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At least 1,513 records · Page 84Linked to original sources
USGS2012

A circumpolar monitoring framework for polar bears

Polar bears ( Ursus maritimus ) occupy remote regions that are characterized by harsh weather and limited access. Polar bear populations can only persist where temporal and spatial availability of sea ice provides adequate access to their marine mammal prey. Observed declines in sea ice availability will continue as long as greenhouse gas concentrations rise. At the same time, human intrusion and pollution levels in the Arctic are expected to increase. A circumpolar understanding of the cumulative impacts of current and future stressors is lacking, long-term trends are known from only a few subpopulations, and there is no globally coordinated effort to monitor effects of stressors. Here, we describe a framework for an integrated circumpolar monitoring plan to detect ongoing patterns, predict future trends, and identify the most vulnerable polar bear subpopulations. We recommend strategies for monitoring subpopulation abundance and trends, reproduction, survival, ecosystem change, human-caused mortality, human–bear conflict, prey availability, health, stature, distribution, behavioral change, and the effects that monitoring itself may have on polar bears. We assign monitoring intensity for each subpopulation through adaptive assessment of the quality of existing baseline data and research accessibility. A global perspective is achieved by recommending high intensity monitoring for at least one subpopulation in each of four major polar bear ecoregions. Collection of data on harvest, where it occurs, and remote sensing of habitat, should occur with the same intensity for all subpopulations. We outline how local traditional knowledge may most effectively be combined with the best scientific methods to provide comparable and complementary lines of evidence. We also outline how previously collected intensive monitoring data may be sub-sampled to guide future sampling frequencies and develop indirect estimates or indices of subpopulation status. Adoption of this framework will inform management and policy responses to changing worldwide polar bear status and trends.

Ursus↗
USGS2006

A Bayesian random effects discrete-choice model for resource selection: Population-level selection inference

Modeling the probability of use of land units characterized by discrete and continuous measures, we present a Bayesian random-effects model to assess resource selection. This model provides simultaneous estimation of both individual- and population-level selection. Deviance information criterion (DIC), a Bayesian alternative to AIC that is sample-size specific, is used for model selection. Aerial radiolocation data from 76 adult female caribou (Rangifer tarandus) and calf pairs during 1 year on an Arctic coastal plain calving ground were used to illustrate models and assess population-level selection of landscape attributes, as well as individual heterogeneity of selection. Landscape attributes included elevation, NDVI (a measure of forage greenness), and land cover-type classification. Results from the first of a 2-stage model-selection procedure indicated that there is substantial heterogeneity among cow-calf pairs with respect to selection of the landscape attributes. In the second stage, selection of models with heterogeneity included indicated that at the population-level, NDVI and land cover class were significant attributes for selection of different landscapes by pairs on the calving ground. Population-level selection coefficients indicate that the pairs generally select landscapes with higher levels of NDVI, but the relationship is quadratic. The highest rate of selection occurs at values of NDVI less than the maximum observed. Results for land cover-class selections coefficients indicate that wet sedge, moist sedge, herbaceous tussock tundra, and shrub tussock tundra are selected at approximately the same rate, while alpine and sparsely vegetated landscapes are selected at a lower rate. Furthermore, the variability in selection by individual caribou for moist sedge and sparsely vegetated landscapes is large relative to the variability in selection of other land cover types. The example analysis illustrates that, while sometimes computationally intense, a Bayesian hierarchical discrete-choice model for resource selection can provide managers with 2 components of population-level inference: average population selection and variability of selection. Both components are necessary to make sound management decisions based on animal selection.

