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At least 991 records · Page 55Linked to original sources
USGS1989

Considerations for monitoring raptor population trends based on counts of migrants

Various problems were identified with standardized hawk count data as annually collected at six sites. Some of the hawk lookouts increased their hours of observation from 1979-1985, thereby confounding the total counts. Data recording and missing data hamper coding of data and their use with modern analytical techniques. Coefficients of variation among years in counts averaged about 40%. The advantages and disadvantages of various analytical techniques are discussed including regression, non-parametric rank correlation trend analysis, and moving averages.

Book chapter↗
USGS1988

Bias of animal population trend estimates

A computer simulation study of the population trend estimator used for the Mourning Dove Call-Count Survey, Woodcock Singing Ground Survey, Breeding Bird Survey and other surveys concluded that the estimator had negligible bias in most situations but that observer covariables should not be used with less than five years of data. With rare species (e.g. two birds per route), at least five years should be used. The estimator is seriously biased towards not detecting population changes with very rare species (e.g. 0.3 birds per route). Other technical recommendations are made.

Book chapter↗
USGS1993

Population trends and management opportunities for neotropical migrants

The Breeding Bird Survey shows that certain Neotropical migrant songbird populations have been declining over the past 26 years. Among them are forest birds that require extensive forest on the breeding grounds and also forested habitats on tropical wintering grounds. Other species have shown significant declines only since the early 1980's. Birds with broader habitat tolerance, such as those that winter commonly in agricultural and early-successional habitats as well as primary forest, show fewer consistent declines. Several grassland species have also been declining for more than two decades. Populations of many other Neotropical migrants have been stable or increasing over these periods. Examples of 26-year population trends are given. A dozen recommendations are given for managing nesting habitat for Neotropical migrants.

Book chapter↗
USGS1998

The Wisconsin Frog and Toad Survey: Update and 1984-97 trends [abstract]

The Wisconsin Frog and Toad Survey (WFTS) is a volunteer-based, roadside auditory count that began in 1981. It's protocols were recently modified for continent-wide use by the North American Amphibian Monitoring Plan (NAAMP). In 1997 we initiated a study to compare data collected by the WFTS and NAAMP protocols, in order to guide WFTS transition from its current methodology to one more compatible with NAAMP, without losing the use of data collected since 1981. In this paper we present results from the first year of this study, along with results from analyses of WFTS data, including distributional maps, 1984-97 population trends, phenological information, and progress on a new web page.

Book chapter↗
USGS2003

Changes in wetland sediment elevation following major storms: implications for estimating trends in relative sea-level rise

Hurricanes can be important agents of geomorphic change in coastal marshes and mangrove forests. Hurricanes can cause large-scale redistribution of sediments within the coastal environment resulting in sedimentation, erosion, disruption of vegetated substrates, or some combination of these processes in coastal wetlands. It has been proposed that such sediment pulsing events are important at maintaining wetland sediment elevations in sediment-poor settings with high rates of relative sea-level rise, such as the Mississippi River Delta. But do these pulsing events result in a net gain in sediment elevation even when substantial amounts of sediment are deposited? Clearly sediment erosion and scour would result in a loss of elevation. But will a substantial sediment deposit on poorly consolidated sediments always result in a net gain in elevation? If the wetland vegetation is killed by wind, tidal surge, or the introduction of saline water, will there be a collapse of sediment elevation in the absence of root production and ongoing decomposition of root matter? During the past decade several wetlands where my colleagues and I have monitored sedimentation and elevation change have been struck by one to several hurricanes. This paper describes the range of sediment elevation responses to hurricane strikes, the suggested mechanisms driving those responses, the implications for estimating long-term trends in relative sea-level rise, and future research needs for improving our understanding of the role that major storms play in wetland sediment elevation dynamics. For many wetlands the change in sediment elevation was directly proportional to the amount of sediment deposited by the storm. But surprisingly, there was a loss of elevation in some wetlands with substantial sediment deposits. In these wetlands, the impact of the storm was either direct (sedimentation and compaction) or indirect (vegetation death), and the effect on sediment elevation was either permanent or temporary. For example, 2 cm of sediment deposited by Hurricane Andrew on a healthy salt marsh in south Louisiana had a direct and positive effect on sediment elevation. But in a deteriorated salt marsh a 3 cm thick sediment deposit was associated with a permanent loss in elevation (we have monitored this site for 10 years). The apparent mechanism driving elevation loss was compaction of the weakened substrate by the weight of the sediment deposit, the storm surge waters, or both. Clearly, storm-related sediment pulses are not going to save this marsh from becoming submerged by rising sea level. A temporary loss in elevation, as much as 2 cm, was observed in a North Carolina salt marsh with a highly organic substrate after each of 3 successive hurricanes even when sediment was deposited. The loss in elevation was apparently related to degassing of the chronically flooded substrate while the rebound in elevation was apparently related to a temporary drawdown of marsh water levels. Interestingly, sediment elevation increased after Hurricane Dennis in 1999, although the increase was less than the thickness of the sediment deposit. Further research is required to determine the mechanisms driving storm-related elevation change (i.e., compaction and expansion) in this marsh. There were two marshes where the gain in sediment elevation was greater than the thickness of the sediment deposit, but the effect was short-lived. In a high salt marsh in southern California, we hypothesize that the temporary spike in elevation was related to the flushing of salts from the hypersaline soils, which enhanced root growth that led to an increase in elevation. In a marsh with a highly organic substrate in north Florida, temporary increases in elevation (as much as 2 cm) greater than the thickness of the sediment deposit were apparently related to groundwater fluxes, which may have been influenced by enhanced runoff from storm rainfall. Lastly, Hurricane Mitch

