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At least 55 records · Page 3Linked to original sources
USGS2019

San Francisco Bay triennial bird egg monitoring program for contaminants, California—2018

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP), administered by the San Francisco Estuary Institute, is a large-scale effort to monitor contaminant trends in water, sediment, fish, and birds throughout San Francisco Bay (San Francisco Estuary Institute, 2016). As part of the RMP and the U.S. Geological Survey (USGS) long-term Wildlife Contaminants Program, the USGS samples doublecrested cormorant ( Phalacrocorax auritus ) and Forster’s tern ( Sterna forsteri ) eggs throughout the San Francisco Bay approximately every 3 years to assess temporal trends in contaminant concentrations. This sampling has previously been carried out by USGS in 2009, 2012, and 2016. This document summarizes egg collections for 2018, as well as mercury concentrations in Forster’s tern eggs on an individual egg basis. These data are available in a USGS data release (Ackerman and others, 2019).

California↗
USGS2018

Monitoring breeding and migration of neotropical migratory birds at Naval Base Coronado, Remote Training Site, Warner Springs, San Diego County, California, 5-year summary, 2013–17

We operated a bird banding station on the Naval Base Coronado, Remote Training Site, Warner Springs (RTSWS), in northeastern San Diego County, California, during the bird breeding season (spring/summer) from 2013 to 2017 and during migration (fall) from 2013 to 2016. The station was established in spring 2013 as part of the Monitoring Avian Productivity and Survivorship (MAPS) program and continued into the fall for the first 4 years as part of a long-term monitoring program for neotropical migratory birds. We captured 705 individuals of 58 species during the MAPS/breeding season from 2013 to 2017 (12–13 days each year in April through August), 79 percent of which were newly banded during the MAPS season (555), 8 percent of which were recaptures banded in previous years (57), and 13 percent of which we released unbanded (64 hummingbirds and 29 other birds that were released or escaped prior to banding). Sixty individuals were captured more than once within a year during MAPS. Bird capture rate averaged 19 ± 1 captures per 100 net-hours (range 17–20) across 5 years. Annual species richness ranged from 28 (2017) to 42 (2014). The average species richness per day was highest in 2014 (9 ± 3) and lowest in 2016 (6 ± 2). Bushtit ( Psaltriparus minimus ) was the most abundant breeding species captured, followed by Spotted Towhee ( Pipilo maculatus ), Oak Titmouse ( Baeolophus inornatus ), Anna’s Hummingbird ( Calypte anna ), House Wren ( Troglodytes aedon ), Ash-throated Flycatcher ( Myiarchus cinerascens ), California Scrub-jay ( Aphelocoma californica ), Bewick’s Wren ( Thryomanes bewickii ), Acorn Woodpecker ( Melanerpes formicivorus ), California Towhee ( Melozone crissalis ), and Western Bluebird ( Sialia mexicana ). Each of these 11 breeding species accounted for at least 5 percent of captures in any 1 year. Fifty-seven percent of known-sex captures were female and 43 percent were male. Thirty-three percent of known-age captures were juveniles. Peaks in number of birds captured were in the first and last weeks of April, and the greatest number of species was captured in early May.

California↗
USGS1995

Dicofol and DDT residues in lizard carcasses and bird eggs from Texas, Florida, and California

