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At least 19 recordsLinked to original sources
USGS2018

International migration patterns of Red-throated Loons (Gavia stellata) from four breeding populations in Alaska

Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons ( Gavia stellata ) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.

Alaska↗
USGS2007

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

Transport and behavior of pink shrimp Farfantepenaeu s duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

Florida↗
USGS1986

The Breeding Bird Survey: Its first fifteen years, 1965-1979

The Breeding Bird Survey (BBS) is an ongoing cooperative program sponsored jointly by the U.S. Fish and Wildife Service and the Canadian Wildlife Service. Its main purpose is to estimate population trends of the many species of birds that nest in North America north of Mexico and that migrate across international boundaries. This survey provides information, both locally by ecological or political regions and on a continental scale, on (1) short-term population changes that can be correlated with specific weather incidents, (2) recovery periods following catastrophic declines, (3) normal year-to-year variations, (4) long-term population trends, and (5) invasions of exotics. The BBS also permits detailed computer mapping of relative abundance of each species, either year by year to show changes in distribution and relative abundance, or the average over a period of years. It provides base-line data with which more intensive local studies can be compared. For biogeographic studies it provides uniform sampling of bird populations by major physiographic regions across the continent. In conjunction with the Audubon Christmas Bird Count, it permits comparison of summer and winter distribution of species that winter in the United States. Most species of North American birds migrate across international boundaries, especially those shared with Canada, Mexico, and the Soviet Union. As part of our responsibility under treaties with these nations, the U.S. Fish and Wildlife Service has developed the BBS to monitor avian population changes so that any adverse trends can be detected early. This provides the opportunity to determine the reasons for any increase or decrease, to define geographic areas in which changes are greatest, to study correlations between avian population changes and land-use changes, and to make recommendations for controlling undesirable bird population trends. For example, the BBS can be used to detect and estimate the extent of losses resulting from widespread use of pesticides, and to reveal whether major population changes of a given species (e.g., Dickcissel) in certain States are related to a continental decline or are merely a result of population shifts within the breeding range. Effects of urban and suburban expansion are often reflected in the loss of forest interior birds. Population trends for 230 species as well as several avian genera and families are discussed and graphed in this report. For most of these species, regional and well as continental trends are shown. The three major regions discussed are the Eastern, Central, and Western, bounded by the Mississippi River and the eastern base of the Rocky Mountains. Additional graphs for certain States or physiographic regions are included for selected species of special interest. The following paragraphs summarize general trends in the major bird families. The native herons in general are maintaining their populations, whereas the exotic Cattle Egret continues its geographic spread and its steady increase. Waterfowl as a group are stable or increasing. Although most widespread species of hawks are on the increase, the rarer species show evidence of decline. Among the gallinaceous birds, the greatest change was a sharp drop in Northern Bobwhite as a result of the exceptionally cold winters of 1976-77 and 1977-78 in the Ohio Valley and the Middle Atlantic States. Killdeer populations, except for a minor decline during these two winters, showed strong increases except in the West. American Woodcock were poorly sampled by the BBS because they were relatively inactive during daylight. Common Snipe and the other common shorebirds that nest in the United States and southern Canada exhibited stable or increasing populations, especially in the Eastern and Central regions. Herring Gull counts varied dramatically and irregularly from year to year. Laughing Gulls increased along the Atlantic coast and Franklin's Gulls declined in the interior of the continen

Resource Publication↗
USGS2019

One hundred pressing questions on the future of global fish migration science, conservation, and policy

Migration is a widespread but highly diverse component of many animal life histories. Fish migrate throughout the world's oceans, within lakes and rivers, and between the two realms, transporting matter, energy, and other species (e.g., microbes) across boundaries. Migration is therefore a process responsible for myriad ecosystem services. Many human populations depend on the presence of predictable migrations of fish for their subsistence and livelihoods. Although much research has focused on fish migration, many questions remain in our rapidly changing world. We assembled a diverse team of fundamental and applied scientists who study fish migrations in marine and freshwater environments to identify pressing unanswered questions. Our exercise revealed questions within themes related to understanding the migrating individual's internal state, navigational mechanisms, locomotor capabilities, external drivers of migration, the threats confronting migratory fish including climate change, and the role of migration. In addition, we identified key requirements for aquatic animal management, restoration, policy, and governance. Lessons revealed included the difficulties in generalizing among species and populations, and in understanding the levels of connectivity facilitated by migrating fishes. We conclude by identifying priority research needed for assuring a sustainable future for migratory fishes.