Book chapter↗
USGS2000

Painted Bunting Breeding Bird Survey trends associated with landscape changes in Georgia and South Carolina

Landscape changes during the first 3 decades of the Breeding Bird Survey (BBS) may account for the Painted Bunting's declining population trend. In the southeastern U.S., it is estimated that this bunting has declined 3.5 % per year since 1966. I collected landscape data centered on identical 5-stop areas (n = 33, 306 ha each) of the BBS during early (1960s - 1970s) and late decades (1980s - 1990s). Peak 30-yr counts for Painted Buntings were found at the center of the 5-stop areas. I used stepwise multiple regression analysis to model the mean number of Painted Buntings (in the area during 3 yr, dependent variable) associated with landscape metrics (independent variables). During the early decades the average amount of edge on developed land (p = 0.10), average patch size of agriculture land (p = 0.01), average size of shrub-scrub and young forest (p = 0.09), and average amount of edge for emergent wetlands (p = 0.03) explained 40% of the variation in Painted Buntings counts. In the late decades average amount of edge on developed land (p = 0.04) and average amount of edge on emergent wetlands (p = 0.005) explained 35% of the variation in Painted Bunting counts. Large losses of agricultural land (proportion = 0.177 to 0.094), which was developed or converted to intensively managed pin plantations, may have reduced potential bunting breeding habitat. Shrub-scrub and young forest habitat was constant (proportion = 0.136 to 0.134) but did not affect mean counts of buntings in the late decades. Protected emergent wetlands remained constnat also from the early to late decades (proportion = 0.056 to 0.06) and may provide habitat to maintain a smaller Painted Bunting population. At this time, it's unclear how develped land, which is increasing (proportion = 0.036 to 0.088), may be affecting the Painted Bunting population in GS and SC.

Book chapter↗
USGS1976

Comments on recent canvasback habitat trends and threats on Chesapeake Bay

During the last 22 years, the North American winter population of canvasbacks has fluctuated from 481,000 in 1955 to 179,000 in 1972. The Chesapeake Bay population has averaged 33 percent of the North American population and 64 percent of the Atlantic Flyway population. In Maryland, significant annual fluctuations have been recorded between the eastern and western shore of Chesapeake Bay. In 1968, 11 percent of the Bay canvasbacks were on the western shore, whereas in 1971, 87 percent of the birds wintered in this area. This increase in 1971 is believed to be in response to large populations of small Rangia cuneata clams. I n recent years, mortality of small clams and reduced spawning have resulted in a larger size class for Rangia making them less desirable as a waterfowl food. Canvasback populations in 1975 and 1976 were more dispersed in Chesapeake Bay when the predominant food of canvasbacks was Macoma balthica. In the last 5 years, the number of canvasbacks wintering in Chesapeake Bay has declined slightly, while the North American and Atlantic Flyway populations have increased. Increases have been noted in New Jersey and North Carolina. This trend may indicate that the quality of canvasback habitat in Chesapeake Bay is declining at a faster rate than other areas along the Atlantic coast.

