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At least 271 records · Page 15Linked to original sources
USGS2007

Waterfowl distribution and abundance during spring migration in Southern Oregon and Northeastern California

We used aerial surveys to study abundance and distribution of waterfowl (ducks, geese, swans, and coots) during spring in southern Oregon and northeastern California (SONEC). Total waterfowl-use days in SONEC during the 119-day, 5 January-3 May, spring period was similar during 2002 (127,977,700) and 2003 (128,076,200) and averaged 1,075,900 birds per day (bpd); these estimates should be adjusted upward 4%-10% to account for areas not surveyed. Waterfowl abundance peaked in mid-March in both years: 2,095,700 in 2002 and 1,681,700 in 2003. Northern Pintail (Anas acuta) was the most abundant species in both years, accounting for 25.6% of the 2002 and 24.5% of the 2003 waterfowl-use days. Pintail abundance peaked during the 13 March survey at 689,300 in 2002 and 532,100 in 2003. All other dabbling ducks accounted for 27.6% and 28.6%, diving ducks for 13.5% and 9.2%, geese for 24.6% and 29.3%, swans for 2.8% and 1.0%, and coots for 5.8% and 6.4% of the spring waterfowl-use days in SONEC during 2002 and 2003, respectively. Although use days changed little for total waterfowl (+0.08%) and dabbling ducks (-0.1%), diving duck use was lower (-32%), and goose use days were greater (+19%) in 2003 than in 2002. Distribution was similar in both years, with the most waterfowl use in the Lower (66%) and Upper (14%) Klamath subregions; 2%-6% occurred in each of the other subregions. Although the Lower Klamath subregion received the greatest overall waterfowl use, distribution among subregions varied among species and surveys, and all subregions were important during some part of the spring for 1 or more species. Peak spring abundance in SONEC during 2002 and 2003 averaged 50.3% of the midwinter abundance in California (all survey regions) and southern Oregon (69-3 survey region) for all waterfowl, 46.1% for dabbling ducks, 62.4% for diving ducks, 68.8% for geese, 109.4% for swans, and 43.8% for coots. Each spring, 75% of all waterfowl use in SONEC occurred on federal, state, or Nature Conservancy lands (i.e., protected areas). On protected areas there was a higher percentage of dabbling ducks (80.5%), geese (70.5%), and coots (81.5%) than diving ducks (60.4%) and swans (49%). Waterfowl use of Klamath Basin National Wildlife Refuge (NWR) averaged 42% greater during spring 2002-2003 (568,500 bpd) than during 1998-2001 (Gilmer et al. 2004). Numerous factors likely impacted magnitude and distribution of waterfowl use of SONEC during spring, including weather, waterfowl populations, SONEC habitat, and species ecology. SONEC is a critical spring staging area for waterfowl that winter in the Central Valley of California and other Pacific Flyway regions and should be a major focus area for waterfowl-habitat conservation efforts.

Western North American Naturalist↗
USGS1978

Estimated oil and gas reserves, Southern California Outer Continental Shelf, January 1, 1977

As of January 1, 1977, approximately 1,450 billion cubic feet of gas and about 670 million barrels of oil* are estimated as remaining recoverable reserves in 11 of the 12 fields in the Outer Continental Shelf (OCS) off Southern California. No estimates were made for the unnamed field on lease P-0234 because well testing was not sufficient to allow a reasonable assessment. Of the 12 recognized fields, only two are producing and none is completely developed. Limits of many of the fields will be further defined by anticipated additional exploratory drilling. Original recoverable reserves in 11 fields are estimated to have been approximately 1,530 billion cubic feet of gas and about 830 million barrels of oil. Reserve estimates for nine fields were based on individual volumetric reservoir studies. Decline curve and volumetric analyses were used to estimate reserves in two fields. The estimates of original and remaining reserves are reported as one total for oil and one for gas within the Southern California OCS. *The term "oil" as used in this report includes crude oil, condensate and gas-plant liquids.

California↗
USGS2008

Timing and location of mortality of fledgling, subadult, and adult California Gulls

We investigated patterns of mortality during post-breeding migrations of California Gulls (Larus californicus) nesting near Laramie, Wyoming, USA. We used 151 recoveries and 647 sightings of banded and patagially-marked gulls to compare ratios of mortalities to observations of live birds (1) during four time periods (early and late fall migration, winter, and spring migration), (2) at two locations (Pacific coast and inland), and (3) among three age-classes of gulls (fledglings, 1- and 2-year-olds, and breeding-age adults). Mortality rates were higher in inland areas (35%) than in coastal areas (15%) and were dependent on season within inland areas, but not in coastal areas. Mortality in inland areas during early fall (21%) was comparable with that in coastal areas (13%) but was higher during late fall (68 vs. 13%) and spring migration (46 vs. 17%). Both fledgling (71%) and adult (64%) gulls experienced high mortality rates during late fall migration, possibly because some gulls were too weak to make their way to the Pacific coast and became trapped by poor weather conditions. Adult gulls also experienced high mortality inland during spring migration; few subadults made the costly migration to and from the breeding area. Some adults also skipped breeding and remained in coastal areas during the breeding season.

