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Understanding the environmental mechanisms that govern population change is a fundamental objective in ecology. Although the determination of how top-down and bottom-up drivers affect demography is important, it is often equally critical to understand the extent to which, environmental conditions that underpin these drivers fluctuate across time. For example, associations between climate and both food availability and predation risk may suggest the presence of trophic interactions that may influence inferences made from patterns in ecological data. Analytical tools have been developed to account for these correlations, while providing opportunities to ask novel questions regarding how populations change across space and time. Here, we combine two modeling disciplines-path analysis and mark-recapture-recovery models-to explore whether shifts in sea-surface temperatures (SSTs) influenced top-down (entanglement in fishing equipment) or bottom-up (forage fish production) population constraints over 60 years, and the extent to which these covarying processes shaped the survival of a long-lived seabird, the Royal tern. We found that hemispheric trends in SST were associated with variation in the amount of fish harvested along the Atlantic coast of North America and in the Caribbean, whereas reductions in forage fish production were mostly driven by shifts in the amount of fish harvested by commercial fisheries throughout the North Atlantic the year prior. Although the indirect (i.e., stock depletion) and direct (i.e., entanglement) impacts of commercial fishing on Royal tern mortality has declined over the last 60 years, increased SSTs during this time period has resulted in a comparable increase in mortality risk, which disproportionately impacted the survival of the youngest age-classes of Royal terns. Given climate projections for the North Atlantic, our results indicate that threats to Royal tern population persistence in the Mid-Atlantic will most likely be driven by failures to recruit juveniles into the breeding population.

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., While the connection between species and their habitats is broadly accepted, the connections between habitat and overall fitness often are less well understood. We compared habitat selection of piping plovers and least terns on the Missouri River (2012–2014) to examine the consequences of those choices on nest and chick survival. Our results suggest that early selection decisions were adaptive, but that relatively high site fidelity and habitat degradation led to reduced benefit over time.

The estimation of abundance is fundamental to ecology and conservation but often is difficult or impossible to accomplish reliably. Recent improvements in wildlife cameras and ecological modelling have allowed for improved accuracy in estimates of abundance. In this study, we paired nest captures and high‐definition nest video camera monitoring with modelling for a novel approach to estimate survival and abundance of threatened Piping Plovers Charadrius melodus breeding on Missouri River sandbars. From 2005 to 2014, we captured individuals on nests and uniquely marked them and recaptured previously marked individuals. In 2015–2017, we resighted marked individuals using small, high‐definition video cameras deployed at nests, and counted the number of marked and unmarked breeding individuals associated with nests. We estimated apparent survival and derived estimates of the abundance of breeding individuals and population growth each year using a state‐space Jolly–Seber superpopulation model with the addition of a binomial band ratio model for data collected using nest video cameras. Apparent survival averaged 0.73 ± 0.03 (mean ± sd) throughout the study. The number of breeding individuals varied, with the population increasing from 2012 to 2017 following a major habitat creation event. This study provides one of the few examples of camera data being used to produce demographic parameter and abundance estimates for an avian species. The camera and modelling methods described in this study may be applicable to other avian species in which some portion of the breeding population is uniquely marked.

The impact of habitat loss on shorebirds may be exacerbated by disturbance from human recreational use, which further reduces the amount of coastal habitat that is functionally available. This can have consequences for the condition of individual birds or for population processes, both of which should be considered in strategies to reduce conflict between shorebirds and recreational users of coastal habitat. Our objectives were to determine the associations between human recreational use, coastal habitat modifications, and Piping Plover (Charadrius melodus) body condition and demography. We monitored banded Piping Plovers throughout their annual cycle to assess variation in body condition, true survival, and site fidelity related to disturbance regimes in 8 geographically proximate, nonbreeding areas along the southeastern Atlantic Coast of North America from 2012 to 2016. Piping Plovers in disturbed sites were 7% lighter than those in less disturbed sites. Additionally, true annual survival was ...

On the Missouri River, the federally endangered interior population of Least Terns (Sternula antillarum) historically nested on sandbars created by sediment deposited during high flows. The Missouri River has been dammed and regulated, however, resulting in decreased flooding and sediment deposition and thus decreased sandbar habitat. In 2011, unusually high water releases created extensive sandbar habitat on the Gavins Point Reach of the Missouri River, and from 2012 to 2014 we examined the post-flood demography of Least Terns. We monitored 382 nests, uniquely marked 672 chicks, and attempted to recapture chicks every 3–4 d until fledging (∼18 d). Daily nest survival was high (0.99 [SE 0.002]), resulting in high mean nest success (0.87 [0.03]). Nest success was highest in 2012 and declined slightly each year. Daily chick survival was 0.96 (0.01), resulting in a mean survival to fledge of 0.44 (0.08). Daily chick survival did not vary by year or by age of chicks but was negatively correlated to h...

