Linking Mesoscale Spatial Variation in Methylmercury Production to Bioaccumulation in Tidal Marsh Food Webs.

Differences in sediment biogeochemistry among tidal marsh features with different hydrological and geomorphological characteristics, including marsh interiors, marsh edges, first-order channels, and third-order channels, can result in spatial variation in MeHg production and availability. To better understand the link between MeHg production in sediments and bioaccumulation in primary and secondary consumer invertebrates and fish, we characterized mesoscale spatial variation in sediment biogeochemistry and MeHg concentrations of sediments, water, and consumer tissues among marsh features. Our results indicated that marsh interiors had biogeochemical conditions, including greater concentrations of organic matter and sulfate reduction rates, that resulted in greater MeHg concentrations in sediments and surface water particulates from marsh interiors compared to other features. Tissue MeHg concentrations of consumers also differed among features, with greater concentrations from marsh edges and interiors compared to channels. This spatial mismatch of MeHg concentrations in sediments and water compared to those in consumers may have resulted from differences in behavior and physiology among consumers that influenced the spatial scale over which MeHg was integrated into tissues. Our results highlight the importance of sampling across a suite of marsh features and considering the behavioral and physiological traits of sentinel taxa for contaminant monitoring studies.

Avian influenza antibody prevalence increases with mercury contamination in wild waterfowl.

Environmental contamination is widespread and can negatively impact wildlife health. Some contaminants, including heavy metals, have immunosuppressive effects, but prior studies have rarely measured contamination and disease simultaneously, which limits our understanding of how contaminants and pathogens interact to influence wildlife health. Here, we measured mercury concentrations, influenza infection, influenza antibodies and body condition in 749 individuals from 11 species of wild ducks overwintering in California. We found that the odds of prior influenza infection increased more than fivefold across the observed range of blood mercury concentrations, while accounting for species, age, sex and date. Influenza infection prevalence was also higher in species with higher average mercury concentrations. We detected no relationship between influenza infection and body fat content. This positive relationship between influenza prevalence and mercury concentrations in migratory waterfowl suggests that immunotoxic effects of mercury contamination could promote the spread of avian influenza along migratory flyways, especially if influenza has minimal effects on bird health and mobility. More generally, these results show that the effects of environmental contamination could extend beyond the geographical area of contamination itself by altering the prevalence of infectious diseases in highly mobile hosts.

REFERENCE VALUES AND COMPARISON OF BLOOD CHEMISTRY AND PLASMA PROTEIN VALUES BETWEEN GOLD STANDARD ANALYZERS AND FOUR POINT-OF-CARE DEVICES IN FREE-RANGING CANVASBACKS (AYTHYA VALISINERIA).

Accurate, timely, and cost-effective blood chemistry analysis is an essential tool for directing emergency treatment, monitoring the health status of captive and free-ranging individuals and flocks, and improving the efficacy of conservation actions. Blood samples were obtained from 52 canvasbacks (Aythya valisineria) that were captured on San Francisco Bay, California, during December 2017 as part of a long-term study. Reference values and clinical agreement were determined for blood chemistry and plasma protein parameters among four commonly used point-of-care devices (VetScan® VS2, i-STAT®, AlphaTRAK®2 glucometer, refractometer) and two gold standard laboratory analyzers (Roche cobas® c501, Helena SPIFE 3000 system). Canvasback reference values were generally within expected ranges for Anatidae species with the exception of higher upper limits for sodium and chloride. Creatine kinase and aspartate transaminase values exceeded a published threshold for diagnosis of capture myopathy even though study birds were captured using low-stress techniques and successfully released. With the exception of higher alkaline phosphatase in hatch-year canvasbacks, no age or sex differences were observed for any analyte in this population that was captured during a nonbreeding period. Analysis of analyzer agreement found raw VetScan aspartate transaminase, calcium, glucose, and uric acid values; corrected VetScan albumin, potassium, sodium, and total protein values; raw i-STAT glucose and potassium values; and corrected i-STAT sodium and chloride values were clinically interchangeable with Roche cobas values. Raw VetScan and i-STAT glucose values were also interchangeable. However, none of the Roche or point-of-care analyzer plasma protein values were in clinical agreement with gold standard electrophoresis values. The findings of this study highlight the need for analyzer- or technique-specific reference values and provide biologists and veterinarians quantitative reference values using currently available analyzers to better assess and respond to the health of individuals and populations.

