Comparative toxicity of lead shot in black ducks (Anas rubripes) and mallards (Anas platyrhynchos)

In winter, pen-reared and wild black ducks (Anas rubripes), and game farm and wild mallards (Anas platyrhynchos), maintained on pelleted feed, were sham-dosed or given one number 4 lead shot. After 14 days, dosed birds were redosed with two or four additional lead shot. This dosing regimen also was repeated in summer using pen-reared black ducks and game farm mallards. Based upon mortality, overt intoxication, weight change, delta-aminolevulinic acid dehydratase activity and protoporphyrin concentration, black ducks and mallards were found to be equally tolerant to lead shot. However, captive wild ducks were more sensitive than their domesticated counterparts, as evidenced by greater mortality and weight loss following lead shot administration. This difference may be related to stress associated with captivity and unnatural diet.     

Experimental inoculation of mallard ducks (Anas platyrhynchos platyrhynchos) with Borrelia burgdorferi

Birds have been incriminated as disseminaters of Borrelia burgdorferi and have the potential to spread the organism over a wide geographic range. Borrelia burgdorferi has been isolated from the liver and blood of passerine birds and from Ixodes dammini removed from passerines. The objective of this study was to determine if waterfowl, specifically mallards (Anas platyrhynchos platyrhynchos), were susceptible to infection with B. burgdorferi. Eight ducks were inoculated with B. burgdorferi; four orally and four intravenously (i.v.) and two ducks were inoculated with phosphate buffered saline as controls. All eight inoculated birds became infected and developed antibodies to B. burgdorferi. The spirochete was isolated from cloacal material from an orally infected duck on day 22 postinoculation (PI) and from an i.v. infected bird on day 29 PI, from the blood of an i.v. infected bird on day 7 PI, and from the kidney of an orally infected bird. Borrelia burgdorferi was detected by indirect immunofluorescence using the B. burgdorferi specific monoclonal antibody H5332 in kidneys of three orally infected birds and one i.v. infected bird and from the mesentery of one orally infected bird. These findings show that mallard ducks are susceptible to infection by B. burgdorferi and that they can be infected orally and shed the organism in the droppings. Thus, mallards could disseminate B. burgdorferi over long distances without the need of an arthropod vector.     

Capillarity and fibre types in locomotory muscles of wild mallard ducks (Anas platyrhynchos)

Six locomotory muscles from wild mallard ducks (Anas platyrhynchos) were analysed by histochemical methods. Special care was taken in sample procedure in order to describe the heterogeneity found throughout each muscle. Capillarity and fibre-type distributions were correlated to the functional implications and physiological needs of each muscle. Comparisons between our results and similar previous reports on dabbling and diving ducks are also discussed. Muscles from the leg presented the most heterogeneous fibre-type distributions, which are correlated to the wide range of terrestrial and aquatic locomotory performances shown by these animals. More specialized muscles such as pectoralis, used almost exclusively for flapping flight, had more homogeneous fibretype distributions, whereas muscles from the wing presented a high proportion of glycolytic fibres probably recruited during non-steady flapping flight. Deep muscle pectoralis zones and parts of the gastrocnemius which are closer to the bone are remarkable for their high capillarity indices and oxidative capacities, which suggests that these parts are recruited during sustained flapping flight and swimming. However, two different strategies for achieving these high oxygen needs are evident, indicating that the fibre cross-sectional area plays an important role in the modulation of the oxygen supply to the muscle cells.Abbreviations AChE acetylcholinesterase - cap mm^-2 number of capillaries per square millimeter - CD capillary density - C/F capillary-to-fibre ratio - EMR muscle extensor metacarpialis radialis - FCSA fibre cross-sectional area - FD fibre density - FG fast glycolytic - FOG fast oxidative glycolytic - GLE muscle gastrocnemius lateralis (pars externa) - GPDH -glycerophosphate dehydrogenase - ITC muscle iliotibialis cranialis - m-ATPase myofibrillar adenosine triphosphatase - OFA oxidative fibre area - OFN oxidative fibre number - PEC muscle pectoralis - SCH muscle scapulohumeralis caudalis - SDH succinate dehydrogenase - SO slow oxidative - TSC muscle scapulotriceps or triceps scapularis     

Inflammatory cell stimulation and wound healing in Sphaeridiotrema globulus experimentally infected mallard ducks (Anas platyrhynchos)