— Habitat quality can have a profound effect on the condition and fitness of individual birds and on population demography. We investigated the effects of habitat metrics (invertebrate abundance and habitat type) on the condition (egg mass, adult mass, pre-fledged chick growth rates) of Piping Plovers (Charadrius melodus) nesting on Missouri River sandbars from 2005–2014. The amount of breeding habitat for Piping Plovers was variable throughout our study with more habitat available after flooding occurred in 2011. In addition, increased demographic rates (e.g., reproductive output, hatch year survival, and population growth) were observed in the post-flood period. We hypothesized that the condition of individuals would be related to habitat quality and that increased demographic rates observed on the Missouri River sandbars throughout the post-flood period would, at least in part, be related to increased condition. Egg mass, pre-fledged chick growth rates, and invertebrate prey abundance had simi...

Even in the presence of environmental safeguards, catastrophic accidents related to anthropogenic activities occur that can result in both immediate and chronic impacts on local biota. However, due to the unplanned nature of catastrophes, studies aimed to identify the effects of these accidents on an ecosystem and its inhabitants often have imperfect study designs that are reactive rather than proactive, resulting in methodological and analytical challenges. On 20 April 2010, following an explosion on the Deepwater Horizon oil rig, a well blowout occurred on the seafloor approximately 80 km off the Louisiana coast in the Gulf of Mexico. This blowout resulted in the largest marine oil spill in United States history, which impacted critical migratory stopover and overwintering habitat for many seabird and shorebird species, including species of high conservation concern such as the piping plover ( Charadrius melodus ). Here, we assessed the potential longer-term demographic impacts of the Deepwater Horizon oil spill on piping plovers in a capture-mark-recapture framework. We examined whether a series of demographic processes, including probabilities of remaining at a specific wintering site, over-winter and annual apparent survival, winter stopover duration, and abundance varied among oiled and unoiled habitats. We found that the perceived amount of oiling on land, in water, and on individual birds, as well as numerous demographic processes, were spatially or temporally variable. However, we found little support that piping plover demography was negatively influenced by the magnitude of oil observed at an impacted area, or that demographic rates substantially varied between reference and oil impacted areas. Nor did we find that piping plovers that were observed to be oiled had lower survival probabilities following the DWH oil spill relative to non-oiled individuals from the same winter population. Although we did not find that the Deepwater Horizon oil spill substantially influenced piping plovers, our methods provide an analytical framework to more appropriately address both the near or long-term impacts of an anthropogenic disturbance on a species.

Juvenile prospecting, or exploratory behavior for gleaning information about areas or events, can have profound effects on the selection of future breeding habitat, particularly for birds with high site fidelity whose initial choice of breeding habitat could represent a lifetime investment in fitness. We present data from a 10-yr study of Piping Plovers (Charadrius melodus) on the Missouri River, USA, to determine whether postfledging, hatch-year (HY) prospecting movements inform second-year (SY) nest site choices. First, we compared the home ranges of HY and adult (after-hatch-year; AHY) plovers to investigate whether differences in habitat use existed between HY and AHY plovers. Second, we evaluated the effects of prospecting, nest density, reproductive success, and nesting and foraging habitat availability on SY plover nest site selection. Lastly, we evaluated the potential reproductive benefits of nesting in prospected areas by comparing the nest success and fledging success of SY plovers tha...

Species listed under the U.S. Endangered Species Act are required to meet stated recovery goals for delisting. These goals often are developed early in the species’ conservation history and may need to be updated or refined as new information becomes available. The Atlantic Coast Piping Plover (Charadrius melodus), which was listed more than 30 yr ago, has not met recovery goals through much of its range. Initial recovery goals included maintaining a reproductive output of 1.5 fledged chicks per pair for 5 yr. This goal was based on modelling that assumed equal survival rates for adults throughout the range, but recent studies suggest that demographic rates may vary with latitude. To investigate latitudinal variation, we developed demographic and population growth estimates for 2 breeding populations of Piping Plovers on the U.S. Atlantic Coast on Fire Island, New York (40.7°N), and on the Outer Banks of North Carolina (35.3°N) in 2013–2017. Breeding success (nest success and pre-fledge chick survival) varied annually but was lower in North Carolina than New York. Average adult true survival in New York (x̅ = 0.73, SE = 0.04) was similar to average survival in North Carolina (x̅ = 0.69, SE = 0.07). Annual post-fledging survival for both sites, however, was variable and often higher than had been previously reported for Atlantic Coast Piping Plovers (0.43–0.66 for New York; 0.31 and 1.0 for North Carolina). While the estimated reproductive output needed for a stationary population for both sites was similar (1.10 chicks per pair for New York, 95% CI: 0.83–1.41; 1.08 for North Carolina, 95% CI: 0.67–1.59), only the New York population achieved or exceeded these values during our study. Our findings suggest that understanding annual and latitudinal demographic variability would be helpful in refining recovery goals.