Effects of Season, Location, Species, and Sex on Hematologic and Plasma Biochemical Values and Body Mass in Free-ranging Grebes (Aechmophorus species).

The effects of season, location, species, and sex on body weight and a comprehensive array of blood chemistry and hematology analytes were compared for free-ranging western (Aechmophorus occidentalis) and Clark's (Aechmophorus clarkii) grebes. Birds (n = 56) were collected from Puget Sound, WA, and Monterey Bay and San Francisco Bay, CA, from February 2007 to March 2011. The data supported generalization of observed ranges for most analytes across Aechmophorus grebe metapopulations wintering on the Pacific coast. Notable seasonal and location effects were observed for packed cell volume (winter 6% greater than fall; winter California [CA] 5% greater than Washington [WA]), total white blood cell count (CA 3.57 × 103 cells/µL greater than WA), heterophils (WA 10% greater than CA), lymphocytes (winter 19% greater than fall), heterophil to lymphocyte ratio (fall 5.7 greater than winter), basophils (CA greater than WA), plasma protein (WA about 10 g/L [1.0 g/dL] greater than CA), plasma protein to fibrinogen ratio (winter about 15 greater than fall), potassium (CA 2 mmol/L greater than WA), and liver enzymes (alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase: WA greater than CA). Within California, season had a greater effect on body mass than sex (mean winter weights about 200 g greater than fall), whereas within a season, males weighed only about 80 g more than females, on average. These data give biologists and veterinarians quantitative reference values to better assess health at the individual and metapopulation level.

Allochthonous marsh subsidies enhances food web productivity in an estuary and its surrounding ecosystem mosaic.

Terrestrial organic matter is believed to play an important role in promoting resilient estuarine food webs, but the inherent interconnectivity of estuarine systems often obscures the origins and importance of these terrestrial inputs. To determine the relative contributions of terrestrial (allochthonous) and aquatic (autochthonous) organic matter to the estuarine food web, we analyzed carbon, nitrogen, and sulfur stable isotopes from multiple trophic levels, environmental strata, and habitats throughout the estuarine habitat mosaic. We used a Bayesian stable isotope mixing model (SIMM) to parse out relationships among primary producers, invertebrates, and a pelagic and demersal fish species (juvenile Chinook salmon and sculpin, respectively). The study was carried out in the Nisqually River Delta (NRD), Washington, USA, a recently-restored, macrotidal estuary with a diverse habitat mosaic. Plant groupings of macroalgae, eelgrass, and tidal marsh plants served as the primary base components of the NRD food web. About 90% of demersal sculpin diets were comprised of benthic and pelagic crustaceans that were fed by autochthonous organic matter contributions from aquatic vegetation. Juvenile salmon, on the other hand, derived their energy from a mix of terrestrial, pelagic, and benthic prey, including insects, dipterans, and crustaceans. Consequently, allochthonous terrestrial contributions of organic matter were much greater for salmon, ranging between 26 and 43%. These findings demonstrate how connectivity among estuarine habitat types and environmental strata facilitates organic matter subsidies. This suggests that management actions that improve or restore lateral habitat connectivity as well as terrestrial-aquatic linkages may enhance allochthonous subsidies, promoting increased prey resources and ecosystem benefits in estuaries.

Pathways for avian influenza virus spread: GPS reveals wild waterfowl in commercial livestock facilities and connectivity with the natural wetland landscape.

