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At least 1,459 records · Page 81Linked to original sources

USGS1979

Organochlorine residues in six species of estuarine birds, South Carolina, 1971-75

In South Carolina between 1971 and 1975, authors evaluated the occurrence of organochlorine residues in the laughing gull (Larus atricilla), white ibis (Eudocimus albus), glossy ibis (Plegadis falcinellus), American oystercatcher (Haematopus palliatus), willet (Catoptrophorus semipalmatus), and ruddy turnstone (Arenaria interpres). Tissues of birds found dead and eggs were analyzed, eggshell thicknesses were measured, and incidental observations were made of reproductive success and population status. Eggshell thickness of the white bis, American oystercatcher, and laughing gull were not significantly different (P less than 0.05) from the pre-1947 norms. DDE and polychlorinated biphenyls (PCBs) were found most frequently and at the highest concentration in eggs. DDE residues declined significantly in oystercatcher eggs, and declined slightly in laughing gull eggs; no change was noted in white ibis eggs. No consistent trends were found for dieldrin and PCBs. Authors found no obvious problems with reproductive success of any species. Populations of the five species breeding in South Carolina appear stable. The white ibis and laughing gull in South Carolina have experienced population explosions over the past 50 years; the glossy ibis has increased substantially since the first documented breeding records in 1947.

Pesticides Monitoring Journal↗

USGS1985

Brown pelican populations and pollutants in Texas 1975-1981

The population status, reproductive success, and levels of environmental contaminants in brown pelicans (P. occidentalis) in Texas were studied from 1975 through 1981. Breeding populations increased from 18 pairs in 1975 to 57 pairs in 1981. All unhatched eggs salvaged for analyses of contaminant residues contained DDT metabolites. Mean DDE levels varied from 0.9 to 2.4 ppm and about 7% of the samples had residues that approached critical levels that could affect reproductive success. DDE levels did not decline from 1975 to 1981 and residues leveled off at higher values than those in South Carolina and Louisiana pelican populations. PCB [polychlorinated biphenyl] residues also remained stable. Endrin was detected only in 1975.

The Wilson Bulletin↗

USGS1980

White-faced ibis populations and pollutants in Texas, 1969-1976

Eggshell thickness, levels of pollutant residues, and population status of the white-faced ibis (Plegadis chihi) were monitored in Texas from 1969 through 1976. Texas ibis nesting populations declined by 42%. Reproductive success apparently was limited by DDE-induced shell thinning and by dieldrin-caused mortality. Eggshells averaged 4% to 10% thinner than the pre-1943 mean thickness. Shells of numerous crushed eggs exceeded 20% thinning. Mean DDE residues in randomly collected eggs decreased from 0.94 ppm in 1970 to 0.25 ppm in 1976. DDE was higher, averaging 2.5 ppm, in thin-shelled eggs. DDE was negatively correlated with shell thickness. Dieldrin and PCB residues increased slightly from 1970 to 1976, but neither was correlated significantly with shell thickness. Residues in brains of many dead and dying ibises collected during years of extreme reproductive failure, 1970 and 1973, contained between 5 and 25 ppm dieldrin. Ibises were exposed to aldrin and dieldrin by feeding in rice fields where aldrin-treated rice seed was planted. Improved nesting success in 1976 may have been related to declining residues of DDE and to the discontinued use of aldrin in rice fields.

Southwestern Naturalist↗

USGS1990

Intersexual and temporal variation in foraging ecology of prothonotary warblers during the breeding season