Frontiers in Ecology and Evolution↗
USGS2018

Migration trends for king and common eiders and yellow-billed loons past Point Barrow in a rapidly changing environment

Most of the king ( Somateria spectabilis ) and common eiders ( S. mollissima v-nigra ) nesting in northern Alaska and northwestern Canada migrate past Point Barrow, Alaska, during the spring and fall migration. Yellow-billed loons ( Gavia adamsii ) also migrate past Point Barrow and are a species of international conservation concern. Spring migration counts of eiders have been conducted approximately every ten years at Point Barrow since 1976, and indicated that both eider species experienced population declines of approximately 50% between 1976 and 1996, and that the declines had stabilized by 2004. Population estimates derived from migration counts have not been previously estimated for yellow-billed loons. We conducted spring counts of eiders and loons in 2015 and 2016 to obtain population estimates to compare with those from 1994, 1995, 2003, and 2004 in order to evaluate long-term and current trends. We estimated (95% confidence intervals) that 796,419 (304,011) king and 96,775 (39,913) common eiders passed Point Barrow in 2015, and 322,381 (145,833) king and 130,390 (34,548) common eiders passed Point Barrow in 2016. Both and king and common eider population estimates increased from 1994 through 2016, however, the increase over time was not significant (F < 5.07, P > 0.087, df = 1). Our population estimates for king eiders were very different between the two years of this study, possibly due to a very short and intense migration peak in 2016, resulting in a population count that was biased low because sampling periods did not adequately capture the peak of migration. The numbers of common eiders were similar between the two years, as well as for the 12 years since the previous count. Photo analysis of flocks indicated that observer counts were on average 4% lower than photo counts (paired t-test; |t| = 3.26, df = 297, P < 0.001) for flocks less than 1400 individuals (observer count). Estimates of yellow-billed loon populations were very variable and are biased low as numbers of loons passing Pt. Barrow were still high when our counts ended in late May. It is important that counts continue to be conducted for these species of conservation and subsistence importance, but that techniques be refined to reduce bias and variability, and to find solutions to the increasing difficulty of conducting a count from the shore-fast ice in spring.

Alaska↗
USGS2018

Migratory hummingbirds make their own rules: The decision to resume migration along a barrier

Knowing how naïve migrants respond to intrinsic and extrinsic factors experienced en route will allow a more thorough understanding of the endogenous migratory programme. To understand how inexperienced individuals respond to ecological features, we tracked the migratory departures of juvenile ruby-throated hummingbirds, Archilochus colubris , one of the smallest (∼ 3 g) and least-studied migrants, along the Gulf of Mexico during southbound migration using an international automated radiotelemetry system. The recent miniaturization of radiotags provides a novel method to track one of the smallest migratory birds, rendering the first information on departure decisions of known hummingbirds in relation to an ecological barrier. Using weather conditions and individual attributes, we also determined which factors influenced the time and direction of departure from a coastal stopover site. Most migrants (83%) departed in the morning, and daily departure time was only influenced by stopover duration, the amount of time spent at a stopover site. The majority (77%) of departure orientations paralleled the coastline, and we found little influence of any factor on departure direction. Our results reveal that (1) juvenile hummingbirds departing coastal Alabama move in a direction indicative of a circum-Gulf path during southbound migration and (2) departure decisions support a fly-and-forage strategy in which hummingbirds likely take advantage of resources along the coast while moving towards their destination.