Wilson Journal of Ornithology↗
USGS2012

Transformation through time: How wildlife disease became a focus of conservation

When I began my career as an assistant waterfowl biologist in 1956, wildlife disease was not a major concern for conservation agencies. Some states— such as California, Michigan, New York, Wyoming, and Colorado— had small internal wildlife disease programs to investigate wildlife mortality events, and the U.S. Fish and Wildlife Service (FWS) had a program focused on migratory birds.

The Wildlife Professional↗
USGS1980

Effect of delayed reporting of band recoveries on survival estimates

Brownie et al. (U.S. Fish and Wildl. Serv., Resource Publ. 131, 1978) presented 14 models based on an array of explicit assumptions for the study of survival in avian populations. These methods are replacing the life table methods previously used to estimate survival rates (e.g., Burnham and Anderson, J. Wildl. Manage. , 43: 356-366, 1979). The new methods allow survival or recovery rates, or both, to be constant, time-specific, or time- and age-specific. In studies to estimate survival rates for birds the data are often from recoveries of birds shot or found dead during the hunting season and reported to the Bird Banding Laboratory by sportsmen, conservation agency employees, or the general public. This note examines the bias in estimating annual survival due to a proportion of the recoveries being incorrectly reported a year late. Specifically, a few recoveries each year of, for example, adult male American Widgeon ( Anas americana ) banded in California are reported as being recovered in year i + 1 when in fact they were actually recovered the previous year i. Delayed reporting might typically be caused by people finding a band in their health clothing in the fall of the year and, being embarrassed about their failure to report the band when it was taken, report it a year late not mentioning the actual year of recovery. Heuristically, delayed reporting should bias estimated annual survival rates upwards because it appears from the data that the birds corresponding to the "delayed" recoveries actually lived an additional year.

Journal of Field Ornithology↗
USGS2025

Combining ecological and genomic diversity surveys to inform conservation and restoration of an endangered wetland plant, soft salty bird’s-beak (Chloropyron molle ssp. molle)

Emergent tidal wetlands are declining globally as a result of sea level rise and land use change. This habitat loss can keenly affect rare plant species within wetlands, and may require restoration to meet species recovery goals related to retaining populations throughout species' ranges. Soft salty bird’s-beak ( Chloropyron molle ssp. molle ) is a federally- and state-endangered hemi-parasitic plant that occurs at the upper marsh transition zone in the San Francisco Bay–Delta, California, USA. We combined field surveys to document habitat associations and trends in abundance with genomic surveys to understand patterns of genetic structure in this rare endemic. We found that C . molle ssp. molle persisted at nine previously occupied marsh sites, although four sites (Hill Slough, MOTCO East, Fagan Marsh, and Joice Island) were smaller in population size than when surveyed in the 1990s. Additionally, twelve sites contained plots with suitable but unoccupied habitat that could be further assessed for restoration. Genomic analysis of over 40,000 single-nucleotide polymorphisms (SNPs) and 253 individuals grouped C . molle ssp. molle into six to seven regional genetic clusters with isolation by distance, and confirmed that C . molle ssp. molle is genetically distinct from adjacent populations of its closest relative ( C . molle ssp. hispidum ). The western-most C . molle ssp. molle sites of Point Pinole and Fagan Marsh were the most genetically and geographically isolated and had the lowest genome-wide diversity. Heterozygosity in sets of genes associated with tidal elevation, salinity, and annual and summer precipitation varied independently across populations. Overall, these genomic patterns indicate that selecting donor sites with similar environmental conditions and utilizing composite seeding approaches from multiple sites could allow for local adaptation to a range of possible environmental conditions. This comprehensive survey of habitat and genomic patterns can allow for the development of restoration actions and build climate-adaptation planning to help prevent the loss of a rare plant.