Thirty laboratory-reared mallard ducks (Anas platyrhynchos) were experimentally infected with Sphaeridiotrema globulus. Host cell-mediated immunity and wound healing in S. globulus infected ducks were evaluated by gross and histological examination. Establishment, location, and life span of S. globulus differed from previous reports of sphaeridiotremiasis in both naturally and experimentally infected waterfowl. No worms were recovered from the ceca, and worm migration occurred anterior to the ileo-cecal valve with greater dispersion (less worm crowding) at higher rates of infectivity. Parasite death and host lesion resolution were evident at days 8 to 10 postinfection (PI) in ducks fed a moderate dose (200 metacercariae, group A) with a 5% mean parasite recovery rate. Host death occurred at days 3 to 6 in ducks fed a high dose (550 metacercariae, group B) with a 16% mean parasite recovery rate. Mast cells increased significantly (P less than 0.005) in group A ducks from days 4 to 10 PI. Eosinophil proliferation was greater in group B than in group A on day 4 PI, but comparatively fewer eosinophils were identifiable in group B ducks on day 6 PI.     

Description of the mallard duck (Anas platyrhynchos) karyotype

The karyotype of the mallard duck, Anas platyrhynchos, was characterised on the basis of R and C bands. Chromosomal preparations obtained from in vitro blood lymphocyte cultures were RBG- and CBG-stained. The structures of nine and 14 pairs of chromosomes were analysed by the RBG and CBG chromosome banding techniques, respectively. The location of R bands, as well as the size and arrangement of constitutive heterochromatin blocks were determined. Ideograms of R and C banded patterns of the analysed chromosomes were drawn. The morphological makeup of the analysed chromosomes was assessed.     

Mechanics of drinking in the mallard (Anas platyrhynchos,anatidae)

Water drinking in the mallard is accomplished by a fine-tuned set of movements of upper and lower jaw and of the tongue. During immersion of the tips of the bill, the oral cavity is formed into smaller volumes containing water and into connecting tubes. Two mechanisms serve the water transport: (1) lingual and jaw movements press water from the water-containing spaces into the tubes; (2) a quantitative simulation of the shape of the oral cavity during immersion shows that the two tubes are so narrow that capillary action also contributes to water transport. Thereafter, the tips of the bill are raised until they point upward. In this “tip-up” position, water flows into the esophagus because of gravity. We conclude that, in addition to normal tip-up drinking observed in almost all Passeriformes and Galliformes, a second type of tip-up drinking may be distinguished in Anseriformes. The integration of the drinking mechanism, keeping the water inside the mouth, and the straining mechanism, expelling the water along the beak rims, is effected by specific actions of the elaborate lingual apparatus.     

Correlations between brain catecholamines,neurosecretion, and serum corticoid levels in osmotically stressed mallard ducks (Anas platyrhynchos)

The effects of depleting brain catecholamines with a combined treatment of reserpine and alpha-methyl-p-tyrosine on serum corticosterone levels and release of immunoreactive neurophysin from the median eminence, in osmotically stressed and unstressed mallard ducks, were studied. Corticoid levels in salt loaded birds were more than three times that of unstressed birds. The combined treatment of reserpine and alpha-methyl-p-tyrosine significantly decreased the concentration of brain monoamines in all experimental groups and raised serum corticoid levels in non-stressed birds to the same level found in the osmotically stressed animals. Immunoreactive neurophysin in the zona externa of the median eminence was depleted in all birds subjected to either osmotic stress and/or reserpine treatment but not in unstressed control birds. These preliminary data indicate that catecholamines may exert an inhibitory influence on both ACTH release from the anterior pituitary and neurophysin from the median eminence and that these two events may in some way be interrelated in the duck.     

Human-induced tachycardia in wild and tame mallard (Anas platyrhynchos)

• 1.1. The effect of regular handling on fear reactions was investigated in mallard (Anas platyrhynchos) by exposing six hand-reared and four wild ducks to an approaching human being and recording heart rates with an external ECG device.
• 2.2. All ducks reacted to the approach with tachycardia, but the response was significantly less in tame birds.
• 3.3. Hand-reared females showed less response than males. No sex-linked differences were apparent in the wild ducks.
• 4.4. Decreasing responses throughout the experiments were only found in tame birds.
• 5.5. Fear or stress reactions can apparently be diminished through habituation induced by regular handling.

