow events increases as predicted under likely climate change scenarios. We found that a four-year return interval would maximize metapopulation abundance, and all subpopulations in the metapopulation would act as sources at a return interval of 15 yr or less. Regardless of disturbance frequency, the presence of even a small, stable source subpopulation buffered the metapopulation and sustained a low metapopulation extinction risk. Therefore, climate change could have positive effects in ecosystems where disturbances have been anthropogenically suppressed when climatic shifts move disturbance regimes toward more historical patterns. Furthermore, stable source populations, even if unintentionally maintained through anthropogenic activities, may be critical for the persistence of metapopulations of early-successional species under both suppressed disturbance regimes and disturbance regimes where climate change has further altered disturbance frequency or scope.
Epidemiology of sarcoptic mange in a geographically constrained insular red fox population
Wails, Christy N.; Helmke, Claire C.; Black, Kathleen M.; Ramirez-Barrios, Roger; Karpanty, Sarah M.; Catlin, Daniel H.; Fraser, James D. (2024-06-06)
Background: Sarcoptic mange is a skin disease caused by the contagious ectoparasite Sarcoptes scabiei, capable of suppressing and extirpating wild canid populations. Starting in 2015, we observed a multi-year epizootic of sarcoptic mange affecting a red fox (Vulpes vulpes) population on Fire Island, NY, USA. We explored the ecological factors that contributed to the spread of sarcoptic mange and characterized the epizootic in a landscape where red foxes are geographically constrained. Methods: We tested for the presence of S. scabiei DNA in skin samples collected from deceased red foxes with lesions visibly consistent with sarcoptic mange disease. We deployed 96–100 remote trail camera stations each year to capture red fox occurrences and used generalized linear mixed-effects models to assess the affects of red fox ecology, human and other wildlife activity, and island geography on the frequency of detecting diseased red foxes. We rated the extent of visual lesions in diseased individuals and mapped the severity and variability of the sarcoptic mange disease. Results: Skin samples that we analyzed demonstrated 99.8% similarity to S. scabiei sequences in GenBank. Our top-ranked model (weight = 0.94) showed that diseased red foxes were detected more frequently close to roadways, close to territories of other diseased red foxes, away from human shelters, and in areas with more mammal activity. There was no evidence that detection rates in humans and their dogs or distance to the nearest red fox den explained the detection rates of diseased red foxes. Although detected infrequently, we observed the most severe signs of sarcoptic mange at the periphery of residential villages. The spread of visual signs of the disease was approximately 7.3 ha/week in 2015 and 12.1 ha/week in 2017. Conclusions: We quantified two separate outbreaks of sarcoptic mange disease that occurred > 40 km apart and were separated by a year. Sarcoptic mange revealed an unfettered spread across the red fox population. The transmission of S. scabiei mites in this system was likely driven by red fox behaviors and contact between individuals, in line with previous studies. Sarcoptic mange is likely an important contributor to red fox population dynamics within barrier island systems.
