Geology Reports⌕ Search

Geology topics

Terry L. Shaffer

Publications and source records attributed to Terry L. Shaffer.

At least 19 recordsLinked to original sources
USGS2022

Reassessing perennial cover as a driver of duck nest survival in the Prairie Pothole Region

Conservation plans designed to sustain North American duck populations prominently feature a key hypothesis stating that the amount of the landscape in perennial cover surrounding upland duck nests positively influences nest survival rates. Recent conflicting research testing this hypothesis creates ambiguity regarding which management actions to pursue and where to prioritize conservation delivery. We compared existing models and new formulations of existing models explaining spatiotemporal variation in nest survival using independent data documenting the fate of >20,000 duck nests within the Drift Prairie, Missouri Coteau, and Prairie Coteau physiographic regions of the United States Prairie Pothole Region during 2002–2018. Our results suggest an inconsistent relationship between perennial cover and survival of upland duck nests, which depended upon physiographic region and current and time-lagged landscape and environmental conditions. The magnitude and direction of how perennial cover correlated with daily nest survival depended on its dominance as a landcover type. A positive relationship existed when perennial cover was a minor component of landcover in all physiographic regions (<30% of a 10.4-km 2 area) and, in the Drift Prairie and Prairie Coteau, when perennial cover was the dominant landcover type (>60%). A constant or negative relationship was predicted at locations of about 30–60% perennial cover. Additionally, environmental conditions (i.e., density of wetlands and estimated gross primary productivity in the previous year) moderated or enhanced the effect of perennial cover on nest survival, depending on physiographic region. Our finding of inconsistency in the relationship between perennial cover and nest survival contradicts the conservation premise that nest survival universally increases linearly when uplands are converted to perennial cover. Promoting policies and management actions designed to increase perennial cover can be expected to be situationally but not consistently associated with higher survival of upland duck nests.

Montana, North Dakota, South Dakota↗
USGS2022

Limited land base and competing land uses force societal tradeoffs when siting energy development

As human populations grow, decisions regarding use of the world's finite land base become increasingly complex. We adopted a land use–conflict scenario involving renewable energy to illustrate one potential cause of these conflicts and resulting tradeoff decisions. Renewable energy industries wishing to expand operations in the United States are limited by multijurisdictional regulations in finding developable land. Interest groups entreat industries to avoid land for various reasons, including avoidance of prime wildlife habitat in accordance with an “avoidance-first” mitigation strategy. By applying a uniform set of rules for renewable energy facilities to the Prairie Pothole Region and portions of the Northern Great Plains, we evaluated the effects of regulations and avoidance of prime wildlife habitat on the amount of land available for development. In our scenario, existing regulations excluded 39% of the project area from potential development, with human infrastructure accounting for 30% (10–66% among states), whereas federally protected species accounted for < 1% at project area and state levels. Unregulated lands accounted for 61% of the project area, with conservation areas predicted as high-quality sites for breeding grassland birds and waterfowl and for migrating whooping cranes Grus americana accounting for 19% within the project area (6–27% among states). This model demonstrated a limited land base available for new development when accounting for regulations and concerns of a subset of societal interest groups. Additional interest groups likely will have different and competing concerns, further emphasizing the complexity of future land-use decisions as the available land base for development diminishes.

Journal of Fish and Wildlife Management↗
USGS2021

Experimental evaluation of predator exclosures on nest, chick, and adult survival of piping plovers