We studied foraging ecology of Prothonotary Warblers ( Protonotaria citrea ) over four breeding seasons to determine if this species exhibited sex-specific or temporal variation in foraging behavior. Significant differences between sexes during the prenestling period were found for foraging height and substrate height (foraging method, plant species/substrate, perch diameter, horizontal location from trunk, and prey location were not significantly different). During the nestling period, this divergence between sexes was evident for foraging height, substrate height, substrate / tree species, and prey location. Additionally, male warblers significantly altered their behavior for all seven foraging variables between the two periods, whereas females exhibited changes similar to those of males for five of the foraging variables. This parallel shift suggests a strong behavioral response by both sexes to proximate factors (such as vegetation structure, and prey abundance and distribution) that varied throughout the breeding season. Sex-specific foraging behavior during the prenestling period was best explained by differences in reproductive responsibilities rather than by the theory of intersexual competition for limited resources. During the nestling period, neither hypothesis by itself explained foraging divergences adequately. However, when integrated with the temporal responses of the warblers to changes in prey availability, reproductive responsibilities seemed to be of primary importance in explaining intersexual niche partitioning during the nestling period. We emphasize the importance of considering both intersexual and intraseasonal variation when quantifying a species' foraging ecology.

The Auk↗

USGS1990

Organochlorines, mercury, and selenium in wintering shorebirds from Washington and California

Dunlins Caldris alpina, and black-bellied plovers, Pluvialis squatarola, were collected in Washington and California during the winter of 1984-85; long-billed dowitchers, Limnodromus scolopaceus, were collected in California. Pooled breast muscles (by species, location, and date) were analyzed for organochlorines and pooled livers for mercury and selenium. DDE was detected in all eight dunlin, three of five dowitcher, and two of nine plover muscle pools. Estimated DDE concentrations in dunlin carcasses at two sites in California were greater than 3 ppm wet wt, a dietary concentration associated with eggshell thinning and decreased reproductive success in raptors. Detectable concentrations of mercury and selenium were found in all liver pools. Selenium concentrations in plovers from two sites in Washington were elevated (26.9 and 29.9 ppm dry wt), but below concentrations shown to affect reproductive success in black-necked stilts, Himantopus mexicanus. Elevated mercury concentrations in livers of dunlin from Bodega Bay (18.9 ppm dry wt) and Salinas River (16.3 ppm dry wt), California were below levels associated with acute toxicity.

California Fish and Game↗

USGS1983

Fifty-ninth Christmas Bird Count. 176. Ocean City, Md

Some organophosphorus insecticides have been reported to interfere with reproduction and even cause the decline of small mammal populations. The effects of such anticholinesterases on plasma LH concentrations were examined in male mice (Peromyscus leucopus noveboracensis) intubated with water (OW) or acephate (50 and 100 mg/kg) and sacrificed after 4 h. Brain acetylcholinesterase (AChE) activity was inhibited by 45 and 56%, and basal LH levels were reduced by 29 and 25% in mice receiving the 2 doses of acephate. Responsiveness to LHRH did not appear to be affected 4 h after intubation with 100 mg/kg acephate, as 5 ug/kg LHRH ip evoked a comparable rise in plasma LH after 30 min (2.4 and 3.6 fold) in OW-control and treated mice. Subchronic dietary exposure to 0, 25, 100, and 400 ppm acephate for 5 days resulted in a dose-dependent decline in brain AChE activity (23, 42, and 57%), but did not affect LH concentration or the weights of testes and seminal vesicles. These findings suggest that acute exposure to organophosphorus insecticides may impair reproductive function by altering LH secretion.

American Zoologist↗

USGS1990

Dicofol (Kelthane) as an environmental contaminant: A review

Dicofol is persistent in soil and on plants. No compelling evidence exists that dicofol breaks down or is metabolized to DDTr in nature. Dicofol does not accumulate in birds as rapidly as DDE, and it has reproductive effects that are less harmful than DDE. Fish, birds, and mammals are reproductively sensitive to dicofol products, but levels presently found in wildlife are below levels shown experimentally to cause significant harm. Eggs of fish-eating wild birds from citrus, cotton, and apple-growing areas should be analyzed for dicofol residues. Nest success of fish-eating birds in the most contaminated populations should be studied to evaluate the environmental effects of dicofol.