Factors affecting Western Atlantic red knots (Calidris canutus rufa) and their prey during spring migration on Virginia's barrier islands
Heller, Erin Leigh (Virginia Tech, 2020-06-24)
Understanding factors that influence a species' distribution and abundance across their annual cycle is needed for range-wide conservation planning. Every year during spring migration, thousands of federally threatened (U.S.A.) and endangered (Canada) migratory Western Atlantic red knots (Calidris canutus rufa, 'red knot') use Virginia's barrier islands as stopover habitat to regain the fat required to continue flights to breeding grounds. Because the red knot completes one of the longest avian migrations in the world and relies on variable prey resources at its stopover grounds, the red knot exemplifies the challenges faced by long-distance migrant shorebirds. These challenges may be exacerbated by climate change, as long-distance migrants may be unable to adapt quickly to changing prey ranges and abundances, resulting in spatial and temporal mismatches between predators and prey. More specifically, as climate change causes ocean temperatures near Virginia's barrier islands to rise, organisms that live within the intertidal zone, like blue mussels (Mytilus edulis), are experiencing range shifts. Here, we 1) confirmed what prey red knots select in Virginia, 2) addressed the factors that affect red knot site selection, red knot flock size, and prey abundances across Virginia's barrier island intertidal shoreline during 2007 – 2018, and 3) predicted the origin of juvenile blue mussels, a key prey resource for red knots in Virginia. To determine which prey are most available to red knots in Virginia, we collected sand and peat substrate core samples from Virginia's ocean intertidal zone and counted the number of prey in each sample. We compared these prey availability data to prey DNA data obtained from fecal DNA metabarcoding analyses on red knot feces (n = 100) collected on peat and sand substrates between 2017 – 2019. Red knots consumed prey from Orders Veneroida (clams), Mytiloida (mussels), Diptera (flies), and Amphipoda/Calanoida (crustaceans). While crustaceans were the most abundant prey on both sand (70.80% of total prey counted) and peat (74.88%) substrates, red knots selected crustaceans less than expected given their availability. Red knots selected clams and mussels, supporting their status as bivalve specialists in Virginia. After determining which prey red knots consumed and selected in Virginia, we predicted the number of red knots using Virginia's barrier island stopover during their migratory stopover (May 14 – 27, 2007 – 2018) annually. We used confirmed prey, tide, distance to known roosts, and red knot winter counts from Tierra del Fuego to inform zero-inflated negative binomial mixed-effects regression models of red knot site selection and flock size in Virginia. We also used generalized linear mixed-effects regression models to determine how climatic and geomorphological factors affected prey abundances. Modeled red knot peak counts were highest in 2012 (11,644) and lowest in 2014 (2,792; x̄ = 7,055, SD = 2,841); the trend over time was variable but there was no evidence of a linear increase or decrease. Red knots selected foraging locations with more prey, though red knot flock size did not consistently relate to prey abundance. Tide, substrate, and water temperature affected prey availability. While different prey responded to these covariates in variable ways, prey generally were most abundant on peat banks at low tide. Given the importance of blue mussels in the red knot's diet and distribution in Virginia, if the blue mussel's range continues to contract northward, red knots could be faced with additional fat replenishment challenges. We analyzed the variation in blue mussels from 2010 – 2018 by collecting core samples on peat banks in Virginia and counting the number of blue mussels in the cores. To approximate the origin of Virginia's juvenile blue mussels and determine how continued ocean temperature warming may further affect the blue mussel's range contraction, we conducted oxygen stable isotope (δ¹⁸O_c) analyses on 74 blue mussel shell umbos (the first portion of the shell precipitated) and shell edges (the most recently precipitated shell) to compare and predict where different portions of the shell were formed. We compared blue mussel shell compositions to δ¹⁸O_c calculated in equilibrium with regional ocean water using recorded δ¹⁸O_w data and sea surface temperature data from ocean buoys between New Hampshire and Virginia. Blue mussel abundance/core sample declined over the duration of our study (Spearman's rank correlation coefficient: ρ(rho) = -0.31, p < 0.001), with the highest abundance in 2010 (x̄ blue mussels/core sample = 537.88, SE = 85.85) and lowest in 2016 (x̄ = 34.08 blue mussels/core sample, SE = 6.96). Blue mussel umbos (x̄ δ¹⁸O_c = -0.23‰, SE = 0.12) contained more positive δ18Oc than shell edges (x̄ δ¹⁸O_c = -0.53‰, SE = 0.20), suggesting that Virginia's blue mussels originated from ocean populations in more saline and/or colder water than that within Virginia's intertidal zone. Blue mussel umbo δ¹⁸O_c were not different than δ¹⁸O_c calculated in equilibrium with regional ocean water off the Virginia and Delaware coasts, suggesting that Virginia's blue mussels originated in ocean waters between Delaware and Virginia; however, they may have originated in waters as far north as New York in some years, potentially decreasing the risk of blue mussels being completely extirpated from Virginia in the near future. While red knots currently use spring migratory stopovers across the United States' Atlantic Coast, from Florida to New Jersey, the largest spring concentrations of knots are confined to the Delaware Bay and Virginia's barrier islands. Because these stopover grounds support large proportions of the red knot's migratory population, any changes in the factors that affect red knots at these stopover sites could have lasting implications for red knots. The blue mussel's range contraction and decline over time in Virginia, for example, is concerning from a conservation perspective. Red knots require easily accessible and abundant prey resources to efficiently replenish fat-stores needed for continued migration and breeding. Additionally, because red knots breed within a narrow period, any delays on stopover grounds could prevent red knots from breeding, even if they survive migration. Our research demonstrates that red knots use prey abundance as a determinant when selecting foraging locations, and that peat banks, while only sporadically available across the barrier islands at mid- to low-tides, contain higher prey abundances than sand. Thus, to continue maximizing the availability of prey in Virginia, measures should continue to be taken to allow natural island migration processes that encourage the presence of both sand and peat substrates. Beach nourishment and stabilization projects are often used on coastal beaches to prevent shoreline erosion; however, such actions prevent the formation of peat banks by blocking island migration processes. A reduction in peat banks could decrease the abundance of prey available to red knots, making weight gain during the critical stopover period more challenging for red knots. Additionally, beach nourishment through sand replenishment buries invertebrate prey, potentially causing mass prey mortality and reducing shorebirds' ability to access deeply buried prey. To prevent the loss of important peat banks on these islands, and to prevent disrupting predator-prey interactions, managers should continue their ongoing focus on allowing natural processes to occur on Virginia's barrier islands.
Factors that affect migratory Western Atlantic red knots (Calidris canutus rufa) and their prey during spring staging on Virginia’s barrier islands
Heller, Erin L.; Karpanty, Sarah M.; Cohen, Jonahan B.; Catlin, Daniel H.; Ritter, Sharon J.; Truitt, Barry R.; Fraser, James D. (PLOS, 2022-07-01)
Understanding factors that influence a species’ distribution and abundance across the annual cycle is required for range-wide conservation. Thousands of imperiled red knots (Calidris cantus rufa) stop on Virginia’s barrier islands each year to replenish fat during spring migration. We investigated the variation in red knot presence and flock size, the effects of prey on this variation, and factors influencing prey abundance on Virginia’s barrier islands. We counted red knots and collected potential prey samples at randomly selected sites from 2007–2018 during a two-week period during early and peak migration. Core samples contained crustaceans (Orders Amphipoda and Calanoida), blue mussels (Mytilus edulis), coquina clams (Donax variabilis), and miscellaneous prey (horseshoe crab eggs (Limulus polyphemus), angel wing clams (Cyrtopleura costata), and other organisms (e.g., insect larvae, snails, worms)). Estimated red knot peak counts in Virginia during 21–27 May were highest in 2012 (11,959) and lowest in 2014 (2,857; 12-year peak migration x̄ = 7,175, SD = 2,869). Red knot and prey numbers varied across sampling periods and substrates (i.e., peat and sand). Red knots generally used sites with more prey. Miscellaneous prey (x̄ = 2401.00/m², SE = 169.16) influenced red knot presence at a site early in migration, when we only sampled on peat banks. Coquina clams (x̄ = 1383.54/m², SE = 125.32) and blue mussels (x̄ = 777.91/m², SE = 259.31) affected red knot presence at a site during peak migration, when we sampled both substrates. Few relationships between prey and red knot flock size existed, suggesting that other unmeasured factors determined red knot numbers at occupied sites. Tide and mean daily water temperature affected prey abundance. Maximizing the diversity, availability, and abundance of prey for red knots on barrier islands requires management that encourages the presence of both sand and peat bank intertidal habitats.