Species of conservation concern often receive intensive management to improve vital rates and facilitate recovery. Piping plovers ( Charadrius melodus ) are federally listed in the United States and concerns over nest depredation have prompted widespread use of plover-permeable predator exclosures placed around nests (0.5–2-m radius). While effectiveness of exclosures for improving nest survival has been demonstrated, concerns remain about decreased chick survival (through predator cueing or density-dependent processes) or increased vulnerability of adults to predation (ambush as adult leaves exclosure). Either one of these concerns could demographically outweigh the benefits of increased nest survival. During 2014–2016, we conducted an experiment designed to evaluate survival of uniquely identified nests ( n = 418), chicks ( n = 453), and adults ( n = 367) at wetlands across the Northern Great Plains, USA. We assigned wetlands ( n 2014 = 26, n 2015 = 28, n 2016 = 25) into 2 groups: wetlands in which half of the nests received exclosures and wetlands in which none of the nests received exclosures. Exclosed nests had greater cumulative survival (0.73 [85% CI = 0.70–0.77]) than unexclosed nests at treatment wetlands (0.58 [0.54–0.62]) or unexclosed nests at control wetlands (0.52 [0.49–0.56]). Survival to fledging was highest for chicks hatched from exclosed nests (0.51 [0.47–0.56]), and similar between chicks hatched from unexclosed nests at treatment (0.34 [0.30–0.39]) and control (0.37 [0.32–0.42]) wetlands. Cumulative survival of adults during incubation varied by exclosure status, but adults associated with exclosed nests (0.90 [0.88–0.93]) and unexclosed nests at treatment wetlands (0.89 [0.86–0.92]) had greater survival than those associated with unexclosed nests at control wetlands (0.75 [0.64–0.84]). Adult annual survival rates varied by year (0.79–0.95) but not by exclosure status. The positive influence of exclosures on nest survival was not offset by a reduction in chick or adult survival, indicating that exclosures are a viable tool for piping plover conservation.

Montana, North Dakota↗
USGS2021

Foraging movements and colony attendance of Least Terns (Sternula antillarum) on the central Platte River, Nebraska, USA

Least Terns ( Sternula antillarum ) are known to forage away from nesting colonies, yet little information is available about movement rates and distances. We used VHF transmitters and a network of datalogging receivers to monitor movements of 23 Least Terns on the central Platte River, Nebraska, USA. We typically detected incubating and brood-rearing birds within 8 km of colonies during daylight hours, and up to 17.5 km away at night. Movement distances were even longer during post-fledging (up to 20 km) and nonbreeding (up to 31 km) periods. Colony attendance differed notably by reproductive stage, being highest for incubating and lowest for post-fledging birds. Birds were most frequently detected on the study area during brood-rearing and nonbreeding periods, and most likely to go undetected during incubation and after fledging a brood. Frequency and success of foraging behaviors were lowest on sandpit sites, intermediate on riverine sites, and highest at the Kearney Diversion Dam on the Platte River, where flow patterns likely enhanced forage fish availability. Foraging movements of Least Terns were temporally and spatially variable, with time of day, reproductive stage, and availability of prey hotspots appearing to be key factors. Management of habitat complexes for breeding Least Terns may benefit from emphasizing the availability of profitable foraging habitat within 8 km of nesting areas, and considering foraging habitat within 8 - 30 km as available.

Nebraska↗
USGS2020

Plasticity of Least Tern and Piping Plover nesting behaviors in response to sand temperature

Birds that nest on the ground in open areas, such as Piping Plovers ( Charadrius melodus ) and Interior Least Terns ( Sternula antillarum athalassos ), are exposed to high temperatures in thermally stressful environments. As a result, some ground-nesting avian species have adapted behavioral strategies to maintain thermal regulation of eggs and themselves. We assessed the impact of sand temperature on shorebird nesting behaviors by installing video cameras and thermocouples at 52 Least Tern and 55 Piping Plover nests on the Missouri River in North Dakota during the 2014–2015 breeding seasons. Daily duration and frequency of shading behaviors exhibited a nonlinear relationship with temperature; therefore, we used segmented regressions to determine at what threshold temperature (mean temperature = 25.7 ⸰ C for shading behavior daily frequency and mean temperature = 25.1 ⸰ C for shading behavior daily duration) shorebird adults exhibited a behavioral response to rising sand temperatures. Daily nest attendance of both species decreased with increasing sand temperatures in our system. Frequency and duration of daily shading behaviors were positively correlated with sand temperatures above the temperature threshold. Piping Plovers exhibited more and longer shading behaviors above and below the temperature thresholds (below: frequency = 10.30 ± 1.69 se, duration = 7.29 min ± 2.35 se; above: frequency = 59.27 ± 6.87 se) compared to Least Terns (below: frequency = −1.37 ± 1.98 se, duration = −0.73 min ± 1.51 se; above: frequency = 31.32 ± 7.29 se). The effects of sand temperature on avian ground-nesting behavior will be critical to understand in order to adapt or develop recovery plans in response to climate change.