Journal of Wildlife Management↗
USGS2004

Using satellite radiotelemetry data to delineate and manage wildlife populations

The greatest promise of radiotelemetry always has been a better understanding of animal movements. Telemetry has helped us know when animals are active, how active they are, how far and how fast they move, the geographic areas they occupy, and whether individuals vary in these traits. Unfortunately, the inability to estimate the error in animals utilization distributions (UDs), has prevented probabilistic linkage of movements data, which are always retrospective, with future management actions. We used the example of the harvested population of polar bears ( Ursus maritimus ) in the Southern Beaufort Sea to illustrate a method that provides that linkage. We employed a 2-dimensional Gaussian kernel density estimator to smooth and scale frequencies of polar bear radio locations within cells of a grid overlying our study area. True 2-dimensional smoothing allowed us to create accurate descriptions of the UDs of individuals and groups of bears. We used a new method of clustering, based upon the relative use collared bears made of each cell in our grid, to assign individual animals to populations. We applied the fast Fourier transform to make bootstrapped estimates of the error in UDs computationally feasible. Clustering and kernel smoothing identified 3 populations of polar bears in the region between Wrangel Island, Russia, and Banks Island, Canada. The relative probability of occurrence of animals from each population varied significantly among grid cells distributed across the study area. We displayed occurrence probabilities as contour maps wherein each contour line corresponded with a change in relative probability. Only at the edges of our study area and in some offshore regions were bootstrapped estimates of error in occurrence probabilities too high to allow prediction. Error estimates, which also were displayed as contours, allowed us to show that occurrence probabilities did not vary by season. Near Barrow, Alaska, 50% of bears observed are predicted to be from the Chukchi Sea population and 50% from the Southern Beaufort Sea population. At Tuktoyaktuk, Northwest Territories, Canada, 50% are from the Southern Beaufort Sea and 50% from the Northern Beaufort Sea population. The methods described here will aid managers of all wildlife that can be studied by telemetry to allocate harvests and other human perturbations to the appropriate populations, make risk assessments, and predict impacts of human activities. They will aid researchers by providing the refined descriptions of study populations that are necessary for population estimation and other investigative tasks. Arctic, Beaufort Sea, boundaries, clustering, Fourier transform, kernel, management, polar bears, population delineation, radiotelemetry, satellite, smoothing, Ursus maritimus

Beaufort Sea, Chukchi Sea↗
USGS2010

Winter fidelity and apparent survival of lesser snow goose populations in the Pacific flyway

The Beringia region of the Arctic contains 2 colonies of lesser snow geese (Chen caerulescens caerulescens) breeding on Wrangel Island, Russia, and Banks Island, Canada, and wintering in North America. The Wrangel Island population is composed of 2 subpopulations from a sympatric breeding colony but separate wintering areas, whereas the Banks Island population shares a sympatric wintering area in California, USA, with one of the Wrangel Island subpopulations. The Wrangel Island colony represents the last major snow goose population in Russia and has fluctuated considerably since 1970, whereas the Banks Island population has more than doubled. The reasons for these changes are unclear, but hypotheses include independent population demographics (survival and recruitment) and immigration and emigration among breeding or wintering populations. These demographic and movement patterns have important ecological and management implications for understanding goose population structure, harvest of admixed populations, and gene flow among populations with separate breeding or wintering areas. From 1993 to 1996, we neckbanded molting birds at their breeding colonies and resighted birds on the wintering grounds. We used multistate mark-recapture models to evaluate apparent survival rates, resighting rates, winter fidelity, and potential exchange among these populations. We also compared the utility of face stain in Wrangel Island breeding geese as a predictor of their wintering area. Our results showed similar apparent survival rates between subpopulations of Wrangel Island snow geese and lower apparent survival, but higher emigration, for the Banks Island birds. Males had lower apparent survival than females, most likely due to differences in neckband loss. Transition between wintering areas was low (<3%), with equal movement between northern and southern wintering areas for Wrangel Island birds and little evidence of exchange between the Banks and northern Wrangel Island populations. Face staining was an unreliable indicator of wintering area. Our findings suggest that northern and southern Wrangel Island subpopulations should be considered a metapopulation in better understanding and managing Pacific Flyway lesser snow geese. Yet the absence of a strong population connection between Banks Island and Wrangel Island geese suggests that these breeding colonies can be managed as separate but overlapping populations. Additionally, winter population fidelity may be more important in lesser snow geese than in other species, and both breeding and wintering areas are important components of population management for sympatric wintering populations.