Zoonotic diseases are of considerable concern to the human population and viruses such as avian influenza (AIV) threaten food security, wildlife conservation and human health. Wild waterfowl and the natural wetlands they use are known AIV reservoirs, with birds capable of virus transmission to domestic poultry populations. While infection risk models have linked migration routes and AIV outbreaks, there is a limited understanding of wild waterfowl presence on commercial livestock facilities, and movement patterns linked to natural wetlands. We documented 11 wild waterfowl (three Anatidae species) in or near eight commercial livestock facilities in Washington and California with GPS telemetry data. Wild ducks used dairy and beef cattle feed lots and facility retention ponds during both day and night suggesting use for roosting and foraging. Two individuals (single locations) were observed inside poultry facility boundaries while using nearby wetlands. Ducks demonstrated high site fidelity, returning to the same areas of habitats (at livestock facilities and nearby wetlands), across months or years, showed strong connectivity with surrounding wetlands, and arrived from wetlands up to 1251 km away in the week prior. Telemetry data provides substantial advantages over observational data, allowing assessment of individual movement behaviour and wetland connectivity that has significant implications for outbreak management. Telemetry improves our understanding of risk factors for waterfowl-livestock virus transmission and helps identify factors associated with coincident space use at the wild waterfowl-domestic livestock interface. Our research suggests that even relatively small or isolated natural and artificial water or food sources in/near facilities increases the likelihood of attracting waterfowl, which has important consequences for managers attempting to minimize or prevent AIV outbreaks. Use and interpretation of telemetry data, especially in near-real-time, could provide key information for reducing virus transmission risk between waterfowl and livestock, improving protective barriers between wild and domestic species, and abating outbreaks.

Host Correlates of Avian Influenza Virus Infection in Wild Waterfowl of the Sacramento Valley, California.

Avian influenza viruses (AIVs) are distributed globally in members of the family Anatidae (waterfowl), and significant disease may occur when these viruses infect commercial poultry or humans. Early detection of AIV through surveillance of wild waterfowl is one measure to prevent future disease outbreaks. Surveillance efforts that are designed to account for host and environmental determinants of susceptibility to infection are likely to be most effective. However, these determinants have not been clearly delineated and may vary with location. Because some regions are at greater risk for AIV outbreaks, the factors that contribute to AIV infection of waterfowl in these areas are of interest. We investigated the prevalence of AIVs in hunter-killed waterfowl at wintering sites in California's Central Valley. Overall, AIV prevalence was 10.5% and, after controlling for age and sex, was greatest in northern shovelers (Spatula clypeata) and lowest in wood ducks (Aix sponsa). Overall, AIV prevalence was higher in females than in males, but this trend was driven by one sampling year and one waterfowl species (green-winged teal, Anas crecca). AIV prevalence in waterfowl was lower in samples collected from brackish wetlands compared with those collected from freshwater wetlands, suggesting that wetland type or other environmental factors contribute to AIV prevalence. This study adds to our understanding of the ecology of AIV infection in waterfowl and may assist in developing more efficient, targeted surveillance efforts for the detection of potentially harmful viruses circulating in North American waterfowl.

Correlación de hospedadores en la infección por el virus de la influenza aviar en aves acuáticas silvestres del Valle de Sacramento en California. Los virus de la influenza aviar se distribuyen globalmente en miembros de la familia Anatidae (aves acuáticas) y pueden ocurrir enfermedades importantes cuando estos virus infectan aves comerciales o a los humanos. La detección temprana de los virus de influenza mediante la vigilancia de aves acuáticas silvestres es una medida para prevenir futuros brotes de enfermedades. Es probable que los esfuerzos de vigilancia diseñados para tener en cuenta los determinantes ambientales y del huésped para la susceptibilidad a la infección sean más eficaces. Sin embargo, estos determinantes no se han delineado claramente y pueden variar según la ubicación. Debido a que algunas regiones tienen un mayor riesgo de brotes de influenza aviar, los factores que contribuyen a la infección de las aves acuáticas en estas áreas son de interés. Se investigó la prevalencia de virus de influenza en aves acuáticas muertas por cazadores en sitios de estancia invernal en el Valle Central de California. En general, la prevalencia de los virus de influenza fue del 10.5% y, después de controlar por edad y sexo, fue mayor en los patos cuchara comunes del norte (Spatula clypeata) y más baja en los patos joyuyo (Aix sponsa). En general, la prevalencia de influenza fue mayor en las hembras que en los machos, pero esta tendencia fue influenciada por un año de muestreo y una especie de ave acuática (cerceta común, Anas crecca). La prevalencia de influenza aviar en aves acuáticas fue menor en las muestras recolectadas de humedales salobres en comparación con las recolectadas de humedales de agua dulce, lo que sugiere que el tipo de humedal u otros factores ambientales contribuyen a la prevalencia de los virus de influenza. Este estudio contribuye al conocimiento de la ecología en la infección por influenza aviar en las aves acuáticas y puede ayudar a desarrollar esfuerzos de vigilancia más eficientes y específicos para la detección de virus potencialmente dañinos que circulan en las aves acuáticas de América del Norte.

