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62 results for “mallard”
Low levels of hybridization between domestic and wild Mallards wintering in the Lower Mississippi Flyway
<p>Mallard ducks are a ubiquitous and socio-economically important game bird in North America. Despite their generally abundant midcontinent population, Mallards in eastern North America are declining, which may be partially explained by extensive hybridization with human-released domestically-derived game-farm Mallards. We investigated the genetic composition of Mallards in the middle and lower Mississippi flyway, key wintering regions for the species. We found that nearly 30% of wild Mallards carried mitochondrial haplotypes derived from domestic mallards present in North America, indicating that the individuals had female game-farm Mallard lineage in their past; however nuclear results identified only 4% of the same sample set as putative hybrids. Recovering 30% of samples with OW A mtDNA haplotypes is concordant with general trends across the Mississippi flyway and this percentage was stable across Mallards we sampled a decade apart. The capture and perpetuation of OW A mtDNA haplotypes is likely due to female breeding structure, whereas reversal of the nuclear signal back to wild ancestry is due to sequential backcrossing and lower and/or declining admixture with game-farm Mallards. Future studies of wild ancestry of Mississippi flyway Mallards will benefit from coupling molecular and spatial technology across flyways, seasons, and years to search for potential transitions of Mallard populations with different genetic ancestry, and whether the genetic ancestry is somehow linked to an individual's natal and subsequent breeding location.</p>
Caught out in the cold: Mallard survival decreased during an extreme climatic event
<p>Extreme climatic events (ECEs) can have profound impacts on individual fitness, affecting survival directly or indirectly. Late winter ECEs may be especially detrimental to fitness due to limited food resources and increased energetic requirements during this time. A polar vortex disruption ECE descended upon the mid-continental United States during 7–20 February 2021 with temperatures as low as −29ºC in areas concurrent with ongoing research on mallard (<em>Anas platyrhynchos</em>) movement ecology and survival in Arkansas, Louisiana, and Tennessee, USA spanning winters 2019–2022. Therefore, we opportunistically evaluated the effects of individual characteristics and latitude on daily survival during the ECE. We extended the survival analysis into March to test for lasting effects of the ECE on survival. We tracked 181 GPS-marked mallards during February 2020, 256 in February 2021, and 324 in February 2022. We documented 22 mortalities during the February 2021 ECE (i.e., 9%), but only 6 mortalities during February 2020 (i.e., 2%) and 2022 (i.e., 1%) when conditions were average. February survival (e.g., 28-day survival) during the ECE was 0.908 (85% CI = 0.879–0.937) but was 0.982 (85% CI = 0.973 – 0.991) during the two non-ECE Februaries. The ECE effect on survival was isolated to February and did not affect March survival. Mallards were 5.4 times more likely to die during the ECE in 2021 compared to non-ECE Februaries. Although large-bodied waterfowl appear cold-tolerant and less sensitive to polar vortex disruptions compared to smaller-bodied passerines, direct mortalities can occur if conditions are severe enough and persist, highlighting the need to consider the influence of ECEs on common, seemingly robust species in future global climate change scenarios.</p>
Morphometrics of mallards in the Lower Mississippi Alluvial Valley and associated climate variables from 1979-2021
<p>Body mass in overwintering waterfowl is an important fitness attribute as it affects winter survival, timing of spring migration, and subsequent reproductive success. Recent research in Europe and the western United States indicates body mass of mallards (<em>Anas platyrhynchos</em>) has increased from the late 1960s to early 2000s. The underlying mechanism is currently unknown; however, researchers hypothesize that increases are due to a more benign winter climate, increased food availability through natural and artificial flooding, introgression of wild mallard populations by game-farm mallards, or shifting of wintering distributions northward. Further investigation of factors related to winter mallard body mass increases and whether this phenomenon is occurring in other major flyways could increase understanding of intrinsic and extrinsic variables influencing waterfowl fitness. We collected and analyzed mallard body mass data in the Lower Mississippi Alluvial Valley from 1979 to 2021 to determine sources of temporal variation. We measured hunter-harvested mallards from private hunting clubs, public hunting areas, and duck-plucking businesses. Mallard body mass increased by approximately 6% among all age-sex classes from 1979 to 2021. We also compiled weather data (rainfall [cm], weather severity index information [WSI], river gage discharge [cfs] and height [m]) to relate to mallard body mass measurements.</p>
Fig. 5 in Threat of cercarial dermatitis in Hungary: A first report of Trichobilharzia franki from the mallard (Anas platyrhynchos) and European ear snail (Radix auricularia) using molecular methods
Fig. 5. Male Bilharziella polonica from the liver of a mallard.