Journal of Wildlife Management↗
USGS1988

Littoral foraging by red phalaropes during spring in the northern Bering Sea

Phalaropes demonstrate considerable plasticity in their choice of foraging habitats. The Red Phalarope ( Phalaropus fulicaria ) alternates use of pelagic environments in winter and migration (Taning 1933, Stanford 1953, Briggs et al 1984) with wet tundra habitats during the breeding season (Kistchinski 1975, Mayfield 1979, Ridley 1980). Foods available and taken in littoral zones of the Arctic Ocean in fall have been identified (Conners and Risebrough 1978, Johnson and Richardson 1980), but otherwise little attention has been devoted to the transition between the marine and terrestrial periods of the Red Phalarope’s life history. We report phalarope use of littoral areas during spring in the northern Bering Sea and Kongkok Bay, St. Lawrence Island, Alaska. In addition, we describe phalarope foraging tactics and foods available in the sur zone, emphasizing this form of littoral foraging as an opportunistic and facultative feeding strategy.

Alaska↗
USGS1992

Density of loons in central Alaska

Loons breed across North America from the high arctic south to about 43 north latitude. (AOU 1983). Populations, particularly of Common Loons ( Gavia immer ) have recently declined in the continental U.S. and southern Canada (Sutcliff 1979, Titus and VanDruff 1981, McIntyre 1988). As a result, state and private natural resource organizations began more intensive monitoring of loon populations (in McIntyre 1986, Strong 1988). These surveys, however, are restricted to areas accessible by road, although recently aircraft were used for more remote areas (Lee and Arbuckle 1988, Strong 1990).

Alaska↗
USGS1994

Residency patterns of migrating sandpipers at a midcontinental stopover

Arctic-nesting shorebirds require several refueling stops during their long migrations between breeding grounds and Central and South American wintering areas. The protection of stopover habitats for transcontinental migrants depends on whether birds fly long distances between a few select sites or fly short distances and stop at several wetlands. Although the Great Plains historically provided a vast array of wetlands for use by migrants, wetland loss and conversion have reduced the availability of stopover sites in recent decades. In this study, we examined (1) residency periods, (2) fat dynamics, and (3) migration chronology of two shorebird species, the Semipalmated Sandpiper ( Calidris pusilla ) and White-rumped Sandpiper ( C. fuscicollis ) at Quivira National Wildlife Refuge (NWR), Kansas. Semipalmated Sandpipers had prolonged periods of species residency with overlapping arrivals and departures. Individual residency periods were highly variable and were unrelated to lipid reserves upon arrival. In contrast, White-rumped Sandpipers arrived and departed more synchronously. Birds that arrived in poor condition stayed longer than those with more body fat in 1991, but not in 1992. Wind direction did not influence patterns of departures of either species. We hypothesize that Semipalmated Sandpipers are ecologically eurytopic when migrating across the Great Plains in the spring. Highly variable patterns in arrival, residency, and lipid levels indicate that spring migration of this species is relaxed and opportunistic. White-rumped Sandpipers showed a pattern of reduced flexibility. Flight range estimates suggest that most birds require intermediate stopovers before reaching the breeding grounds. Interior wetlands appear to function as migration stopovers rather than staging areas for shorebirds.

The Condor↗
USGS1993

Survival and pre-fledging body mass in juvenile emperor geese

A positive relationship exists between fledgling body mass and juvenile survival for some altricial (Krementz et al. 1989, Magrath 1991, Linden et al. 1992) and precocial (Owen and Black 1989, Longcore et al. 1991, Francis et al. 1992) species. Because the energetic demands of migration are high, physiologic condition may be a proximate determinate of juvenile survival in geese. Owen and Black (1989) found that pre-fledging body mass of Barnacle Geese ( Branta leucopsis ) was positively related to juvenile survival to winter. First-year survival in Lesser Snow Geese ( Chen caerulescens caerulescens ) was also affected by pre-fledging body mass (Francis et al. 1992). It is not clear, however, when such mass-related mortality occurs. Both species migrate >3,000 km to wintering areas, but make use of fall staging areas while en route (Owen 1980, Francis and Cooke 1992). Survival fo geese between fledging and staging areas has not been addressed. Measurement of survival during this interval could provide insight to the timing of juvenile mortality in arctic geese.

