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.     

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.     

Acute toxicity of lead, steel, and an iron-tungsten-nickel shot to mallard ducks (Anas platyrhynchos)

Twenty mallards (Anas platyrhynchos) of both sexes were dosed by oral gavage with Heavi-Shot (H-S; Environ-Metal, Inc., Sweet Home, Oregon, USA) pellets, 20 with steel shot, and 10 with lead (Pb) pellets, all of equal size. All pellets were fired from a shotgun into an absorbent material, retrieved, and weighed prior to introduction into the ducks. Birds were fed whole kernel corn and grit and observed for signs of toxicity for 30 days following dosing. Hevi-Shot pellets lost an average of 6.2% of their mass and steel shot pellets lost 57% of their mass in the birds' gizzards. Almost all (90%) of the Pb shot dosed birds died before the end of the study, while no mortality was observed in the steel or H-S dosed groups. Even though total food consumption differed between the H-S and steel shot groups, mean bird weight change was not different. There were no significant morphologic or histopathologic abnormalities of the liver and kidney in the H-S and steel shot groups. Results indicated that mallards dosed orally with eight No. 4 H-S pellets were not adversely affected over a 30-day period, and that H-S provides another environmentally safe nontoxic shot for use in waterfowl hunting.     

Teratogenic effects of external egg applications of methyl mercury in the mallard, Anas platyrhynchos

The embryotoxic potential of external applications of methyl mercury on mallard eggs was investigated to assess the possible impact of mercury transferred from the plumage of effluent-contaminated aquatic birds to their eggs. Eggs were treated on day 3 of development with microliter applications of methyl mercury that was dissolved with ethyl acetate into an aliphatic hydrocarbon vehicle. Mercury analysis by atomic absorption indicated that almost half of the mercury applied entered the eggs past the shell membranes within several days of treatment. Most mortality occurred within this period at doses of 9 microgram of mercury per egg or higher. Decreased embryonic growth resulted with similar doses. A significant incidence of malformations occurred at a dose of 1 microgram per egg. These malformations were mainly minor skeletal aberrations and incomplete ossification. With higher doses of mercury, defects included gross external ones such as micromella, gastroschisis, and eye and brain defects. Application of the aliphatic hydrocarbon vehicle did not result in any of these defects.     

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     

In vitro binding of radioiodinated rat follicle-stimulating hormone to the testis of the mallard duck, Anas platyrhynchos l

The binding of 125I-labelled rat FSH to homogenates and frozen sections of mallard duck testis was investigated. The equilibrium association constant (Ka) in the homogenates (8.5 x 10(9) M-1) was similar to those reported in other avian and mammalian species. Autoradiography suggested that the binding sites for the labelled hormone were localized in the tubular compartment.     

Bone typology and growth rate: testing and quantifying 'Amprino's rule' in the mallard (Anas platyrhynchos)

Periosteal bone histology expresses its rate of deposition. This fundamental relationship between bone structure and growth dynamics, first assumed by Amprino many decades ago, was quantified in preliminary studies, but never statistically tested. Moreover, the precise typological characters of bone tissue linked to growth rate remained poorly known. Here, we present the first statistical analysis of 'Amprino's rule', measured on comprehensive growth series of the mallard, Anas platyrhynchos. Growth rates were assessed by fluorescent labelling. Bone typology was described according to Ricqlès' typological classification. Results show that the presence and proportion of primary osteons, two consequences of bone initial porosity at the time of its deposit, are strongly related to bone growth rate. However, no significant relationship between primary osteons orientation and bone growth rate could be detected, at least for osteonal orientations (longitudinal, laminar and reticular) and growth rates values observed in mallard long bones. These results suggest that Amprino's rule holds for some major typological characters of primary compact bone tissues (i.e. primary osteons presence and proportion). However, it is irrelevant to some other characters (i.e. osteonal orientation), the meaning of which remains to be discovered.     

It's just ducky to be clean: the water repellency and water penetration resistance of swimming mallard Anas platyrhynchos ducklings

Ducklings reared by a hen swim with dry plumage a day or two after hatching, while incubator-hatched ducklings of the same age may sink and even drown when placed in water. The common interpretation is that wild-reared chicks receive preen oil from the parent, and this oil makes them more waterproof. Using mallard ducklings Anas platyrhynchos we tested the effect of preen and other oils, as well as hydrophilic or surfactant contaminants, on the water resistance of down. We found that the true cause for the difference between incubator and hen-reared ducklings is the presence of hydrophilic hatching fluid residues in the down of incubator-hatched ducklings. Once well rinsed and dried, incubator-hatched ducklings can swim for over an hour with essentially dry down. Other tests showed that clean down is quite water resistant, and that water resistance was not improved by preen or other oils. Small amounts of preen or other oils had no effect on water repellency or wetting during surface swimming. However, oil decreased the hydraulic pressure needed to penetrate down. Down lacks the stabilizing interlocking structure of adult contour feathers, and small amounts of oil apparently cause barbules to stick together and reduce the effective number of down fibers. Detergent decreases water repellency and increases water retention, and has a more severe effect on oiled down or when applied in combination with oil. The penetration pressure of a clean down coat, 866±154 Pa, could allow static immersion to ca. 8cm before water would saturate the down and increase thermal conductance. Thus, clean ducklings have a 2×–3× safety margin for surface swimming. Saturation increases the thermal conductance of the down coat from 14.3±1.38 W/m²-°C to 193±25 W/m²-°C. Thus, water pollution or down contamination causing wetting can significantly increase energy use and the frequency of hypothermia.     

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.     

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.     