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. Funding was provided by the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service, and Virginia Tech.

Piping Plovers (Charadrius melodus) are primarily monogamous birds that usually raise only one brood per season, but rare instances of double brooding have been documented. Piping Plovers breeding in the northern Great Plains, USA were studied in two locations: the Missouri River near the Gavins Point Dam (2005– 2013) and the lower Platte River (2008–2013). There were 25 confirmed instances of double brooding on the Missouri River across the 9-year duration of the study. There were no instances of double brooding observed locally on the lower Platte River. However, in 2013, two female Piping Plovers successfully hatched eggs and fledged chicks from nests on the lower Platte River and later were observed nesting for a second time on the Missouri River. Factors predicted to increase the frequency of double brooding are: early nest initiation, male biased sex ratio, age of breeding adults, and decreased nesting density. Our results indicate density is an important factor that accounts for some of t...

Each breeding season, seasonally monogamous birds can divorce or reunite with their previous year's mate, assuming both partners survive and return. We tested a suite of variables related to mate choice and site choice to determine which of 4 prominent mate fidelity hypotheses (better [mate] option, habitat mediated, musical chairs, and bet-hedging) best explained the interyear reunion rate and breeding dispersal of a seasonally monogamous shorebird, Piping Plover (Charadrius melodus), nesting on dynamic sandbars on the Missouri River, USA, 2005–2012. Of 252 pairs in which both members returned to the breeding grounds the following year, only 20% reunited. Pairs with an early-arriving male had the highest mate fidelity. Reunited pairs returned to previous nest sites (median breeding dispersal = 39 m), and divorced and widowed birds tended to move farther (median = 229 m and 193 m, respectively). Overall, site fidelity was higher in males than females. Previous reproductive success of a pair did n...

The goal of many animal conservation efforts is to improve short-term demography, but there is growing interest in the potential for producing more fit individuals, resulting in long-lasting demographic impacts. The environments that animals experience prior to independence from their parents can have profound, life-long effects on individual fitness and population demography that managers can potentially exploit. Environmental variables can affect fitness directly through early mortality, delayed maturity, reduced probability of recruitment, decreased fecundity, or a combination of these factors. We studied the imperiled piping plover (Charadrius melodus) nesting on the Missouri River to determine if body condition affected their long-term survival, and, if so, whether these factors could be used to improve conservation and management. We captured and measured adult and hatchling piping plovers during the breeding season (April–August, 2005–2012) to obtain measures of condition (mass, wing-chord length, culmen length). We assessed the effect of environmental variables on plover growth, and the effect of chick condition at fledging on subsequent survival as an adult. Plover chicks grew faster and achieved larger body size if they hatched earlier in the season, were exposed to lower density, and were hatched in higher quality habitat compared to other chicks. Plovers that were heavier at fledging had a higher survival rate (as much as 9%) than lighter plovers during their first year as well as in subsequent years, which could make a significant impact on population viability and an individual’s lifetime fitness. Where the factors that affect development are manageable, they offer an opportunity for conservation to capitalize on these long-term effects. For example, habitat creation, restoration, and protection projects should ensure that adequate food resources are available or created not only to maximize reproductive output, but also to improve the condition of offspring where possible.

