Adult Mallards Research Articles

Highly pathogenic avian influenza virus H5N2 (clade 2.3.4.4) challenge of mallards age appropriate to the 2015 midwestern poultry outbreak.

BackgroundThe 2015 highly pathogenic avian influenza virus (HPAIV) H5N2 clade 2.3.4.4 outbreak in upper midwestern U.S. poultry operations was not detected in wild birds to any great degree during the outbreak, despite wild waterfowl being implicated in the introduction, reassortment, and movement of the virus into North America from Asia. This outbreak led to the demise of over 50 million domestic birds and occurred mainly during the northward spring migration of adult avian populations.ObjectivesThere have been no experimental examinations of the pathogenesis, transmission, and population impacts of this virus in adult wild waterfowl with varying exposure histories—the most relevant age class.MethodsWe captured, housed, and challenged adult wild mallards (Anas platyrhynchos) with HPAIV H5N2 clade 2.3.4.4 and measured viral infection, viral excretion, and transmission to other mallards.ResultsAll inoculated birds became infected and excreted moderate amounts of virus, primarily orally, for up to 14 days. Cohoused, uninoculated birds also all became infected. Serological status had no effect on susceptibility. There were no obvious clinical signs of disease, and all birds survived to the end of the study (14 days).ConclusionsBased on these results, adult mallards are viable hosts of HPAIV H5N2 regardless of prior exposure history and are capable of transporting the virus over short and long distances. These findings have implications for surveillance efforts. The capture and sampling of wild waterfowl in the spring, when most surveillance programs are not operating, are important to consider in the design of future HPAIV surveillance programs.

Prototype Development of Small Mobile Robots for Mallard Navigation in Paddy Fields: Toward Realizing Remote Farming

This study was conducted to develop robot prototypes of three models that navigate mallards to achieve high-efficiency rice-duck farming. We examined two robotics navigation approaches based on imprinting and feeding. As the first approach, we used imprinting applied to baby mallards. They exhibited follow behavior to our first prototype after imprinting. Experimentally obtained observation results revealed the importance of providing imprinting immediately up to one week after hatching. As another approach, we used feed placed on the top of our second prototype. Experimentally obtained results showed that adult mallards exhibited wariness not only against the robot, but also against the feeder. After relieving wariness with provision of more than one week time to become accustomed, adult mallards ate feed in the box on the robot. However, they ran away immediately at a slight movement. Based on this confirmation, we developed the third prototype as an autonomous mobile robot aimed for mallard navigation in a paddy field. The body width is less than the length between rice stalks. After checking the waterproof capability of a body waterproof box, we conducted an indoor driving test for manual operation. Moreover, we conducted outdoor evaluation tests to assess running on an actual paddy field. We developed indoor and outdoor image datasets using an onboard monocular camera. For the outdoor image datasets, our segmentation method based on SegNet achieved semantic segmentation for three semantic categories. For the indoor image datasets, our prediction method based on CNN and LSTM achieved visual prediction for three motion categories.

GEOGRAPHIC AND ECOLOGIC ASPECTS OF THE COMMUNITY STRUCTURE OF TREMATODES OF MALLARDS (ANAS PLATYRHYNCHOS) IN NORTHERN POLAND AND THE CZECH REPUBLIC.