Habitat selection and potential fitness consequences of two early‐successional species with differing life‐history strategies
Catlin, Daniel H.; Gibson, Daniel; Friedrich, Meryl J.; Hunt, Kelsi L.; Karpanty, Sarah M.; Fraser, James D. (Wiley, 2019-11-19)
Habitat selection and its relationship to fitness is a fundamental concept in ecology, but the mechanisms driving this connection are complex and difficult to detect. Despite the difficulties in understanding such intricate relationships, it is imperative that we study habitat selection and its relationship with fitness. We compared habitat selection of least terns (Sternula antillarum) and piping plovers (Charadrius melodus) on the Missouri River (2012–2014) to examine the consequences of those choices on nest and chick survival. We hypothesized that plovers and terns would select habitat that minimized the chance of flooding and predation of eggs, chicks, and adults, but that plovers would also select habitat that would provide foraging habitat for their chicks. We developed an integrated habitat selection model that assessed selection across multiple scales (sandbar and nest scales) and directly modeled the effect of selection on nest and chick survival. In general, the species selected habitat in keeping with our hypotheses, such that predation and flooding, in particular, may have been reduced. Sandbar selection had either a negative or no appreciable effect on nest survival for both species across years. Nest‐site selection in 2012 had a generally positive effect on nest survival and chick survival for both terns and plovers, and this trended toward a negative effect by 2014. This result suggested that early selection decisions appeared to be adaptive, but we speculate that relatively high site fidelity and habitat degradation led to reduced benefit over time. Our results highlight the complex nature of habitat selection and its relationship to fitness.
Hurricane and human-induced habitat changes on Fire Island and Westhampton Island, New York, and the effects on breeding piping plovers (Charadrius melodus)
Bellman, Henrietta A. (Virginia Tech, 2019-02-01)
Barrier islands are dynamic environments facing increasing vulnerability to climate changes, sea level rises, and anthropogenic activities. Hurricane Sandy (October 2012) modified the Atlantic coast of the United States. On Fire Island and Westhampton Island, New York, multiple overwashes and three breaches occurred. The U.S. Army Corps of Engineers filled two breaches, increased dune elevation and stabilized dunes by planting American beachgrass (Ammophila breviligulata). They built two restoration areas to mitigate the impact of an island stabilization project to federally listed breeding piping plovers (Charadrius melodus). The goal of this thesis was to quantify habitat changes after Hurricane Sandy, and assess habitat use of piping plovers specifically in human-created restoration areas. We created land cover maps using an object-based classification method (overall accuracy 85%), and field-collected data from four post-hurricane habitat types. Vegetation cover increased across all habitat types, especially in manipulated (30.1% increase) and natural overwashes (37.9% increase), while dry sand for nesting declined by 8%. Vegetation density indices were higher in natural overwashes than planted engineered dunes, likely a reflection of plant age and establishment. We monitored 83 nests (67 pairs) of piping plovers from 2015–2017. Restoration areas were successful in attracting breeding piping plovers, although pair densities were lowest in this habitat in 2016, and in 2017 plovers selected against the restoration areas (�2 = 29.47, df = 3, p<0.0001). There was no effect of habitat type on reproductive parameters. We suggest vegetation removal may be necessary to maintain early successional habitats for piping plover management.