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. Nebraska Environmental Trust Nebraska State Wildlife Grant Program Nebraska Wildlife Conservation Fund U.S. Army Corps of Engineers U.S. Fish and Wildlife Service (USFWS) USFWS North Atlantic Landscape Conservation Cooperative Virginia Tech Funding was provided by the Nebraska Environmental Trust, the Nebraska State Wildlife Grant Program, the Nebraska Wildlife Conservation Fund, the U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service (USFWS), the USFWS North Atlantic Landscape Conservation Cooperative, and Virginia Tech. We thank C. Aron, K. Brennan, R. Cobb, K. Crane, E. Dowd-Stukel, C. Huber, K. Kreil, C. Kruse, G. Pavelka, G. Wagner, W. Werkmeister, S. Wilson, L. Yager, and cooperators from the National Park Service, U.S. Fish and Wildlife Service, South Dakota Department of Game, Fish, and Parks, Nebraska Game and Parks Commission, and the Missouri River Institute for support throughout the project. We would like to thank sand and gravel mining companies and lakeshore housing development communities for access to property. We acknowledge the tireless efforts of our many technicians from 2005 to 2013. We also thank five anonymous reviewers, T. Simmons, and C. McGowan (USGS) for their comments on earlier drafts of this manuscript. This work was conducted under Institutional Animal Care and Use Committee permits 877 and 14-003, and U.S. Fish and Wildlife Service Threatened and Endangered Species Permits TE070027-0 and TE103272-3. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Evaluating the possible effects of intensive research on species being studied and on the results of studies is important for both ethical and scientific reasons. We captured, banded, recaptured, and measured prefledged Piping Plover (Charadrius melodus) chicks during the 2010 breeding season at Lewis and Clark Lake on the Missouri River in South Dakota. We evaluated the potential for increased mortality related to frequent handling of chicks with an experiment that compared the survival of chicks handled a single time for banding (N = 48) to chicks handled repeatedly from hatch to fledge (N = 50). Estimates of daily survival rate (ϕ) for chicks in the two treatments did not differ (ϕsingle-capture = 0.984 ± 0.006, ϕmultiple-capture = 0.985 ± 0.006). Similar to previous studies, we found little evidence of increased prefledge mortality associated with frequent handling of Piping Plover chicks. However, because the effects of frequent handling of shorebird chicks may vary among species and other factors such as habitat quality (e.g., food availability), we suggest that, where possible, researchers include experiments similar to ours to evaluate possible research impacts, especially when studying threatened and endangered species. RESUMEN Efecto de la frecuencia de captura en la sobrevivencia de pichones de Charadrius melodus El evaluar los posibles efectos de investigaciones intensivas, en las especies estudiadas, y los resultados de dichos trabajos son muy importantes por razones tanto cientificas como eticas. Capturamos, medimos y anillamos pre-volantones de Charadrius melodius, durante la temporada reproductiva, en el lago Lewis y Clark del rio Missouri en Dakota del Sur. Evaluamos el potencial de incrementar la mortalidad, relacionada con la frecuencia de manipular pichones, en un experimento que comparo, la sobrevivencia de pichones que fueron capturados una sola vez, para ser anillados (N = 48), con pichones repetidamente manipulados desde que nacieron hasta que volaron (N = 50). No se encontro diferencia en los estimados de la tasa diaria de sobrevivencia (ϕ) para las dos categorias (ϕcaptura simple = 0.984 ± 0.006, ϕcaptura multiple = 0.985 ± 0.006). Al igual que en otros estudios, encontramos muy poca evidencia entre la frecuencia de manipulacion e incremento en la mortalidad en estas aves. Sin embargo, debido a que el efecto de la manipulacion de playeros, pudiera variar entre especies y otros factores como la calidad del habitat (ej. disponibilidad de alimento), sugerimos, cuando sea posible, que los investigadores incluyan experimentos similares a los nuestros, para evaluar el posible impacto del estudios, particularmente cuando se este trabajando con especies en peligro de extincion.

Snowy Plovers (Charadrius nivosus) have recently expanded their breeding range into the northern Great Plains. We studied the nest success and survival of Snowy Plovers nesting on the Missouri River between Nebraska and South Dakota from 2008–2011 by monitoring nests every 2–3 days and banding adults and chicks. We used the logistic exposure method to estimate nest success and capture-recapture models in Program MARK to estimate adult and chick survival. Snowy Plover nests had a daily survival rate of 0.978 ± 0.008, and annual adult apparent survival rate was 0.588 ± 0.119. In addition, we estimated that 0.63 ± 0.12 of Snowy Plover chicks survived to fledging (30 days) during our study. The results for Snowy Plovers were similar to results for Piping Plovers (Charadrius melodus) breeding in the same area, and the demographic rates in this study were similar to those reported from established portions of the species' range. Recent breeding range expansion may be due to spring flooding on establis...

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. Electronic supplementary material The online version of this article (doi:10.1186/s40462-016-0072-y) contains supplementary material, which is available to authorized users.