Book chapter↗
USGS1980

Estimating the size and trend of the California condor population, 1965-1978

During 1965-1978, three principal methods were used to measure the size and trend of the California Condor (Gymnogyps californianus) population. An October survey conducted by as many as 136 observers had limited value because daily activity patterns of condors were unpredictable and because analysis of results could not be standardized. Evaluation of 4,381 condor observations by cooperators, and results of comparative surveys done in 1970-1971 and 1977-1978 show declines in numbers of condor sightings, numbers of condors per sighting, and in the numbers of sightings including more than one immature-plumaged bird. The data cannot be evaluated statistically, but they suggest a marked decline in the condor population between 1965 and 1978. Future refinements of survey techniques are dependent on having individually recognizable condors in the population.

California Fish and Game↗
USGS1994

Estimating equations estimates of trends

The North American Breeding Bird Survey monitors changes in bird populations through time using annual counts at fixed survey sites. The usual method of estimating trends has been to use the logarithm of the counts in a regression analysis. It is contended that this procedure is reasonably satisfactory for more abundant species, but produces biased estimates for less abundant species. An alternative estimation procedure based on estimating equations is presented.

Bird Populations↗
USGS2011

Analysis of trends in climate, streamflow, and stream temperature in north coastal California

As part of a broader project analyzing trends in climate, streamflow, vegetation, salmon, and ocean conditions in northern California national park units, we compiled average monthly air temperature and precipitation data from 73 climate stations, streamflow data from 21 river gaging stations, and limited stream temperature data from salmon-bearing rivers in north coastal California. Many climate stations show a statistically significant increase in both average maximum and average minimum air temperature in early fall and midwinter during the last century. Concurrently, average September precipitation has decreased. In many coastal rivers, summer low flow has decreased and summer stream temperatures have increased, which affects summer rearing habitat for salmonids. Nevertheless, because vegetative cover has also changed during this time period, we cannot ascribe streamflow changes to climate change without first assessing water budgets. Although shifts in the timing of the centroid of runoff have been documented in snowmelt-dominated watersheds in the western United States, this was not the case in lower elevation coastal rivers analyzed in this study.

California↗
USGS2008

Turning population trend monitoring into active conservation: Can we save the cascades frog (Rang cascadae) in the Lassen Region of California?

Monitoring the distribution, population size, and trends of declining species is necessary to evaluate their vulnerability to extinction. It is the responsibility of scientists to alert management professionals of the need for preemptive action if a species approaches imminent, regional extirpation. This is the case with Rana cascadae (Cascades Frog) populations near Lassen Peak From 1993 to 2007, we conducted 1,873 amphibian surveys at 856 sites within Lassen Volcanic National Park and Lassen National Forest, California, USA. These surveys encompassed all R. cascadae habitats: ponds, lakes, meadows, and streams on those lands. We found frogs at only six sites during 14 years of surveys, and obtained one report of a single frog at one additional locality. These sites represented < 1% of the historically suitable habitat within the Lassen region. The number of R. cascadae in the Lassen area has declined since 1991, and one population is now extirpated. We found no evidence of reproduction in most of the populations, and reproduction at all but one of the other sites remained lower than the annual reproductive output of one breeding pair for > 12 years. Causes for the decline remain unclear, but introduced trout, disease, and pesticides are likely factors. We recommend that (1) additional protection for R. cascadae within 50 km of Lassen Peak; (2) investigation of the genetics of R. cascadae in California; (3) research into the role of possible causative factors in these declines; and (4) implementation of a feasibility study to captive breed and reintroduce R. cascadae in the Lassen area. Copyright ?? 2008. Gary Fellers. All rights reserved.

Herpetological Conservation and Biology↗
USGS1985

QUALITY ASSURANCE PROGRAM FOR WET DEPOSITION SAMPLING AND CHEMICAL ANALYSES FOR THE NATIONAL TRENDS NETWORK.