Hurricane Sandy and engineered response created habitat for a threatened shorebird
Walker, Katie M.; Fraser, James D.; Catlin, Daniel H.; Ritter, Shannon J.; Robinson, Samantha G.; Bellman, Henrietta A.; DeRose-Wilson, Audrey; Karpanty, Sarah M.; Papa, Steven T. (ESA, 2019-04-22)
The intensity of Atlantic Ocean hurricanes is predicted to increase, and although disturbance is recognized as a fundamental driver of ecological processes, the benefits of hurricanes to ecological systems are seldom acknowledged. In October 2012, Hurricane Sandy overwashed Fire Island and Westhampton Island, New York. The storm flattened dunes, buried vegetation, and breached the barrier islands in several places. To reduce future overwashing, engineers attempted to stabilize the islands. We studied nest-site selection, suitable habitat, and abundance of a threatened shorebird, the piping plover (Charadrius melodus), before and after Hurricane Sandy. Prior to the hurricane, piping plovers selected nest sites (n = 62) farther from the ocean (x least-cost distance = 82.8 m) and bay (x Euclidean distance = 697.7 m; x least-cost distance = 24,160.6 m) than would be expected if they were selecting nest sites at random. Following the hurricane, piping plovers selected nest sites (n = 45) predominantly in or near storm overwash habitat, which was close to, and had unobstructed walking access to, the ocean (x least-cost distance = 123.4 m) and newly created bayside foraging habitats (x Euclidean distance = 468.0 m; x least-cost distance = 728.9 m). Areas overwashed by the hurricane contained the most suitable piping plover habitat across all new habitat types. Piping plover abundance increased 93% by 2018 from pre-Hurricane Sandy abundances, with most pairs nesting in new habitats. However, only 58% of suitable piping plover habitat was protected from recreational use and few piping plovers used unprotected habitats for nesting. Our results suggest that the ecological benefits of increased storminess may be maximized by coupling coastal stabilization with targeted conservation of storm-created habitats.
Leveraging Partial Identity Information in Spatial Capture-Recapture Studies with Applications to Remote Camera and Genetic Capture-Recapture Surveys
Augustine, Ben C. (Virginia Tech, 2018-04-03)
Noninvasive methods for monitoring wildlife species have revolutionized the way population parameters, such as population density and survival and recruitment rates, are estimated while accounting for imperfect detection using capture-recapture models. Reliable estimates of these parameters are vital information required for making sound conservation decisions; however to date, noninvasive sampling methods have been of limited use for a vast number of species which are difficult to identify to the individual level–a general requirement of capture-recapture models. Capture-recapture models that utilize partial identity information have only recently been introduced and have not been extended to most types of noninvasive sampling scenarios in a manner that uses the spatial location where noninvasive samples were collected to further inform complete identity (i.e. spatial partial identity models). Herein, I extend the recently introduced spatial partial identity models to the noninvasive methods of remote cameras for species that are difficult to identify from photographs and DNA from hair or scat samples. The ability of these novel models to improve parameter estimation and extend study design options are investigated and the methods are made accessible to applied ecologists via statistical software. This research has the potential to greatly improve wildlife conservation decisions by improving our knowledge of parameters related to population structure and dynamics that inform those decisions. Unfortunately, many species of conservation concern (e.g., Florida panthers, Andean bears) are managed without having the necessary information on population status or trends, largely a result of the cost and difficulty of studying species in decline and because of the difficulty of applying statistical models to sparse data, which can produce imprecise and biased estimates of population parameters. By leveraging partial identity information in noninvasive samples, the models I developed will improve these parameter estimates and allow noninvasive methods to be used for more species, leading to more informed conservation decisions, and a more efficient allocation of conservation resources across species and populations.
