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At least 289 records · Page 16Linked to original sources
USGS1981

Habitat size and bird community management

The purpose of this paper is to review the results in the literature that show the effect of area of forest on nesting migratory bird species, and to present the results of additional field work that we have conducted in forest habitats in western Maryland. These results indicate the area sensitivity of many long distance migrants. Because 80 to 95 percent of the breeding birds in the northeastern deciduous forest are neotropical migrants, the changes in bird species composition as a result of forest fragmentation can be immense. Management strategies based on habitat size are suggested to assist in maintaining communities of nesting migratory birds.

Transactions of the North American Wildlife and Na↗
USGS2019

Paleoclimate of the subtropical Andes during the latest Miocene, Lauca Basin, Chile

Uplift of the Andean Cordillera during the Miocene and Pliocene produced large-scale changes in regional atmospheric circulation that impacted local ecosystems. The Lauca Basin (northern Chilean Altiplano) contains variably fluvial and lacustrine sedimentary sequences spanning the interval from 8.7 to 2.3 Ma. Field samples were collected from paleo-lacustrine sediments in the basin. Sediments were dated using detrital zircon geochronology on volcanic tuffs, yielding an age range between ~5.57 and 5.44 Ma. These new age constraints provided an opportunity to evaluate changes in the Lauca Basin ecosystem across this dynamic Miocene-Pliocene transition. We employed multiple proxies (lithofacies analysis, diatoms, pollen, and oxygen stable isotopes of authigenic carbonates) to interpret ancient lacustrine and terrestrial paleoenvironments. Alternations among mudstone, carbonate, and evaporitic facies indicate lake-level variability through time. The diatom assemblage is characterized by meso- to hypersaline and alkaline-tolerant taxa typical of shallow lakes. The δ 18 O values ranged from −8.96 to −2.22‰ indicating fluctuations in water balance. Pollen taxa in the outcrop are typical of a transitional stage between seasonal cloud forest and open grassland. Together, these proxies indicate that the Lauca paleolake sediments were deposited under a wetter-than-modern climate with high temporal variability. Our results refine previous studies in the Lauca Basin and are consistent with other regional studies suggesting that the South American summer monsoon at the Miocene-Pliocene transition was more intense than it is at present.

Palaeogeography, Palaeoclimatology, Palaeoecology↗
USGS1995

Migratory bird population changes in North Dakota

The status of migratory bird populations in North America has received increased attention in recent years. Much of this consideration has been on Neotropical migrants, especially those associated with eastern forests. The status of migratory bird populations in the Great Plains has received far less attention. During the past quarter-century, populations of many species of birds that breed in the northern Great Plains have increased or declined, as indicated by trends from the North American Breeding Bird Survey. In 1967 Stewart and Kantrud (1972) conducted a survey of breeding bird populations throughout North Dakota. This study offered a rare glimpse of bird populations breeding in the northern Great Plains as well as important baseline data on breeding bird populations. These data help us evaluate relationships between birds and habitat conditions. We repeated the survey to compare bird populations in North Dakota during 1967 with those in 1992 and 1993.

North Dakota↗
USGS2007

Relationships between land uses and rainwater quality in a southcentral Pennsylvania watershed

ABSTRACT: Spatial and temporal variability in rainfall concentrations of nutrients, major ions, and herbicides was monitored at 7 locations in or near the Conodoguinet Creek watershed in south-central Pennsylvania from 1991.1993. Results were used to (1) compare precipitation quality in forested, agricultural and urban areas, and (2) assess the practicality of using volunteer citizen monitoring in such a study.

Journal of the American Water Resources Associatio↗
USGS2011

Spatial organization of northern flying squirrels, Glaucomys sabrinus : Territoriality in females?

We determined home-range overlap among northern flying squirrels ( Glaucomys sabrinus ) to assess their spatial organization. We found extensive home-range overlap among females, and though this overlap could reflect social behavior, we found no evidence of attraction among females, with only one instance of den sharing. Instead, our results suggest that females share foraging areas but may be territorial in portions of the home range, especially around den trees and during young-rearing. Home-range overlap could also result from, the extrinsic effect of forest fragmentation due to timber harvest, which might impede dispersal and force squirrels to cluster on remaining fragments of suitable habitat.