North Dakota↗
USGS2019

Demographic responses of least terns and piping plovers to the 2011 Missouri River flood—A large-scale case study

A catastrophic flood event on the Missouri River system in 2011 led to substantial changes in abundance and distribution of unvegetated sand habitat. This river system is a major component of the breeding range for interior Least terns ( Sternula antillarum ; “terns”) and piping plovers ( Charadrius melodus ; “plovers”), both of which are Federally listed ground-nesting birds that prefer open, unvegetated sand and gravel nesting substrates on sandbars and shorelines. The 2011 flood inundated essentially all tern and plover nesting habitat during 2011, but it had potential to generate post-flood habitat conditions that favored use by terns and plovers in subsequent years. We compared several tern and plover demographic parameters during the pre-flood and post-flood periods on the Garrison Reach and Lake Sakakawea, North Dakota, to determine how this event influenced these species (both species on the Garrison Reach, and plovers only on Lake Sakakawea). The principal parameters we measured (nest survival, chick survival, and breeding population) showed spatial and temporal variation typical of opportunistic species occupying highly variable habitats. There was little evidence that nest survival of least terns differed between pre- and post-flood. During 2012 when habitat was most abundant on the Garrison Reach and Lake Sakakawea, piping plover nest survival was higher than in any other year in the study, but returned to rates comparable to pre-flood years in 2013. Chick survival for terns on the Garrison Reach and plovers on Lake Sakakawea showed a similar pattern to plover nest survival, with the 2012 rate exceeding all other years of the study, and the remaining pre-flood and post-flood years being generally similar but slightly higher in post-flood years. However, plover chick survival on the Garrison Reach in 2012 was similar to pre-flood years, and increased annually thereafter to its highest rate in 2014. Although wide confidence intervals precluded firm conclusions about flood effects on breeding populations, the general pattern suggested lower populations of plovers but higher populations of least terns immediately after the flood. Despite near total absence of breeding habitat on either study area during the flood of 2011, populations of both species persisted after the flood due to their propensity to disperse and/or forgo breeding for at least a year. Tern and plover populations have similarly persisted and recovered after the flood, but their mechanisms for persistence likely differ. Data on tern dispersal is generally lacking, but they are thought to show little fidelity to their natal grounds, have a propensity to disperse potentially long distances, and routinely forgo breeding until their second year, thus a lost opportunity to breed in a given area may be easily overcome. Plovers exhibit stronger demographic ties to the general area in which they previously nested, yet they occupy much broader nesting habitat features than terns and exploit three major landforms in the Dakotas (free-flowing rivers, reservoir shorelines, and wetland shorelines). Consequently, dispersal to and from non-Missouri River habitats and potential to exploit non-traditional habitats likely sustained the Northern Great Plains population through the flood event. Terns and plovers normally occupy similar habitats on the Missouri River and both species experienced similar loss of a breeding season due to the flood. Persistence of these populations after the flood underscores the importance of understanding their unique demographic characteristics and the context within which the Missouri River operates.

North Dakota↗
USGS2018

Accuracy of nest fate classification and predator identification from evidence at nests of least terns and piping plovers

For federally listed species such as Least Tern Sternula antillarum and Piping Plover Charadrius melodus , correct determination of nest fates and causes of nest failure is crucial for understanding population dynamics and improving monitoring programmes. We used video cameras to evaluate nest fate misclassification rate and to identify factors that may cause researchers monitoring nests at different intervals to classify Least Tern and Piping Plover nest fates incorrectly. During the 2013–2015 breeding seasons, we installed miniature surveillance cameras at 65 of 294 Least Tern and 89 of 551 Piping Plover nests under observation on the Missouri River in North Dakota. Nest fates were assigned in the field from remains found at the nest‐site and then again by an independent researcher who reviewed camera footage. We used ordinal logistic regressions to examine whether monitoring interval, clutch age or temporal factors influenced a correct, partially misclassified (probable successful in the field vs. successful by camera) or misclassified nest fate classification. During a 7‐day monitoring interval between visits, 45% of nests were partially and 27.5% were fully misclassified. The percentage of partially (20%) and fully (8.0%) misclassified nests decreased with a more intensive (3‐day) monitoring schedule. Researchers were also less likely to correctly classify nest fates for Least Terns than for Piping Plovers, and as clutch age and monitoring interval increased for both species. Furthermore, causes of failure (e.g. predators, weather) as determined from field evidence vs. video disagreed for 53.5% of nests. The ability to identify accurately nest fate and cause of nest failure will facilitate a better understanding of factors that limit productivity and will lead to better informed management decisions for improving nest survival.