Management and Mother Nature: piping plover demography and condition in response to flooding on the Missouri River
Hunt, Kelsi L. (Virginia Tech, 2016-11-17)
Globally, riparian ecosystems are in decline due to anthropogenic modifications including damming, channelization and the conversion of the floodplain for human use. These changes can profoundly affect riparian species as many have adapted to the historical dynamism of these ecosystems. On the managed Missouri River, an imperiled shorebird, the piping plover (Charadrius melodus) uses riverine sandbars to breed. From 2004 to 2009, due to limited breeding habitat and low population numbers, the U.S. Army Corps of Engineers constructed 255 ha of sandbar habitat to benefit piping plovers and least terns (Sternula antillarum). During the breeding seasons of 2010 and 2011, historically high flows resulted in the creation of 1,887 ha of suitable sandbar habitat. Our study compared the demographic response and the condition of piping plovers to these anthropogenic and natural habitat creation events. From 2005–2014 we monitored 1,071 nests, and from those nests we uniquely banded 968 adults and 2,021 piping plover chicks. We obtained 405 egg (clutch) mass measurements, 1,285 mass measurements from 633 adults, and 7,093 mass measurements from 1,996 plover chicks resulting in 3,175 mass measurements from 654 broods of chicks. We also collected 3,347 invertebrate prey samples. We used a random effects logistic exposure model to estimate nest success, a random effects Cormack-Jolly-Seber model in RMARK to estimate pre-fledge chick survival and the Barker model in RMARK to estimate hatch-year (HY) and after hatch-year (AHY) survival and fidelity to our study area. We then used estimates from these analyses to calculate reproductive output, reproductive output necessary for a stationary population, and population growth (λ). For adult condition and egg (clutch) mass we used generalized linear mixed regression, and for pre-fledge chick growth rates we used a modified Richard's model to estimate the effects of habitat type (pre- vs. post-flood). We also tested for differences in invertebrate prey abundance between habitat types using negative binomial regression. Our results indicated that AHY survival varied throughout our study and was lowest during the flood (2010 and 2011). We found that nest success, pre-fledge chick survival, reproductive output, and HY survival and fidelity were consistently higher on the flood-created habitat than engineered habitat, leading to sustained population growth after the flooding, as compared to just one year of population growth prior to the flood. Unlike pre-flood engineered habitat, the demographic parameters we measured did not decrease as the post-flood habitat aged. These differences were related to increased sandbar habitat, low nesting densities, and decreased nest and chick predation on the post-flood habitat. Although we hypothesized that increased demographic rates would be reflected by increased piping plover condition following the flood, we found that our measured condition variables (adult mass, clutch mass, and pre-fledge chick growth rates) remained unchanged following the flood. We also found evidence that clutch mass, chick growth rates and invertebrate prey abundance decreased as the post-flood sandbar habitat aged. As the condition of individuals did not appear to contribute directly to the increased demographic rates following the flood, we suggest that the change in density-dependent predation pressure may explain the discrepancy. As many ecosystems have previously been altered, it's rare that ecologists have the opportunity to compare management practices with natural ecosystem processes. Results from this study suggest that management intervention may not be an equivalent substitute for natural ecosystem processes and provide insight on future management of riparian ecosystem.
Metapopulation viability of an endangered shorebird depends on dispersal and human-created habitats: piping plovers (Charadrius melodus) and prairie rivers
Catlin, Daniel H.; Zeigler, Sara L.; Brown, Mary B.; Dinan, Lauren R.; Fraser, James D.; Hunt, Kelsi L.; Jorgensen, Joel G. (2016-03-15)
Background Many species are distributed as metapopulations in dynamic landscapes, where habitats change through space and time. Individuals locate habitat through dispersal, and the relationship between a species and landscape characteristics can have profound effects on population persistence. Despite the importance of connectivity in dynamic environments, few empirical studies have examined temporal variability in dispersal or its effect on metapopulation dynamics. In response to this knowledge gap, we studied the dispersal, demography, and viability of a metapopulation of an endangered, disturbance-dependent shorebird. We examined three subpopulations of piping plovers (Charadrius melodus) on the lower Platte and Missouri rivers from 2008–2013. High flow events from an upstream dam on the Missouri River in 2010 and 2011 allowed us to assess the effect of total habitat loss and the subsequent creation of new habitat associated with a large disturbance at one ‘natural’ study location. The other two sites within the metapopulation, which were maintained by anthropogenic activities (e.g., mining, development, habitat restoration), were largely unaffected by this disturbance, resulting in a controlled natural experiment. Results High flow events were associated with increased emigration, decreased immigration, and decreased survival in the subpopulation that experienced high flows. Following the high flow event, immigration into that subpopulation increased. Dispersal rates among subpopulations were negatively correlated with distance. The metapopulation had a low probability of extinction over 100 years (0 %) under the current disturbance interval and associated dispersal and survival rates. However, persistence depended on relatively stable, human-created habitats, not the dynamic, natural habitat (47.7 % extinction probability for this subpopulation). Conclusions We found that functional connectivity, as measured by the rate of dispersal among subpopulations, increased as a result of the high flow event in our study metapopulation. Plovers also increased reproductive output following this event. Although the study metapopulation had a low overall probability of extinction, metapopulation persistence depended on anthropogenically created habitats that provided a small but stable source of nesting habitat and dispersers through time. However, all subpopulations remained small, even if persistent, making them individually vulnerable to extinction through stochastic events. Given the highly dynamic nature of habitat availability in this system, maintaining several subpopulations within the metapopulation and stable sources of habitat will be critical, and this species will likely remain conservation-reliant.