Trematode infestation of Mallards (Anas platyrhynchos) varies between northern Poland and the Czech Republic. We determined the trematode fauna of juvenile and adult Mallards from Poland in 2010-16 (n=79 Mallards) and from the Czech Republic in 1964-2001 (n=296). Infracommunity diversity of trematodes from juvenile Mallards, defined by the Brillouin index and mean number of species, was significantly greater in Poland than it was in the Czech Republic. There were more species and greater biodiversity in the trematode communities of Mallards from Poland, where the environment is more natural and less altered by human activity than it is in the Czech Republic. In the trematode community of juvenile Mallards, the Simpson's index of biodiversity was higher in the Czech Republic than it was in Poland. The Berger-Parker dominance index was comparable in both countries. In terms of prevalence, the structure of the trematode fauna was hierarchic, and trematode species had different positions in this hierarchy in the two countries. Statistically significant differences in the epidemiologic indices between infection of juvenile Mallards from Poland and the Czech Republic were noted for Bilharziella polonica, Echinostoma miyagawai, Echinostoma revolutum, Prosthogonimus cuneatus, Prosthogonimus ovatus, Notocotylus attenuatus, Echinoparyphium recurvatum, Australapatemon minor, Apatemon gracilis, Cyathocotyle prussica, Hypoderaeum conoideum, Metorchis xanthosomus, Psilochasmus oxyurus, and Cotylurus cornutus.

Mallard (Anas platyrhynchos) Mortality and Recovery Rates Vary by Wing Molt Status at Time of Banding

Abstract. Recovery (i.e., shot, retrieved, and reported) rates and daily mortality risk of 52,330 adult Mallards (Anas platyrhynchos) leg-banded during pre-molt, in-molt, or post-molt during 1985–2011 were evaluated to better understand mortality during wing molt in dynamics of the Mallard population in California, USA. Recovery rates and non-hunting mortality risk varied by molt status at time of banding and California region where banded. Mallards banded during post-molt were 1.22 (95% credible interval = 1.10–1.32) times more likely to be recovered than Mallards banded pre-molt; recovery probability was similar for pre-molt and in-molt Mallards. Mallards banded post-molt had 0.43 (0.17–0.98) and in-molt 0.87 (0.51–1.49) times the daily risk of non-hunting mortality as Mallards banded pre-molt. Mallards were 0.92 (0.86–0.98) times as likely to be recovered, and daily risk of non-hunting mortality was 2.93 (1.79–4.94) times greater, if banded in Northeastern California than in California's Central Valley...

Polychlorinated biphenyls (PCBs) in adult and juvenile mallards (Anas platyrhynchos) from the Hudson River, New York, USA

The Hudson River, NY, USA is contaminated for over 300 km with polychlorinated biphenyls (PCBs) released from two General Electric (GE) capacitor plants. We collected adult and juvenile mallards (Anas platyrhynchos) from four different areas of the river; an area upstream of the GE plants (n = 38), two areas directly downstream of the GE plants (n = 41, n = 38), and an area more than 100 km downstream in the freshwater tidal river (n = 20). Collections occurred during July and August (2008) when ducks were flightless to ensure ducks were “resident” and exposures were local. Fat and muscle tissue were analyzed for PCBs. PCBs were detected in all samples, and mallards below the GE plant sites on the Hudson River had orders of magnitude higher concentrations of PCBs than those above the plants. Juvenile mallards from areas directly downstream of the GE plant sites tended to have higher PCB concentrations in fat than adults. The patterns of PCB congeners and homolog groups varied across the study areas, with areas directly downstream of the GE plants dominated by tetra-chloro biphenyls whereas samples from upstream and the freshwater tidal river tended towards higher chlorinated congeners. Congener patterns between male and female and juvenile and adult mallards were generally similar within study areas, with the exception of one area downstream of the GE plants where adult birds exhibited different patterns than juveniles. Evidence of PCBs from the GE plant sites was detected in the tidal Hudson River, more than 100 km downstream of the plant sites. More than 90% of the ducks collected in areas downstream of the GE plants but above the tidally influenced river exceed the USFDA tolerance level for PCBs in poultry, which should be a concern for consumers of waterfowl taken in proximity to the upper Hudson River.

