Marsh Bird Species Research Articles

Water depth influences survival and predator-specific patterns of nest loss in three secretive marsh bird species.

Wetlands have become increasingly rare in the United States, negatively influencing wetland-dependent birds, and many remaining wetlands are intensively managed through seasonal dewatering mimicking historic flood pulses during spring and summer. However, water around nests may provide protection from terrestrial predators, and lowering water levels during the breeding season of wetland birds may increase predation risk and exacerbate marsh bird population declines. Understanding interactions between water depth, nesting marsh birds, and nest predators is critical to aid managers in developing a multi-species management approach in emergent wetlands. During the 2020 and 2021 breeding seasons, we examined nest survival of 148 marsh bird nests (American Coot, Fulica americana, n = 1; Common Gallinule, Gallinula galeata, n = 64; and Least Bittern; Ixobrychus exilis, n = 83) and installed cameras at 78 nests to identify predators at a large, restored floodplain wetland in Illinois where the primary management technique is seasonal water removal to stimulate germination of moist soil plants. We found nest predation of, and abandonment by, Least Bittern and Common Gallinule were related to shallower water, and early season, high volume dewatering. Least Bitterns nested more commonly along wetland edges and nests farther from the shore were more likely to survive. Similarly, we found mammalian depredation of nests and nest abandonment decreased when deeper water was present around nests. Alternatively, snake predation was observed earlier in the year prior to water removal from inundated emergent vegetation. Our results demonstrate water depth may be an important deterrent of nest predators, especially mammals, during the breeding season. Further, we recommend managers delay dewatering until after the nesting season at sites where management for conservation-priority marsh birds is a focus.

King Rail (Rallus elegans) presence in the Midwestern United States is predicted by local-scale factors and avian community.

The King Rail (Rallus elegans) is a wetland dependent species of conservation concern. Our objective was to gain a better understanding of the breeding habitat associations of King Rails in the Midwestern United States and the relationship of this species to other obligate marsh birds using occupancy and MaxEnt models. To collect data pertaining to occupancy, we placed trail cameras at 50 random points in coastal wetlands in the western Lake Erie basin where calls of King Rails were continuously broadcast at night. Data pertaining to other marsh bird species were collected via call-broadcast surveys and camera surveys at each sample point. For MaxEnt modeling, we obtained presence data for King Rails and other obligate marsh birds from eBird and habitat data from GIS databases. Trail cameras and call-broadcast surveys captured 10 detections of King Rails at nine sites, an 18% naive occupancy rate. King Rail occupancy was positively related to amount of interspersion, average water depth, and percent cover of emergent vegetation at local scales within a 5-m radius. Our MaxEnt models indicated that, at a broader scale, the presence of other rail species such as the Sora (Porzana carolina) may be more important for predicting King Rail presence than other marsh birds or coarse wetland categories such as "emergent vegetation." Our results could help wetland managers to predict where King Rails occur and to adapt management plans to incorporate King Rail conservation.