The purpose of the National Trends Network is to delineate the major inorganic constituents in the wet deposition in the United States. The approach chosen to monitor the Nation's wet deposition is to install approximately 150 automatic sampling devices with at least one collector in each state. Samples are collected at one week intervals, removed from collectors, and transported to an analytical laboratory for chemical analysis. The quality assurance program has divided wet deposition monitoring into 5 parts: (1) Sampling site selection, (2) sampling device, (3) sample container, (4) sample handling, and (5) laboratory analysis. Each of these five components is being examined using existing designs or new designs. Each existing or proposed sampling site is visited and a criteria audit is performed.

Conference Paper↗
USGS1995

Trend analyses of sediment data for the DEC project

Daily stream discharge, suspended-sediment concentration, and suspended-sediment discharge data were collected at eight sites in six watersheds of the Demonstration Erosion Control project in the Yazoo River Basin in north-central Mississippi during the period July 1985 through September 1991. The project is part of an ongoing interagency program of planning, design, construction, monitoring, and evaluation to alleviate flooding, erosion, sedimentation, and water-quality problems for watersheds located in the bluff hills upstream of the Mississippi River alluvial plain. This paper presents preliminary results of trend analyses for stream discharge and sediment data for the eight project sites. More than 550 stream discharge measurements and 20,000 suspended-sediment samples have been collected at the eight sites since 1985.

Conference Paper↗
USGS2001

Trends in Northern Hemisphere surface cyclone frequency and intensity

One of the hypothesized effects of global warming from increasing concentrations of greenhouse gases is a change in the frequency and/or intensity of extratropical cyclones. In this study, winter frequencies and intensities of extratropical cyclones in the Northern Hemisphere for the period 1959-97 are examined to determine if identifiable trends are occurring. Results indicate a statistically significant decrease in midlatitude cyclone frequency and a significant increase in high-latitude cyclone frequency. In addition, storm intensity has increased in both the high and midlatitudes. The changes in storm frequency correlate with changes in winter Northern Hemisphere temperature and support hypotheses that global warming may result in a northward shift of storm tracks in the Northern Hemisphere.

Journal of Climate↗
USGS2004

Edwards plateau: Analysis of land cover trends

The Land Cover Trends project studies the rates, causes, and consequences of contemporary (1973-2000) change in land use and land cover in the United States on an ecoregional basis. The Edwards Plateau ecoregion is the focus of this report. Landsat imagery from five dates during a nearly 30-year period are interpreted for randomly selected sample blocks. The resulting data provide the foundation for estimating change. Along with the image analysis, site visits to 90% of the sampled areas, geographical profiles, and socioeconomic data for the ecoregion are synthesized to assess regional driving forces and consequences of change. Complete project methodology can be found in Loveland et al [1].

Conference Paper↗
USGS2011

Distribution, population status and trends of Kittlitz's murrelet Brachyramphus brevirostris in Lower Cook Inlet and Kachemak Bay, Alaska

Lower Cook Inlet (LCI) in south-central Alaska is unusual among the breeding areas of Kittlitz's Murrelet Brachyramphus brevirostris because of human impacts on the marine and terrestrial environments and because of the lack of tidewater glaciers. In LCI the Kittlitz's Murrelet co-exists with the more abundant Marbled Murrelet, which complicates abundance estimates because of the difficulty of species identification. We compared survey data for an area with overlapping coverage in LCI (Core area) in 1993 (June) and from 1996 to 1999 (July-early August). Within this LCI Core area, the surveys in 1996-1999 estimated ~1600 Kittlitz's Murrelets and ~17 000 Marbled Murrelets, including prorated unidentified murrelets. The Kittlitz's Murrelet population declined between 1993 and 1999 at 26% per annum (84% overall). Simultaneously, Marbled Murrelets declined by 12% per annum (56% overall), though the decline was not statistically significant. Declines were estimated conservatively because the 1993 survey was conducted in June, when both murrelet species are less abundant on the water. We also surveyed Kachemak Bay, a large embayment of LCI, during mid-summer (July) of 2005-2007 and estimated a population of 2047 Kittlitz's Murrelets (SD 1120, n = 3 years) residing primarily in the inner bay. Marbled Murrelets numbered 11 040 (SD 1306) and were found throughout the bay. On one transect set in inner Kachemak Bay, Kittlitz's Murrelet density in late summer (1-16 August) declined 7.5% per annum between 1988 and 2007 (n = 6 years), and Marbled Murrelet density increased 4.9% per annum. On two other transect sets in the inner bay, however, neither murrelet species showed a change in density between 1996 and 2007. Inner Kachemak Bay is a persistent hotspot for Kittlitz's Murrelet and may attract murrelets from LCI and beyond. We recommend monitoring murrelet populations in Kachemak Bay, although Kittlitz's Murrelets likely move between the main body of Cook Inlet and Kachemak Bay, and a complete LCI survey is needed to gauge regional population trends.