Accuracy of aging ducks in the U.S. Fish and Wildlife Service Waterfowl Parts Collection Survey

ABSTRACTThe U.S. Fish and Wildlife Service conducts an annual Waterfowl Parts Collection Survey to estimate composition of harvested waterfowl by species, sex, and age (i.e., juv or ad). The survey relies on interpretation of duck wings by a group of experienced biologists at annual meetings (hereafter, flyway wingbees). Our objectives were to estimate accuracy of age assignment at flyway wingbees and to explore how accuracy rates may influence bias of age composition estimates. We used banded mallards (Anas platyrhynchos; n = 791), wood ducks (Aix sponsa; n = 242), and blue‐winged teal (Anas discors; n = 39) harvested and donated by hunters as our source of birds used in accuracy assessments. We sent wings of donated birds to wingbees after the 2002–2003 and 2003–2004 hunting seasons and compared species, sex, and age determinations made at wingbees with our assessments based on internal and external examination of birds and corresponding banding records. Determinations of species and sex of mallards, wood ducks, and blue‐winged teal were accurate (>99%). Accuracy of aging adult mallards increased with harvest date, whereas accuracy of aging juvenile male wood ducks and juvenile blue‐winged teal decreased with harvest date. Accuracy rates were highest (96% and 95%) for adult and juvenile mallards, moderate for adult and juvenile wood ducks (92% and 92%), and lowest for adult and juvenile blue‐winged teal (84% and 82%). We used these estimates to calculate bias for all possible age compositions (0–100% proportion juv) and determined the range of age compositions estimated with acceptable levels of bias. Comparing these ranges with age compositions estimated from Parts Collection Surveys conducted from 1961 to 2008 revealed that mallard and wood duck age compositions were estimated with insignificant levels of bias in all national surveys. However, 69% of age compositions for blue‐winged teal were estimated with an unacceptable level of bias. The low preliminary accuracy rates of aging blue‐winged teal based on our limited sample suggest a more extensive accuracy assessment study may be considered for interpreting age compositions of this species. Published 2013. This article is a U.S. Government work and is in the public domain in the USA

Quantitative and Qualitative Approaches to Identifying Migration Chronology in a Continental Migrant

The degree to which extrinsic factors influence migration chronology in North American waterfowl has not been quantified, particularly for dabbling ducks. Previous studies have examined waterfowl migration using various methods, however, quantitative approaches to define avian migration chronology over broad spatio-temporal scales are limited, and the implications for using different approaches have not been assessed. We used movement data from 19 female adult mallards (Anas platyrhynchos) equipped with solar-powered global positioning system satellite transmitters to evaluate two individual level approaches for quantifying migration chronology. The first approach defined migration based on individual movements among geopolitical boundaries (state, provincial, international), whereas the second method modeled net displacement as a function of time using nonlinear models. Differences in migration chronologies identified by each of the approaches were examined with analysis of variance. The geopolitical method identified mean autumn migration midpoints at 15 November 2010 and 13 November 2011, whereas the net displacement method identified midpoints at 15 November 2010 and 14 November 2011. The mean midpoints for spring migration were 3 April 2011 and 20 March 2012 using the geopolitical method and 31 March 2011 and 22 March 2012 using the net displacement method. The duration, initiation date, midpoint, and termination date for both autumn and spring migration did not differ between the two individual level approaches. Although we did not detect differences in migration parameters between the different approaches, the net displacement metric offers broad potential to address questions in movement ecology for migrating species. Ultimately, an objective definition of migration chronology will allow researchers to obtain a comprehensive understanding of the extrinsic factors that drive migration at the individual and population levels. As a result, targeted conservation plans can be developed to support planning for habitat management and evaluation of long-term climate effects.