California↗
USGS2002

Contaminants without borders: A regional assessment of the Colorado River Delta ecosystem

The Colorado River Delta Region (CRDR) is comprised of large agricultural areas in the U.S. (Imperial and Yuma districts) and Mexico (Mexicali and San Luis districts), the Salton Sea, and the Lower Colorado River from southern Arizona to the Gulf of California (Valdés-Casillas et al., 1998). Before agricultural development, the lower delta comprised large riparian and wetland areas (Sykes, 1937; Glenn et al., 1999). Currently, most water from the Colorado River below Imperial Dam is used for irrigation in California and Mexico, and only remnants of the former CRDR wetlands remain. However, the Cienega de Santa Clara and the Rio Hardy wetlands (Figure 111.1) provide important habitat for many resident and migratory birds, including endangered species such as the desert pupfish (scientific names are provided in Table 111.1) and the Yuma clapper rail (Abarca et al., 1993; Mellink et al., 1997). Detailed descriptions of the CRDR and its wetlands are provided elsewhere (Sykes, 1937; Glenn et al., 1995; 1999; Friederici, 1998; Valdés-Casillas et al., 1998).

California↗
USGS2021

A decision tool to identify population management strategies for common ravens and other avian predators

Some avian species have developed the capacity to leverage resource subsidies associated with human manipulated landscapes to increase population densities in habitats with naturally low carrying capacities. Elevated corvid densities and new territory establishment have led to an unsustainable increase in depredation pressure on sympatric native wildlife prey populations as well as in crop damage. Yet, subsidized predator removal programs aimed at reducing densities are likely most effective longer-term when conducted in tandem with subsidy control, habitat management, and robust assessment monitoring programs. We developed decision support software that leverages stage structured Lefkovitch population matrices to compare and identify treatment strategies that reduce subsidized avian predator densities most efficiently, in terms of limiting both cost and take levels. The StallPOPd (Version 4; available at https://doi.org/10.7298/sk2e-0c38.4) software enables managers to enter the area of their management stratum and the demographic properties (vital rates) of target bird population(s) of interest to evaluate strategies to decrease or curtail further population growth. Strategies explicitly include the reduction in fertility (i.e., eggs hatched) and/or the culling of hatchlings, non-breeders and/or breeders, but implicitly comprise reduction in survival or reproduction through subsidy denial. We illustrate the utilities of the software with examples using common ravens ( Corvus corax; ravens) in the Mojave Desert of California, USA. Unfortunately, the survival and reproduction effects of each unit of a particular subsidy in that system have remained elusive, though this is the priority of current research. Because the software leverages a life history representation that is known to characterize hundreds of wildlife species in addition to ravens, the work expands the suite of tools available to wildlife managers and agricultural industry specialists to abate bird damage and impacts on sensitive wildlife in habitats with persistent human subsidies.

Human-Wildlife Interactions↗
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↗
USGS2021

Megafires and thick smoke portend big problems for migratory birds

In 2020, the fire season affecting the western United States reached unprecedented levels. The 116 fires active in September consumed nearly 20,822 km 2 ( https://inciweb.nwcg.gov/accessible-view/ Accessed 2020-09-29) with eighty percent of this footprint (16,567 km 2 ) from 68 fires occurring within California, Oregon, and Washington. Although the 2020 fire season was the most extreme on record, it exemplified patterns of increased wildfire size, number, timing, return frequency, and extent which are linked to climate-driven changes in precipitation and temperature affecting fire ignition and severity (Westerling 2016, Goss et al. 2020, Weber and Yadav 2020).

California, Oregon, Washington↗
USGS2012

Role of bird movements in the epidemiology of West Nile and avian influenza virus

Avian influenza virus (AIV) is influenced by site fidelity and movements of bird hosts. We examined the movement ecology of American crows ( Corvus brachyrhynchos ) as potential hosts for West Nile virus (WNV) and greater white-fronted geese ( Anser albifrons frontalis ) as potential hosts for AIVs. Research was based on radio-telemetry studies conducted in the Central Valley of California, USA. While crows were restricted to a small area of only a few square kilometers, the distribution of the geese encompassed the northern Central Valley. The crows used 1.5 to 3.5 different roosting areas monthly from February through October, revealing lower roost fidelity than the geese that used 1.1 to 1.5 roosting areas each month from November through March. The crows moved a mean distance of 0.11 to 0.49 km/month between their roosting sites and 2.5 to 3.9 km/month between roosting and feeding sites. In contrast, the geese moved 4.2 to 19.3 km/month between roosting areas, and their feeding range varied from 13.2 to 19.0 km/month. Our comparison of the ecological characteristics of bird movements suggests that the limited local movements of crows coupled with frequent turnover of roosts may result in persistence of focal areas for WNV infection. In contrast, widespread areas used by geese will provide regular opportunities for intermixing of AIVs over a much greater geographic area.

