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Demography study sites at which mark-recapture data for saltmarsh sparrows were collected. Number of unique individuals captured at each study site is given for saltmarsh sparrow (SALS) and saltmarsh x Nelson's sparrow hybrids (HYBRID).
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Demographic rates are rarely estimated over an entire species range, limiting empirical tests of ecological patterns and theories, and raising questions about the representativeness of studies that use data from a small part of a range. The uncertainty that results from using demographic rates from just a few sites is especially pervasive in popula...
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Context 1
... estimate annual survival, we conducted standardized mist-netting at 21 plots in major marsh complexes (referred to as 'sites' below) from New Jersey to Maine, USA (Table 1). We surveyed most plots in 2011-2014; see Table 1 for spe- Figure 1. ...Context 2
... estimate annual survival, we conducted standardized mist-netting at 21 plots in major marsh complexes (referred to as 'sites' below) from New Jersey to Maine, USA (Table 1). We surveyed most plots in 2011-2014; see Table 1 for spe- Figure 1. The distribution of demographic sampling plots (black circles on map; tick marks along inset histogram). ...Context 3
... magnitude of this variation was moderate, however, and the credible intervals for site-level estimates were largely overlapping (Fig. 4). Survival rates were highest in Maine, USA (Jones Creek; Table 1), and had 95% credible intervals that were non-overlapping with the sites that had the lowest survival rates: the three southern-most sites (New Jersey, USA), as well as five sites in the core of the saltmarsh sparrow range (Long Island Sound, USA; effect of plot size on capture rate was negative (-0.67; -1.0 to -0.31), suggesting that we were able to more completely sample smaller plots. The parameter estimate for the effect of sex (male 1) was positive for survival, but overlapped zero (0.21; -0.075 to 0.48), and negative for capture rate (-0.79; -1.2 to -0.37), suggesting that males had lower capture rates than females. ...Citations
... However, point counts do not assess whether females specifically are present or whether they are nesting successfully, which is problematic given the unusual life history of the Saltmarsh Sparrow (females are responsible for all reproductive effort after mating). Prior studies have shown that abundance measured by point counts cannot measure the quality of Saltmarsh Sparrow breeding habitat (e.g., Field et al. 2018), making them inappropriate for understanding sparrow response to restoration in occupied areas. Consequently, it was critical to develop a method to directly monitor reproductive success that could be implemented more rapidly than conventional Saltmarsh Sparrow demographic monitoring. ...
... Fourth priority: Monitoring at reference sites Reference sites are different from control areas in that they represent ideal conditions local to the restoration area of impact. While data collection at reference sites is helpful to add local context, data collection at these sites are lower priority than before implementation or at control areas because significant data collection has already occurred at high-quality sites for Saltmarsh Sparrows and other tidal marsh obligate species (e.g., Field et al. 2017, Ruskin et al. 2018. ...
This document was developed to encourage monitoring for Saltmarsh Sparrows and other tidal marsh sparrows at salt marsh restoration sites from Maine to Virginia. We provide guidance for effective Saltmarsh Sparrow monitoring for salt marsh restoration projects which includes considerations for monitoring implementation, including methods, sampling/design, timing, cost estimates, and strategies for prioritizing work when resources are limited. This document will be updated regularly as we learn more about this system and the effects of restoration on tidal marsh birds. https://www.acjv.org/documents/monitoring_guidance_SALS.pdf
... has conducted intensive demographic sampling at 40 tidal marsh study plots from Maine to Virginia, ranging from 6 to 21 plots per year. At each intensive demographic plot, we used mist-netting to capture sparrows for survival estimation (Field et al., 2018) and nest searching and monitoring to estimate reproductive success (Ruskin, Etterson, Hodgman, Borowske, Cohen, Elphick, Field, Kern, et al., 2017). -2022(n = 91 sites, ME to VA, Sanchez Jr., 2023. ...