Fish and Wildlife Technical Report↗

USGS2002

Reducing predation by common ravens on desert tortoises in the Mojave and Colorado Deserts

Conflicts between humans and natural populations often result from habitat fragmentation and degradation that accompanies human activities. Common raven populations in the Mojave Desert have benefited by human-provided resources; they've expanded precipitously in recent years. Because ravens prey on juveniles of the threatened desert tortoise, they have become the focus of management concerns to help recover dwindling tortoise populations. I have outlined herein a series of management recommendations designed to reduce raven predation on desert tortoises thereby facilitating juvenile tortoise recruitment into the population of reproductive adults. The recommendations are based on the best available scientific information and are intended to provide a basis for a long-term reduction in raven impacts. The recommendations fall into four basic categories. (1) Modify anthropogenic sources of food, water, and nesting substrates to reduce their use by ravens. This includes modifying landfill operations, septage containment practices, livestock management, and other commercial and private practices that help facilitate raven survival and dispersal by providing food and water. Most of these measures are long-term actions deigned to reduce the carrying capacity of the desert for ravens. This action is critical and must be done over very large areas. (2)Lethal removal of ravens by shooting or euthanizing following live trapping. Specific ravens known to prey on tortoises would be targeted as well as all ravens found foraging within specific high-priority desert tortoise management zones (e.g., Desert Tortoise Natural Areas, DTNA). These actions would primarily be deployed on a short-term emergency basis to give specific tortoise populations a necessary boost until other measures become fully implemented and achieve their goals. (3) Conduct research on raven ecology, raven behavior, and methods to reduce raven predation on tortoises. Results of these studies would be used to design future phases of the raven management program. (4) All actions should be approached within an adaptive management framework. As such monitor, actions should be designed as experiments so that monitoring of actions will yield reliable and scientifically sound results. Coordinating and oversight teams should be convened to facilitate cooperation and coordination among agencies and to ensure that the actions are being implemented effectively. Recommendations made herein were developed to help recover tortoise populations by reducing raven predation on juvenile tortoises. If the recommendations made are implemented in concert with actions reducing other causes of mortality, ill health, and lowered reproductive output, they should aid in the long-term recovery of desert tortoise populations. Many important aspects of raven population dynamics, raven predation on tortoises, and how to manage raven populations and behavior are as yet unknown. Because of this, any raven management program must be implemented within an adaptive management framework. Doing so would allow for sufficient flexibility to modify the program as new information is gained.

Report↗

USGS1985

PROCEDURES FOR ACCURATE PRODUCTION OF COLOR IMAGES FROM SATELLITE OR AIRCRAFT MULTISPECTRAL DIGITAL DATA.

Because the display and interpretation of satellite and aircraft remote-sensing data make extensive use of color film products, accurate reproduction of the color images is important. To achieve accurate color reproduction, the exposure and chemical processing of the film must be monitored and controlled. By using a combination of sensitometry, densitometry, and transfer functions that control film response curves, all of the different steps in the making of film images can be monitored and controlled. Because a sensitometer produces a calibrated exposure, the resulting step wedge can be used to monitor the chemical processing of the film. Step wedges put on film by image recording machines provide a means of monitoring the film exposure and color balance of the machines.

Journal of Imaging Technology↗

USGS1999

Intraspecific phylogeography of Lasmigona subviridis (Bivalvia: Unionidae): Conservation implications of range discontinuity

A nucleotide sequence analysis of the first internal transcribed spacer region (ITS-1) between the 5.8S and 18S ribosomal DNA genes (640 bp) and cytochrome c oxidase subunit I (COI) of mitochondrial DNA (mtDNA) (576 bp) was conducted for the freshwater bivalve Lasmigona subviridis and three congeners to determine the utility of these regions in identifying phylogeographic and phylogenetic structure. Sequence analysis of the ITS-1 region indicated a zone of discontinuity in the genetic population structure between a group of L. subviridis populations inhabiting the Susquehanna and Potomac Rivers and more southern populations. Moreover, haplotype patterns resulting from variation in the COI region suggested an absence of gene exchange between tributaries within two different river drainages, as well as between adjacent rivers systems. The authors recommend that the northern and southern populations, which are reproductively isolated and constitute evolutionarily significant lineages, be managed as separate conservation units. Results from the COI region suggest that, in some cases, unionid relocations should be avoided between tributaries of the same drainage because these populations may have been reproductively isolated for thousands of generations. Therefore, unionid bivalves distributed among discontinuous habitats (e.g. Atlantic slope drainages) potentially should be considered evolutionarily distinct. The DNA sequence divergences observed in the nuclear and mtDNA regions among the Lasmigona species were congruent, although the level of divergence in the COI region was up to three times greater. The genus Lasmigona, as represented by the four species surveyed in this study, may not be monophyletic.