Age- and sex-related dietary specialization facilitate seasonal resource partitioning in a migratory shorebird.

Dietary specialization is common in animals and has important implications for individual fitness, inter- and intraspecific competition, and the adaptive potential of a species. Diet composition can be influenced by age- and sex-related factors including an individual's morphology, social status, and acquired skills; however, specialization may only be necessary when competition is intensified by high population densities or increased energetic demands.To better understand the role of age- and sex-related dietary specialization in facilitating seasonal resource partitioning, we inferred the contribution of biofilm, microphytobenthos, and benthic invertebrates to the diets of western sandpipers (Calidris mauri) from different demographic groups during mid-winter (January/February) and at the onset of the breeding migration (April) using stable isotope mixing models. Western sandpipers are sexually dimorphic with females having significantly greater body mass and bill length than males.Diet composition differed between seasons and among demographic groups. In winter, prey consumption was similar among demographic groups, but, in spring, diet composition differed with bill length and body mass explaining 31% of the total variation in diet composition. Epifaunal invertebrates made up a greater proportion of the diet in males which had lesser mass and shorter bills than females. Consumption of Polychaeta increased with increasing bill length and was greatest in adult females. In contrast, consumption of microphytobenthos, thought to be an important food source for migrating sandpipers, increased with decreasing bill length and was greatest in juvenile males.Our results provide the first evidence that age- and sex-related dietary specialization in western sandpipers facilitate seasonal resource partitioning that could reduce competition during spring at the onset of the breeding migration.Our study underscores the importance of examining resource partitioning throughout the annual cycle to inform fitness and demographic models and facilitate conservation efforts.

Disentangling the effects of habitat biogeochemistry, food web structure, and diet composition on mercury bioaccumulation in a wetland bird.

Methylmercury (MeHg) is a globally pervasive contaminant with known toxicity to humans and wildlife. Several sources of variation can lead to spatial differences in MeHg bioaccumulation within a species including: biogeochemical processes that influence MeHg production and availability within an organism's home range; trophic positions of consumers and MeHg biomagnification efficiency in food webs; and individual prey preferences that influence diet composition. To better understand spatial variation in MeHg bioaccumulation within a species, we evaluated the effects of habitat biogeochemistry, food web structure, and diet composition in the wetland-obligate California black rail (Laterallus jamaicensis coturniculus) at three wetlands along the Petaluma River in northern San Francisco Bay, California, USA. The concentration of MeHg in sediments differed significantly among wetlands. We identified three sediment and porewater measurements that contributed significantly to a discriminant function explaining differences in habitat biogeochemistry among wetlands: the porewater concentration of ferrous iron, the percent organic matter, and the sediment MeHg concentration. Food web structure and biomagnification efficiency were similar among wetlands, with trophic magnification factors for MeHg ranging from 1.84 to 2.59. In addition, regurgitation samples indicated that black rails were dietary generalists with similar diets among wetlands (percent similarity indices > 70%). Given the similarities in diet composition, food web structure, and MeHg biomagnification efficiency among wetlands, we concluded that variation in habitat biogeochemistry and associated sediment MeHg production was the primary driver of differences in MeHg concentrations among black rails from different wetlands.

LIMITED DETECTION OF ANTIBODIES TO CLADE 2.3.4.4 A/GOOSE/GUANGDONG/1/1996 LINEAGE HIGHLY PATHOGENIC H5 AVIAN INFLUENZA VIRUS IN NORTH AMERICAN WATERFOWL.