Dicofol is an organochlorine agricultural pesticide used to control mites. The principal commercial dicofol product is known as Kelthane TM. More than 70% of dicofol product (about 3 million Ib or 1.4 million kg) sold annually in the U.S. is applied in California, Arizona, Texas, and Florida. Florida citrus and California cotton receive more than half the total (Clark 1990). In laboratory studies, dicofol, which is structurally similar to DDT, had adverse impacts on reproduction in fish (deformed larvae, delayed hatching), birds (reduced eggshell thickness, reduced hatchability), and mammals (reduced insemination rate, reduced pregnancy rate, failure to produce young) (see Clark 1990 for review). Overall, the reproduction of birds seems less sensitive to dicofol than to DDE. However, in birds, dietary concentrations of dicofol between 1 and 10 µg/g (wet weight) fed to captive adult females caused such problems as eggshell thinning, reduced hatching success, or reduced fertility in American kestrels ( Falco sparverius ) (Fry et al. 1988, Clark et al. 1990) and eastern screech-owls ( Otus asio ) (Wiemeyer et al. 1989). In spite of these laboratory findings, there have been no intensive field investigations of possible reproductive effects of dicofol on wild birds. Such studies must wait until field residue data are sufficient to identify populations with high exposure. If dicofol accumulates in birds in the field and heavily exposed populations can be identified, then their reproduction can be studied. Residues have not been reported from reptiles. Analytical screening of wildlife tissue samples for organochlorine chemicals only rarely includes dicofol, and this may explain why the relative hazard of dicofol to wildlife populations is poorly known.

California, Florida, Texas↗
USGS2015

Estimating exposure of piscivorous birds and sport fish to mercury in California lakes using prey fish monitoring: a predictive tool for managers

Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water Ambient Monitoring Program (SWAMP), via the Bioaccumulation Oversight Group (BOG), has recently completed statewide surveys of contaminants in sport fish tissue from more than 250 lakes and rivers in California and throughout coastal waters. This effort focused on human health issues but did not include beneficial uses by wildlife. Many piscivorous birds such as grebes, terns, cormorants, and mergansers eat fish smaller than those that were sampled by BOG, and sport fish Hg concentrations are not always indicative of wildlife exposure to Hg; therefore, the BOG surveys could not address whether wildlife were at risk due to Hg-induced reproductive impairment in these lakes. We used western grebes ( Aechmophorus occidentalis ) and Clark’s grebes ( Aechmophorus clarkii ) as our index of wildlife exposure to Hg in California lakes. Grebes are widely distributed in lakes throughout California and, as piscivorous waterbirds, are near the top of the food chain in lakes. Additionally, grebes become flightless after they arrive at their summer locations. Thus, grebes are useful representatives for wildlife risk from local, lake-specific contaminant exposure. Grebes also breed at many lakes throughout California, making them susceptible to impaired reproduction due to local Hg contamination. We developed a tool for estimating wildlife and sport fish risk from Hg exposure based on Hg concentrations in prey fish. This quantitative tool can be used to predict Hg concentrations in grebe blood, grebe eggs, and sport fish, thus facilitating a feasible alternative for adequately estimating wildlife exposure when more comprehensive wildlife sampling is not possible. Specifically, we sampled grebes, prey fish, and sport fish simultaneously at 25 lakes throughout California during the spring and summer of 2012 and 2013 when breeding birds are particularly vulnerable to Hg-induced reproductive impairment. We selected lakes based on a combination of factors, including lakes from southern and northern California, of various sizes, shapes, and elevations, with a range of sport fish Hg exposure levels , where largemouth bass ( Micropterus salmoides ) was the primary sport fish, and with a history of use by grebes. Using these factors ensured that our results are representative of a broad range of lakes and reservoirs in California and are comparable to prior BOG studies. Specifically, we addressed three management questions: Does methylmercury pose significant risks to aquatic life in a representative sample of California lakes and reservoirs? Can a correlational approach be applied on a statewide basis to estimate risks to birds? What are appropriate water-quality monitoring requirements to address methylmercury exposure in wildlife?