INVESTIGATION OF THE LINK BETWEEN AVIAN VACUOLAR MYELINOPATHY AND A NOVEL SPECIES OF CYANOBACTERIA THROUGH LABORATORY FEEDING TRIALS

Avian vacuolar myelinopathy (AVM) is a neurologic disease affecting Bald Eagles (Haliaeetus leucocephalus), American Coots (Fulica americana), and other birds in the southeastern United States. The cause of the disease has not yet been determined, although it is generally thought to be a natural toxin. Previous studies have linked AVM to aquatic vegetation, and the current working hypothesis is that a species of cyanobacteria growing epiphytically on that vegetation is producing a toxin that causes AVM. Surveys of epiphytic communities have identified a novel species of cyanobacteria in the order Stigonematales as the most likely suspect. The purpose of this study was to further examine the relationship between the suspect Stigonematales species and induction of AVM, by using animal feeding trials. Adult Mallards and domestic chickens were fed aquatic vegetation from two study sites containing the suspect cyanobacterial epiphyte, as well as a control site that did not contain the Stigonematales species. Two trials were conducted. The first trial used vegetation collected during mid-October 2003, and the second trial used vegetation collected during November and December 2003. Neither treatment nor control birds in the first trial developed AVM lesions. Ten of 12 treatment Mallards in the second trial were diagnosed with AVM, and control birds were not affected. This study provides further evidence that the novel Stigonematales species may be involved with AVM induction, or at the least it is a good predictor of AVM toxin presence in a system. The results also demonstrate the seasonal nature of AVM events.

Manipulated density of adult mallards affects nest survival differently in different landscapes

Breeding success in many birds including wildfowl is mainly determined by nest predation. Few studies address cues used by predators to find duck nests, and the same is true for spacing patterns that ducks might use to reduce predation. We designed a crossover experiment in agricultural and forested settings to test the assumption that nest predation rate is related to density of adult birds on a lake. We used introduced wing-clipped mallards ( Anas platyrhynchos L., 1758) to increase local pair density and semi-natural nests to assess predation rate. Depredation patterns were analyzed by model fitting in program MARK, using introduction and landscape type as main effects and abundance of avian predators and wild waterbirds as covariates. Depredation was higher at agricultural lakes than at forest lakes. Nest survival decreased with increasing abundance of wild waterfowl, whereas it tended to increase with the abundance of “other waterbirds”. There was a landscape-dependent effect of increased mallard pair density: positive at agricultural lakes and negative at forest lakes. Avian predators found 91% of depredated “known-predator” nests at agricultural lakes and 25% at forest lakes; mammals found 9% at agricultural lakes and 75% at forest lakes. The landscape-dependent density effect may in part be due to different predator communities in these landscape types.

The Syrinx of the Male Mallard (Anas platyrhynchos): Special Anatomical Features

The aim of this study was to investigate the special anatomical and topographical features of the syrinx in male adult stock ducks (Anas platyrhynchos). The syrinx of the mallard is a tracheobronchial type, consisting of a tympanum, a pessulus, medial tympaniform membranes, interanular membranes, an interbronchial ligament (bronchidesmus), and bronchosyringeal cartilage semi-rings. Using a frozen sagittal section, it was possible to document the syringeal valve at the right lateral side of the tympanum. In the male stock duck the pessulus was massive and showed a longish oval, transparent area ventrally. The middle part of the pessulus had a nose-shaped process on its left side, on which the left medial tympaniform membrane originated. The left-sided, pear-shaped syringeal bulla was divided into a left major and right minor chamber by a double-walled, semilunar and opaque septum, approximately 5-6 mm in height. The first left and right C-shaped bronchosyringeal cartilage was more prominent than the other ones and showed partial ossification. In addition, the first left bronchosyringeal cartilage was obviously thicker than the right one. In conclusion, it can be stated that the syrinx in male adult mallards shows some notable specific anatomical features that might have an influence on vocalization. However, to understand the complex mechanism of vocalization in mallards, more investigations, especially obtained by sonography and endoscopy, will be needed.