Gulf of Mexico↗
USGS2017

Semi-quantitative assessment of disease risks at the human, livestock, wildlife interface for the Republic of Korea using a nationwide survey of experts: A model for other countries

Wildlife-associated diseases and pathogens have increased in importance; however, management of a large number of diseases and diversity of hosts is prohibitively expensive. Thus, the determination of priority wildlife pathogens and risk factors for disease emergence is warranted. We used an online questionnaire survey to assess release and exposure risks, and consequences of wildlife-associated diseases and pathogens in the Republic of Korea (ROK). We also surveyed opinions on pathways for disease exposure, and risk factors for disease emergence and spread. For the assessment of risk, we employed a two-tiered, statistical K -means clustering algorithm to group diseases into three levels (high, medium and low) of perceived risk based on release and exposure risks, societal consequences and the level of uncertainty of the experts’ opinions. To examine the experts’ perceived risk of routes of introduction of pathogens and disease amplification and spread, we used a Bayesian, multivariate normal order-statistics model. Six diseases or pathogens, including four livestock and two wildlife diseases, were identified as having high risk with low uncertainty. Similarly, 13 diseases were characterized as having high risk with medium uncertainty with three of these attributed to livestock, six associated with human disease, and the remainder having the potential to affect human, livestock and wildlife (i.e., One Health). Lastly, four diseases were described as high risk with high certainty, and were associated solely with fish diseases. Experts identified migration of wildlife, international human movement and illegal importation of wildlife as the three routes posing the greatest risk of pathogen introduction into ROK. Proximity of humans, livestock and wildlife was the most significant risk factor for promoting the spread of wildlife-associated diseases and pathogens, followed by high density of livestock populations, habitat loss and environmental degradation, and climate change. This study provides useful information to decision makers responsible for allocating resources to address disease risks. This approach provided a rapid, cost-effective method of risk assessment of wildlife-associated diseases and pathogens for which the published literature is sparse.

Transboundary and Emerging Diseases↗
USGS2022

Perceptions of conservation introduction to inform decision support among U.S. Fish and Wildlife Service employees

Executive Summary Around the globe, fish and wildlife managers are facing increasingly complex management issues because of multiscale ecological effects like climate change, species invasion, and land-use change. Managers seeking to prevent extinctions or preserve ecosystems are increasingly considering more interventionist techniques to overcome the resulting changes. Among those techniques, translocation methods that intentionally move species into new, less impacted habitats are being considered. These types of translocations are known by a range of terms, including “managed relocation” and “assisted migration,” but the International Union for the Conservation of Nature’s Species Survival Commission (IUCN SSC, 2013) has proposed “conservation introduction” (CI) as a standard term. As defined by the IUCN SSC, CI is the intentional movement of a species or population outside its indigenous range for conservation purposes. CI can be divided into two forms: assisted colonization and ecological replacement. Assisted colonization is moving species outside its indigenous range to prevent extinction or extirpation of a population. Ecological replacement is moving species to fulfill an important niche that is necessary within an ecosystem. Proponents suggest these methods are necessary to address the ecological challenges managers are trying to overcome. Opponents point out the potential for species to become invasive, introduce disease or parasites, and cause other cascading impacts throughout the ecosystem. The result is controversy and disagreement. As such, it will be imperative to develop clear guidelines and best practices to be followed within wildlife management agencies to prevent potential To this end, the U.S. Fish and Wildlife Service (USFWS) partnered with the U.S. Geological Survey (USGS) to develop the current project. The intent was to describe the perceptions of USFWS personnel across many aspects of CI so that the USFWS could use this information in the planning and development of their own internal decision-support framework for CI. This report is presented in five sections. Section 1 introduces the project and provides an in-depth overview of background literature related to CI. Section 2 describes the study design, methods, and study participant characteristics. Section 3 describes key results and recommendations related to the development of a USFWS decision framework. Section 4 investigates a range of perceptions held by participants and establishes baseline information for how USFWS personnel may view CI and its application. Types of viewpoints surveyed include preferred terms and definitions, perceived barriers, perceived risks and tradeoffs, and aspects of success. Perceived barriers refers to factors that may prevent successful implementation of CI and perceived risks refers to potential negative outcomes that may occur as a result of implementing CI. Section 5 provides an overview of our conclusions for this project. Overall, we found that CI is likely to be viewed positively within the USFWS, but employees offered cautions and caveats. Most participants we interviewed feel that it is a necessary tool that will be indispensable in certain situations but also feel that there is more risk associated than with more traditional methods. For this reason, many participants are concerned about the assessment and planning that should be conducted prior to any CI effort. Our results indicate that many USFWS personnel will be open to CI being adopted more regularly but will be looking for clear guidance on how it should be implemented.