California↗
USGS2013

Stratigraphy and paleogeographic significance of the Pennsylvanian-Permian Bird Spring Formation in the Ship Mountains, southeastern California

A thick sequence of limestone, dolomite, and minor sandstone assigned to the Pennsylvanian and lower Permian Bird Spring Formation is exposed in the Ship Mountains about 85 kilometers (km) southwest of Needles, California, in the eastern Mojave Desert. These strata provide a valuable reference section of the Bird Spring Formation in a region where rocks of this age are not extensively exposed. This section, which is about 900 meters (m) thick, is divided into five informal members. Strata of the Bird Spring Formation in the Ship Mountains originated as shallow-water marine deposits on the broad, southwest-trending continental shelf of western North America. Perpendicular to the shelf, the paleogeographic position of the Ship Mountains section is intermediate between those of the thicker, less terrigenous, more seaward section of the Bird Spring Formation in the Providence Mountains, 55 km to the northwest, and the thinner, more terrigenous, more landward sections of the Supai Group near Blythe, 100 km to the southeast. Parallel to the shelf, the Ship Mountains section is comparable in lithofacies and inferred paleogeographic position to sections assigned to the Callville Limestone and overlying Pakoon Limestone in northwestern Arizona and southeastern Nevada, 250 km to the northeast. Deposition of the Bird Spring Formation followed a major rise in eustatic sea level at about the Mississippian- Pennsylvanian boundary. The subsequent depositional history was controlled by episodic changes in eustatic sea level, shelf subsidence rates, and sediment supply. Subsidence rates could have been influenced by coeval continental-margin tectonism to the northwest.

Arizona, California, Nevada↗
USGS1975

The role of indigenous wild, semidomestic, and exotic birds in the epizootiology of velogenic viscerotropic Newcastle disease in southern California, 1972-1973

During an epornitic of velogenic viscerotropic Newcastle disease (VVND) in southern California, free-flying wild birds, captive and free-ranging semidomestic birds, and exotic birds were collected from the quarantine area to determine their role in the epizootiology of the disease. The VVND virus was isolated from 0.04% of 9,446 free-flying wild birds, 0.76% of 4,367 semidomestic birds, and 1.01% of 3,780 exotic birds examined. Three house sparrows and 1 crow directly associated with infected poultry flocks were the only free-flying wild birds from which VVND virus was isolated. Among semidomestic species, ducks, quail, chukars, pheasants, peafowl, pigeons, and doves were found to be infected. Psittacines, pittas, and toucans accounted for 92% of the VVND virus isolations from exotic birds. In addition, domestic Newcastle disease virus (NDV) was isolated from 0.29% of the free-flying wild birds, from 1.65% of the semidomestic birds, and from 0.19% of the exotic birds collected. Hemagglutination-inhibition against domestic NDV was demonstrated in 0.24% of 3,796 wild bird serums, 8.28% of 2,004 semidomestic bird serums, and 3.90% of 231 exotic bird serums tested.Although few free-flying wild birds were infected with VVND virus in this epornitic, the isolation of domestic NDV strains from free-flying wild ducks and mourning doves suggests the potential for transportation of NDV over long distances by migratory birds.

Journal of the American Veterinary Medical Associa↗
USGS1994

Contaminants in eggs of aquatic birds from the grasslands of central California

Eggs were collected from the Grasslands of western Merced County, California, during 1986 and 1987, and at the Mendota Wildlife Area in Fresno County in 1987, as part of a reproductive study of nesting ducks and shorebirds. The eggs were analyzed to evaluate the effects of contaminants in agricultural drainwater on avian reproduction. Agricultural drainwater was the major source of water for irrigation and fall flooding in the Grasslands until the fall of 1985 when drainwater was mostly replaced by uncontaminated water. Drainwater had not been used at Mendota. Concentrations of arsenic and boron in eggs from all sites were lower than those known to harm avian reproduction. However, mean concentrations of selenium, a trace element known to impair avian reproduction at high dietary levels, were higher in eggs from the Grasslands than in eggs from the uncontaminated site. Although some selenium concentrations were as high as those found to have caused death or deformities at other sites, reproductive impairment was not observed in any ducks or shorebirds nesting in the Grasslands in 1986 or 1987.