Fig. 8 in Threat of cercarial dermatitis in Hungary: A first report of Trichobilharzia franki from the mallard (Anas platyrhynchos) and European ear snail (Radix auricularia) using molecular methods
Fig. 8. (continued).
Fig. 7 in Threat of cercarial dermatitis in Hungary: A first report of Trichobilharzia franki from the mallard (Anas platyrhynchos) and European ear snail (Radix auricularia) using molecular methods
Fig. 7. Ocellata-type of furcocercaria emerged from Radix auricularia.
Effects of released farmed mallards on species richness of breeding waterbirds and amphibians in natural, restored, and constructed wetlands
<p>Common practices in current game management are wetland restoration and creation, as well as releases of quarry species. We studied the impact of releases of mallard ducklings on species richness of wild waterbirds and amphibians on three types of wetlands: natural, constructed and restored. Data on species richness, macrophyte cover and water characteristics (total phosphorous and pH) were collected at 32 sites in an agricultural landscape in southern Sweden. In total, 14 species of waterbirds were recorded, ranging from zero to seven per wetland and survey. Amphibians were present in 24 of the 32 wetlands; in total five species were found, ranging from zero to three per wetland. By using generalized linear modelling we found that wetland type best predicted waterbird species richness. Constructed wetlands had significantly more waterbird species, regardless of whether they were used for mallard releases or not. There were breeding amphibians in 62% of natural, 100% of restored and 77% of constructed wetlands. Breeding amphibians were present in 84% of wetlands without, and in 62% of wetlands with releases. However, included variables did not explain amphibian species richness in the wetlands. Releasing large numbers of mallards on a wetland and providing food ad libitum is likely to affect water quality, nutrient availability and predation pressure. Indeed, phosphorous levels were significantly higher in release wetlands, but no differences were found between wetland types.This means that mallard releases may increase nutrient loads in environments that are already eutrophied. However, in our study system releases did not influence species richness of waterbirds and amphibians locally. Constructing wetlands for mallard releases can thus have positive local effects on species richness.</p>
Wintering mallard survival is unaffected by brief anthropogenic disturbance on protected areas
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Caught out in the cold: Mallard survival decreased during an extreme climatic event
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Low levels of hybridization between domestic and wild Mallards wintering in the Lower Mississippi Flyway
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Effects of released farmed mallards on species richness of breeding waterbirds and amphibians in natural, restored, and constructed wetlands
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Hunting constrains wintering mallard response to habitat and environmental conditions
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Raw GPS data of wild and farmed mallards in southern Sweden
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Morphometrics of mallards in the Lower Mississippi Alluvial Valley and associated climate variables from 1979-2021
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Data from: Mallard resource selection trade‐offs in a heterogeneous environment during autumn and winter
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Mallard response to experimental human disturbance on sanctuary areas is mediated by hunting
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Data from: Endozoochory of aquatic ferns and angiosperms by mallards in Central Europe
1. Modern literature on plant dispersal by birds focuses mainly on the importance of frugivory and scatter-hoarding, yet recent studies show that endozoochory by migratory waterbirds is an important mechanism of long-distance dispersal for a broad range of plants. Nevertheless, there is a lack of empirical field studies that identify the plants dispersed by waterbirds, and relate them to expectations based on dispersal syndromes. To date, there are no detailed studies of the level of spatial variation in the plant taxa dispersed by a waterbird vector. 2. Five sets of faecal samples (total n = 215) were collected from mallards Anas platyrhynchos on autumn migration in the Tisza and Balaton regions in Hungary, central Europe. Intact diaspores were extracted, identified and their germinability assessed under standard conditions. The plant communities recorded at different sites were compared with PERMANOVA and other multivariate methods. 3. Macrospores of the floating watermoss Salvinia natans were recorded in 32 samples, and a total of 16 macrospores germinated, providing the first field demonstration of endozoochory of ferns by birds. Of 21 angiosperm taxa recorded (of which 8 germinated), 13 were terrestrial species, although the most abundant taxa were aquatic species such as the alkali bulrush Bolboschoenus maritimus and the sago pondweed Potamogeton pectinatus. Two naturalized alien species, the common fig (Ficus carica) and the hackberry (Celtis occidentalis) were also recorded. The plant taxa dispersed varied at two different spatial scales, with minor but significant differences between samples from sites separated by less than 1 km, and major differences between the two regions separated by approximately 220 km. 4. Synthesis. This is a unique study of the spatial variation in plants dispersed by endozoochory by a migratory waterfowl species, with the first demonstration of avian endozoochory of ferns. Most taxa dispersed are generally assumed to disperse by water, wind or self-dispersal, and waterfowl will provide much greater maximum dispersal distances. More such studies are essential before we can understand which plants are dispersed by migratory birds, because morphological dispersal syndromes do not allow us to make adequate a priori predictions.
