Geology topics

Shiloh A. Schulte

Publications and source records attributed to Shiloh A. Schulte.

6 recordsLinked to original sources

USGS2024

The Amazon Basin’s rivers and lakes support Nearctic-breeding shorebirds during southward migration

Identifying the migration routes and stopover sites used by declining species is critical for developing targeted conservation actions. Long-distance migratory shorebirds are among the groups of birds declining most rapidly, yet we frequently lack detailed knowledge about the routes and stopover sites they use during their hemisphere-spanning migrations. This is especially true for species that migrate through mid-continental regions in the Western Hemisphere. We therefore used satellite transmitters to track 212 individuals of 6 shorebird species during their southward migrations— Pluvialis dominica (American Golden-Plover), Limosa haemastica (Hudsonian Godwit), Tringa flavipes (Lesser Yellowlegs), and Calidris subruficollis (Buff-breasted Sandpiper), C. melanotos (Pectoral Sandpiper), and Bartramia longicauda (Upland Sandpiper)—as they crossed the Amazon Basin of South America, a region from which reports of shorebird numbers are increasing but remain relatively rare. Our results make clear that the Amazon Basin provides stopover habitat for a large number of shorebirds: more than 74% of individuals tracked crossing the Amazon Basin stopped over in the region for an average of 2–14 days, with some spending the entire nonbreeding season there. All species selected stopover sites along the region’s many rivers and lakes, while within stopover sites each species exhibited distinct habitat preferences. The timing of stopovers within sub-basins of the Amazon Basin also coincided with periods of low water, when the muddy, shallow water habitats preferred by most shorebirds are likely plentiful. Together, our results highlight the need for detailed investigations into shorebird abundance and distribution within the Amazon Basin, threats to shorebirds within particular subbasins, and links between shorebird conservation efforts and those targeting the myriad other species that inhabit this dynamic, hyper-diverse region.

Amazon Basin↗

USGS2018

Hematological indices of injury to lightly oiled birds from the Deepwater Horizon oil spill

Avian mortality events are common following large‐scale oil spills. However, the sublethal effects of oil on birds exposed to light external oiling are not clearly understood. We found that American oystercatchers (area of potential impact n = 42, reference n = 21), black skimmers (area of potential impact n = 121, reference n = 88), brown pelicans (area of potential impact n = 91, reference n = 48), and great egrets (area of potential impact n = 57, reference n = 47) captured between 20 June 2010 and 23 February 2011 following the Deepwater Horizon oil spill experienced oxidative injury to erythrocytes, had decreased volume of circulating erythrocytes, and showed evidence of a regenerative hematological response in the form of increased reticulocytes compared with reference populations. Erythrocytic inclusions consistent with Heinz bodies were present almost exclusively in birds from sites impacted with oil, a finding pathognomonic for oxidative injury to erythrocytes. Average packed cell volumes were 4 to 19% lower and average reticulocyte counts were 27 to 40% higher in birds with visible external oil than birds from reference sites. These findings provide evidence that small amounts of external oil exposure are associated with hemolytic anemia. Furthermore, we found that some birds captured from the area impacted by the spill but with no visible oiling also had erythrocytic inclusion bodies, increased reticulocytes, and reduced packed cell volumes when compared with birds from reference sites. Thus, birds suffered hematologic injury despite no visible oil at the time of capture. Together, these findings suggest that adverse effects of oil spills on birds may be more widespread than estimates based on avian mortality or severe visible oiling.

Environmental Toxicology and Chemistry↗

USGS2015

Factors affecting the reproductive success of American Oystercatchers Haematopus palliatus on the outer banks of North Carolina

We used an information-theoretic approach to assess the factors affecting the reproductive success of American Oystercatchers Haematopus palliatus on the Outer Banks of North Carolina. We evaluated survival with respect to nesting island, year, time of season, brood age, distance to tide (m), presence of off-road vehicles and proximity of foraging habitat. The daily nest survival (mean 0.981, standard error [SE] 0.002) was affected by year and island, and declined over the nesting season. Mammals were responsible for 54% of identified nest failures. Daily brood survival (mean 0.981, SE 0.002) varied by island and increased non-linearly with age, with highest mortality in the seven days after hatching. Model results indicate direct access to foraging sites has a positive effect on brood survival, whereas presence of off-road vehicles has a negative effect. We studied chick behavior and survival using radio telemetry and direct observation and found that vehicles caused mortality and affected behavior and resource use by oystercatcher chicks. We identified the source of mortality for 37 radio-tagged chicks. Six (16%) were killed by vehicles, 21 (57%) by predators, and 10 (27%) by exposure and starvation. From 1995 to 2008, 25 additional oystercatcher chicks were found dead, 13 (52%) killed by vehicles. Chicks on beaches closed to vehicles used beach and intertidal zones more frequently than chicks on beaches open to vehicles. Chick predators included Great Horned Owls Bubo virginianus, Fish Crows Corvus ossifragus, cats Felis catus, mink Mustela vison, raccoons Procyon lotor, and ghost crabs Ocypode albicans. The factors affecting reproductive success differed between the incubation and chick-rearing stages. Management actions that influence chick survival will have a larger effect on total productivity than actions affecting nest survival.