Conference Paper↗

USGS1999

Pyometra in a Siberian Polecat (Mustela eversmanni)

A 2-year-old Siberian polecat (Mustela eversmanni) from a breeding colony presented for ultrasound evaluation for pregnancy. It was paired with a male for 2.75 months and had remained absent of pregnancy signs when it was anesthetized and clinically evaluated. Until this time, the animal had eaten well and shown no outward signs of debility. On palpation, the animal had a fluid-filled tubular structure in the caudal abdomen, consistent in location and size with the uterus. No sign of vaginal discharge was present. Ultrasonography revealed 10 fluid-filled evaginations (approximately 12 mm in diameter) of the uterine horns. A presumptive diagnosis of a fluid-filled reproductive tract and likely reproductive failure was made in light of the animal's history, its clinical signs, and the ultrasound findings. Euthanasia was performed because the animal was nonreproductive and might yield information relevant to the breeding colony as a whole. Necropsy of the polecat revealed a distended fluctuant uterus containing mildly odiferous, thick, yellow-green, purulent material. Histopathology confirmed the diagnosis of pyometra. A pure and heavy growth of Enterococcus fecalis was cultured from the uterine contents. In light of results from routine minimal inhibitory concentration antibiotic sensitivity screening, this isolate was resistant to all antibiotics tested in the standard teaching hospital screen.

Contemporary Topics in Laboratory Animal Science↗

USGS2003

Assessing recovery feasibility for piping plovers using optimization and simulation

Optimization and simulation modeling can be used to account for demographic and economic factors simultaneously in a comprehensive analysis of endangered-species population recovery. This is a powerful approach that is broadly applicable but underutilized in conservation biology. We applied the approach to a population recovery analysis of threatened and endangered piping plovers (Charadrius melodus) in the Great Plains of North America. Predator exclusion increases the reproductive success of piping plovers, but the most cost-efficient strategy of applying predator exclusion and the number of protected breeding pairs necessary to prevent further population declines were unknown. We developed a linear programming model to define strategies that would either maximize fledging rates or minimize financial costs by allocating plover pairs to 1 of 6 types of protection. We evaluated the optimal strategies using a stochastic population simulation model. The minimum cost to achieve a 20% chance of stabilizing simulated populations was approximately $1-11 million over 50 years. Increasing reproductive success to 1.24 fledglings/pair at minimal cost in any given area required fencing 85% of pairs at managed sites but cost 23% less than the current approach. Maximum fledging rates resulted in >20% of simulated populations reaching recovery goals in 30-50 years at cumulative costs of <$16 million. Protecting plover pairs within 50 km of natural resource agency field offices was sufficient to increase simulated populations to established recovery goals. A range-wide management plan needs to be developed and implemented to foster the involvement and cooperation among managers that will be necessary for recovery efforts to be successful. We also discuss how our approach can be applied to a variety of wildlife management issues.

Wildlife Society Bulletin↗

USGS2006

Does life history predict risk-taking behavior of wintering dabbling ducks?