Saltmarsh (Ammospiza caudacuta) and Nelson's (A. nelsoni) sparrows are sister taxa that breed in tidal marshes along the coast of the Northeastern United States and Canada. The Saltmarsh Sparrow breeds from mid-coast Maine south to Virginia, while the Acadian Nelson's Sparrow breeds from the Canadian maritime provinces south to northern Massachusetts. Here, we present three extralimital observations of breeding Saltmarsh (n = 2) and Nelson's (n = 1) sparrows. In 2021 and 2022, we observed Saltmarsh Sparrow females attending nests at Mendall Marsh, ME, and Milbridge, ME, respectively, approximately 60 and 110 km beyond the documented northern extent of the Saltmarsh Sparrow breeding range. In 2022, we observed a breeding-condition male Nelson's sparrow singing in the upriver portion of a marsh on Cape Cod, Massachusetts, approximately 115 km beyond the previously documented southern extent of the Nelson's Sparrow breeding range. We confirmed morphological species identification using a panel of microsatellite DNA loci. Due to both the well-documented population declines of these species in the region and the intensity of sampling effort undertaken in recent years, we suggest that these observations likely are not indicative of range expansion. However, they do indicate that these 2 taxa have the capacity to use and successfully reproduce in marshes well beyond their established breeding limits. Our findings provide novel insight into the potential for these taxa to occur and successfully breed outside their documented breeding ranges. Given increased interest in their conservation, these results support the idea that management actions aimed at creating or maintaining nesting habitat across both species ranges could benefit both taxa.
... A portion of the samples analyzed in this study were collected in 2007-2008 for a study evaluating fine-scale genetic structure in Saltmarsh Sparrows in the northern portion of their range (Walsh et al. 2012) and in 2012-2013 while studying patterns of introgression between Saltmarsh Sparrows and their sister species, the Nelson's Sparrow . The majority of the remaining samples were collected during a 3-yr (2011-2013) study investigating survival and fecundity of Saltmarsh Sparrows (Ruskin et al. 2017a, Field et al. 2018. We captured adult individuals using mist nets and banded each individual with uniquely numbered aluminum USGS bands. ...
Determining factors that shape a species’ population genetic structure is beneficial for identifying effective conservation practices. We assessed population structure and genetic diversity for Saltmarsh Sparrow (Ammospiza caudacuta), an imperiled tidal marsh specialist, using 13 microsatellite markers and 964 individuals sampled from 24 marshes across the breeding range. We show that Saltmarsh Sparrow populations are structured regionally by isolation-by-distance, with gene flow occurring among marshes within ~110–135 km of one another. Isolation-by-resistance and isolation-by-environment also shape genetic variation; several habitat and landscape features are associated with genetic diversity and genetic divergence among populations. Human development in the surrounding landscape isolates breeding marshes, reducing genetic diversity and increasing population genetic divergence, while surrounding marshland and patch habitat quality (proportion high marsh and sea-level-rise trend) have the opposite effect. The distance of the breeding marsh to the Atlantic Ocean also influences genetic variation, with marshes farther inland being more divergent than coastal marshes. In northern marshes, hybridization with Nelson’s Sparrow (A. nelsoni) strongly influences Saltmarsh Sparrow genetic variation, by increasing genetic diversity in the population; this has a concomitant effect of increasing genetic differentiation of marshes with high levels of introgression. From a conservation perspective, we found that the majority of population clusters have low effective population sizes, suggesting a lack of resiliency. To conserve the representative breadth of genetic and ecological diversity and to ensure redundancy of populations, it will be important to protect a diversity of marsh types across the latitudinal gradient of the species range, including multiple inland, coastal and urban populations, which we have shown to exhibit signals of genetic differentiation. It will also require maintaining connectivity at a regional level, by promoting high marsh habitat at the scale of gene flow (~130 km), while also ensuring “stepping stone” populations across the range.
... This result may be because of the taller than average vegetation present in NYC that likely aided in concealing higher nests. declines in this species to the point of extinction by mid-century (Field et al. 2017(Field et al. , 2018. Vegetation height may therefore be a valuable consideration in addition to marsh zone when planning restoration, especially at smaller, urbanized, or otherwise degraded sites. ...