North Dakota↗
USGS2018

Density and success of upland duck nests in native‐ and tame‐seeded conservation fields

The Conservation Reserve Program (CRP) generates substantial benefits to continental duck populations by providing grassland nesting habitat in rested cropland. Seeding mixes of CRP grasslands vary among numerous conservation practices, but one contrast of interest in the Prairie Pothole Region is the use of introduced, or “tame” versus native grass. Although the benefits of CRP to duck populations are well‐known, relative values of these planting practices to nesting ducks have received little attention. Understanding differences in benefits to ducks due to planting practices would aid in prioritizing and selecting management practices for CRP and other restoration activities. We evaluated nest survival and density of ducks nesting in tame‐ and native‐seeded CRP fields in 36 study areas in the Prairie Pothole Region of North Dakota and South Dakota, USA, during 2002–2003. We searched for duck nests in 209 fields totaling 5,386 ha and found 2,941 nests. We found no support for differences in nest survival for any upland‐nesting duck species between fields seeded to tame versus native grass based on a design and analyses that accounted for spatial and temporal variation. Additionally, nest densities, adjusted for nest survival rates, of all duck species were similar between tame‐seeded and native‐seeded fields. We conclude that benefits to nesting ducks from native‐grass seeding practices of CRP were similar to those of tame‐grass seeding practices. Although there may be other reasons to plant native seed mixes when establishing CRP tracts (e.g., native pollinators or insects, other wildlife species, etc.), our study suggests that duck nesting density and nest survival are not among those reasons.

North Dakota, South Dakota↗
USGS2017

Northern Prairie Wildlife Research Center—Celebrating 50 years of science

The Northern Prairie Wildlife Research Center (NPWRC) celebrated its 50-year anniversary in 2015. This report is written in support of that observance. We document why and how the NPWRC came to be and describe some of its many accomplishments and the influence the Center’s research program has had on natural resource management. The history is organized by major research themes, proceeds somewhat chronologically within each theme, and covers the Center’s first 50 years of research. During that period, Center scientists authored more than 1,700 publications and reports. More than 1,000 seasonal or temporary field personnel, and more than 100 graduate students, contributed to the Center’s success; many went on to have exemplary careers in natural resource management, conservation, and education. The mission of the Northern Prairie Wildlife Research Center today remains true to the original vision: to provide the knowledge needed to understand, conserve, and manage the Nation’s natural resources for current and future generations, with an emphasis on species and ecosystems of the northern Great Plains. The Center’s first 50 years of applied biological research provides a deep scientific foundation on which to address emerging issues for the natural resources in the northern Great Plains and beyond.

Circular↗
USGS2017

Sparrow nest survival in relation to prescribed fire and woody plant invasion in a northern mixed-grass prairie

Prescribed fire is used to reverse invasion by woody vegetation on grasslands, but managers often are uncertain whether influences of shrub and tree reduction outweigh potential effects of fire on nest survival of grassland birds. During the 2001–2003 breeding seasons, we examined relationships of prescribed fire and woody vegetation to nest survival of clay-colored sparrow ( Spizella pallida ) and Savannah sparrow ( Passerculus sandwichensis ) in mixed-grass prairie at Des Lacs National Wildlife Refuge in northwestern North Dakota, USA. We assessed relationships of nest survival to 1) recent fire history, in terms of number of breeding seasons (2, 3, or 4–5) since the last prescribed fire, and 2) prevalence of trees and tall (>1.5 m) shrubs in the landscape and of low (≤1.5 m) shrubs within 5 m of nests. Nest survival of both species exhibited distinct patterns related to age of the nest and day of year, but bore no relationship to fire history. Survival of clay-colored sparrow nests declined as the amount of trees and tall shrubs within 100 m increased, but we found no relationship to suggest nest parasitism by brown-headed cowbirds ( Molothrus ater ) as an underlying mechanism. We found little evidence linking nest survival of Savannah sparrow to woody vegetation. Our results suggest that fire can be used to restore northern mixed-grass prairies without adversely affecting nest survival of ≥2 widespread passerine species. Survival of nests of clay-colored sparrow may increase when tall woody cover is reduced by fire. Our data lend support to the use of fire for reducing scattered patches of tall woody cover to enhance survival of nests of ≥1 grassland bird species in northern mixed-grass prairies, but further study is needed that incorporates experimental approaches and assessments of shorter term effects of fire on survival of nests of grassland passerines.