California↗
USGS2012

Distributional changes of American martens and fishers in eastern North America, 1699-2001: Chapter 4

Contractions in the geographic distributions of the American marten ( Martes americana) and fi sher ( M. pennanti) in eastern North America south of the St. Lawrence River between Colonial times (ca. 1650–1800) and the fi sher’s recent range expansion (ca. 1930–present) are well documented, but causal factors in these range contractions have only partially been studied. Traditional explanations for range contractions by both species are forest clearing and unregulated trapping; little consideration has been given to alternative explanations. It has been hypothesized that deep snow limits the distribution of fi shers, and that high fi sher populations limit the distribution of martens. I assessed the potential contributions of these factors to observed range contractions for these species by evaluating expected patterns of change in their historical distributions since Colonial times. Using published data on the distribution of martens and fi shers in eastern North America, including early and contemporary fur-harvest records ( n = 60,702), I found that broad-scale changes in their geographic distributions in eastern North America were consistent with 3 of those expectations, and partially so with a 4th. I recognize that retrospective analyses cannot establish the relative importance of land clearing, unregulated trapping, and changing climatic conditions on observed range contractions; nevertheless, when historical data from eastern North America are viewed in the context of long-term climate warming and the results of recent ecological studies, they suggest that traditional arguments may only partially explain historical range contractions for both species. This study further suggests that under a warming climate, northern range boundaries for the fi sher will expand, and southern range boundaries for the American marten will continue to contract.

Book chapter↗
USGS2011

Illuminating Northern California’s Active Faults

Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary faults of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major active fault zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google EarthTM and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2)

California↗
USGS2017

100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends

We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+ yr interval (~ 115–15 ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age"depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈ OIS2–5 d). This site thus provides the first evidence for an essentially complete series of "Dansgaard"Oeschger" climate events in the MAR. These data reveal that the ~ 100,000 yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.

Quaternary Research↗
USGS2003

Stratigraphy and palaeoclimatic significance of Late Quaternary loess-palaeosol sequences of the Last Interglacial-Glacial cycle in central Alaska

Loess is one of the most widespread subaerial deposits in Alaska and adjacent Yukon Territory and may have a history that goes back 3 Ma. Based on mineralogy and major and trace element chemistry, central Alaskan loess has a composition that is distinctive from other loess bodies of the world, although it is quartz-dominated. Central Alaskan loess was probably derived from a variety of rock types, including granites, metabasalts and schists. Detailed stratigraphic data and pedologic criteria indicate that, contrary to early studies, many palaeosols are present in central Alaskan loess sections. The buried soils indicate that loess sedimentation was episodic, or at least rates of deposition decreased to the point where pedogenesis could keep ahead of aeolian input. As in China, loess deposition and pedogenesis are likely competing processes and neither stops completely during either phase of the loess/soil formation cycle. Loess deposition in central Alaska took place before, and probably during the last interglacial period, during stadials of the mid-Wisconsin period, during the last glacial period and during the Holocene. An unexpected result of our geochronological studies is that only moderate loess deposition took place during the last glacial period. Our studies lead us to conclude that vegetation plays a key role in loess accumulation in Alaska. Factors favouring loess production are enhanced during glacial periods but factors that favour loess accumulation are diminished during glacial periods. The most important of these is vegetation; boreal forest serves as an effective loess trap, but sparsely distributed herb tundra does not. Thus, thick accumulations of loess should not be expected where tundra vegetation was dominant and this is borne out by modern studies near the treeline in central Alaska. Much of the stratigraphic diversity of North American loess, including that found in the Central Lowlands, the Great Plains, and Alaska is explained by a new model that emphasizes the relative importance of loess production factors versus loess accumulation factors.

Quaternary Science Reviews↗
USGS2017

Differences in breeding bird assemblages related to reed canary grass cover cover and forest structure on the Upper Mississippi River