Marshbird response to herbicide control of cattail in northwestern Minnesota

AbstractWetlands provide essential habitat for a wide variety of wildlife species. In the once wetland‐rich Prairie Pothole Region and adjacent areas of central North America, many wetlands have been converted to agricultural production. Many remaining wetlands experience ecological change via the invasion and spread of non‐native plant species, such as non‐native narrowleaf (Typha angustifolia) and hybrid cattail (Typha x glauca), which spread aggressively and displace native vegetation, especially in large, impounded wetlands. Management of wetlands in these landscapes often includes broad‐scale herbicide application intended to break up mats of cattail and restore areas to more wildlife‐friendly conditions. Although restoration of wildlife habitat is a common goal of such management, marshbird response to invasive cattail control is poorly understood. To evaluate the effects of cattail management on wetland wildlife, we conducted standardized call‐broadcast surveys for 5 species of marshbirds at 9 study sites that included survey locations associated with areas treated with herbicide and paired areas not treated with herbicide in wetland impoundments in northwestern Minnesota, USA, using a before‐after, control‐impact study design. We surveyed American bitterns (Botaurus lentiginosus), least bitterns (Ixobrychus exilis), pied‐billed grebes (Podilymbus podiceps), soras (Porzana carolina), and Virginia rails (Rallus limicola) during the breeding season prior to herbicide application (late summer and early autumn of 2015) and during the 3 breeding seasons after herbicide application (2016–2018). We modeled species counts using a generalized linear mixed model with year‐by‐treatment interactions as fixed effects and site as a random effect. Before herbicide application, expected mean counts did not differ between treatment and control survey locations. Three years post‐treatment, we detected significant increases in expected mean counts at treatment compared to control survey locations for soras (t193 = −3.373, P = 0.020) and Virginia rails (t193 = −3.167, P = 0.037), and point estimates for all species except least bittern were higher at treatment survey locations. Overall, our results suggest that these marshbird species responded positively to herbicide control of invasive cattail and that breeding marshbirds in these and similar wetland systems may experience positive population response over a period of at least 3 years following treatment.

Secretive marsh bird occupancy across a spectrum of hydroelectric reservoir management in western montane Canada

AbstractDam construction projects have created opportunities for water security, targeted flood protection, and energy production but at the cost of increasing anthropogenic pressure on affected aquatic ecosystems. Wetland ecosystems are often among the most vulnerable, as underlying hydrological regimes influence overall wetland structure and function. Marsh bird species are wetland and riparian habitat specialists, many of which are experiencing population declines across North America. We examined how the alteration of hydrological regimes for generating hydroelectric power affected the occurrence of secretive marsh bird species in the western montane region of British Columbia, Canada. We established survey stations in wetlands across 2 regions, the West Kootenay and the Columbia Wetlands, sampling across a spectrum of hydrological regimes and other potentially relevant factors. At each station, we assessed wetland occupancy during the breeding season using broadcast‐callback surveys focused on 5 secretive marsh bird species: American bittern (Botaurus lentiginosus), American coot (Fulica americana), pied‐billed grebe (Podilymbus podiceps), sora (Porzana carolina), and Virginia rail (Rallus limicola). Additionally, we measured vegetation structure and the proximity and size of nearby water bodies for each survey station. We then used occupancy models to assess important correlates behind wetland occupancy for these marsh bird species, considering water management operations, regional differences, and local‐ and landscape‐level wetland characteristics. Secretive marsh bird species were more likely to occupy wetlands in areas with less frequently altered hydrological regimes. Occupancy models highlighted local‐ and landscape‐level characteristics as important correlates for wetland occupancy by marsh birds. Wetlands with frequently altered hydrological regimes had more open water cover and less tall vegetation present, conditions that were negatively associated with occupancy. Altered wetlands in this study were farther from the next nearest wetland, which was also negatively associated with occupancy. We suggest reservoir management is altering vegetation communities within these wetlands, indirectly promoting lower occupancy of secretive marsh bird species.

Abundance Estimates for Marsh Bird Species in the Columbia Wetlands, British Columbia, Canada

Abundance Estimates for Marsh Bird Species in the Columbia Wetlands, British Columbia, Canada

A high-quality de novo genome assembly for clapper rail (Rallus crepitans).