North Dakota↗
USGS2017

Contrasting nest survival patterns for ducks and songbirds in northern mixed-grass prairie

Management actions intended to protect or improve habitat for ducks may benefit grassland-nesting passerines, but scant information is available to explore this assumption. During 1998–2003, we examined nest survival of ducks and songbirds to determine whether effects of prescribed fire and other habitat features (e.g., shrub cover and distance to habitat edges) were similar for ducks and passerines breeding in North Dakota. We used the logistic-exposure method to estimate survival of duck and songbird nests ( n = 3,171). We used an information-theoretic approach to identify factors that most influenced nest survival. Patterns of nest survival were markedly different between taxonomic groups. For ducks, nest survival was greater during the first postfire nesting season (daily survival rate [DSR] = 0.957, 85% CI = 0.951–0.963), relative to later postfire nesting seasons (DSR = 0.946, 85% CI = 0.942–0.950). Furthermore duck nest survival and nest densities were inversely related. Duck nest survival also was greater as shrub cover decreased and as distance from cropland and wetland edges increased. Passerines had lower nest survival during the first postfire nesting season (DSR = 0.934, 85% CI = 0.924–0.944), when densities also were low compared to subsequent postfire nesting seasons (DSR = 0.947, 85% CI = 0.944–0.950). Parasitism by brown-headed cowbirds ( Molothrus ater ) reduced passerine nest survival and this effect was more pronounced during the first postfire nesting season compared to subsequent nesting seasons. Passerine nest survival was greater as shrub cover decreased and perhaps for more concealed nests. Duck and songbird nest survival rates were not correlated during this study and for associated studies that examined additional variables using the same dataset, suggesting that different mechanisms influenced their survival. Based on our results, ducks should not be considered direct surrogates for passerines when predicting effects of prescribed fire, shrub cover, and habitat edges on nest survival.

North Dakota↗
USGS2016

Demographics and movements of least terns and piping plovers in the Central Platte River Valley, Nebraska

The Central Platte River Valley provides breeding habitat for a variety of migratory birds, including federally endangered interior least terns ( Sternula antillarum ; least tern) and threatened piping plovers ( Charadrius melodus ). Since 2009, researchers have collected demographic data on both species that span their lifecycle (that is, from egg laying through survival of adults). Demographic data were used to estimate vital rates (for example, nest survival, chick survival, and so on) for both species and assess how these vital rates were related to type and age of nesting habitat. Nest survival of both species was unrelated to the age of the site a nest was initiated on. Piping plover chick survival to fledging age was not related to the age of the site it was hatched at, however, the probability of a least tern chick surviving to fledging was higher at older sites. In general there were fewer piping plover nests than least tern nests found at sites created through either the physical construction of a new site or new vegetation management regimes, during 2009–14. Mean daily least tern nest survival was 0.9742 (95-percent confidence interval [CI]: 0.9692–0.9783) and cumulative nest survival was 0.59 (95-percent CI: 0.53–0.65). Mean daily least tern chick survival was 0.9602 (95-percent CI: 0.9515–0.9673) and cumulative survival to fledging was 0.54 (95-percent CI = 0.48–0.61). Annual apparent survival rates were estimated at 0.42 (95-percent CI = 0.22–0.64) for adult least terns nesting in the Central Platte River Valley and an apparent survival rate of 0.14 (95-pecent CI = 0.04–0.41) for juvenile least terns. The number of least tern nests present at sites created during 2009–14 was associated with the age of the site; more least tern nests were associated with older sites. During 2009–14, there were four (less than 1 percent of all chicks marked) least tern chicks hatched from the Central Platte River Valley that were subsequently captured on nests as adults. Two of these least terns returned to nest at the same site they had hatched from. Ten instances were documented in which an adult least tern could either switch to nest at a new location or remain at the previous location with the onset of a new year. In five (50 percent) of these instances, least terns returned to nest on the site where they had nested in a previous year. For piping plovers, mean daily apparent nest survival was 0.9880 (95-pecent CI: 0.9836–0.9912) and cumulative nest survival was 0.66 (95-pecent CI: 0.57–0.74). Mean daily piping plover chick survival was 0.9621 (95-pecent CI: 0.9514–0.9706) and cumulative survival to fledging was 0.46 (95-pecent CI = 0.37– 0.56). The annual apparent survival estimate for adult piping plovers nesting in the Central Platte River Valley was 0.76 (95-pecent CI = 0.65–0.85) and was 0.20 (95-pecent CI = 0.14–0.29) for juvenile piping plovers. The number of piping plover nests present at sites created through either the physical construction of a new site or new vegetation management regimes was also associated with site age, with more piping plover nests associated with older sites; however, in general there were fewer piping plover nests found at created sites than least tern nests. Only first-year adult piping plovers were observed on sites in the first year of availability, whereas older sites had a higher proportion of after-first-year adult piping plovers than first-year adult piping plovers. Twelve piping plover chicks (approximately 3 percent of all chicks marked) hatched from the Central Platte River Valley and were subsequently documented on nests as adults. All piping plovers returned to nest on different sites from the one on which they hatched. A total of 45 instances were documented in which an adult plover could either switch to nest at a new location or remain at the previous location with the onset of a new year. In 39 instances (87 percent), the adult nested on the same site as its prior documented nesting attempt and in 6 of these instances the adult switched to a new nesting location between years. There were 13 of 75 uniquely identifiable piping plovers observed to renest (that is, initiate more than one nest in a season) during 2009–14; no renests were observed among uniquely identifiable least terns. In all but one case, piping plover renests were found at the same site as the first nest initiated that season. For birds that renested, the mean initiation date of the first nest was May 6 and the mean initiation date of the second nest was June 8. On average, renests were initiated 7.5 days plus or minus 7.3 (SD [standard deviation]) following the date the initial nesting attempt was ‘fated’ (considered either failed or hatched).