Floodplain forest of the Upper Mississippi River provides habitat for an abundant and diverse breeding bird community. However, reed canary grass Phalaris arundinacea invasion is a serious threat to the future condition of this forest. Reed canary grass is a well-known aggressive invader of wetland systems in the northern tier states of the conterminous United States. Aided by altered flow regimes and nutrient inputs from agriculture, reed canary grass has formed dense stands in canopy gaps and forest edges, retarding tree regeneration. We sampled vegetation and breeding birds in Upper Mississippi River floodplain forest edge and interior areas to 1) measure reed canary grass cover and 2) evaluate whether the breeding bird assemblage responded to differences in reed canary grass cover. Reed canary grass was found far into forest interiors, and its cover was similar between interior and edge sites. Bird assemblages differed between areas with more or less reed canary grass cover (.53% cover breakpoint). Common yellowthroat Geothlypis trichas , black-capped chickadee Parus atricapillus , and rose-breasted grosbeak Pheucticus ludovicianus were more common and American redstart Setophaga ruticilla , great crested flycatcher Myiarchus crinitus , and Baltimore oriole Icterus galbula were less common in sites with more reed canary grass cover. Bird diversity and abundance were similar between sites with different reed canary grass cover. A stronger divergence in bird assemblages was associated with ground cover ,15%, resulting from prolonged spring flooding. These sites hosted more prothonotary warbler Protonotaria citrea , but they had reduced bird abundance and diversity compared to other sites. Our results indicate that frequently flooded sites may be important for prothonotary warblers and that bird assemblages shift in response to reed canary grass invasion.

Upper Mississippi River↗
USGS2023

Spatial variation in density of American black bears in northern Yellowstone National Park

The quality and availability of resources are known to influence spatial patterns of animal density. In Yellowstone National Park, relationships between the availability of resources and the distribution of grizzly bears ( Ursus arctos ) have been explored but have yet to be examined in American black bears ( Ursus americanus ). We conducted non-invasive genetic sampling during 2017–2018 (mid-May to mid-July) and applied spatially explicit capture-recapture models to estimate density of black bears and examine associations with landscape features. In both years, density estimates were higher in forested vegetation communities, which provide food resources and thermal and security cover preferred by black bears, compared with non-forested areas. In 2017, density also varied by sex, with female densities being higher than males. Based on our estimates, the northern range of Yellowstone National Park supports one of the highest densities of black bears (20 black bears/100 km 2 ) in the northern Rocky Mountains (6–12 black bears/100 km 2 in other regions). Given these high densities, black bears could influence other wildlife populations more than previously thought, such as through displacement of sympatric predators from kills. Our study provides the first spatially explicit estimates of density for black bears within an ecosystem that contains the majority of North America's large mammal species. Our density estimates provide a baseline that can be used for future research and management decisions of black bears, including efforts to reduce human–bear conflicts.

Montana, Wyoming↗
USGS2006

Small clusters of fast-growing trees enhance forest structure on restored bottomland sites

Despite the diversity of trees in bottomland forests, restoration on bottomland sites is often initiated by planting only a few species of slow-growing, hard mast?producing trees. Although successful at establishing trees, these young forests are slow to develop vertical structure, which is a key predictor of forest bird colonization. Furthermore, when natural seed sources are few, restored sites may be depauperate in woody species. To increase richness of woody species, maximum tree height, and total stem density, I supplemented traditional plantings on each of 40 bottomland restoration sites by planting 96 Eastern cottonwood (Populus deltoides) and American sycamore (Platanus occidentalis) in eight clusters of 12 trees. First year survival of cottonwood stem cuttings (25%) and sycamore seedlings (47%) was poor, but survival increased when afforded protection from competition with weeds. After five growing seasons, 165 of these 320 supplemental tree clusters had at least one surviving tree. Vegetation surrounding surviving clusters of supplemental trees harbored a greater number of woody species, increased stem density, and greater maximum tree height than was found on paired restoration sites without supplemental trees. These increases were primarily accounted for by the supplemental trees.

Restoration Ecology↗
USGS2010

Responding to climate change: A toolbox of management strategies: Chapter 11

Climate change and its effects are writ large across the landscape and in the natural and cultural heritage of parks and wilderness. They always have been and always will be. The sculpted walls of Yosemite National Park and the jagged scenery of the Sierra Nevada wilderness would not be as spectacular if periods of glaciation had not been followed by periods of deglaciation. High biodiversity in forests of the Great Smoky Mountains reflects a legacy of climate change, migrating species, and isolated climatic refugia. Fossils unearthed at Dinosaur National Monument reflect a time when the climate was very different than it is today, as do ruins left by peoples who practiced agriculture in places in the American Southwest where food production is not possible today. Over eons, climate change has molded the diversity of life and landscape in areas now protected as parks and wilderness.