Marine Ornithology: Journal of Seabird Research an↗
USGS2011

Status and trend of the Kittlitz's Murrelet Brachyramphus brevirostris in Glacier Bay, Alaska

We conducted standardized surveys for marine birds in Glacier Bay in seven years between 1991 and 2008. From our most recent survey, a combination of line- and strip-transect methods completed in 2008, we estimated that 4981 (95% CI 1293–8670) Kittlitz’s Murrelets Brachyramphus brevirostris resided in Glacier Bay during the month of June, together with 12 195 (5607–18 783) Marbled Murrelets B. marmoratus . When counts were prorated to assign unidentified Brachyramphus murrelets to species, population estimates increased to 5641 Kittlitz’s Murrelets and 13 810 Marbled Murrelets. Our surveys of bird numbers in Glacier Bay between 1991 and 2008 revealed that Kittlitz’s Murrelet declined by ≥85% during this period. Trend analysis suggested a rate of decline between -10.7% and -14.4% per year. No direct human impacts (e.g., bycatch, oil pollution, vessel disturbance) in our study area could fully account for a decline of this magnitude. Widespread declines of Brachyramphus murrelets and Harbor Seals Phoca vitulina in the Gulf of Alaska during the 1980s-1990s suggest large-scale influences on these marine predators, perhaps related to climate-mediated cycles in food supply. Other natural factors that may impact Glacier Bay populations include predation by avian and terrestrial predators, widespread glacial retreat and its effect on nesting and foraging habitats, and competition for food with marine predators whose abundance in Glacier Bay has increased markedly in recent years (Humpback Whales Megaptera novaeangliae and Steller Sea Lions Eumetopias jubatus ).

Alaska↗
USGS1997

Pesticides in ground water: distribution, trends, and governing factors

A comprehensive review of published information on the distribution and behavior of pesticides and their transformation products in ground water indicates that pesticides from every chemical class have been detected in ground waters of the United States. Many of these compounds are commonly present at low concentrations in ground water beneath agricultural land. Little information is available on their occurrence beneath non-agricultural land, although the intensity of their use in such areas (on lawns, golf courses, rights of way, timberlands, etc.) is often comparable to, or greater than agricultural use. Information on pesticides in ground water is not sufficient to provide either a statistically representative view of pesticide occurrence in ground water across the United States, or an indication of long-term trends or changes in the severity or extent of this contamination over the past three decades. This is largely due to wide variations in analytical detection limits, well selection procedures, and other design features among studies conducted in different areas or at different times. Past approaches have not been well suited for distinguishing "point source" from "nonpoint source" pesticide contamination. Among the variety of natural and anthropogenic factors examined, those that appear to be most strongly associated with the intensity of pesticide contamination of ground water are the depth, construction and age of the sampled wells, the amount of recharge (by precipitation or irrigation), and the depth of tillage. Approaches commonly employed for predicting pesticide distributions in the subsurface--including computer simulations, indicator solutes (e.g., nitrate or tritium), and ground-water vulnerability assessments--generally provide unreliable predictions of pesticide occurrence in ground water. Such difficulties may arise largely from a general failure to account for the preferential transport of pesticides in the subsurface. Significant improvements in understanding and predicting the occurrence and fate of pesticides in ground water are likely to depend on: (1) greater coordination of ground-water sampling across the nation to ensure consistency of study design, and thus comparability of results; (2) more extensive analyses for pesticide transformation products during ground-water monitoring studies; (3) substantially enhanced communication among investigators conducting laboratory experiments, small-scale field studies and large-scale monitoring studies; and (4) more routine testing of predictions of pesticide behavior and ground-water vulnerability against actual field observations of pesticide occurrence in ground water

Book↗