California↗
USGS2007

Status review of the Marbled Murrelet (Brachyramphus marmoratus) in Alaska and British Columbia

The Marbled Murrelet ( Brachyramphus marmoratus ) is a small, diving seabird inhabiting inshore waters of the Northeastern Pacific Ocean. This species feeds on small, schooling fishes and zooplankton, and nests primarily on the moss-covered branches of large, old-growth conifers, and also, in some parts of its range, on the ground. We reviewed existing information on this species to evaluate its current status in the northern part of its range—Alaska (U.S.) and British Columbia (Canada). Within the southern part of its range (Washington, Oregon, and California, U.S.), the Marbled Murrelet was listed as a threatened species under the Endangered Species Act (ESA) in 1993, and the U.S. Fish and Wildlife Service (USFWS) needed information on the species throughout its range for ESA deliberations. We compiled published information on the conservation status, population biology, foraging ecology, population genetics, population status and trends, demography, marine and nesting habitat characteristics, threats, and ongoing conservation efforts for Marbled Murrelets in Alaska and British Columbia. We conducted a new genetic study using samples from a segment of the range that had not been included in previous studies (Washington, Oregon) and additional nuclear intron and microsatellite markers. We also analyzed available at-sea survey data from several locations for trend. To understand the reasonableness of the empirical trend data, we developed demographic models incorporating stochasticity to discern what population trends were possible by chance. The genetic studies substantially confirmed previous findings on population structure in the Marbled Murrelet. Our present work finds three populations: (1) one comprising birds in the central and western Aleutian Islands; (2) one comprising birds in central California; and (3) one comprising birds within the center of the range from the eastern Aleutians to northern California. Our knowledge of genetic structure within this central population is limited and it requires additional study. Compiling available abundance information, we estimated that in the recent past, Marbled Murrelets in Alaska numbered on the order of 1 million birds. We were unable to generate a similar estimate for historical population size in British Columbia. Using trend information from at-sea surveys spanning a wide geographic range in Alaska, murrelet numbers declined significantly at five of eight trend sites at annual rates of -5.4 to -12.7 percent since the early 1990s. Applying these rates of decline to the historical population estimate, the current murrelet population in Alaska is projected to be on the order of 270,000 birds. This represents an overall population decline of about 70 percent during the past 25 years. In British Columbia, available trend data indicate that murrelet populations there have experienced similar declines. We updated a recent (2002) population estimate for British Columbia, concluding that there are now between 54,000 and 92,000 murrelets in British Columbia. The rates of decline we observed are within, but at the high end of, a range of rates expected by chance. Given that declines were estimated for sites over essentially the entire northern range of the species, there is cause for concern about the species’ status. In their marine habitats, Marbled Murrelets overlap with salmon (Oncorhynchus sp.) gillnetting operations in British Columbia and in Alaska (especially in Prince William Sound and Southeast Alaska), and annual bycatch mortality is likely in the low thousands per year, although bycatch rates are difficult to measure. The species’ inshore distribution coincides with high levels of vessel traffic and makes them especially vulnerable to both chronic oil pollution and to catastrophic spills (e.g., the 1989 Exxon Valdez oil spill [EVOS] in south-central Alaska, which is estimated to have killed 12,000 to 15,000 murrelets). In their forested nesting habitats, Marbled Murrelets have lost about 15 percent of their suitable nesting habitat in Southeast Alaska, and 33 to 49 percent in British Columbia, from industrial-scale logging within the past half century. Increased predation also may be a threat to murrelet populations, related to fragmentation and edge effects from logging and development, and recent population increases observed for some important murrelet predators, including Bald Eagles ( Haliaeetus leucocephalus ), Common Ravens ( Corvus corax ), and Steller’s Jays ( Cyanocitta stelleri ). Nesting habitat losses cannot explain the declines observed in areas where industrial logging has not occurred on a large scale (e.g., Prince William Sound) or at all (Glacier Bay). The apparent change in population size and rates of decline reported for the Marbled Murrelet are large, and we therefore considered alternative explanations and precedents for changes of similar magnitude in other marine wildlife populations in the Northeastern Pacific Ocean. The declines are likely real, and related to combined and cumulative effects from climate-related changes in the marine ecosystem (most likely the 1977 regime shift) and human activities (logging, gillnet bycatch, oil pollution). Much uncertainty about the decline could be alleviated by continuing to repeat boat surveys in Prince William Sound and lower Cook Inlet, and by repeating the boat survey of Southeast Alaska that was conducted in 1994. This survey used a statistically sound design and covered the region that has been and likely remains the center of the species’ abundance. Important questions remain to be addressed about methods for measuring population status and change, adult mortality (major sources, density dependence, seasonal concordance), and the movements of wintering populations.