Understanding habitat selection and its fitness consequences in remnant populations of birds in fragmented and urbanized habitat may provide guidance to land managers for imperiled species conservation. We studied Saltmarsh Sparrow, Ammospiza caudacuta, and Seaside Sparrow, A. maritima, nest site selection and nest survival at five sites in New York City (NYC) and one site on western Long Island, New York in 2012 and 2013. We compared marsh vegetation and nest structure characteristics between our study sites and other studied sites for these species in the Northeastern United States. Saltmarsh Sparrows in NYC selected nest sites with the tall form of low-elevation marsh grass (at two sites this was above the proportion available), which is atypical for this species, and Seaside Sparrows selected an upland shrub species at one site, possibly to compensate for a lack of tall low-elevation marsh grasses. Daily nest survival at New York sites increased with nest height above the ground for both species, contrary to previous studies for Saltmarsh Sparrows in intact habitat. Mean nest height for both species was found to be taller in NYC than at other studied locations, and NYC sites may have had taller than average vegetation available, indicating that these sparrows may be able to adapt to some changing marsh characteristics. The difference in nest site selection observed in NYC populations from published studies did not appear to have a cost to nest survival in at least one year. Although high-elevation marsh is the optimal habitat restoration target for Saltmarsh Sparrows, it may be difficult to create in small, urbanized marshes, and our results suggest that other approaches may be successful. A mix of substrates and vegetation heights may allow sparrows to exhibit variation in nest site selection and promote nest survival in the face of changing limiting factors.
... The saltmarsh sparrow is considered "globally endangered" by the International Union for Conservation of Nature in response to rapid population declines (BirdLife International 2020), decreasing at 9% per year with over 70% of the global population lost since the 1990s (Correll et al., 2017;Roberts et al., 2019). Sea-level rise and increased tidal flooding risk are the major drivers of population loss for this species, as approximately 60% of all nest failures occur due to flooding (Shriver et al., 2007;Gjerdrum et al., 2008), and are projected to cause extinction by the middle of the 21st century (Field et al., 2017(Field et al., , 2018Roberts et al., 2019). Because salt marshes and coastal estuaries are often impacted by polluted urban runoff (Schwarzbach et al., 2006), heavy metal contamination may present additional challenges to sparrow reproductive success and survival. ...
... Sea-level rise is the principal driver of tidal marsh sparrow population declines (Shriver et al., 2007;Gjerdrum et al., 2008), and could cause the extinction of the saltmarsh sparrow by mid-century (Correll et al., 2017;Field et al., 2017Field et al., , 2018Roberts et al., 2019). Concurrently, some tidal marsh sparrows may face challenges coming from industrial practices in terrestrial systems that expose them and other wildlife to potentially dangerous levels of Hg contamination. ...
Saltmarsh sparrows (Ammospiza caudacuta) and seaside sparrows (A. maritima) are species of conservation concern primarily due to global sea-level rise and habitat degradation. Environmental mercury (Hg) contamination may present additional threats to their reproductive success and survival. To assess site-specific total mercury (THg) exposure and identify environmental correlates of THg detection, we sampled blood from adult male saltmarsh and seaside sparrows at 27 sites between Maine and Virginia, USA. The mean THg concentration (±1 SD) throughout the entire sampling range was 0.531 ± 0.287 µg/g wet weight (ww) for saltmarsh sparrows and 0.442 ± 0.316 µg/g ww for seaside sparrows. Individual THg concentrations ranged from 0.135–1.420 µg/g ww for saltmarsh sparrows and 0.153–1.530 µg/g ww for seaside sparrows. Model averaging from a suite of linear mixed models showed that saltmarsh sparrows averaged 20.1% higher blood THg concentrations than seaside sparrows, potentially due to differences in diet or foraging behavior. We found no evidence for a relationship between sparrow THg concentrations and land cover surrounding sampled marshes or average precipitation-based Hg deposition. Overall, our results suggest considerable, unexplained variation in tidal marsh sparrow blood THg concentrations over their co-occurring breeding ranges.
... These populations are of particular conservation interest because they largely or entirely breed in tidal marshes. Population trajectories vary from annual declines of 9% or more and projected extinction within the next few decades, to current stability (Correll et al. 2017;Field et al. 2017aField et al. , b, 2018Roberts et al. 2019). Population estimates for each of the five species were derived from a comprehensive regional marsh bird survey in 2011 and 2012 . ...