Effects of perfluorooctane sulfonate on mallard and northern bobwhite quail exposed chronically via the diet

Adult mallard ducks and northern bobwhite quail were exposed to 0, 10, 50, or 150 mg perfluorooctane sulfonate (PFOS)/kg in the diet for up to 21 weeks. Adult health, body and liver weight, feed consumption, gross morphology and histology of body organs, and reproduction were examined. Due to mortality, birds exposed to 50 or 150 mg PFOS/kg feed were terminated by Week 7. In quail, the lowest observable adverse effect level (LOAEL) was 10 mg PFOS/kg feed based on decreased survivorship of 14-day-old quail offspring. For adult female quail fed 10 mg/kg feed, there was a slight but statistically significantly PFOS-related increase in liver weight when compared to controls. When liver weight was normalized to body weight, the statistically significant differences were still observed indicating that PFOS affected liver size. However, no other pathological effects were observed livers of quail from this treatment group which suggests that this enlargement may have been an adaptive response. For adult mallards, no treatment-related effects on feed consumption, body or liver weight, growth, or reproductive performance were observed. There was a slightly greater incidence of small testes (length) in adult male mallards and quail exposed to 10 mg PFOS/kg, feed when compared to controls. However, spermatogenesis was not affected and there was no effect on the rates of egg fertilization. Due to transfer to eggs, concentrations of PFOS measured in the liver and blood at study termination were greater in male birds than female birds.

Vulnerability of mallards to hunting with a spinning-wing decoy in Manitoba

We examined the vulnerability of mallards (Anas platyrhynchos) to hunting with a spinning-wing decoy (SWD) during the 2001 and 2002 autumn hunting seasons in Manitoba, Canada. Between 8 September and 11 November 2001, we conducted 72 experimental marsh hunts, and between 8 September and 30 October 2002, we conducted 27 experimental marsh and 55 experimental field hunts. Each hunt consisted of a series of equal and alternating 15-minute experimental (SWD on) and control (SWD off) periods, separated by a 3-minute buffer. Duration of total hunts ranged from 1.0–3.0 hours, with an average of 1.4 ± 0.5 hours. Experimental marsh hunts in 2001 and 2002 indicated that mallards were 1.9 times more likely to fly within gun range (P < 0.001), the mean number killed/hour/hunter was 5.0 times greater (P < 0.001), and the crippling rate was 1.7 times lower when the SWD was on than off (P = 0.02). Additionally, body condition index (size-adjusted body mass) of harvested mallards was greater when the SWD was on than off (P = 0.03). Experimental field hunts in 2002 indicated that mallards were 6.4 times more likely to fly within gun range (P < 0.001), the mean number killed/hour/hunter was 33 times greater (P < 0.001), and, although similar in the early season (before 5 October), crippling rate was 3.7 times lower when the SWD was on than off during the late season (P = 0.047). A SWD activity by age interaction (P = 0.05) indicated that when the SWD was on, harvested adult mallards had a greater body condition index than juveniles but were similar when the SWD was off. Use of a SWD increased mallard flock response, provided more shooting opportunity to hunters, increased kill rate, reduced crippling rates, and, in marsh hunts, resulted in mallards harvested with a greater body condition index. Lastly, quantifying SWD use throughout Canada and the United States will be necessary to estimate its impact on overall harvest.

The effect of lead exposure on survival of adult mallards in the Camargue, southern France

1 In those countries where lead shot is still in use, a secondary effect of waterfowl hunting is lead poisoning from shot ingested by birds during bottom feeding. Moreover, waterfowl injured during hunting can die undetected as a direct or indirect consequence of wounds. The occurrence and influence of these types of lead exposure have often been estimated by the inspection of dead bodies, but this method will yield biased estimates if dead birds are not a random sample of the population. 2 We analysed a historical set of recoveries of adult mallard Anas platyrynchos ringed in the Camargue, southern France, over the period 1960–71, for which the amount and type of lead exposure had been determined by X-ray inspection before release. It was therefore possible to investigate the prevalence and effect of lead shot, avoiding the problem of post-stratification that may arise when only dead individuals are considered. 3 Among the captured birds, the proportion of gizzard-contaminated birds was constant (0·11) during the study period. In contrast, the proportion of birds carrying pellets in muscles increased linearly from 0·19 to 0·29. Males and females were similarly exposed to shot from both sources. 4 The relative survival of lead-affected mallards was 19% lower than unaffected birds for both types of lead exposure. The two sources of mortality were additive on a logarithmic scale and unaffected by sex. 5 Attempts to estimate the consequence of lead poisoning on population dynamics were not conclusive because of large confidence intervals in survival estimates. Moreover, it was still not clear how much mortality due to lead exposure should be considered as additive to other causes. We nevertheless advocate measures to control the long-term impact of lead exposure on waterfowl populations. 6 This work presents a new approach to the analysis of survival, in which the standard recovery models were reformulated in terms of monthly survival. This allows for the effect of a long ringing period during which mortality cannot be ignored. It also allows the estimation of parameters for newly marked birds without additional information. Since any within-year time interval can be considered, this approach can be used to investigate seasonal changes in mortality.