Alaska, British Columbia↗
USGS2006

Effects of contaminants on reproductive success of aquatic birds nesting at Edwards Air Force Base, California

Contamination by organochlorine pesticides (OCs), polychlorinated biphenyls, metals, and trace elements at Edwards Air Force Base (EAFB), located in the Mojave Desert, could adversely affect nesting aquatic birds, especially at the sewage lagoons that comprise Piute Ponds. Estimates of avian reproduction, in conjunction with analyses of eggs and avian foods for contaminant residues, may indicate the potential for negative effects on avian populations. From 1996 to 1999, we conducted studies at the Piute Ponds area of EAFB to evaluate the impacts of contaminants on nesting birds. Avian reproduction was evaluated in 1999. Eggs were collected for chemical analyses in 1996 and 1999, and African clawed frogs (Xenopus laevis), a likely food source, were collected for chemical analyses in 1998. Avian species occupying the higher trophic levels-black-crowned night-heron (Nycticorax nycticorax), white-faced ibis (Plegadis chihi), and American avocet (Recurvirostra americana)-generally bioaccumulated higher concentrations of contaminants in their eggs. Reproductive success and egg hatchability of night-herons and white-faced ibises in the Piute Ponds were similar to results observed at other western colonies. Deformities were observed in only one embryo in this study, but concentrations of contaminants evaluated in this ibis embryo were considered insufficient to have caused the deformities. Because clawed frogs, a primary prey item for night-herons at Piute Ponds, had no detectable levels of any OCs, it is likely that OCs found in night-heron eggs were acquired from the wintering grounds rather than from EAFB. The presence of isomers of dichlorodiphenyltrichloroethane (DDT) in ibis eggs indicated recent exposure, but invertebrates used for food by ibises were not sampled at Piute Ponds, and conclusions about the source of OCs in ibis eggs could not be made. Concentrations of contaminants in random and failed eggs of individual species were not different, and we concluded that contaminants did not cause the observed egg failures. ?? 2006 Springer Science+Business Media, Inc.

Archives of Environmental Contamination and Toxico↗
USGS2017

Population trends of birds wintering in the Central Valley of California

Since the 1970s, the Central Valley of California has seen a large investment in preservation and restoration of wetlands and riparian areas. At the same time, grasslands have been lost to vineyards, orchards, and residential development at an accelerating rate. We analyzed data from 17 Christmas Bird Count circles that were surveyed regularly between winter 1978–79 and winter 2013–14 to document population trends for birds wintering in this region. We selected 112 taxa (species or species groups) that were relatively abundant and widespread in the Central Valley during winter and used a hierarchical model to estimate annual rates of population change from the count data while accounting for varying survey effort. A much larger proportion of taxa showed positive (46%) than negative (18%) trends; about a third (36%) showed no detectable change. Central Valley habitats that showed the highest proportion of taxa with increasing vs. decreasing trends were riparian (59% vs. 9%; n = 32), wetlands (49% vs. 11%; n = 47), and open water (44% vs. 0%; n = 9), likely reflecting the conservation efforts in these habitats in recent decades. In contrast, a greater proportion of the taxa associated with grasslands and other open habitats (n = 25) showed decreases (48%) than increases (28%). As expected, species that adapt well to areas of human habitation showed stable or increasing trends. Examples of such species with strong positive trends include Anna's Hummingbird ( Calypte anna ), Black Phoebe ( Sayornis nigricans ) and recent Central Valley arrivals, Eurasian Collared-Dove ( Streptopelia decaocto ) and Great-tailed Grackle ( Quiscalus mexicanus ). Scavenging, opportunistic species such as Turkey Vulture ( Cathartes aura ) and Common Raven ( Corvus corax ) also showed strong positive trends. Trends in wintering populations were largely concordant with estimated trends available from breeding areas in California and western North America. Overall, these abundance data suggest that recent efforts to preserve and restore wetland and riparian habitats may be benefiting birds. However, a similar focus on conservation of the Central Valley's remaining grasslands may be needed to maintain populations of grassland-associated birds.