During 2014, highly pathogenic (HP) influenza A viruses (IAVs) of the A/Goose/Guangdong/1/1996 lineage (GsGD-HP-H5), originating from Asia, were detected in domestic poultry and wild birds in Canada and the US. These clade 2.3.4.4 GsGD-HP-H5 viruses included reassortants possessing North American lineage gene segments; were detected in wild birds in the Pacific, Central, and Mississippi flyways; and caused the largest HP IAV outbreak in poultry in US history. To determine if an antibody response indicative of previous infection with clade 2.3.4.4 GsGD-HP-H5 IAV could be detected in North American wild waterfowl sampled before, during, and after the 2014-15 outbreak, sera from 2,793 geese and 3,715 ducks were tested by blocking enzyme-linked immunosorbent assay and hemagglutination inhibition (HI) tests using both clade 2.3.4.4 GsGD-HPH5 and North American lineage low pathogenic (LP) H5 IAV antigens. We detected an antibody response meeting a comparative titer-based criteria (HI titer observed with 2.3.4.4 GsGD-HP-H5 antigens exceeded the titer observed for LP H5 antigen by two or more dilutions) for previous infection with clade 2.3.4.4 GsGD-HP-H5 IAV in only five birds, one Blue-winged Teal (Spatula discors) sampled during the outbreak and three Mallards (Anas platyrhynchos) and one Canada Goose (Branta canadensis) sampled during the post-outbreak period. These serologic results are consistent with the spatiotemporal extent of the outbreak in wild birds in North America during 2014 and 2015 and limited exposure of waterfowl to GsGD-HP-H5 IAV, particularly in the central and eastern US.

Mass Mortality Attributed to Acanthocephaliasis at a Gull-billed Tern (Gelochelidon nilotica) Colony in Coastal California, USA.

From 12 May 2013 to 29 May 2013, the Gull-billed Tern (Gelochelidon nilotica) colony at the San Diego Bay National Wildlife Refuge, California, US, experienced a mass die-off of at least 92 adults, representing 71-92% of the breeding population on the US west coast. Cause of death was determined to be peritonitis due to perforations of the intestine by a large quantity of acanthocephala (Profilicollis [=Polymorphus] altmani). This is a unique report of P. altmani infecting G. nilotica, and a report of a great impact to a tern population in southern California. Mole crabs (Emerita analoga), the intermediate host for P. altmani and a major component of the Gull-billed Tern diet in San Diego, were found in the stomachs of necropsied terns along with cystacanths, and are the presumed source of the parasite infection. The tern's dietary reliance upon mole crabs likely amplified parasite transmission and infection. We suggest additional research to determine factors that influence parasite infection of intermediate and definitive hosts, particularly mole crabs, given that they are a vital resource for migrating birds within the coastal zone.

Post-release survival of surf scoters following an oil spill: an experimental approach to evaluating rehabilitation success.

Birds are often the most numerous vertebrates damaged and rehabilitated in marine oil spills; however, the efficacy of avian rehabilitation is frequently debated and rarely examined experimentally. We compared survival of three radio-marked treatment groups, oiled, rehabilitated (ORHB), un-oiled, rehabilitated (RHB), and un-oiled, non-rehabilitated (CON), in an experimental approach to examine post-release survival of surf scoters (Melanitta perspicillata) following the 2007 M/V Cosco Busan spill in San Francisco Bay. Live encounter-dead recovery modeling indicated that survival differed among treatment groups and over time since release. The survival estimate (±SE) for ORHB was 0.143±0.107 compared to CON (0.498±0.168) and RHB groups (0.772±0.229), suggesting scoters tolerated the rehabilitation process itself well, but oiling resulted in markedly lower survival. Future efforts to understand the physiological effects of oil type and severity on scoters are needed to improve post-release survival of this species.

Mercury bioaccumulation and risk to three waterbird foraging guilds is influenced by foraging ecology and breeding stage.

We evaluated mercury (Hg) in five waterbird species representing three foraging guilds in San Francisco Bay, CA. Fish-eating birds (Forster's and Caspian terns) had the highest Hg concentrations in their tissues, but concentrations in an invertebrate-foraging shorebird (black-necked stilt) were also elevated. Foraging habitat was important for Hg exposure as illustrated by within-guild differences, where species more associated with marshes and salt ponds had higher concentrations than those more associated with open-bay and tidal mudflats. Importantly, Hg concentrations increased with time spent in the estuary. Surf scoter concentrations tripled over six months, whereas Forster's terns showed an up to 5-fold increase between estuary arrival and breeding. Breeding waterbirds were at elevated risk of Hg-induced reproductive impairment, particularly Forster's terns, in which 48% of breeding birds were at high risk due to their Hg levels. Our results highlight the importance of habitat and exposure timing, in addition to trophic position, on waterbird Hg bioaccumulation and risk.