Scientific Investigations Report↗
USGS2011

Relationship of external fish condition to pathogen prevalence and out-migration survival in juvenile steelhead

Understanding how the external condition of juvenile salmonids is associated with internal measures of health and subsequent out‐migration survival can be valuable for population monitoring programs. This study investigated the use of a rapid, nonlethal, external examination to assess the condition of run‐of‐the‐river juvenile steelhead Oncorhynchus mykiss migrating from the Snake River to the Pacific Ocean. We compared the external condition (e.g., body injuries, descaling, external signs of disease, fin damage, and ectoparasite infestations) with (1) the internal condition of a steelhead as measured by the presence of selected pathogens detected by histopathology and polymerase chain reaction analysis and (2) out‐migration survival through the Snake and Columbia rivers as determined by passive integrated transponder (PIT) tag technology. The results from steelhead captured and euthanized ( n = 222) at Lower Monumental Dam on the lower Snake River in 2008 indicated that external condition was significantly correlated with selected measures of internal condition. The odds of testing positive for a pathogen were 39.2, 24.3, and 5.6 times greater for steelhead with severe or moderate external signs of disease or more than 20% descaling, respectively. Capture–recapture models of 22,451 PIT‐tagged steelhead released at Lower Monumental Dam in 2007–2009 indicated that external condition was significantly correlated with juvenile survival. The odds of out‐migration survival for steelhead with moderate or severe external signs of disease, more than 20% descaling, or severe fin damage were 5.7, 4.9, 1.6, and 1.3 times lower, respectively, than those for steelhead without these external conditions. This study effectively demonstrated that specific measures of external condition were associated with both the internal condition and out‐migration survival of juvenile steelhead.

Oregon, Washington↗
USGS2013

Cost-effectiveness analysis of sandhill crane habitat management

Invasive species often threaten native wildlife populations and strain the budgets of agencies charged with wildlife management. We demonstrate the potential of cost-effectiveness analysis to improve the efficiency and value of efforts to enhance sandhill crane ( Grus canadensis ) roosting habitat. We focus on the central Platte River in Nebraska (USA), a region of international ecological importance for migrating avian species including sandhill cranes. Cost-effectiveness analysis is a valuation process designed to compare alternative actions based on the cost of achieving a pre-determined objective. We estimated costs for removal of invasive vegetation using geographic information system simulations and calculated benefits as the increase in area of sandhill crane roosting habitat. We generated cost effectiveness values for removing invasive vegetation on 7 land parcels and for the entire central Platte River to compare the cost-effectiveness of management at specific sites and for the central Platte River landscape. Median cost effectiveness values for the 7 land parcels evaluated suggest that costs for creating 1 additional hectare of sandhill crane roosting habitat totaled US $1,595. By contrast, we found that creating an additional hectare of sandhill crane roosting habitat could cost as much as US $12,010 for some areas in the central Platte River, indicating substantial cost savings can be achieved by using a cost effectiveness analysis to target specific land parcels for management. Cost-effectiveness analysis, used in conjunction with geographic information systems, can provide decision-makers with a new tool for identifying the most economically efficient allocation of resources to achieve habitat management goals.

Nebraska↗
USGS1981

Development of the benethic nepheloid layer on the south Texas continental shelf, western Gulf of Mexico

A monitoring study of suspended sediment on the South Texas Continental Shelf indicates that a turbid benthic nepheloid layer is regionally persistent. A sequence of quasi-synoptic measurements of the water column obtained during six cruises in an 18-month period indicates substantial spatial and temporal variability in nepheloidlayer characteristics. Regionally, the thickness of the shelf nepheloid layer increases both seaward and in a convergent alongshelf direction. Greatest thicknesses occur over a muddy substrate, indicating a causal relationship; maximum observed local thickness is 35 m which occurs along the southern shelf break. Analyses of suspended particulate matter in shelf bottom waters indicate mean concentrations ranging from 49 · 10 4 to 111 · 10 4 particle counts/cc; concentrations persistently increase shoreward throughout the region. Bottom particulate matter is predominantly composed of inorganic detritus. Admixtures of organic skeletal particles, primarily diatoms, are generally present but average less than 10% of the total particulate composition. Texturally, the particulate matter in bottom waters is predominantly poorly sorted sediment composed of very fine silt (3.9–7.8 μm). The variability in nepheloid-layer characteristics indicates a highly dynamic shelf feature. The relationship of nepheloid-layer characteristics to hydrographic and substrate conditions suggests a conceptual model whereby nepheloid-layer development and maintenance are the results of the resuspension of sea-floor sediment. Bottom turbulence is attributed primarily to vertical shear and shoaling progressive internal waves generated by migrating shelf-water masses, especially oceanic frontal systems, and secondarily to shoaling surface gravity waves.