The clapper rail (Rallus crepitans), of the family Rallidae, is a secretive marsh bird species that is adapted for high salinity habitats. They are very similar in appearance to the closely related king rail (R. elegans), but while king rails are limited primarily to freshwater marshes, clapper rails are highly adapted to tolerate salt marshes. Both species can be found in brackish marshes where they freely hybridize, but the distribution of their respective habitats precludes the formation of a continuous hybrid zone and secondary contact can occur repeatedly. This system, thus, provides unique opportunities to investigate the underlying mechanisms driving their differential salinity tolerance as well as the maintenance of the species boundary between the 2 species. To facilitate these studies, we assembled a de novo reference genome assembly for a female clapper rail. Chicago and HiC libraries were prepared as input for the Dovetail HiRise pipeline to scaffold the genome. The pipeline, however, did not recover the Z chromosome so a custom script was used to assemble the Z chromosome. We generated a near chromosome level assembly with a total length of 994.8 Mb comprising 13,226 scaffolds. The assembly had a scaffold N50 was 82.7 Mb, L50 of four, and had a BUSCO completeness score of 92%. This assembly is among the most contiguous genomes among the species in the family Rallidae. It will serve as an important tool in future studies on avian salinity tolerance, interspecific hybridization, and speciation.

Using Breeding Bird Survey and eBird data to improve marsh bird monitoring abundance indices and trends

The elusive nature of many marsh-breeding birds presents a challenge for effective population monitoring. The Great Lakes Marsh Monitoring Program (GLMMP), delivered by Birds Canada, addressed these challenges by concentrating survey efforts in marsh bird habitats and by using survey protocols aimed at maximizing marsh bird detections. GLMMP data suggest that numerous marsh bird species are declining. Here we consider the value of other avian monitoring programs to support our understanding of marsh bird population trends. Our goal was to compare the GLMMP, North American Breeding Bird Survey (BBS), and eBird with each other and with a combined survey, by evaluating frequency of detection, annual indices of abundance, and trend estimates. Using 23 years (1997–2019) of GLMMP, BBS, and eBird data, we calculated annual indices of abundance and trends for each survey for 18 marsh-breeding species across southern Ontario, Canada. We found that the GLMMP had more frequent detections, greater counts, and/or more precise trends for 8 species that breed almost exclusively in marshes, whereas 10 species with more variable habitat preferences had more frequent detections, greater counts, and/or more precise trends based on eBird and/or BBS. We found that combining counts from the GLMMP, BBS, and eBird increased the precision around trend estimates for 11/18 (61%) species; however, trend estimates for combined data tended to be positively biased relative to GLMMP trends for species that also frequent non-marsh habitats. We, therefore, provide evidence that combining citizen science data from multiple sources could increase the power to detect changes in marsh-dependent bird populations. Integrated datasets thus provide a promising avenue for future marsh bird conservation and management.

King Rail ( Rallus elegans ) response to audio playback: implications for population estimation, monitoring methodology, and trapping approach

Conspecific audio can be broadcast to improve detection probability (detectability) of secretive marsh bird species for population monitoring purposes and as a lure to more effectively trap individuals. Our primary objective was to describe King Rail (<em>Rallus elegans</em>) detectability as a function of distance and so determine if the distance sampling assumption of perfect detectability immediately adjacent to survey points was violated during call-broadcast surveys. We also described what factors affected King Rail detectability during audio broadcast surveys, and how and when this species was detected, and compared effectiveness of various King Rail call recordings used during trapping attempts. To accomplish these objectives, we experimentalized trapping efforts, radio-tagged 12 King Rails, and conducted repeated call-broadcast surveys for each radio-tagged individual in Michigan and Ohio, USA during the 2020 and 2021 breeding seasons. We found that King Rail detectability during 81 surveys was 0.39, which violates the aforementioned distance sampling assumption and necessitates a correction factor. Detectability within survey segments varied among survey periods, though overall detectability remained relatively constant, even after call-broadcast surveys in our study area typically end (post-survey period: 15 June to 10 July), which indicates that King Rail monitoring could effectively continue later than currently occurs. We found that grunt calls resulted in more captures than kek calls and that a multi-call track was most effective at trapping King Rails. Our findings could improve King Rail population estimates and increase success during trapping efforts, and may inform similar efforts for other secretive marsh birds.

Using autonomous recording units to detect individual marsh birds in the Northern Gulf of Mexico.