Weak negative associations between avian influenza virus infection and movement behaviour in a key host species,the mallard Anas platyrhynchos

Animal movements may contribute to the spread of pathogens. In the case of avian influenza virus, [migratory] birds have been suggested to play a role in the spread of some highly pathogenic strains (e.g. H5N1, H5N8), as well as their low pathogenic precursors which circulate naturally in wild birds. For a better understanding of the emergence and spread of both highly pathogenic (HPAIV) and low pathogenic avian influenza virus (LPAIV), the potential effects of LPAIVs on bird movement need to be evaluated. In a key host species, the mallard Anas platyrhynchos, we tested whether LPAIV infection status affected daily local (< 100 m) and regional (> 100 m) movements by comparing movement behaviour 1) within individuals (captured and sampled at two time points) and 2) between individuals (captured and sampled at one time point). We fitted free‐living adult males with GPS loggers throughout the autumn LPAIV infection peak, and sampled them for LPAIV infection at logger deployment and at logger removal on recapture. Within individuals, we found no association between LPAIV infection and daily local and regional movements. Among individuals, daily regional movements of LPAIV infected mallards in the last days of tracking were lower than those of non‐infected birds. Moreover, these regional movements of LPAIV infected birds were additionally reduced by poor weather conditions (i.e. increased wind and/or precipitation and lower temperatures). Local movements of LPAIV infected birds in the first days of tracking were higher when temperature decreased. Our study thus demonstrates that bird‐assisted dispersal rate of LPAIV may be lower on a regional scale than expected on the basis of the movement behaviour of non‐infected birds. Our study underlines the importance of understanding the impact of pathogen infection on host movement in order to assess its potential role in the emergence and spread of infectious diseases.     

Cellular elements organization in the trachea of mallard (Anas platyrhynchos) with a special reference to its local immunological role

Protoplasma - Many studies have been carried out to investigate the histological structure of the trachea in many species of birds. However, the cellular organization of the trachea in the mallard...     

Topographical representation of the jaw muscles within the trigeminal motor nucleus. An HRP study in the mallard, Anas platyrhynchos

The location of the trigeminal motoneurons of the jaw muscles has been determined in the brainstem of the mallard utilizing retrograde axonal transport of horseradish peroxidase (HRP). Injections with HRP into the jaw muscles or application of HRP to the mandibular nerve showed that the trigeminal motor nucleus can be subdivided into five subnuclei, mV1-mV5. Three functional groups of jaw muscles are represented in separate subnuclei. The most lateral subnucleus mV2 innervates all but one adductor muscles, the intermediate mV1 innervates the pterygoid muscles + one adductor and the medial mV4 the two protractor muscles. The most ventral subnucleus mV3 contains the neurons innervating two extrinsic tongue muscles as well as some perikarya of adductor muscles. Subnucleus mV5 lies dorsomedial to mV4 and contains the motoneurons of the depressor muscle of the lower eye lid. Elements of the proprioceptive system, viz. presumptive gamma-neurons and mesencephalic trigeminal nucleus cells, could also be visualized. The topological and functional aspects of the subdivision of the motor nucleus are discussed.     

Identification of in vitro cytochrome P450 modulators to detect induction by prototype inducers in the mallard duckling (Anas platyrhynchos)

Seven modulators of mammalian monooxygenase activity were screened for their ability to selectively stimulate or inhibit in vitro monooxygenase activities of hepatic microsomes from mallard ducklings treated with phenobarbital, β-naphthoflavone, 3,3′,4,4′,5-pentachlorobiphenyl or vehicle. Microsomes were assayed fluorometrically for four monooxygenases: benzyloxy-, ethoxy-, methoxy-, and pentoxyresorufin-O-dealkylase, in combination with each of the seven modulators. Four combinations: α-naphthoflavone and 2-methylbenzimidazole with benzyloxyresorufin, and Proadifen with methoxy- and ethoxyresorufin, respectively, were evaluated further. β-Naphthoflavone-treated groups were clearly distinguished from the corn oil vehicle control group by all of the assays and by the effects of the modulators in three of the four assay/modulator combinations. Enzyme activities of the phenobarbital and saline groups were statistically similar (P≥0.05) when assayed without modulator added, but each assay/modulator combination distinguished between these groups. The PCB-treated group was distinguished from the corn oil vehicle control group only for BROD activity, with or without the presence of modulator. Graphing of per cent modulation of BROD activity versus initial BROD activity provided the clearest distinction between all of the study groups. Identification of these selective in vitro modulators may improve detection and measurement of low level cytochrome P450 induction in avian species. Also, both the monooxygenase activities induced and the impacts of the modulators indicated differences between mammalian and avian cytochromes P450.     

Variations in body weight, wing length and condition of Mallard Anas platyrhynchos platyrhynchos and their relationship to environmental changes

This paper describes the analysis of over 15,000 weights of Mallard caught for ringing at Borough Fen Decoy, Northamptonshire, during a 13 year period. Weights are corrected to give condition indices by using wing length to give an indication of body size. The weight of pectoral muscles varies with body weight but as the fat stores increase in weight the proportion of body weight made up of flight muscles decreases. Body weight corrected for size gives a better indication of the bird's condition (defined as its fitness for its present and future needs) than the relative weight of the pectoral muscles or the shape of the breast.
The relationships between food availability and weather, and condition are examined. Only occasionally can a drop in condition following hard weather be detected; the birds normally emigrate to the coast after a few days of adverse conditions. There is a relationship between the condition of Mallard in autumn and the amount of grain left on their stubble feeding grounds after harvest. The implications of variations in winter condition on survival and breeding success are briefly discussed.