Texas↗
USGS2007

Aquifer susceptibility to perchlorate contamination in a highly urbanized environment

Perchlorate contamination from anthropogenic sources has been released into the Rialto-Colton, California, USA, groundwater flow system since the 1940s during its production, distribution, storage, and use. Preliminary analysis of lithological, geophysical, and water-chemistry data provided new understanding of the pathways of perchlorate migration that aid in assessing the susceptibility of drinking-water supplies to contamination within the Rialto-Colton basin. Vertical migration of perchlorate into the main water-producing aquifers is restricted by an areally extensive old soil surface; however, perchlorate data indicate contamination below this soil surface. Possible pathways for the downward migration of the contaminated water include wellbore flow and discontinuities in the old soil surface. Horizontal migration of perchlorate is influenced by lithology and faults within the basin. The basin fill is a heterogeneous mixture of boulders, gravel, sand, silt, and clay, and internal faults may restrict perchlorate migration in some areas.

California↗
USGS2023

Pacific Barrow’s Goldeneye refine migratory phenology in response to overwintering temperatures and annual snow melt

Timing of seasonal bird migrations is broadly determined by internal biological clocks, which are synchronized by photoperiod, but individuals often refine their migratory timing decisions in response to external factors. Using 11 years of satellite telemetry data, we show that Pacific Barrow’s Goldeneye ( Bucephala islandica ), at higher latitudes, initiated spring and molt migrations later and fall migration earlier than individuals at lower latitudes. We further show that individuals refined migratory timing in response to interannual variation in environmental conditions. Individual Barrow’s Goldeneye initiated spring migration earlier in years with warmer springs at their overwintering locations and concluded spring migration earlier in years with earlier annual snow melt on their breeding grounds. Because individuals respond to conditions both where they initiate and where they conclude spring migration, our results suggest that Barrow’s Goldeneye update their migratory decisions en route. For all three migrations in their annual cycle, birds delayed initiating migration if they had been captured and tagged prior to that migration. Birds that initiated migration late for their latitude were less likely to include a stopover and completed that migration faster, partially compensating for delayed departures. Our results are consistent with the hypothesis that Barrow’s Goldeneye use a combination of endogenous cues and environmental cues in migratory decision making. Sensitivity to environmental cues suggests that Barrow’s Goldeneye may have behavioural plasticity that is adaptive when faced with ongoing climate change.

Alaska, Alberta, British Columbia↗
USGS2009

International importance of the eastern Chukchi Sea as a staging area for migrating king eiders

The evaluation of habitats used by arctic birds on migration is crucial for their conservation. We explored the importance of the eastern Chukchi Sea (ECS) as a staging area for king eiders (Somateria spectabilis) migrating between breeding areas in Siberia and western North America and wintering areas in the Bering Sea. We tracked 190 king eiders with satellite transmitters between 1997 and 2007. In late summer, 74% of satellite-tracked king eiders migrating south staged in the ECS for 13 ?? 13 (SD) days between late June and early November. During spring migration, king eiders staged in the ECS between mid-April and early June for 21 ?? 10 days. All instrumented birds migrating to breeding grounds in western North America (n = 62), and 6 of 11 males migrating to breeding grounds in Siberia, used this area for at least 1 week during spring migration. The importance of this staging area renders it possible that industrial development could adversely affect king eider populations in both Siberia and North America. ?? 2009 US Government.