Book chapter↗
USGS2024

Antibodies to influenza A virus in Lesser (Aythya affinis) and Greater Scaup (Aythya marila) in the USA

Scaup, including both Lesser and Greater ( Aythya affinis and Aythya marila , respectively), are a grouping of populous and widespread North American diving ducks. Few influenza type A viruses (IAV) have been reported from these species despite a high prevalence of antibodies to IAV being reported. Existing virologic and serologic data indicate that IAV infection routinely occurs in scaup, yet it is unknown which IAV subtypes are linked to these infections. In this study, we aimed to gain a more complete picture of IAV natural history in Lesser and Greater Scaup from two coastal flyways in North America in 2015–18 (302 samples from California in the Pacific Flyway and 471 samples from Maryland in the Atlantic Flyway). Low prevalence of active IAV infection was detected by real-time reverse-transcription PCR in Lesser Scaup sampled in Maryland and California (2.8% and 8.1%, respectively). A single IAV (H1N1) was isolated in embryonated chicken eggs from a bird sampled in California. Similarly low levels were observed in Greater Scaup in California (3.3%). Antibodies to the nucleoprotein as detected with a commercial blocking ELISA were observed in all species and flyway combinations. Antibody seroprevalence estimates were higher in adult Lesser Scaup than in juveniles at both the ≤0.5 ( P <0.001, z=–3.582) and ≤0.7 serum-sample-to-negative-control absorbance thresholds ( P =0.003, z=–2.996). Neutralizing antibodies to H1–H12, H14, and H15 were detected using a microtiter virus neutralization assay, with the highest prevalence of antibodies against H1 (38%), H6 (36%), and H11 (35%). The high prevalence of antibodies to IAV and evidence of previous exposure to numerous subtypes are consistent with a high level of population immunity and a low prevalence of infection. These results must be interpreted in the context of season (winter sampling), as results may vary with the annual influx of naïve juvenile birds.

California, Maryland↗
USGS2014

Mercury in birds of San Francisco Bay-Delta, California: trophic pathways, bioaccumulation, and ecotoxicological risk to avian reproduction

San Francisco Bay Estuary in northern California has a legacy of mercury contamination, which could reduce the health and reproductive success of waterbirds in the estuary. The goal of this study was to use an integrated field and laboratory approach to evaluate the risks of mercury exposure to birds in the estuary. We examined mercury bioaccumulation, and other contaminants of concern, in five waterbird species that depend heavily on San Francisco Bay Estuary for foraging and breeding habitat: American avocets ( Recurvirostra americana ), black-necked stilts ( Himantopus mexicanus ), Forster&rsquo;s terns ( Sterna forsteri ), Caspian terns ( Hydroprogne caspia ), and surf scoters ( Melanitta perspicillata ). These species have different foraging habitats and diets that represent three distinct foraging guilds within the estuary&rsquo;s food web. In this report, we provide an integrated synthesis of the primary findings from this study and results are synthesized from 54 peer-reviewed publications generated to date with other unpublished results.