Marsh birds are highly elusive and select wetland habitats that are difficult to navigate, as well as easily damaged by human observers. Autonomous recording units (ARUs) have been used to determine presence or absence of marsh bird species, but little is known about distance effects on detection probability. Therefore, our objectives were to 1.) evaluate if ARUs can be used to accurately count three marsh bird species (e.g., Clapper Rail, Least Bittern, Seaside Sparrow), 2.) estimate detection probability curves based on ARU recordings, and 3.) determine the area surveyed by the ARU for the three species. We arranged ARUs to record calls from our marsh bird species broadcasted from Bluetooth speakers at fixed distances. We replicated natural calling scenarios by playing calls in different number combinations of individuals, ranging from 1 to 10 birds. To reduce interference from real bird vocalizations, we conducted our experiment in a recently burned pine savanna habitat that had similar herbaceous vegetation structure to the coastal emergent wetland habitats preferred by these species in southern Mississippi. We used Raven Pro bioacoustics software to produce sonogram images of the broadcasted calls to count individuals in each recording. Detection probability of each species by distance was calculated in program R. Results showed that ARUs may be useful for counting individuals at close distances for some species (&lt; 100m), but most counts biased low. In Clapper Rails and Least Bitterns, count accuracy decreased between 100 and 125 meters from the ARU but closer (50-100 meters) for Seaside Sparrows. There was also a significant decline in count accuracy with increasing chorus size. With further study and advancing technology, ARUs may be able to supplement marsh bird surveys and limit logistical issues.

Habitat edges influence the distribution of nest predators for Seaside Sparrows, but not nest placement or success

Abstract Nest failure for coastal marsh bird species is primarily caused by predation and nest flooding. As sea level rise makes nest flooding more likely, the threat of nest predation will constrain the potential adaptive responses of marsh nesting species. Thus, understanding the predictors of nest predation is important for the conservation of salt marsh-dwelling bird species, such as the Seaside Sparrow (Ammospiza maritima). Predator activity may be influenced by landscape features (particularly habitat edges), potentially making nest predation predictable. We aimed to understand the predictability of Seaside Sparrow nest predation relative to two major landscape features: roads and tidal rivers, as both of these edges may be entryways or attractants for predators in marshes. In coastal Georgia, USA, we assessed mammalian predator activity relative to the two features of interest, and hypothesized that mammalian predator activity would be greater close to roads and tidal rivers. We also recorded Seaside Sparrow nest locations and nest predation events and hypothesized that nest predation events would increase with increasing predator activity. Consistent with our first hypothesis, mammalian predator activity increased close to roads and tidal rivers, but mammalian predator distribution did not explain the spatial variation in Seaside Sparrow nest predation thus not supporting our second hypothesis. Seaside Sparrows also placed their nests in locations with high mammalian predator activity, indicating that the ability to avoid nesting in high-risk areas may be constrained by habitat or resource limitations. Additionally, mammals may not be the primary nest predators, as we found that one bird species—Marsh Wren (Cistothorus palustris)—contributed substantially to nest predation rates. Understanding the predictability of mammalian predator distribution can allow for focused predator management efforts, such as exclusion, to habitat edges where we found the highest mammalian predator activity, which could relax the constraint of nest predation on Seaside Sparrow’s ability to respond to the intensifying threat of sea level rise.

Marsh bird response to restored shallow lakes: Implications for future management