Polar Biology↗
USGS2010

Geologic controls on the recent evolution of oyster reefs in Apalachicola Bay and St. George Sound, Florida

Apalachicola Bay and St. George Sound contain the largest oyster fishery in Florida, and the growth and distribution of the numerous oyster reefs here are the combined product of modern estuarine conditions in the bay and its late Holocene evolution. Sidescan-sonar imagery, bathymetry, high-resolution seismic profiles, and sediment cores show that oyster beds occupy the crests of a series of shoals that range from 1 to 7 km in length, trend roughly north-south perpendicular to the long axes of the bay and sound, and are asymmetrical with steeper sides facing to the west. Surface sediment samples show that the oyster beds consist of shelly sand, while much of the remainder of the bay floor is covered by mud delivered by the Apalachicola River. The present oyster reefs rest on sandy delta systems that advanced southward across the region between 6400 and 4400 yr BP when sea level was 4–6 m lower than present. Oysters started to colonize the region around 5100 yr BP and became extensive by 1200 and 2400 yr BP. Since 1200 yr BP, their aerial extent has decreased due to burial of the edges of the reefs by the prodelta mud that continues to be supplied by the Apalachicola River. Oyster reefs that are still active are narrower than the original beds, have grown vertically, and become asymmetrical in cross-section. Their internal bedding indicates they have migrated westward, suggesting a net westerly transport of sediment in the bay.

Florida↗
USGS2014

Migration, foraging, and residency patterns for Northern Gulf loggerheads: implications of local threats and international movements

Northern Gulf of Mexico (NGoM) loggerheads ( Caretta caretta ) make up one of the smallest subpopulations of this threatened species and have declining nest numbers. We used satellite telemetry and a switching state-space model to identify distinct foraging areas used by 59 NGoM loggerheads tagged during 2010&ndash;2013. We tagged turtles after nesting at three sites, 1 in Alabama (Gulf Shores; n = 37) and 2 in Florida (St. Joseph Peninsula; n = 20 and Eglin Air Force Base; n = 2). Peak migration time was 22 July to 9 August during which >40% of turtles were in migration mode; the mean post-nesting migration period was 23.0 d (&plusmn;13.8 d SD). After displacement from nesting beaches, 44 turtles traveled to foraging sites where they remained resident throughout tracking durations. Selected foraging locations were variable distances from tagging sites, and in 5 geographic regions; no turtles selected foraging sites outside the Gulf of Mexico (GoM). Foraging sites delineated using 50% kernel density estimation were located a mean distance of 47.6 km from land and in water with mean depth of &minus;32.5 m; other foraging sites, delineated using minimum convex polygons, were located a mean distance of 43.0 km from land and in water with a mean depth of &minus;24.9 m. Foraging sites overlapped with known trawling activities, oil and gas extraction activities, and the footprint of surface oiling during the 2010 Deepwater Horizon oil spill (n = 10). Our results highlight the year-round use of habitats in the GoM by loggerheads that nest in the NGoM. Our findings indicate that protection of females in this subpopulation requires both international collaborations and management of threats that spatially overlap with distinct foraging habitats.

Gulf of Mexico↗
USGS2013

Origin and lateral migration of linear dunes in the Qaidam Basin of NW China revealed by dune sediments, internal structures, and optically stimulated luminescence ages, with implications for linear dunes on Titan: discussion

Zhou et al. (2012) proposed that longitudinal dunes in the Qaidam Basin, China, formed like yardangs: by erosion into sediment that was not deposited by those dunes. Because erosion occurs on the upwind flanks of most migrating dunes ( Rubin and Hunter, 1982 , 1985 ), the key to demonstrating a yardang-like origin is to show that the dunes did not deposit the strata that they contain. Zhou et al. made this argument by proposing that: (1) The dunes have not deposited cross-strata in the past 810 yr. (2) Cross-bedding within the dunes was not deposited by the dunes on the present-day land surface, but rather by older dunes that had a different morphology. (3) The present dunes are a later generation, &ldquo;most likely of erosional origin similar to yardangs with orientations controlled by strikes of joints,&rdquo; (p. 1147). (4) Rates of deflation in the dune field have been extremely high for the past 810&ndash;2440 yr. This commentary reviews these conclusions, reviews contradictory observations, and considers alternative interpretations.

GSA Bulletin↗