Alaska↗
USGS1996

Black brant from Alaska staging and wintering in Japan

Black brant (Branta bernicla nigricans) nest in colonies in arctic Canada, Alaska, and Russia (Derksen and Ward 1993, Sedinger et al. 1993). Virtually the entire population stages in fall at Izembek Lagoon near the tip of the Alaska Peninsula (Bellrose 1976) before southward migration (Dau 1992) to winter habitats in British Columbia, Washington, Oregon, California, and Baja California (Subcommittee on Black Brant 1992). A small number of black brant winter in Japan, Korea, and China (Owen 1980). In Japan 3,000&ndash;5,000 brant of unknown origin stop over in fall, and a declining population (<1,000) of birds winter here, primarily in the northern islands (Brazil 1991, Miyabayashi et al. 1994). Here, we report sightings of brant in Japan that were marked in Alaska and propose a migration route based on historical and recent observations and weather patterns.

Alaska↗
USGS1998

Leucocytozoon simondi in Emperor Geese from the Yukon-Kuskokwim Delta in Alaska

We surveyed Emperor Geese ( Chen canagica ) in western Alaska for avian hematozoa. Blood smears were collected from 134 adults and goslings in late July 1996, on their breeding grounds on the Yukon-Kuskokwim Delta. One of 134 (0.7%) Emperor Geese harbored Leucocytozoon simondi , representing a new host record for this parasite. No other hematozoa were detected. This is one of few reports of avian blood parasites from the arctic tundra.

Alaska↗
USGS1996

Population delineation of polar bears using satellite collar data

To produce reliable estimates of the size or vital rates of a given population, it is important that the boundaries of the population under study are clearly defined. This is particularly critical for large, migratory animals where levels of sustainable harvest are based on these estimates, and where small errors may have serious long-term consequences for the population. Once populations are delineated, rates of exchange between adjacent populations can be determined and accounted/corrected for when calculating abundance (e.g., based on mark-recapture data). Using satellite radio-collar locations for polar bears in the western Canadian Arctic, we illustrate one approach to delineating wildlife populations that integrates cluster analysis methods for determining group membership with home range plotting procedures to define spatial utilization. This approach is flexible with respect to the specific procedures used and provides an objective and quantitative basis for defining population boundaries.

Ecological Applications↗
USGS1996

A bayesian approach to classification criteria for spectacled eiders

To facilitate decisions to classify species according to risk of extinction, we used Bayesian methods to analyze trend data for the Spectacled Eider, an arctic sea duck. Trend data from three independent surveys of the Yukon-Kuskokwim Delta were analyzed individually and in combination to yield posterior distributions for population growth rates. We used classification criteria developed by the recovery team for Spectacled Eiders that seek to equalize errors of under- or overprotecting the species. We conducted both a Bayesian decision analysis and a frequentist (classical statistical inference) decision analysis. Bayesian decision analyses are computationally easier, yield basically the same results, and yield results that are easier to explain to nonscientists. With the exception of the aerial survey analysis of the 10 most recent years, both Bayesian and frequentist methods indicated that an endangered classification is warranted. The discrepancy between surveys warrants further research. Although the trend data are abundance indices, we used a preliminary estimate of absolute abundance to demonstrate how to calculate extinction distributions using the joint probability distributions for population growth rate and variance in growth rate generated by the Bayesian analysis. Recent apparent increases in abundance highlight the need for models that apply to declining and then recovering species.