Life-history theory predicts that longer-lived, less fecund species should take fewer risks when exposed to predation than shorter-lived, more fecund species. We tested this prediction for seven species of dabbling ducks (Anas) by measuring the approach behavior (behavior of ducks when approaching potential landing sites) of 1099 duck flocks during 37 hunting trials and 491 flocks during 13 trials conducted immediately after the 1999-2000 waterfowl hunting season in California, USA. We also experimentally manipulated the attractiveness of the study site by using two decoy treatments: (1) traditional, stationary decoys only, and (2) traditional decoys in conjunction with a mechanical spinning-wing decoy. Approach behavior of ducks was strongly correlated with their life history. Minimum approach distance was negatively correlated with reproductive output during each decoy treatment and trial type. Similarly, the proportion of flocks taking risk (approaching landing sites to within 45 m) was positively correlated with reproductive output. We found similar patterns of approach behavior in relation to other life-history parameters (i.e., adult female body mass and annual adult female survival rate). Thus, species characterized by a slower life-history strategy (e.g., Northern Pintail [A. acuta]) were more risk-averse than species with a faster life-history strategy (e.g., Cinnamon Teal [A. cyanoptera]). Furthermore, although we were able to reduce risk-averseness using the spinning-wing decoy, we were unable to override the influence of life history on risk-taking behavior. Alternative explanations did not account for the observed correlation between approach behavior and life-history parameters. These results suggest that life history influences the risk-taking behavior of dabbling ducks and provide an explanation for the differential vulnerability of waterfowl to harvest. ?? The Cooper Ornithological Society 2006.

Condor↗

USGS2006

Demographic patterns of postfire regeneration in Mediterranean-climate shrublands of California

This study uses detailed demographic data to determine the extent to which functional groupings, based on seedling recruitment and resprouting response to fire, capture the dynamics of postfire responses and early successional change in fire-prone ecosystems. Following massive wildfires in southern California, USA, we sampled chaparral and sage scrub vegetation in nested 0.1-ha plots from 90 sites for five postfire years. Prefire density of woody skeletons and cover and density of all postfire species were recorded. Functional types of postfire obligate seeder, facultative seeder, and obligate resprouter are broadly useful but fail to capture much of the dynamics of postfire succession in these shrublands. For the woody flora, stratifying these three regeneration modes by life-form captures important differences. Postfire obligate-seeding shrubs exhibit a single postfire seedling cohort whereas the faster growing suffrutescent species reach reproductive maturity by the second year and produce multiple seedling cohorts. Postfire obligate-resprouting shrubs reach reproductive maturity early but have very limited seedling recruitment in the early postfire years, whereas obligate-resprouting subshrubs flower the first year from resprouts and have seedling recruitment pulses in the second and subsequent postfire years. For the rich herbaceous flora, further subdivisions are needed to capture the range of variation. Herbaceous perennials are nearly all postfire obligate resprouters, and there are important demographic differences during early succession in different growth forms such as geophytes and rhizomatous grasses. Annuals lack resprouting ability and are postfire obligate seeders. Some exhibit extreme life-history specialization and are present only in the immediate postfire year(s). Others are highly specialized on fire but persist during early succession, and still others are opportunistic species widely distributed on open sites but can expand their populations during early succession. ?? 2006 by the Ecological Society of America.

Ecological Monographs↗

USGS2010

A comparison of litter production in young and old baldcypress (Taxodium distichum L.) stands at Caddo Lake, Texas

Aboveground primary productivity for cypress forests was assessed from measurements of litter production in two age groups and in two hydrological regimes (standing water and free-flowing). Caddo Lake, located in northeast Texas on the Texas-Louisiana border, offered a unique study site since it is dominated by extensive stands composed entirely of Taxodium distichum (L.) Rich, (baldcypress) in different age groups. Young stands (approximately 100 years old) are found along the shoreline and on shallow flooded islands. Old stands (-150 to 300 years old) are found in deeper water where they were continuously flooded. Litter production over three years from October 1998 to September 2001 was measured. Litter consisting of leaves, twigs, bark, reproductive parts, and Tillandsia usneoides (L.) L. (Spanish moss) was collected monthly using 0.5 m 2 floating traps. Tree diameters were measured within 200 m 2 circular plots in each stand. The young stands supported densities greater than 2,000 stems/ha and a mean stand basal area of 72.3 m 2 /ha, whereas old stands supported lower densities of about 500 stems/ha but with a similar mean stand basal area of 73.3 m 2 /ha. There was a significant difference between old and young stands for overall yearly litter production, averaging about 670 g/m 2 /yr in the young stands and 460 g/m 2 /yr in the old stands. Leaves and twigs were significantly greater in the young stands, while reproductive parts were higher in old stands. Litter collections between years or hydrological regimes were not significantly different.