Book chapter↗
USGS1990

Climatic control of vegetation distribution: The role of the water balance

The water balance describes climate as it is sensed by plants, as the interaction of energy and water in the environment. Discriminant analysis showed that the distribution of North American plant formations was more highly correlated with the water balance (actual evapotranspiration and deficit) than with the more traditional measures of climate (such as temperature and precipitation) used in several studies, including those used in the well-known works of Thornthwaite, Holdridge, and Whittaker. Much of the improved correlation could be attributed to the ability of the water balance to distinguish between climates similar in mean annual energy and water supplies but different in the seasonal timing of the two. Consideration of the water balance aided in the interpretation of possible mechanisms controlling the distribution of plant formations. For example, coniferous forest occurred at low actual evapotranspiration (low simultaneous availability of energy and water), consistent with the suggestion that conifers are better adapted than deciduous trees to environments with a low potential for primary production. A better understanding of the mechanisms by which climate controls vegetation distribution will help us predict the effects of changing climate on the future distribution of vegetation types.

American Naturalist↗
USGS2011

A multitemporal (1979-2009) land-use/land-cover dataset of the binational Santa Cruz Watershed

Trends derived from multitemporal land-cover data can be used to make informed land management decisions and to help managers model future change scenarios. We developed a multitemporal land-use/land-cover dataset for the binational Santa Cruz watershed of southern Arizona, United States, and northern Sonora, Mexico by creating a series of land-cover maps at decadal intervals (1979, 1989, 1999, and 2009) using Landsat Multispectral Scanner and Thematic Mapper data and a classification and regression tree classifier. The classification model exploited phenological changes of different land-cover spectral signatures through the use of biseasonal imagery collected during the (dry) early summer and (wet) late summer following rains from the North American monsoon. Landsat images were corrected to remove atmospheric influences, and the data were converted from raw digital numbers to surface reflectance values. The 14-class land-cover classification scheme is based on the 2001 National Land Cover Database with a focus on "Developed" land-use classes and riverine "Forest" and "Wetlands" cover classes required for specific watershed models. The classification procedure included the creation of several image-derived and topographic variables, including digital elevation model derivatives, image variance, and multitemporal Kauth-Thomas transformations. The accuracy of the land-cover maps was assessed using a random-stratified sampling design, reference aerial photography, and digital imagery. This showed high accuracy results, with kappa values (the statistical measure of agreement between map and reference data) ranging from 0.80 to 0.85.

Arizona↗
USGS1977

A comparison of 2 techniques for estimating deer density

We applied mark-resight and area-conversion methods to estimate deer abundance at a 2,862-ha area in and surrounding the Gettysburg National Military Park and Eisenhower National Historic Site during 1987-1991. One observer in each of 11 compartments counted marked and unmarked deer during 65-75 minutes at dusk during 3 counts in each of April and November. Use of radio-collars and vinyl collars provided a complete inventory of marked deer in the population prior to the counts. We sighted 54% of the marked deer during April 1987 and 1988, and 43% of the marked deer during November 1987 and 1988. Mean number of deer counted increased from 427 in April 1987 to 582 in April 1991, and increased from 467 in November 1987 to 662 in November 1990. Herd size during April, based on the mark-resight method, increased from approximately 700-1,400 from 1987-1991, whereas the estimates for November indicated an increase from 983 for 1987 to 1,592 for 1990. Given the large proportion of open area and the extensive road system throughout the study area, we concluded that the sighting probability for marked and unmarked deer was fairly similar. We believe that the mark-resight method was better suited to our study than the area-conversion method because deer were not evenly distributed between areas suitable and unsuitable for sighting within open and forested areas. The assumption of equal distribution is required by the area-conversion method. Deer marked for the mark-resight method also helped reduce double counting during the dusk surveys.

American Birds↗
USGS2016

Genetic diversity of Wolbachia endosymbionts in Culex quinquefasciatus from Hawai`i, Midway Atoll, and Samoa