Condition Indices of Live-Trapped American Black Ducks and Mallards

We compared condition indices of interacting American black ducks (Anas rubripes) and mallards (A. platyrhynchos) during staging to contrast changes in energy reserves that potentially influence survival or other population parameters. We live-trapped and banded 1,126 black ducks and 1,292 mallards from October through January during 1990-1993 on Ottawa National Wildlife Refuge (NWR) in Ohio, USA. Ducks were aged, sexed, and weighed; total body length, wing chord, culmen, and tarsus were measured to compute condition indices. The condition indices were used as dependent variables in multiple regression models to measure influences of annual date, species, and ambient temperature for each age-sex class. Adult male black ducks usually had slightly higher (1% to 3%) condition indices than adult male mallards. Initially, in 1990 and 1992, juvenile female mallards had 6% higher condition indices than juvenile female black ducks, but during these 2 years, black duck juvenile females improved condition at higher rates than their mallard counterparts. Temperature effects on condition of live-trapped birds were noted, especially during November 1991, when decreased body weights corresponded with frozen wetland foraging areas. Daily temperature similarly influenced black duck and mallard egress from the Lake Erie marshes. Species differences in breeding chronology and breeding ground productivity could influence the body condition of these birds and the observed seasonal trends. The poor body condition of juvenile black duck females observed during some years could possibly contribute to lower survival and reproductive performance during the following spring if these differences continue through the remainder of the winter.

Reproductive effects and duckling survivability following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Tungsten-iron and tungsten-polymer shot were given conditional approval for waterfowl hunting by the U.S. Fish and Wildlife Service based partly on the results of a 30-day acute toxicity trial utilizing mallards (Anas platyrhynchos). Final approval of the two tungsten-containing shot was contingent on the results of a 150-day study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult mallards. Reproductive data are presented in this paper. Sixteen male and 16 female adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). Reproductive performance was assessed during the last 90 days (day 61 to day 150) of the trial. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-iron- and tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards during the 150 day trial did not adversely affect reproduction or their offspring.

Hematological effects and metal residue concentrations following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

The U.S. Fish and Wildlife Service required a chronic dosing study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult game-farm mallards (Anas platyrhynchos) prior to granting permanent approval of the shot for waterfowl hunting. Herein, we present the effects of tungsten-iron and tungsten-polymer shot on various hematologic parameters and metal residue concentrations in the femur, liver, kidneys, and gonads. Thirty-two-bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150 day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) received eight #4 lead shot (positive control) on day 0 of the study. Lead-dosed mallards had significantly decreased hematocrit, hemoglobin concentration, and whole-blood delta aminolevulinic acid dehydratase activity on day 7, as well as significant changes in a number of plasma chemistry parameters compared to ducks in the control, tungsten-iron, or tungsten-polymer groups. Mallards dosed with tungsten-iron or tungsten-polymer shot had occasional significant differences in hematocrit and plasma chemistry values when compared to control mallards over the 150 day period, but these changes were not considered to be indicative of deleterious effects. Low concentrations of tungsten were detected in gonad and kidney samples from males and females and in liver samples from females dosed with tungsten-polymer shot. Tungsten was also detected in femur samples from tungsten-polymer-dosed mallards. Higher concentrations of tungsten were detected in femur, liver, kidney, and gonad samples from tungsten-iron-dosed ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not cause adverse hematological effects during the 150 day trial. Concentrations of tungsten in the femur, liver, kidneys, and gonads were generally higher in tungsten-iron-dosed ducks when compared to tungsten-polymer-dosed ducks.

Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Permanent approval of shot composed of tungsten-iron and tungsten-polymer for waterfowl hunting by the U.S. Fish and Wildlife Service was pending the results of the present study that examined the health and reproductive effects of the two shot types on mallards (Anas platyrhynchos) over a 150-day period. We collected data pertaining to the effects of tungsten-iron and tungsten-polymer shot on mortality, body weight, organ weight, tissue pathology, and shot erosion. Thirty-two bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) were dosed orally with eight #4 lead shot (positive control) on day 0 of the study. All lead-dosed ducks died by day 25, whereas no ducks died in the other treatment groups. Significant liver hemosiderosis was present in all control and tungsten-iron-dosed males, in five of eight control and three of eight tungsten-iron-dosed females, and in one tungsten-polymer-dosed male examined. The rate of shot erosion was highest for tungsten-polymer shot (99%), followed by tungsten-iron (72%), and steel (55%) shot. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys.

Field evaluation of lead effects on Canada geese and mallards in the Coeur d'Alene River Basin, Idaho.

Hatch year (HY) mallards (Anas platyrhynchos) in the Coeur d'Alene (CDA) River Basin had higher concentrations of lead in their blood than HY Western Canada geese (Branta canadensis moffitti) (geometric means 0.98 versus 0.28 microg/g, wet weight). The pattern for adults of both species was similar, although geometric means (1.77 versus 0. 41 microg/g) were higher than in HY birds. HY mallards captured in the CDA River Basin in 1987 contained significantly lower lead concentrations in their blood than in 1994-95 (0.36 versus 0.98 microg/g); however, some very young mallards were sampled in 1987, and concentrations in adults were not significantly different in 1987, 1994, or 1995 (1.52, 2.07, 1.55 microg/g, respectively). Both species in the CDA River Basin in 1994-95 showed significantly reduced red blood cell delta-aminolevulinic acid dehydratase (ALAD) activity compared to the reference areas: Canada geese (HY -65.4 to -86.0%, adults -82.3%), and mallards (HY -90.7 to -95.5%, adults -94. 1%). Canada goose goslings were divided into size classes, and the two smaller classes from the CDA River Basin had significantly elevated free erythrocyte protoporphyrin (protoporphyrin) levels compared to the reference area (15.2x and 6.9x). HY and adult mallards both had significantly elevated protoporphyrin (5.9x and 7. 5x). Recognizing that interspecific differences exist in response and sensitivity to lead, it appears (at least for hemoglobin and hematocrit) that Canada geese were more sensitive to lead than mallards, i.e., adverse hematologic effects occur at lower blood lead concentrations. Only Canada geese from the CDA River Basin, in spite of lower blood lead concentrations, had significantly reduced mean hemoglobin and hematocrit values. No euthanized Canada geese (all HYs) from CDA River Basin were classified as clinically lead poisoned, but 38 Canada geese found dead in the CDA River Basin during a concurrent study succumbed to lead poisoning between 1992 and 1997. Only 6 (15.8%) of these 38 contained ingested lead shot, which contrasts greatly with the 75-94% incidence of ingested lead shot when mortality was due to lead shot ingestion. Lead from other contaminated sources (i.e., sediments and vegetation) in the CDA River Basin was strongly implicated in most Canada goose deaths. Based on the 31 live mallards and Canada geese collected in the CDA River Basin, which were representative of the live populations blood sampled only, the prevalence of subclinical and clinical lead poisoning (as determined by liver lead concentrations, excluding birds with ingested lead shot) was higher in mallards: subclinical (4 of 8, 50% HYs and 6 of 11, 55% adults); clinical (0% HYs and 4 of 11, 36% adults), with less data available for Canada geese (only 1 of 9, 11% HYs marginally subclinical). The clinically lead-poisoned mallards had extremely high concentrations of lead in blood (2.69-8. 82 microg/g) and liver (6.39-17.89 microg/g). Eight mallards found dead in the CDA River Basin during a concurrent study were diagnosed as lead poisoned, and only one (12.5%) contained ingested lead shot, which again strongly implicates other lead sources. The finding of dead lead poisoned Canada geese together with the high percentage of live mallards classified as subclinically or clinically lead poisoned, in combination with the low incidence of ingested lead shot causes us concern for both of these species, which live in association with lead-contaminated sediment in the CDA River Basin.