     

Cutaneous herpesvirus infection in a mallard duck (Anas platyrhynchos)

Investigations of mortalities involving wild mallard ducks (Anas platyrhynchos) revealed the presence of a herpesvirus associated with skin lesions on the plantar surface of the foot web of one duck. Ultrastructurally, the paracrystalline arrays of viral core particles and unencapsidated nucleoids in the nucleus, and the enveloped viruses in cytoplasmic vacuoles are compatible with a herpesvirus. This appears to be the first report of cutaneous lesions in a mallard duck attributable to a herpesvirus. Whether this lesion is due to duck virus enteritis (DVE), suggesting that cutaneous shedding is possible, or due to another uncharacterized herpesvirus of ducks is unclear.     

Cardiovascular function in adrenalectomized Pekin ducks (Anas platyrhynchos)

Cardiovascular function was progressively impaired in Pekin ducks following surgical adrenalectomy. Diastolic and systolic arterial pressures (Pa) were respectively 45% and 28% lower in adrenalectomized (ADX) ducks than in sham-operated (SHAM) controls within 3 days after surgery. Adrenalectomy caused cardiac frequency (fH) to approximately double, diminished cardiac stroke volume, decreased body weight, and decreased plasma norepinephrine, epinephrine, osmolal, Na and Cl concentrations. Adrenalectomy did not alter blood volume, hematocrit, or plasma concentrations of Ca and Mg. Administration of a synthetic glucocorticoid, betamethasone, prevented hypotension and prolonged the survival of ADX ducks. ADX and SHAM ducks maintained with betamethasone for up to 8 days did not differ in Pa, body weight, hematocrit, or plasma concentrations of Na and K. These experiments demonstrate the critical importance of glucocorticoid activity for blood pressure, Na and Cl regulation in birds.     

Lincoln estimates of mallard (Anas platyrhynchos) abundance in North America

Estimates of range‐wide abundance, harvest, and harvest rate are fundamental for sound inferences about the role of exploitation in the dynamics of free‐ranging wildlife populations, but reliability of existing survey methods for abundance estimation is rarely assessed using alternative approaches. North American mallard populations have been surveyed each spring since 1955 using internationally coordinated aerial surveys, but population size can also be estimated with Lincoln's method using banding and harvest data. We estimated late summer population size of adult and juvenile male and female mallards in western, midcontinent, and eastern North America using Lincoln's method of dividing (i) total estimated harvest, , by estimated harvest rate, , calculated as (ii) direct band recovery rate, , divided by the (iii) band reporting rate, . Our goal was to compare estimates based on Lincoln's method with traditional estimates based on aerial surveys. Lincoln estimates of adult males and females alive in the period June–September were 4.0 (range: 2.5–5.9), 1.8 (range: 0.6–3.0), and 1.8 (range: 1.3–2.7) times larger than respective aerial survey estimates for the western, midcontinent, and eastern mallard populations, and the two population estimates were only modestly correlated with each other (western: r = 0.70, 1993–2011; midcontinent: r = 0.54, 1961–2011; eastern: r = 0.50, 1993–2011). Higher Lincoln estimates are predictable given that the geographic scope of inference from Lincoln estimates is the entire population range, whereas sampling frames for aerial surveys are incomplete. Although each estimation method has a number of important potential biases, our review suggests that underestimation of total population size by aerial surveys is the most likely explanation. In addition to providing measures of total abundance, Lincoln's method provides estimates of fecundity and population sex ratio and could be used in integrated population models to provide greater insights about population dynamics and management of North American mallards and most other harvested species.     

Differential effects of early- and late-life access to carotenoids on adult immune function and ornamentation in mallard ducks (Anas platyrhynchos)