Sea-level rise (SLR) is projected to increase dramatically with profound effects on tidal marshes, yet uncertainty stemming from underlying climate change scenarios, model specifications, and temporal scale is a major hurdle to conservation planning. We compared likely effects of SLR for 2030 and 2050 under static inundation and dynamic response model predictions for the northeastern USA, where tidal marshes experience elevated rates of SLR compared to global averages. Static inundation and dynamic response models of SLR, which differ in how they incorporate uncertainty associated with local processes and biophysical feedbacks, have historically been applied at different scales, and generally differ in spatial and temporal predictions of marsh vulnerability. We used population estimates for five tidal marsh bird species of conservation concern to predict patterns of population change for each SLR model and examined how uncertainty affects planning decisions for these species. Static inundation and dynamic response models differed markedly in their predictions for 2030, yet both models predicted with reasonable certainty that only 10–15% of tidal marsh in northeastern USA is likely (> 66% chance; as defined by the IPCC) to remain by 2050. Most (85–90%) of the marsh is predicted to be as likely as not (33–66% chance) to disappear, representing high potential for the loss of habitat for > 85% of current populations of four of the five bird species. We propose a planning approach using guidelines established by the IPCC to categorize uncertainty associated with marsh loss due to SLR and apply it to prioritize key sites for preservation.
... Survey window, temperature, and wind speed were positively related to detection probability, while hours after midnight was negatively related with Saltmarsh Sparrow detection probability ( Table 2). The quadratic effect of latitude on abundance in the top model predicts that sparrow abundance peaks at southcentral latitudes (Table 2, Figure 1), similar to the findings of previous studies (Wiest et al. 2016;Field et al. 2018). We also found support for a positive association between the percentage of high marsh at a survey location and sparrow abundance ( Table 2). ...
The Saltmarsh Sparrow (Ammospiza caudacuta) is a tidal marsh bird facing rapid population decline throughout its range, largely caused by degradation and loss of breeding habitat. Thus, there is a need to preserve tidal marshes in the northeastern United States, but to do so requires an understanding of the habitat features that support robust populations. Previous studies have shown Saltmarsh Sparrow abundance increases with marsh size, but in similar bird species, area sensitivity is more directly linked to edge avoidance. Whether additional landscape features affect the abundance of Saltmarsh Sparrows is unknown. We explored how the height of objects on the horizon, an index of habitat openness, affected the abundance of Saltmarsh Sparrows. Our primary goal was to determine whether the angle to the highest point on the horizon (“angle to maximum horizon”) predicted abundance better than marsh area or distance to the marsh edge. We used N-mixture models to evaluate the combination of spatial factors that best predicted Saltmarsh Sparrow abundance while also accounting for survey-level variables that could influence detection probability. We found that the interaction between distance to edge and angle to maximum horizon best predicted abundance. Taller objects on the horizon were negatively correlated with bird abundance, and this effect was strongest within 50 m of the marsh edge. When we considered the predictive powers of patch area, distance to edge, and angle to maximum horizon individually, angle to maximum horizon was the best single predictor. We found the highest abundance of Saltmarsh Sparrows at point locations where the angle to maximum horizon was 0.0°, and at angles greater than 12° the predicted abundance fell below 1 bird per survey point. We propose that managers should prioritize marsh openness and experimentally test the effect of marsh edge manipulations when making conservation decisions for this rapidly declining species.
... The ecological context and disturbance regime for our application was populations that (1) are not dispersal limited and do not show strong spatial trends in vital rates (e.g. Field et al. 2018), but do show strong annual variation (e.g. Bayard & Elphick 2011) and (2) face large disturbances primarily from Atlantic hurricanes, which are likely strengthening but not becoming more frequent (Holland & Bruy ere 2014). ...
Changes in the frequency and severity of extreme weather may introduce new threats to species that are already under stress from gradual habitat loss and climate change. We provide a probabilistic framework that quantifies potential threats by applying concepts from ecological resilience to single populations. Our approach uses computation to compare disturbance–impacted projections to a population's normal range of variation, quantifying the full range of potential impacts. We illustrate this framework with projection models for coastal birds, which are commonly depicted as vulnerable to disturbances, especially hurricanes and oil spills. We found that populations of coastal specialists are resilient to extreme disturbances, with high resistance to the effects of short‐term reductions in vital rates and recovery within 20 years. Applying the general framework presented here across disturbance‐prone species and ecosystems would improve understanding of population resilience and generate specific projections of resilience that are needed for effective conservation planning.
... Both species are of management interest, but for distinct reasons. The Saltmarsh Sparrow faces near-term extinction (Field et al. 2017(Field et al. , 2018, whereas the Clapper Rail is a more abundant, but declining, popular game species (Correll et al. 2017). Together, they represent the full range of marsh habitat and could bring together different stakeholders needed to achieve conservation success at regional scales (e.g., Powell et al. 2017). ...