California↗
USGS1981

Mesurol as a bird repellent on wine grapes in Oregon and California

Field tests were conducted in California and Oregon from July to October 1978 to evaluate the effectiveness of Mesurol as a repellent to reduce bird damage to ripening wine grapes. A block of vines composed of two similar, adjacent plots was delineated at each of 20 vineyards. One randomly chosen plot within each block was treated with up to three applications of Mesurol (75% wettable powder) at a mean rate of 3.1 kg/ha. Damage assessments at harvest showed that the treatment significantly reduced bird damage in both states, but the actual level of bird damage protection provided by the treatment could not be calculated. Based on bird censuses, the primary grape-depredating species in Oregon vineyards was the American robin ( Turdus migratorius ), whereas house finches ( Carpodacus mexicanus ), California quail ( Lophortyx californicus ), goldfinches ( Spinus spp.), and robins were the primary species in California.

American Journal of Enology and Viticulture↗
USGS1954

Studies on avian malaria in vectors and hosts of encephalitis in Kern County, California. I. Infections in avian hosts

An epizoological study of Plasmodium infections in wild birds of Kern County, California, in the years 1946 through 1951 greatly extended knowledge of the occurrence of these parasites and their behavior in nature. Examination of 10,459 blood smears from 8,674 birds representing 73 species resulted in the observation of Plasmodium spp. in 1,094 smears representing 888 individual birds of 27 species. Seven species of Plasmodium were found: relictum, elongatum, hexamerium, nucleophilum, polare, rouxi and vaughani. Plasmodium relictum was by far the most frequently observed species, occurring in at least 79 per cent of the infected birds. Twelve new host species are recorded for this parasite. Sufficient morphological variation was observed to indicate that two strains of this species probably exist in nature. Numerous new host records were made of plasmodia with elongate gametocytes. The finding of parasites believed to be P. rouxi in two new host species represents the first record of the occurrence of this Plasmodium outside of Algeria. Multiple smears were obtained from a number of individual birds over varying time periods. Evidence of prolonged parasitemia was unusual, but some individuals had parasitemia on consecutive months and even for three successive years. In most individuals, parasitemias were of short duration. The inoculation of blood from wild birds into canaries led to the demonstration of many infections not observed on blood smear examination of donors. Use of these two complementary techniques led to more complete host records and a truer picture of the prevalence of infection. Three age classes of birds were studied--nestling, immature (less than 1 year of age) and adult. Parasites were observed in all three groups but infections in the younger individuals were most susceptible to interpretation. As to time of onset, numerous records were obtained of infection in nestling birds. Prevalence rates in immature birds after a single season's exposure ranged from 64 to 100 per cent in the house finch and 17 to 68 per cent in the English sparrow in different areas and years. Marked differences were found in the prevalence rates in different summer months, years and areas. It is believed these differences reflect variation in a number of environmental factors. This study indicates the extensive distribution of Plasmodium infection in a wide range of wild avian hosts. The observations are of possible importance in epidemiological studies of other arthropod-borne diseases such as the viral encephalitides for which these birds serve as hosts.

California↗
USGS1983

Organochlorine pesticides and PCB's: A continuing problem for the 1980s

In general. decreases in OC contamination in North America are unmistakable. This is documented by the NPMP. but. more importantly. it is borne out by improvements in the reproduction and population status of the brown pelican. bald eagle, peregrine falcon, and osprey. However, some OC contamination still persists, and several species, particularly predatory birds and insectivorous bats, continue to be vulnerable. Current OC problems in North America result from present and past usage and from industrial contamination. In addition, some studies suggest that some migrant bird species that winter south of the U.S. border are exposed to higher levels of OC pesticide than non-migrants. However, heavy OC pesticide contamination is known to exist in Arizona, New Mexico, and in southern California where migratory birds might stop during migration. At this time, we do not have the information to assess specifically the sources of contamination for most migrant species. From the number of recent OC problems identified in North America, it is apparent that OC's are not confined to the past and that we must continue to monitor and study OC's during this decade. However, current administrative, management, and research priorities are being directed toward the search for potential impacts of newer pesticides, air pollution. industrial waste, and other contaminants. Although it is necessary to build a body of scientific data on these types of contaminants, we feel that we cannot neglect continued work on OC's for which harmful effects impacting our wildlife resources are already known.

Transactions of the North American Wildlife and Na↗