Piping Plover (Charadrius melodus) demography, behavior, and movement on the Outer Banks of North Carolina
Weithman, Chelsea E. (Virginia Tech, 2019-06-10)
The Piping Plover (Charadrius melodus) is an imperiled shorebird that inhabits sandy beaches along the North American Atlantic Coast. The species' decline has been attributed to habitat loss, disturbance, and predation throughout its range, although most conservation efforts have focused on increasing reproductive output during the breeding season. On the coast of North Carolina, Piping Plovers breed in areas with large amounts of recreational and tourism use. Beach recreation is known to reduce nest success, chick survival, and potentially fitness in other parts of the species' range. To reduce potential negative effects from human activities on breeding Piping Plovers, managers close areas to pedestrian and vehicle access using exclusion buffers delineated by symbolic fencing. However, the reproductive success and population size of Piping Plovers in parts of North Carolina has not appeared to increase as a result of these management strategies, despite the importance of the park and its protections to these birds on their southward migration in the fall. To understand how disturbance and attempts to mitigate it affected plover demography, we examined Piping Plover population dynamics, brood movement, and migration in North Carolina from 2015–2017. We monitored 46 nests and 19 broods, and we used a logistic exposure nest survival model and Cormack-Jolly-Seber model to estimate reproductive success. We uniquely banded 77 adults and 49 chicks to understand annual survival and fidelity rates using a live encounter mark-recapture model. During the pre-fledge period, we observed movements of Piping Plover broods, and we gathered information on their environment that may affect their behavior. We recorded 191 brood locations, collected 132 focal chick behavior samples, and 113 potential disturbance environmental samples. We used multiple linear regression to evaluate several hypotheses regarding daily and hourly brood movement rates. We also conducted 22 migratory surveys after the breeding season in 2016 at an area in Cape Hatteras National Seashore thought to be used by large numbers of south-bound migrating Piping Plovers. We used integrated Jolly-Seber and binomial count models on resighting and count data to estimate stopover superpopulation and stopover duration of migrating birds based on their breeding region of origin. Annual survival of adults from North Carolina (x ̅ = 0.69, SE = 0.07) was not different from another population on Fire Island, New York (x ̅ = 0.73, SE = 0.04), but the North Carolina population annually had low reproductive success, primarily due to low rates of chick survival. As a result, the North Carolina population was predicted to decline during the study period (λ<1 each year). Historically this population has not met the estimated rate of reproductive output needed for a stationary population (1.07 chicks per pair, SE = 0.69); therefore, it is likely the population is sustained by immigration from an unknown source. Daily (x ̅ = 71.5m/24hr) and hourly (x ̅ = 183.3m/hr) brood movements each had considerable variation (Daily: SD = 70.6, range = 0.0–327.2m; Hourly: SD = 262.3, range = 0.2–1450.9m). Chicks did not appear to move in response to the environmental factors we examined. The rate of brood movement suggests regular daylight monitoring is necessary to adequately protect unfledged broods from anthropogenic disturbance under current management methods. We found that 569 Piping Plovers (95% CI: 502–651), nearly 15% of the estimated Atlantic Coast population, stopped at a single area in Cape Hatteras National Seashore, North Carolina during fall migration. Birds stayed an average 4–7 weeks, depending on the breeding region from which they migrated, and they primarily used a relatively new protected area. These findings suggest that North Carolina is an important area for Piping Plover ecology during multiple stages of their annual cycle.

Browsing by Author "Catlin, Daniel H."

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