Insufficient time and funding remain obstacles to collecting data across broad spatial scales on the fine-scale distribution of multiple species, their life histories, and interactions with other species and the environment. This often necessitates the use of focal species to inform conservation and management decisions. We used the systematic conservation-planning software Marxan to assess quantitatively whether a focal species can aid in conservation and management of tidal marsh birds. Using a metric of relative cost in the region and current protected areas, we identified priority areas for conservation of 5 specialist taxa—Clapper Rail (Rallus crepitans), Eastern Willet (Tringa semipalmata semipalmata), Acadian Nelson's Sparrow (Ammospiza nelsoni subvirgatus), Saltmarsh Sparrow (A. caudacuta), and Seaside Sparrow (A. maritima)—that nest primarily in tidal marshes in the northeastern United States. We compared the spatial prioritization of sites and cost-effectiveness of alternative protection scenarios that considered individual species, groups of species, and all species simultaneously to evaluate the appropriateness of a focal-species approach. Scenarios that prioritized areas for conservation based on single-species targets were poorly correlated across species. Scenarios based on Saltmarsh Sparrow conservation were most strongly related (rs = 0.759) to site prioritizations that considered all 5 tidal marsh specialists simultaneously. When comparing multispecies combinations to prioritizations based on the Saltmarsh Sparrow alone, the estimated costs, area of land protection, and number of individuals of each species protected were similar. These results suggest that no species is a good surrogate for another but that the Saltmarsh Sparrow may be a viable focal species for conservation planning to protect tidal marsh birds as a group. By evaluating protection scenarios for all species, we were able to identify areas where conservation is likely to have little or no effect, which could be as important for decision making as identifying the best sites.
... This plasticity, however, is likely insufficient in the face of sealevel rise, which reduces high marsh habitat and modifies tidal regimes that disrupt synchronous breeding of sparrows with the 28-day tidal cycle. The direct impacts of sea-level rise are predicted to reduce the reproductive success of saltmarsh sparrows (Bayard & Elphick, 2011), which have already declined at a rate of 9% annually from 1998 to 2012 (Correll et al., 2016), leaving the species vulnerable to extinction within the next 50 years (Field et al., 2016(Field et al., , 2017. The apparent adaptive capacity of saltmarsh sparrows, however, may enhance their ability to respond to management interventions targeted to mitigate nest flooding. ...
If individuals can perceive and manage risks, they may alter their behaviors based on prior experience. This expectation may apply to nest site selection of breeding birds, for which adaptive behavioral responses may enhance fitness. Birds that nest in tidal marshes have adapted to the challenges posed primarily by periodic, monthly tidal flooding and secondarily by predation. We investigated adaptive responses in nesting behavior of the saltmarsh sparrow (Ammospiza caudacutus), an obligate tidal‐marsh‐breeding bird, using 536 nests monitored across 5 years. Using linear mixed effects models, we tested whether nest characteristics differed among nests that were successful, depredated, or flooded, and we investigated whether females made changes in nest structure and placement according to outcome of their previous nesting attempt. Nest characteristics differed among females with different nest fates. Fledged and depredated nests were built higher in the vegetation and in higher elevation areas of the marsh than those that flooded. Successful nests had more canopy cover and were comprised of a lower proportion of high marsh vegetation (Spartina patens) than those that were flooded or depredated. Females with nests that failed due to flooding constructed subsequent nests higher in the vegetation and at higher elevation than those that were successful in their prior attempt, consistent with a response to previous experience. Eighty‐five percent of females renested within the average home range core area distance (77 m), indicating a high degree of nest placement fidelity. Females for which nests were depredated in their prior nesting attempt renested at a greater distance than females for which the previous nesting attempts were successful. Our findings suggest saltmarsh sparrows exhibit plasticity in nesting behavior, which may be important for balancing selective pressures in a dynamic environment. This plasticity, however, is insufficient to enable them to adapt to the increased flooding predicted with sea‐level rise. Perceiving risks and responding accordingly may be important to balance selective pressures in a dynamic environment. Tidal‐marsh‐nesting birds that are subject to competing risks of predation and flooding make changes to their nesting behavior based on their prior experience. Females that experienced nest flooding increased the height of their subsequent nests and renested in a higher elevation area of the marsh, thereby adopting behaviors that mitigate flooding, while those that were depredated renested lower in the vegetation, reducing visibility to predators. Females had high fidelity in their nest site locations, although those with failed nests had a tendency to renest a farther distance from their prior nest than those that with successful nests.