Nebraska↗
USGS2015

Do ducks and songbirds initiate more nests when the probability of survival is greater?

Nesting chronology in grassland birds can vary by species, locality, and year. The date a nest is initiated can influence the subsequent probability of its survival in some grassland bird species. Because predation is the most significant cause of nest loss in grassland birds, we examined the relation between timing of nesting and nest survival. Periods of high nest survival that correspond with the peak of nesting activity might reflect long-term adaptations to specific predation pressures commonly recurring during certain periods of the nesting cycle. We evaluated this theory by comparing timing of nesting with date-specific nest survival rates for several duck and passerine species breeding in north-central North Dakota during 1998–2003. Nest survival decreased seasonally with date for five of the seven species we studied. We found little evidence to support consistent relations between timing of nesting, the number of nest initiations, and nest survival for any species we studied, suggesting that factors other than nest predation may better explain nesting chronology for these species. The apparent mismatch between date-specific patterns of nest survival and nest initiation underscores uncertainty about the process of avian nest site selection driven mainly by predation. Although timing of nesting differed among species, the general nesting period was fairly predictable across all years of study, suggesting the potential for research activities or management actions to be timed to take advantage of known periods when nests are active (or inactive). However, our results do not support the notion that biologists can take advantage of periods when many nests are active and survival is also high.

North Dakota↗
USGS2014

Landscape selection by piping plovers has implications for measuring habitat and population size

How breeding birds distribute in relation to landscape-scale habitat features has important implications for conservation because those features may constrain habitat suitability. Furthermore, knowledge of these associations can help build models to improve area-wide demographic estimates or to develop a sampling stratification for research and monitoring. This is particularly important for rare species that have uneven distributions across vast areas, such as the federally listed piping plover (Charadrius melodus; hereafter plover). We examined how remotely-sensed landscape features influenced the distribution of breeding plover pairs among 2-km shoreline segments during 2006–2009 at Lake Sakakawea in North Dakota, USA. We found strong associations between remotely-sensed landscape features and plover abundance and distribution (R 2 = 0.65). Plovers were nearly absent from segments with bluffs (>25 m elevation increase within 250 m of shoreline). Relative plover density (pairs/ha) was markedly greater on islands (4.84 ± 1.22 SE) than on mainlands (0.85 ± 0.17 SE). Pair numbers increased with abundance of nesting habitat (unvegetated-flat areas β^=0.28±0.08SE ). On islands, pair numbers also increased with the relative proportion of the total area that was habitat ( β^=3.27±0.46SE ). Our model could be adapted to estimate the breeding population of plovers or to make predictions that provide a basis for stratification and design of future surveys. Knowledge of landscape features, such as bluffs, that exclude use by birds refines habitat suitability and facilitates more accurate estimates of habitat and population abundance, by decreasing the size of the sampling universe. Furthermore, techniques demonstrated here are applicable to other vast areas where birds breed in sparse or uneven densities.