Retrograde movement of urine into the gut of salt water acclimated Mallards (Anas platyrhynchos)

The influence of sex and salt-water intake on retrograde movement of urine into the hindgut was examined in captive adult wild Mallards (Anas platyrhynchos). Ducks were given intravenous injections of tritiated polyethylene glycol (3H-PEG) and killed 3 h later. The fluid content of each gut segment and its concentrations of3H-PEG, sodium, and potassium were determined. Retrograde movement of urine into each gut segment was estimated from the quantity of3H-PEG recovered there. In both ducks that drank tap water and those that drank saline, about 20% of the urine was moved into the hindgut, two-thirds of this into the ceca. Males deposited more urine in the ceca and reabsorbed more water from this urine than did females (P &lt; 0.01). We conclude that retrograde movement of urine into the hindgut was unaffected by the salinity of drinking water and was greater in males than in females. Reabsorption of urinary sodium and water in the hindgut, particularly the ceca, may play an important role in osmoregulation in birds with salt glands.

Acute effects of lead, steel, tungsten-iron, and tungsten-polymer shot administered to game-farm mallards.

Sixteen-bird groups (sexes equal) of adult mallards (Anas platyrhynchos) were orally dosed with eight #4 steel short, eight #4 lead shot, eight BB-size tungsten-iron shot, eight BB-size tungsten-polymer shot, or were sham-dosed and maintained for 30 days (16 January 1996 to 15 February 1996). Half of the lead-dosed ducks (five males, three females) died during the study, whereas no ducks died in the other dosage groups. For lead-dosed ducks, hematocrit and hemoglobin concentration were decreased on day 15 of the trial, but not on day 30. Delta aminolevulinic acid dehydratase activity in lead-dosed ducks was lower when compared to steel-dosed ducks only. Plasma activities of selected enzymes were elevated in lead-dosed ducks when compared to enzyme activities of ducks in the other groups. For lead-dosed ducks, relative heart, liver, and kidney weights increased in comparison to relative weights of those organs of ducks in other groups. Histology of tissues indicated that renal nephrosis accompanied by biliary stasis was present in the eight lead-dosed ducks that died. For the eight lead-dosed ducks that survived, six had mild to severe biliary stasis. Mild biliary stasis was noted in five tungsten-iron dosed ducks and three tungsten-polymer dosed ducks. Amounts of lead in the femur, liver, and kidneys were higher in lead-dosed ducks than in ducks of the other four groups. Small amounts of tungsten were detected in the femur and kidneys of two tungsten-polymer dosed ducks. Higher concentrations of tungsten were detected in the femur, liver, and kidneys of all tungsten-iron dosed ducks. The rate of shot erosion was highest (80%) for the tungsten-polymer shot, followed by tungsten-iron (55%), lead (50%), and steel shot (33%). Results indicated that tungsten-iron or tungsten-polymer shot (8 shot/duck) orally administered to mallards did not adversely affect them during a 30-day trial.