AbstractThe restoration of shallow lakes has the potential to provide habitat for obligate breeding marsh birds, including secretive marsh birds. However, the degree of marsh bird response to wetland restoration may vary over time as prairie wetlands are subject to variation in water depth and vegetation characteristics (e.g., height, density, distribution) because of management and biotic and abiotic factors. We investigated the effects of shallow lake restoration age and habitat covariates on the abundance of 3 secretive marsh bird species and marsh bird species richness at shallow lakes in northern Iowa from 2009–2010 and again from 2016–2017. We found that the interspersion of water and emergent vegetation, shallow lake area, and water depth influenced the abundance of pied‐billed grebes (Podilymbus podiceps). Restoration age (β = −0.52, 95% CI = −0.87, −0.18) had a quadratic effect on abundance of pied‐billed grebes, peaking at 6 years post‐restoration. Percent cattail (β = 1.95, 95% CI = 0.55, 3.35) and restoration age (β = 0.51, 95% CI = 0.14, 0.87) were important predictors for Virginia rail (Rallus limicola) abundance. Species richness was greater at restored shallow lakes ( = 2.72, 95% CI = 2.23, 3.23) compared to non‐restored shallow lakes ( = 3.91, 95% CI = 3.41, 4.56) and at shallow lakes with a greater percentage of cattail ( = 2.54, 95% CI = 2.13, 3.07 at 0% cattail to = 4.27, 95% CI = 3.47, 5.15 at 100% cattail). Restoration age did not significantly influence least bittern (Ixobrychus exilis) abundance or species richness, but both variables tended to peak between 5 to 8 years after restoration. Our findings illustrate the need to evaluate habitat characteristics of individual shallow lake restorations as they age to inform continued management efforts for breeding marsh birds.

Secretive marsh bird habitat relationships at mid‐continent spring migration stopover sites

AbstractDespite several secretive marsh bird (SMB) species being listed as critically imperiled throughout the mid‐continent of North America, limited information on SMB distribution and habitat use within primary migratory corridors results in uncertainty on contributions of wetlands in mid‐latitude states toward their annual cycle needs. Our objectives were to quantify temporal patterns of SMB wetland occupancy during spring migration at a mid‐latitude state and evaluate the relationships between SMB colonization probability and water‐level management practices, and the resulting habitat conditions during spring migration. We conducted a 2‐year, dynamic occupancy study (2013–2014) that included 6 rounds of repeated call‐back surveys to detect the presence of 5 SMB species (i.e., Virginia rail [Rallus limicola], sora [Porzana carolina], king rail [R. elegans], least bittern [Ixobrychus exilis], and American bittern [Botaurus lentiginosus]) during spring (Apr–Jun) on 107 wetlands across 8 conservation areas and 4 national wildlife refuges throughout Missouri, USA. We detected sora most frequently, followed by least bittern, American bittern, Virginia rail, and king rail. Coefficient estimates indicated colonization probability for all species was positively associated with emergent vegetation cover and negatively associated with amount of open water. Open water was the only variable in the best supported model explaining American bittern site colonization, to which they were negatively associated. Virginia rail colonization had a strong positive association with vegetation height, whereas least bittern and sora site colonization were influenced positively by water depth and agriculture, respectively. Based on the habitat associations within and among SMB species identified in this study, wetland managers can tailor management strategies to optimize spring migration habitat for single‐ or multi‐species objectives.

Estimating Detection and Occupancy of Secretive Marsh Bird Species in Low and High Saline Marshes in Southwestern Louisiana Using Automated Recording Units

Estimating Detection and Occupancy of Secretive Marsh Bird Species in Low and High Saline Marshes in Southwestern Louisiana Using Automated Recording Units

High uncertainty over the future of tidal marsh birds under current sea-level rise projections

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.

Bogatstvo ornitofaune Spomenika prirode "Lalinačka slatina" kod Niša

Systematic research of the ornithofauna of the Natural Monument "Lalinačka slatina" salt marsh has not been conducted so far, and data on some species of salt marsh birds are given only in the conservation study of this area. The first systematic surveys of ornithofauna were conducted in the period 2020-2021 with an emphasis on the nesting period of most species. The collected data were combined with data from the conservation study and indicated the presence of 72 bird species from 24 families and 12 orders. Migratory statuses have shown that the area is dominated by nesting birds, as many as 42 species have been recorded, as well as 24 species of strays, 5 species of wintering birds and 1 passer-by. Most of the bird species found in the "Lalinačka slatina" area are included in the various national and international lists, and are important considering the aspect of protection since they are endangered and rare.