California↗
USGS2019

Noninvasive identification of cryptic herpetofauna from fecal samples: A novel approach pairing conservation dog surveys and genetic analysis

Noninvasive fecal sampling combined with genetic analysis is a powerful technique allowing the study of elusive or otherwise difficult to monitor species without the need for direct contact. While this method is widely used in birds and mammals, it has never been successfully applied on a large scale in reptiles. The blunt-nosed leopard lizard (Gambelia sila) is an endangered species endemic to the San Joaquin Desert of California. Presently, acquiring data on G. sila for research and management involves more traditional methods such as live capture to obtain tissue samples for DNA analysis, or observation via visual surveys, which are also used for regulatory monitoring in accordance with wildlife agency protocols. Here we describe an innovative approach for gathering additional information, that combines use of conservation detection dogs trained to locate G. sila scat samples with genetic analysis for identifying and distinguishing among sympatric lizard species. We developed two PCR assays that produce fluorescently labelled amplicons of species-specific fragment length for six lizard species in the study area. Using these assays we genetically identifed to species 78% (255 of 327) of samples collected by dog-handler teams across four years. The majority of the genetically identifed samples (82.4%; 210 of 255) were confirmed as originating from G. sila. Beyond the immediate application of these techniques for the study and monitoring of G. sila, our ability to recover usable DNA and to differentiate among a diverse group of lizards highlights the broad potential of our methodology for noninvasive sampling in reptiles.

California↗
USGS2007

Calculating background levels for ecological risk parameters in toxic harbor sediment

Establishing background levels for biological parameters is necessary in assessing the ecological risks from harbor sediment contaminated with toxic chemicals. For chemicals in sediment, the term contaminated is defined as having concentrations above background and significant human health or ecological risk levels. For biological parameters, a site could be considered contaminated if levels of the parameter are either more or less than the background level, depending on the specific parameter. Biological parameters can include tissue chemical concentrations in ecological receptors, bioassay responses, bioaccumulation levels, and benthic community metrics. Chemical parameters can include sediment concentrations of a variety of potentially toxic chemicals. Indirectly, contaminated harbor sediment can impact shellfish, fish, birds, and marine mammals, and human populations. This paper summarizes the methods used to define background levels for chemical and biological parameters from a survey of ecological risk investigations of marine harbor sediment at California Navy bases. Background levels for regional biological indices used to quantify ecological risks for benthic communities are also described. Generally, background stations are positioned in relatively clean areas exhibiting the same physical and general chemical characteristics as nearby areas with contaminated harbor sediment. The number of background stations and the number of sample replicates per background station depend on the statistical design of the sediment ecological risk investigation, developed through the data quality objective (DQO) process. Biological data from the background stations can be compared to data from a contaminated site by using minimum or maximum background levels or comparative statistics. In Navy ecological risk assessments (ERA's), calculated background levels and appropriate ecological risk screening criteria are used to identify sampling stations and sites with contaminated sediments.

California↗
USGS1992

A new subspecies of Chamaea fasciata (Wrentit) from Oregon (Aves: Timaliinae)

Geographic variation in plumage color of Chamaea fasciata (Wrentit) from northern California and southern Oregon is related to climate. A new subspecies, Chamaea fasciata margra , is described from a disjunct population of southern interior Oregon. Colonization of C. fasciata in interior Oregon was perhaps from birds crossing coniferous forests via isolated balds of Ceonothus . Recent increases of Wrentits in interior Oregon may be in response to habitat alterations (deforestation, fires) and concurrent global warming.

Oregon↗
USGS2012

Patterns of mortality in free-ranging California condors (Gymnogyps californianus)

We document causes of death in free-ranging California Condors (Gymnogyps californianus) from the inception of the reintroduction program in 1992 through December 2009 to identify current and historic mortality factors that might interfere with establishment of self-sustaining populations in the wild. A total of 135 deaths occurred from October 1992 (the first post-release death) through December 2009, from a maximum population-at-risk of 352 birds, for a cumulative crude mortality rate of 38%. A definitive cause of death was determined for 76 of the 98 submitted cases, 70% (53/76) of which were attributed to anthropogenic causes. Trash ingestion was the most important mortality factor in nestlings (proportional mortality rate [PMR] 73%; 8/11), while lead toxicosis was the most important factor in juveniles (PMR 26%; 13/50) and adults (PMR 67%; 10/15). These results demonstrate that the leading causes of death at all California Condor release sites are anthropogenic. The mortality factors thought to be important in the decline of the historic California Condor population, particularly lead poisoning, remain the most important documented mortality factors today. Without effective mitigation, these factors can be expected to have the same effects on the sustainability of the wild populations as they have in the past.