Environmental conditions early in life can affect an organism's phenotype at adulthood, which may be tuned to perform optimally in conditions that mimic those experienced during development (Environmental Matching hypothesis), or may be generally superior when conditions during development were of higher quality (Silver Spoon hypothesis). Here, we tested these hypotheses by examining how diet during development interacted with diet during adulthood to affect adult sexually selected ornamentation and immune function in male mallard ducks (Anas platyrhynchos). Mallards have yellow, carotenoid-pigmented beaks that are used in mate choice, and the degree of beak coloration has been linked to adult immune function. Using a 2 × 2 factorial experimental design, we reared mallards on diets containing either low or high levels of carotenoids (nutrients that cannot be synthesized de novo) throughout the period of growth, and then provided adults with one of these two diets while simultaneously quantifying beak coloration and response to a variety of immune challenges. We found that both developmental and adult carotenoid supplementation increased circulating carotenoid levels during dietary treatment, but that birds that received low-carotenoid diets during development maintained relatively higher circulating carotenoid levels during an adult immune challenge. Individuals that received low levels of carotenoids during development had larger phytohemagglutinin (PHA)-induced cutaneous immune responses at adulthood; however, dietary treatment during development and adulthood did not affect antibody response to a novel antigen, nitric oxide production, natural antibody levels, hemolytic capacity of the plasma, or beak coloration. However, beak coloration prior to immune challenges positively predicted PHA response, and strong PHA responses were correlated with losses in carotenoid-pigmented coloration. In sum, we did not find consistent support for either the Environmental Matching or Silver Spoon hypotheses. We then describe a new hypothesis that should be tested in future studies examining developmental plasticity.     

Experimental evidence for density-dependent survival in mallard (Anas platyrhynchos) ducklings

It is unresolved to what extent waterfowl populations are regulated by density-dependent processes. By doing a 2-year crossover perturbation experiment on ten oligotrophic boreal lakes we addressed the hypothesis that breeding output is density dependent. Wing-clipped mallard (Anas platyrhynchos) hens were introduced with their own brood and then monitored for 24 days. Predicted responses were that per capita duckling and hen survival would be lower in high-density than in low-density treatments. Survival was evaluated by model fitting in program MARK. Density, year, and lake were used as main effects, while day after introduction, a weather harshness index, and presence of hens were covariates. Daily survival in ducklings was lower in the high-density treatment, but this effect was year dependent. The highest-ranking model for duckling survival also included a positive effect of duckling age and presence of hens, and a negative effect of harsh weather. Density did not affect female survival although there was a prominent year effect. The highest-ranking model for female survival also included negative effects of day after introduction and harsh weather. This is the first study to report density-dependent survival in experimentally introduced ducklings in a natural setting. Implications for population dynamics and management of harvested populations are far-reaching if such regulation occurs in some years, but not in others.     

Effects of short-term changes in electrolyte intake on the adrenal steroidogenic responses of juvenile mallard ducks (Anas platyrhynchos)

1. Adjusting the Na+ and K+ intake of juvenile mallard ducks caused the plasma concentrations of corticosterone (B) and aldosterone (Aldo) to increase independently of one another, but none of these changes in electrolyte intake had a significant effect on the deoxycorticosterone (DOC) concentration. 2. With the exception of DOC in birds consuming the control diet, the plasma concentration of each hormone, regardless of diet, increased significantly following exposure to stress. 3. Stress-induced increases in Aldo concentration were greatest in birds given diets containing low concentrations of Na+. 4. Unlike the mammal and some other species of birds, Na+ may be the primary secretagogue responsible for the regulation of both corticosterone and aldosterone synthesis in the mallard duck.     

Changes in mallard (Anas platyrhynchos) serum chemistry due to age, sex, and reproductive condition

Selected serum constituents were analyzed from 50 adult mallards (Anas platyrhynchos) of both sexes during several stages of reproduction: pre-egg laying, egg laying, incubating, molting, and postreproductive. Similar assays were conducted on sera from ducklings aged 5 to 58 days. Values for total protein (TPR), albumin (ALB), glucose (GLU), gamma-glutamyl transferase (GGT), calcium (CA), phosphorus (PHOS) and magnesium (MG) differed by sex. When all data were combined and analyzed for sex-related differences within each reproductive condition separately, all assays except lactate dehydrogenase (LD-L), cholinesterase (CHE), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CRN) and direct bilirubin (BIDI) differed between sexes during one or more reproductive periods. Each assay showed differences among the various reproductive conditions regardless of gender. The pattern of change differed between sexes. All assays except ALB, GLU, CA and MG showed age-related changes. Lipemia in the sample interfered with all chemistries except TPR, LD-L and CA. Results indicate that when using clinical chemistry as a diagnostic tool in the mallard, age and reproductive condition should be determined in order to compare the data to appropriate control values.