Data from: 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, H, by estimated harvest rate, h, calculated as (ii) direct band recovery rate, f, divided by the (iii) band reporting rate, p. 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.
Data from: ddRAD‐seq data reveal significant genome‐wide population structure and divergent genomic regions that distinguish the mallard and close relatives in North America
Recently evolved species typically share genetic variation across their genomes due to incomplete lineage sorting and/or ongoing gene flow. Given only subtle allele frequency differences at most loci and the expectation that divergent selection may affect only a tiny fraction of the genome, distinguishing closely related species based on multi‐locus data requires substantial genomic coverage. In this study, we used ddRAD‐seq to sample the genomes of five recently diverged, New World "mallards" (Anas spp.), a group of dabbling duck species characterized by diagnosable phenotypic differences but minimal genetic differentiation. With increased genomic sampling, we aimed to characterize population structure within this group and identify genomic regions that may have experienced divergent selection during speciation. We analyzed 3,017 autosomal ddRAD‐seq loci and 177 loci from the Z‐chromosome. In contrast to previous studies, the ddRAD‐seq data were sufficient to assign individuals to their respective species or subspecies and to generate estimates of gene flow in a phylogenetic framework. We find limited evidence of contemporary gene flow between the dichromatic mallard and several monochromatic taxa, but find evidence for historical gene flow between some monochromatic species pairs. We conclude that the overall genetic similarity of these taxa likely reflects retained ancestral polymorphism rather than recent and extensive gene flow. Thus, despite recurring cases of hybridization in this group, our results challenge the current dogma predicting the genetic extinction of the New World monochromatic dabbling ducks via introgressive hybridization with mallards. Moreover, ddRAD‐seq data were sufficient to identify previously unknown outlier regions across the Z‐chromosome and several autosomal chromosomes, regions that may have been involved in the diversification of species in this recent radiation.
Persistence of an endangered native duck, feral mallards, and multiple hybrid swarms across the main Hawaiian Islands
Interspecific hybridization is recognized as an important process in the evolutionary dynamics of both speciation and the reversal of speciation. However, our understanding of the spatial and temporal patterns of hybridization that erode versus promote species boundaries is incomplete. The endangered, endemic koloa maoli (or Hawaiian duck, Anas wyvilliana) is thought to be threatened with genetic extinction through ongoing hybridization with an introduced congener, the feral mallard (A. platyrhynchos). We investigated spatial and temporal variation in hybrid prevalence in populations throughout the main Hawaiian Islands, using genomic data to characterize population structure of koloa, quantify the extent of hybridization, and compare hybrid proportions over time. To accomplish this, we genotyped 3,308 double-digest restriction-site-associated DNA (ddRAD) loci in 425 putative koloa, mallards, and hybrids from populations across the main Hawaiian Islands. We found that despite a population decline in the last century, koloa genetic diversity is high. There were few hybrids on the island of Kauaʻi, home to the largest population of koloa. By contrast, we report that sampled populations outside of Kauaʻi can now be characterized as hybrid swarms, in that all individuals sampled were of mixed koloa × mallard ancestry. Further, there is some evidence that these swarms are stable over time. These findings demonstrate spatial variation in the extent and consequences of interspecific hybridization, and highlight how islands or island-like systems with small population sizes may be especially prone to genetic extinction when met with a congener that is not reproductively isolated.
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