Texas↗

USGS2008

Contaminant levels in eggs of American white pelicans, Pelecanus erythrorhynchos, from Chase Lake, North Dakota

American White Pelicans (Pelecanus erythrorhynchos) are colonial nesters, making them susceptible to site-specific mortality factors. One of the largest known breeding colonies is at Chase Lake National Wildlife Refuge in North Dakota. In 2004, this colony suffered total reproductive failure. In 2005, we collected abandoned eggs from this colony to test for environmental contaminants. Nine eggs were analyzed for 28 organochlorine pesticides, total polychlorinated biphenyls, and 26 inorganic elements. Based on concentrations in this sample of eggs and levels linked to reproductive problems in birds, adult pelicans in the Chase Lake breeding colony are not at known risk from any of the environmental contaminants we measured.

North Dakota↗

USGS2012

Population dynamics of introduced rodents in Hawaii Volcanoes National Park 1986-1990

We determined seasonal and geographical distribution patterns for four species of introduced rodents in Hawai‘i Volcanoes National Park from 1986-1990. We surveyed black rats (Rattus rattus), Polynesian rats (R. exulans), Norway rats (R. norvegicus) and house mice (Mus musculus) along an elevation gradient ranging from 90–1,820 m above sea level in five different sites using baited snap traps. Rodent community structure differed by elevation: there were more mice at montane sites and more Polynesian rats in the lowlands. We found that breeding occurred throughout the year for all species at all sites but that seasonal peaks in reproductive activity were common. Reproduction tended to be more common in the summer months at higher elevation sites and in the winter months at lower elevations. Rodents of all species were more abundant in our study in the winter than in the summer, but the differences were not significant. The overall sex ratio did not vary from a 1:1 ratio, but seasonally there were differences in sex ratio which varied with species and site. We calculated the minimum distance traveled from an assessment line and found that larger-bodied species traveled longer average distances. Pelage color in black rats was darkest in wet forest which may have adaptive value. Black and Polynesian rats were widespread in almost all habitat types, whereas mice were limited to dry and mesic sites; Norway rats were the rarest component of our sampling and found only in wet montane forest (‘Ōla‘a Forest).

Hawaii↗

USGS2013

Adaptive harvest management for the Svalbard population of pink-footed geese: assessment for the 2013-2015 hunting seasons

This report describes progress on the development of an adaptive harvestmanagement strategy for maintaining the Svalbard population of pink-footed geese near their agreed target level (60,000) by providing for sustainable harvests in Norway and Denmark. Specifically, this report provides an optimal harvest quota for the 2013-2015 hunting seasons and describes a process for evaluating whether emergency hunting closures would be needed during that period. By combining varying hypotheses about survival and reproduction, a suite of nine models have been developed that represent a wide range of possibilities concerning the extent to which demographic rates are density dependent or independent, and the extent to which spring temperatures are important. The most current set of monitoring information was used to update model weights for the 1991 – 2012 period. Current model weights suggest no evidence for density-dependent survival. These results suggest that the pink-footed goose population may have recently experienced a release from density-dependent mechanisms, corresponding to the period of most rapid growth in population size. There was equivocal evidence for the effect of May temperature days (number of days with temperatures above freezing) on survival and on reproduction. The optimal harvest strategy suggests that the appropriate annual harvest quota for the 20132015 period is 15,000; hence there is no need to take emergency measures to close the upcoming hunting season. For comparison, the estimated harvest in 2012 was 11,000. If the harvest quota of 15,000 were met, the autumn 2013 population count is expected to be 76,000. If only the most recent 3-year mean harvest were realized (11,500), an autumn population size of 80,000 thousand is expected. Thus, it may be that harvest is approaching the magnitude needed to stabilize the population.

Svalbard↗