Journal of Wildlife Diseases↗
USGS2022

Both real-time and long-term environmental data perform well in predicting shorebird distributions in managed habitat

Highly mobile species, such as migratory birds, respond to seasonal and inter-annual variability in resource availability by moving to better habitats. Despite the recognized importance of resource thresholds, species distribution models typically rely on long-term average habitat conditions, mostly because large-extent, temporally-resolved, environmental data are difficult to obtain. Recent advances in remote sensing make it possible to incorporate more frequent measurements of changing landscapes; however, there is often a cost in terms of model building and processing and the added value of such efforts is unknown. Our study tests whether incorporating real-time environmental data increases the predictive ability of distribution models, relative to using long-term average data. We developed and compared distribution models for shorebirds in California's Central Valley based on high temporal resolution (every 16-days), and 17-year long-term average, surface water data. Using abundance-weighted boosted regression trees, we modeled monthly shorebird occurrence as a function of surface water availability, crop type, wetland type, road density, temperature, and bird data source. While modeling with both real-time and long-term average data provided good fit to withheld validation data (0.79 < AUC < 0.89 across taxa), there were small differences in model performance. The best models incorporated long-term average conditions and spatial pattern information for real-time flooding (e.g. perimeter-area ratio of real-time water bodies). There was not a substantial difference in the performance of real-time and long-term average data models within time periods when real-time surface water differed substantially from the long-term average (specifically during drought years 2013-2016) and in intermittently flooded months or locations. Spatial predictions resulting from the models differed most in the southern region of the study area where there is lower water availability, fewer birds, and lower sampling density. Prediction uncertainty in the southern region of the study area highlights the need for increased sampling in this area. Because both sets of data performed similarly, the choice of which data to use may depend on the management context. Real-time data may ultimately be best for guiding dynamic, adaptive conservation actions whereas models based on long-term averages may be more helpful for guiding permanent wetland protection and restoration.

Ecological Applications↗
USGS1999

Behavioral correlates of heart rates of free-living Greater White-fronted Geese

We simultaneously monitored the heart rate and behavior of nine free-living Greater White-fronted Geese (Anser albifrons) on their wintering grounds in northern California. Heart rates of wild geese were monitored via abdominally-implanted radio transmitters with electrodes that received electrical impulses of the heart and emitted a radio signal with each ventricular contraction. Post-operative birds appeared to behave normally, readily rejoining flocks and flying up to 15 km daily from night-time roost sites to feed in surrounding agricultural fields. Heart rates varied significantly among individuals and among behaviors, and ranged from less than 100 beats per minute (BPM) during resting, to over 400 BPM during flight. Heart rates varied from 80 to 140 BPM during non-strenuous activities such as walking, feeding, and maintenance activities, to about 180 BPM when birds became alert, and over 400 BPM when birds were startled, even if they did not take flight. Postflight heart rate recovery time averaged < 10 sec. During agonistic encounters, heart rate exceeded 400 BPM; heart rates during social interactions were not predictable solely from postures, as heart rates were context-dependent, and were highest in initial encounters among individuals. Instantaneous measures of physiological parameters, such as heart rate, are often better indicators of the degree of response to external stimuli than visual observations and can be used to improve estimates of energy expenditure based solely on activity data.

Condor↗
USGS2005

Mercury burdens in Chinese mitten crabs (Eriocheir sinensis) in three tributaries of southern San Francisco Bay, California, USA

Chinese mitten crabs (Eriocheir sinensis), endemic to Asia, were first reported in the San Francisco Bay in 1992. They are now established in nearly all San Francisco Bay tributaries. These crabs accumulate more metals, such as mercury, than crustaceans living in the water column. Because their predators include fish, birds, mammals and humans, their mercury burdens have an exceptional potential to impact the ecosystem and public health. We sought to elucidate the potential threat of mitten crab mercury burdens in three adjacent streams in southern San Francisco Bay, one of which is known to be contaminated with mercury. Mitten crabs had hepatopancreas concentrations of total mercury and methylmercury that did not differ among streams. The maximum burden we measured was below the action level of 1 ppm recommended by the USEPA. Hepatopancreas concentrations of methylmercury declined with increasing crab size, suggesting a mechanism for mercury excretion and that predators might reduce mercury exposure if they select larger crabs. Because mercury may be heterogeneously distributed among tissues, estimation of the impacts of crab mercury burdens on the environment requires more data on the feeding preferences of predators. Hepatopancreas concentrations of mercury decline with crab size, which may have important consequences for bio-magnification in food webs. ?? 2004 Elsevier Ltd. All rights reserved.

Environmental Pollution↗