Dual visible‐thermal camera approach facilitates drone surveys of colonial marshbirds

AbstractWaterbirds are important indicators of wetland health, and understanding their status and trends is necessary for appropriate management and conservation. However, certain species are challenging to survey due to their sensitivity to disturbance and the difficulty of accessing their breeding habitats. This is especially true for colonially breeding marshbirds, for which a multi‐species survey protocol that maximizes accuracy of counts and minimizes disturbance does not exist. Small drone aircraft have shown promise for conducting accurate and low‐disturbance surveys of colonial waterbirds. However, complex marsh vegetation structures and the cryptic nature of some marshbird nests make them difficult to detect in aerial imagery. We used synchronous high‐resolution visible imagery (0.8–2 cm/pixel) and thermal‐infrared imagery (6–16 cm/pixel) captured from a drone to count nests of five species of marshbirds at eight colonies in Saskatchewan, Canada. We compared counts from the imagery to those obtained from traditional ground‐based surveys, generally considered the most accurate survey method for these species. The two types of imagery proved highly complementary, as heat signatures helped detect and confirm nests not easily spotted in the visible imagery, while the detailed visible imagery allowed species identification. For four species (Western Grebe Aechmophorus occidentalis, Franklin's Gull Leucophaeus pipixcan, Forster's Tern Sterna forsteri, and Black‐crowned Night‐Heron Nycticorax nycticorax), drone‐based counts (range 74–1524 nests per colony) were within 5% of ground‐based counts (range 75–1582), while for smaller Black Tern Chlidonias niger colonies (range 3–7 nests), counts from the two methods were always within one nest of each other. Furthermore, an assessment of flight behavior before, during, and after drone surveys found no significant evidence of disturbance by the drone. Our drone‐borne dual visible‐thermal camera approach proved promising for surveying colonial marshbirds and could potentially be implemented in a range of situations where wildlife subjects are difficult to survey with visible or thermal imagery alone.

Effects of barrier island salt marsh restoration on marsh bird occurrence in the northern Gulf of Mexico

In the northern Gulf of Mexico, salt marshes are threatened by sea level rise, erosion, and loss of protective barrier islands. These barrier islands provide critical habitat for wildlife, including globally significant populations of marsh and shorebirds. We investigated salt marsh restoration on two Louisiana barrier islands using presence of eight marsh bird species as an index to evaluate restoration success. Land loss was extensive for both islands prior to restoration, with submerged marsh restored by backfilling sediment into the marsh platform. Restoration methods were similar between the two islands, although Raccoon Island was built to a higher elevation (1.1 m) than Whiskey Island (0.8 m). Avian presence was estimated via passive acoustic monitoring and point counts. To evaluate restoration success, we modeled influence of habitat covariates on index species presence in restored and reference (intact) sites over three breeding seasons and modeled occupancy for six species. On Whiskey Island, index richness was higher in restored sites. Marsh specialists Seaside Sparrows (Ammospiza maritima) and Least Bitterns (Ixobrychus exilis) had higher occupancy in restored areas on Whiskey, while generalist species showed no response to site. These results are likely due to a strong association between habitat and vegetation type, with restored sites dominated by Spartina alterniflora and reference sites by Avicennia germinans. On Raccoon Island, species richness was low across all sites. Our results suggest that restoration efforts were successful in creating salt marsh habitat on Whiskey but not Raccoon as of the time of our study.