Alaska↗
USGS2017

Notes on the Archaeology of the Utukok River, Northwestern Alaska

Early in May 1947, a United States Geological Survey field party of five was flown by ski plane to the headwaters of the Utukok River in northwestern Alaska, about 200 miles southwest of Barrow. Three 18–foot canvas boats of a special folding design were taken in along with enough equipment for four months. Food caches had been flown in to six localities on the 200–mile–long river a short time before the group landed. When the “break–up” came late in May the party started down the river working out the geology of the area from a series of 18 camps which were established before reaching the Arctic Ocean in August. During the season 17 archaeological sites were discovered. It is believed that most of these sites are of Eskimo origin and are probably fairly recent. However, an important exception is a well–made Folsom point, announcement of which has been made.

Alaska↗
USGS1998

Routes and travel rates of migrating Peregrine Falcons Falco peregrinus and Swainson's Hawks Buteo swainsoni in the Western Hemisphere

We describe and compare the migration routes, length of migration, and duration of migration of Peregrine Falcons Falco peregrinus tundrius and Swainson's Hawks Buteo swainsoni in the Western Hemisphere. We radio tracked migrants using the Argos satellite system. Our initial samples were 34 Swainson's Hawks from representative areas of their breeding range, and 61 Peregrine Falcons captured at nest sites across the North American boreal forest and low Arctic or on the migration routes along the mid-Atlantic and Gulf of Mexico coasts. The average distance of migration for Peregrines was 8,624 km southward, and 8,247 km northward. Peregrines travelled at an average rate of 172 km/d southward and 198 km/d going north. Peregrine Falcons used at least three broad, general routes south from the breeding areas, and individuals stopped migrating as far north as the U.S.A. mid-Atlantic coast and as far south as central Argentina. The radiomarked Peregrine Falcons used coastal routes, mid-continental routes, and water-crossing routes: the Davis Strait and Caribbean Sea. During northward migration, Peregrines migrating through at Padre Island, Texas diverged for destinations from central Alaska across the continent to central West Greenland. Swainson's Hawks migrated an average of about 13,504 km southward and 11,952 km northward, and travelled 188 km/d southward and 150 km/d northward. Swainson's Hawks converged in eastern Mexico on the Gulf of Mexico coast. Southward, these hawks followed a narrow, well-defined path through Central America, across the Andes Mountains in Columbia, and east of the Andes to central Argentina where they all spent the austral summer. Swainson's Hawks northward migration largely retraced their southward route.

Journal of Avian Biology↗
USGS1995

Spring-staging ecology of midcontinent greater white-fronted geese

A major part of the midcontinent greater white-fronted goose ( Anser albifrons ) population stages for several weeks in spring in the Rainwater Basin Area (RBA) of south-central Nebraska where substantial mortality from disease occurs periodically. Effective management of this population requires better data on use of habitat, vulnerability to disease, and the role of staging areas in migration and reproduction. We studied use of habitat, foods, nutrient dynamics, and effect of changes in agriculture on food availability and habitat needs in spring 1979-80. During daylight, geese were observed primarily in harvested cornfields (76%) and growing winter wheat (23%). Corn grain and winter wheat shoots composed 90 and 9%, respectively, of foods consumed by collected geese ( n = 42). Feeding activity did not vary among post-harvest cornfield treatments except that little feeding occurred ( P < 0.05) in moldboard-plowed fields (<1%). Fat content for all geese increased ( P ≤ 0.01) with Julian date; protein content increased ( P = 0.03) only among adult females, and there was no evidence ( P > 0.05) of temporal variation in calcium content. Adult geese storing 14.2 g of fat per day deposited approximately 582 g of fat between 22 February and 8 April. Energy requirements for thermal regulation were small compared with requirements for fat synthesis and probably had little effect on nutrient deposition. The 34,000 white-fronted geese present on the Harvard Marsh and Prairie Dog Marsh study areas in March 1980 probably used <20% of the corn available within a 5-km radius. We believe that midcontinent white-fronted geese arrive on Arctic breeding grounds with larger and less variable fat reserves than prior to modern agricultural development. We attribute this response to increased food availability on staging areas where the net effect of agricultural changes has been an increase in corn availability. Waterfowl managers can increase dispersion of geese and provide favorable foraging conditions by maintaining well-distributed wetland roosting habitat and by working with private landowners to ensure access to grain in the vicinity of wetlands.