North Dakota↗
USGS2014

Detection probability of least tern and piping plover chicks in a large river system

Monitoring the abundance and stability of populations of conservation concern is often complicated by an inability to perfectly detect all members of the population. Mark-recapture offers a flexible framework in which one may identify factors contributing to imperfect detection, while at the same time estimating demographic parameters such as abundance or survival. We individually color-marked, recaptured, and re-sighted 1,635 federally listed interior least tern (Sternula antillarum; endangered) chicks and 1,318 piping plover (Charadrius melodus; threatened) chicks from 2006 to 2009 at 4 study areas along the Missouri River and investigated effects of observer-, subject-, and site-level covariates suspected of influencing detection. Increasing the time spent searching and crew size increased the probability of detecting both species regardless of study area and detection methods were not associated with decreased survival. However, associations between detection probability and the investigated covariates were highly variable by study area and species combinations, indicating that a universal mark-recapture design may not be appropriate.

Nebraska;North Dakota;South Dakota↗
USGS2014

Establishing endangered species recovery criteria using predictive simulation modeling

Listing a species under the Endangered Species Act (ESA) and developing a recovery plan requires U.S. Fish and Wildlife Service to establish specific and measurable criteria for delisting. Generally, species are listed because they face (or are perceived to face) elevated risk of extinction due to issues such as habitat loss, invasive species, or other factors. Recovery plans identify recovery criteria that reduce extinction risk to an acceptable level. It logically follows that the recovery criteria, the defined conditions for removing a species from ESA protections, need to be closely related to extinction risk. Extinction probability is a population parameter estimated with a model that uses current demographic information to project the population into the future over a number of replicates, calculating the proportion of replicated populations that go extinct. We simulated extinction probabilities of piping plovers in the Great Plains and estimated the relationship between extinction probability and various demographic parameters. We tested the fit of regression models linking initial abundance, productivity, or population growth rate to extinction risk, and then, using the regression parameter estimates, determined the conditions required to reduce extinction probability to some pre-defined acceptable threshold. Binomial regression models with mean population growth rate and the natural log of initial abundance were the best predictors of extinction probability 50 years into the future. For example, based on our regression models, an initial abundance of approximately 2400 females with an expected mean population growth rate of 1.0 will limit extinction risk for piping plovers in the Great Plains to less than 0.048. Our method provides a straightforward way of developing specific and measurable recovery criteria linked directly to the core issue of extinction risk. Published by Elsevier Ltd.

Biological Conservation↗
USGS2014

Measuring and predicting abundance and dynamics of habitat for piping plovers on a large reservoir

Measuring habitat and understanding habitat dynamics have become increasingly important for wildlife conservation. Using remotely-sensed data, we developed procedures to measure breeding habitat abundance for the federally listed piping plover (Charadrius melodus) at Lake Sakakawea, North Dakota, USA. We also developed a model to predict habitat abundance based on past and projected water levels, vegetation colonization rates, and topography. Previous studies define plover habitat as flat areas (<10% slope) with ≤30% obstruction of bare substrate. Compared to ground-based data, remotely-sensed habitat classifications (≤30/>30% bare-substrate obstruction) were 76% correct and omission and commission errors were equal. Due to water level fluctuations, habitat abundance varied markedly among years (1986–2009) ranging from 9 to 5195 ha. The proportion bare substrate declined with the number of years since a contour was inundated until 5 years (&beta; = -0.65, SE = 0.05), then it stabilized near zero, and the decline varied by shoreline segment (5, 50, and 95 percentile were &beta; = -0.19, SE = 0.05, &beta; = -0.63, SE = 0.05, and &beta; = -0.91, SE = 0.05, respectively). Years since inundated predicted habitat abundance well at shoreline segments (R 2 = 0.77), but it predicted better for the whole lake (R 2 = 0.86). The vastness and dynamics of plover habitat on Lake Sakakawea suggest that this is a key area for conservation of this species. Model-based habitat predictions can benefit resource conservation because they can (1) form the basis for a sampling stratification, (2) help allocate monitoring efforts among areas, and (3) help inform management through simulations or what-if scenarios.

North Dakota↗