Incompatible insect techniques are potential methods for controlling Culex quinquefasciatus and avian disease transmission in Hawai‘i without the use of pesticides or genetically modified organisms. The approach is based on naturally occurring sperm-egg incompatibilities within the Culex pipiens complex that are controlled by different strains of the bacterial endosymbiont Wolbachia pipientis (wPip). Incompatibilities can be unidirectional (crosses between males infected with strain A and females infected with strain B are fertile, while reciprocal crosses are not) or bidirectional (reciprocal crosses between sexes with different wPip strains are infertile). The technique depends on release of sufficient numbers of male mosquitoes infected with an incompatible wPip strain to suppress mosquito populations and reduce transmission of introduced avian malaria ( Plasmodium relictum ) and Avipoxvirus in native forest bird habitats. Both diseases are difficult to manage using more traditional methods based on removal and treatment of larval habitats and coordination of multiple approaches may be needed to control this vector. We characterized the diversity of Wolbachia strains in C. quinquefasciatus from Hawai‘i, Kaua‘i, Midway Atoll, and American Samoa with a variety of genetic markers to identify compatibility groups and their distribution within and between islands. We confirmed the presence of wPip with multilocus sequence typing, tested for local genetic variability using 16 WO prophage genes, and identified similarities to strains from other parts of the world with a transposable element (tr1). We also tested for genetic differences in ankyrin motifs (ank2 and pk1) which have been used to classify wPip strains into five worldwide groups (wPip1–wPip5) that vary in compatibility with each other based on experimental crosses. We found a mixture of both widely distributed and site specific genotypes based on presence or absence of WO prophage and transposable element markers on Hawai‘i Island (Volcano, Pu‘u Wa‘awa‘a, Laupāhoehoe, Kaumana, Kahuku, Nīnole, and Maulua Gulch), Kaua‘i Island (Kawaikōī, Mōhihi, Kalāheo, Lāwa‘i and Hanapepe) and Midway Atoll. Genotypes from American Samoa were unique and formed their own clade. Based on analysis of ankyrin motifs, wPip strains from Hawai‘i, Kaua‘i, and Midway Atoll were most similar to wPip5 strains of Australasian origin. By contrast, Wolbachia strains from Culex quinquefasciatus collected in American Samoa were most similar to wPip3 strains of American origin. We detected a single Culex mosquito from Pu‘u Wa‘awa‘a on Hawai‘i Island that was infected with a unique wPip3 genotype. This discovery, plus a rarefaction analysis of genotypes from Kaua‘i and Hawai‘i Islands suggests that limited sampling may have underestimated diversity of wPip in our study. Mosquitoes infected with wPip5 and wPip3 are bidirectionally compatible with each other based on prior studies, which would support their ability to coexist within the same population on Hawai‘i Island. Available evidence from prior studies suggests that genotype wPip4 from Africa, the Middle East, Europe, and Asia is bidirectionally incompatible with genotype wPip5 and varies in compatibility with genotype wPip3 depending on geographic origin. Since wPip5 appears to be the most common compatibility group in Hawai‘i based on limited sampling, logical next steps are to 1) expand the current survey to include additional islands and localities, 2) infect a laboratory colony of Hawaiian Culex with wPip4 through tetracycline treatment of Hawaiian mosquitoes and backcross with Culex from Europe, North Africa, and the Middle East that are naturally infected with wPip4, 3) conduct cage trials to confirm bidirectional incompatibilities between Hawaiian Culex infected with wPip4 and wPip5, and 4) conduct field trials to evaluate whether release of incompatible males can be applied at small scales to suppress local populations.

American Samoa, Hawaii↗
USGS2006

A review of the population estimation approach of the North American landbird conservation plan

As part of their development of a continental plan for monitoring landbirds (Rich et al. 2004), Partners in Flight (PIF) applied a new method to make preliminary estimates of population size for all 448 species of landbirds present in the continental United States and Canada (Table 1). Estimation of the global population size of North American landbirds was intended to (1) identify the degree of vulnerability of each species, (2) provide estimates of the current population size for each species, and (3) provide a starting point for estimating population sizes in states, provinces, territories, and Bird Conservation Regions (Rich et al. 2004). A method proposed by Rosenberg and Blancher (2005) was used to derive population estimates from available survey data. To enhance the credibility of these estimates, PIF organized a review of the methodology used to estimate North American landbird population sizes. A planning committee selected members from the ornithological and biometrical communities (hereafter “the panel”), with the aim of selecting individuals from academia, state natural-resource agencies, and the U.S. and Canadian federal governments, including the Canadian Wildlife Service, the U.S. Geological Survey, and the U.S. Department of Agriculture Forest Service. The panel addressed three questions: (1) Were the methods of population estimation proposed by PIF reasonable? (2) What actions could be taken to improve the data or analyses on which the PIF population estimates were based? and (3) How should the PIF population estimates be interpreted?

The Auk↗