Nebraska↗
USGS1998

Grizzly bears and calving caribou: What is the relation with river corridors?

Researchers have debated the effect of the Trans-Alaska Pipeline (TAP) and associated developments to caribou ( Rangifer tarandus ) of the central Arctic herd (CAH) since the 1970s. Several studies have demonstrated that cows and calves of the CAH avoided the TAP corridor because of disturbance associated with the pipeline, whereas others have indicated that female caribou of the CAH avoided riparian habitats closely associated with the pipeline. This avoidance was explained as a predator-avoidance strategy. We investigated the relation between female caribou and grizzly bear ( Ursus arctos ) use of river corridors on the yet undisturbed calving grounds of the Porcupine caribou herd (PCH) in northeastern Alaska. On the coastal plain, caribou were closer to river corridors than expected (P = 0.038), but bear use of river corridors did not differ from expected (P = 0.740). In the foothills, caribou use of river corridors did not differ from expected (P = 0.520), but bears were farther from rivers than expected (P = 0.001). Our results did not suggest an avoidance of river corridors by calving caribou or a propensity for bears to be associated with riparian habitats, presumably for stalking or ambush cover. We propose that PCH caribou reduce the risks of predation to neonates by migrating to a common calving grounds, where predator swamping is the operational antipredator strategy. Consequently, we hypothesize that nutritional demands, not predator avoidance strategies, ultimately regulate habitat use patterns (e.g., use of river corridors) of calving PCH caribou.

Alaska↗
USGS1993

Autumn diet of lesser snow geese staging in northeastern Alaska

The coastal plain of the Arctic National Wildlife Refuge (ANWR) is used by lesser snow geese ( Chen caerulescens caerulescens ) in autumn for premigratory staging. To better understand the potential impacts of human disturbance on snow geese, we investigated species composition of, and temporal and age-related variation in, their diet during staging. Depending on age and time of collection, between 35.2 and 94.1% of the diet (aggregate percent wet mass, n = 75) consisted of 2 species of plants; underground stems of tall cotton-grass ( Eriophorum angustifolium ), and aerial shoots of northern scouring rush ( Equisetum variegatum ). The diet varied between August and September ( P = 0.0089), morning and afternoon ( P < 0.0001), but not between age classes ( P = 0.066). Throughout staging, snow geese consumed more tall cotton-grass during the afternoon than during the morning ( P < 0.05). Tall cotton-grass was a larger component of the afternoon diet in September than in August ( P < 0.05). In September, snow geese consumed more northern scouring rush in the mornings than in the afternoon ( P < 0.05). Nighttime freezing, interspecific differences in nutritional quality, and plant senescence likely constrained the diet of snow geese to a small number of food items. Because alternative foods may not be available, human disturbance should be minimized in areas that provide these forage species.

Alaska↗
USGS1989

Autumn use of Izembek Lagoon, Alaska, by brant from different breeding areas

Thirty-three adult brant ( Branta bernicla ) were radiomarked at 4 widely separated areas of the western Canadian arctic and 1 area in western Alaska during June-August 1987. Their use of the Izembek Lagoon on the Alaska Peninsula was monitored through the 1987 fall staging period (Sep-Dec). Eighty percent of the brant (n = 33), including ≥50% of individuals from each of the marking areas, were located at Izembek Lagoon. The mean arrival time for brant marked nearest to Izembek (the Yukon-Kuskokwim Delta [YK], Alas. [900 km away]) was 18 September, followed by those from the Mackenzie Delta, Northwest Territories, (3,500 km away) on 26 September, and brant from Victoria, Melville, and Prince Patrick islands, Northwest Territories [NT], (approx 4,500 km away) on 3 October. The mean duration of their stay at Izembek was 49 days. Within the 48-km-long lagoon there was considerable segregation between black brant ( B. b. nigricans ) and gray-bellied brant (intermediate between black brant and B. b. hrota ).

Alaska↗