North Carolina↗

USGS2014

A global assessment of the conservation status of the American Oystercatcher Haematopus palliatus

The American Oystercatcher Haematopus palliatus is the most widely distributed of the four oystercatcher species in the Western Hemisphere. Its range covers almost the entire Atlantic Coast from northeastern United States to southern Argentina; on the Pacific Coast it is found from northern Mexico to central Chile. This assessment covers the entire range of the species, and is not intended to serve as a substitute or update for conservation plans that cover the U.S. Atlantic and Gulf Coast populations. Readers are advised to refer to those plans, available at www.whsrn.org, for more detailed information about U.S. populations. The subspecific taxonomy of H. palliatus is far from clear, but five races are recognized in this assessment, primarily to facilitate reference to specific populations (Fig. 1). These are nominate H. p. palliatus (coasts of eastern and southern United States; eastern Mexico; Pacific and Caribbean coasts of Central America; the Caribbean; and northern and eastern South America); H. p. frazari (Gulf of California and western Mexico); H. p. pitanay (coast of western South America); H. p. durnfordi (coast of southeast South America) and H. p. galapagensis (Galapagos Islands). The Galapagos race may deserve species status. Based on a review of existing population estimates and an extrapolation of data from quantitative surveys throughout its range, revised estimates are given for the populations of all five subspecies, and a total population of about 43,000 individuals. The nominate race is the most abundant with an estimated population size of about 20,000 individuals, while the least abundant is H. p. galapagensis , with just 300 individuals estimated. Biogeographic population estimates were used to determine 1% threshold levels and identify sites of regional and global conservation importance. A total of 20 sites have been identified for H. p. palliatus , 5 for H. p. frazari , 10 for H. p. pitanay and 10 for H. p. durnfordi . No key sites were identified for H. p. galapagensis as it is found in low density scattered throughout the islands. Of these 45 sites, 14 have counts that surpass the 1% level of the global population, and are thus of global conservation significance for the species. Because the species is a dispersed breeder, the 1% threshold is of limited value in identifying key breeding sites. For the time being, these have been defined as sites holding 20 or more breeding pairs; 17 such sites have been identified, with all but four in the United States. It is hoped that a more rigorous approach for identifying key breeding sites can be developed in the future. As an obligate coastal species, American Oystercatcher is at risk from widespread habitat loss due to coastal development, and recreational activities that lead to nest disturbance and increased predation. This is exacerbated by the species’ low population size and low reproductive success. Climate change also poses a significant future threat, especially with regard to sea-level rise. To address these threats, conservation actions are proposed that focus on increased legal protection for the species and on the conservation of key sites and important habitats. Conservation could include implementing beneficial management practices, such as restoration of nest and roost sites, controlling predation, and reducing disturbance. Education and outreach programs are needed throughout the species’ range, especially for beach users and urban planners. Training programs will be necessary to ensure successful implementation of many of the priority conservation actions. Finally, a key first step in conserving this species across its range is the creation of a H. palliatus Working Group. Modelled after the U.S. American Oystercatcher Working Group this organization could unite researchers, conservationists, and educators from across the hemisphere to foster coordinated research, conservation action, and monitoring as outlined in this assessment.

International Wader Studies↗

USGS2010

Optimal control of native predators

We apply decision theory in a structured decision-making framework to evaluate how control of raccoons ( Procyon lotor ), a native predator, can promote the conservation of a declining population of American Oystercatchers ( Haematopus palliatus ) on the Outer Banks of North Carolina. Our management objective was to maintain Oystercatcher productivity above a level deemed necessary for population recovery while minimizing raccoon removal. We evaluated several scenarios including no raccoon removal, and applied an adaptive optimization algorithm to account for parameter uncertainty. We show how adaptive optimization can be used to account for uncertainties about how raccoon control may affect Oystercatcher productivity. Adaptive management can reduce this type of uncertainty and is particularly well suited for addressing controversial management issues such as native predator control. The case study also offers several insights that may be relevant to the optimal control of other native predators. First, we found that stage-specific removal policies (e.g., yearling versus adult raccoon removals) were most efficient if the reproductive values among stage classes were very different. Second, we found that the optimal control of raccoons would result in higher Oystercatcher productivity than the minimum levels recommended for this species. Third, we found that removing more raccoons initially minimized the total number of removals necessary to meet long term management objectives. Finally, if for logistical reasons managers cannot sustain a removal program by removing a minimum number of raccoons annually, managers may run the risk of creating an ecological trap for Oystercatchers.

North Carolina↗

USGS2005

Population size and winter distribution of eastern American oystercatchers

Conservation of the eastern subspecies of the American oystercatcher ( Haematopus palliatus palliatus ) is a high priority in the U.S. Shorebird Conservation Plan, but previous population estimates were unreliable, information on distribution and habitat associations during winter was incomplete, and methods for long-term monitoring had not been developed prior to this survey. We completed the aerial survey proposed in the U.S. Shorebird Conservation Plan to determine population size, winter distribution, and habitat associations. We conducted coastal aerial surveys from New Jersey to Texas during November 2002 to February 2003. This area comprised the entire wintering range of the eastern American oystercatcher within the United States. Surveys covered all suitable habitat in the United States for the subspecies, partitioned into 3 survey strata: known roost sites, high-use habitat, and inter-coastal tidal habitat. We determined known roost sites from extensive consultation with biologists and local experts in each state. High-use habitat included sand islands, sand spits at inlets, shell rakes, and oyster reefs. Partner organizations conducted ground counts in most states. We used high resolution still photography to determine detection rates for estimates of the number of birds in particular flocks, and we used ground counts to determine detection rates of flocks. Using a combination of ground and aerial counts, we estimated the population of eastern American oystercatchers to be 10,971 /− 298. Aerial surveys can serve an important management function for shorebirds and possibly other coastal waterbirds by providing population status and trend information across a wide geographic scale.

Journal of Wildlife Management↗