Broadcasting Regional Call Dialects Has Little Influence on the Effectiveness of Call-Broadcast Surveys for Marsh Birds

Emergent wetlands have declined in North America and, in response, many wetland-dependent animals have declined in abundance. For example, many species of secretive marsh birds in North America have declined during the last century. However, estimates of population decline and efforts to assess the effects of management actions are hampered because marsh birds are difficult to detect using conventional survey techniques. Call-broadcast surveys can improve detection probability of marsh birds; however, the effectiveness of call-broadcast varies regionally for some marsh birds, which might reflect differential responsiveness to call dialects. Here, we evaluated differential responses by least bitterns (Ixobrychus exilis) and clapper rails (Rallus crepitans) to different call dialects by using 679 paired call-broadcast surveys in Florida and South Carolina. We detected similar numbers of least bitterns and clapper rails responding to the different call dialects, except in Florida, where least bitterns responded more frequently to a more-distant (Louisiana) dialect than a more-local (Florida) dialect. Our results suggest that, at least for clapper rails and least bitterns, it may not be necessary to incorporate regional call dialects into standardized surveys. However, additional research is needed in more regions of North America and with other species.

Prioritizing coastal wetlands for marsh bird conservation in the U.S. Great Lakes

Human activity surrounding the Laurentian Great Lakes basin has significantly degraded coastal wetland habitats, resulting in severe marsh bird population declines and reduced coastal resilience to changing environmental conditions. Given the need to conserve remaining coastal wetlands for wildlife and people, we developed a spatial prioritization to identify the most important U.S. Great Lakes coastal wetlands for 14 marsh bird species. We modeled occurrence and relative abundance of each species using boosted regression trees, a machine learning algorithm, to relate standardized monitoring data to ten remotely-sensed environmental covariates. We then used Zonation conservation planning software to rank every wetland cell based on its importance for the suite of marsh bird species. Evaluation of the drivers of marsh bird occurrence and abundance revealed that open water, herbaceous wetland, latitude, longitude, and impervious surface were the most important predictors across focal species. The high-priority wetlands for marsh birds (defined as grid cells ranked in the top 20%) occurred along the shores of eastern Lake Ontario, western Lake Erie/St. Clair, Saginaw Bay, Green Bay, northern lakes Michigan and Huron, and western Lake Superior. Overall, less than half (42%) of high-priority coastal wetlands across the Great Lakes basin are currently under some level of protection, with Lake Ontario priority wetlands being the least protected (25%). Our findings represent an opportunity to improve coastal wetland conservation in a region where wetland loss and degradation continue to threaten marsh bird populations and the integrity of one of the world's largest freshwater ecosystems.

Detection of local-scale population declines through optimized tidal marsh bird monitoring design

Evaluating the efficacy of monitoring designs is crucial for the successful monitoring and conservation of populations. For tidal marsh bird species of conservation concern, detecting population declines at local spatial scales within actionable time frames is a top priority. We examined and compared the effectiveness of alternative monitoring strategies for detecting local-scale population declines using count data from 1176 spatially-independent salt marsh sampling points throughout the northeastern United States (Maine to Virginia). We used abundance estimates that accounted for imperfect detection as initial conditions to simulate annual population declines of 5%, 10%, 30%, and 50% over a 5-year sampling period. Under an optimal monitoring design with biennial sampling, we were able to successfully detect annual population declines of ≥30% for each species and for all species combined. However, this required a minimum of 15–20 points per site being sampled. Power to detect declines, although low for detecting smaller annual declines (i.e., <10%), improved substantially when points were visited twice per season, yet a third visit provided a reduced benefit. When testing factors that could potentially influence power to detect declines, we found that the power within sites was positively related to species abundance. Power was similar between biennial sampling (3 of 5 years) and annual sampling (5 of 5 years), suggesting a more cost-effective approach would be to sample every other year. We found that within most sites, detecting annual declines of 10% or less over a relatively short 5-year duration would be difficult. Hence, we recommend that salt marsh bird monitoring programs in the northeastern United States conduct two visits to each site per sampling year, include 15 or more sampling points per site (without confounding spatial independence), and conduct monitoring efforts every other year. This approach will maximize the efficacy of site-level monitoring of tidal marsh birds, which can aid in assessments of coastal wetland conservation and related habitat management efforts.