Incidence of ingested lead gunshot in wild grey partridges (Perdix perdix) from the UK

From 1947 to 1992, successive pathologists at The Game Conservancy Trust carried out 1,318 post-mortems on adult wild grey partridges found dead in the UK. During a study of chick food from 1968 to 1978 on the Sussex Downs, the gizzards of 29 wild chicks aged up to 6 weeks were also examined. This paper reports the incidence of lead gunshot ingestion in these two groups of birds. On the assumption that there is no temporal bias, the incidence of lead poisoning increased from 1947–1958 to 1963–1992. During 1963–1992, the incidence of lead gunshot ingestion was 4.5±1.0% in adults and 6.9±4.7% in chicks. The weights of individual lead shot in the chick gizzards showed a rapid rate of erosion, indicating a short retention time in the gizzard, as also reported for adult waterfowl and game birds. The incidence rates in grey partridge and waterfowl found dead can therefore be compared. From 1963 to 1992, the overall incidence of ingested lead gunshot in the grey partridge in the UK was 52% of that of waterfowl (Anatidae excluding mute swan), significantly lower.     

A comparison of two methods to establish the prevalence of lead shot ingestion in mallards (Anas platyrhynchos) from The Netherlands

Two collection methods for screening the mallard (Anas platyrhynchos) population in the Netherlands for the ingestion of spent lead shot were compared. One method consisted of examination of gizzards from mallards shot by hunters (n = 2,859) and the other method consisted of examination of gizzards from mallards caught in duck traps (n = 865). The 95% confidence interval of lead shot ingestion in the mallard population estimated by the first method was 1.7 to 2.9% and by the second method 1.1 to 3.1%. These values were not significantly different. From the numbers of lead pellets embedded in the gizzard wall in hunter-killed and trapped mallards it was estimated that at least 22 to 68% of the trapped ducks had been hit by lead shot previously, but survived. Furthermore, this study shows that it is reasonable to assume that a substantial part of the pellets which are identified (in this study and other studies) as ingested, may well have been shot into the gizzard lumen at some time before the birds were actually killed. To avoid lead poisoning in mallards and in raptors depredating waterfowl hit by lead shot, a change to steel shot is advocated.     

Lead shot poisoning of a pacific loon in Alaska

Lead poisoning, associated with ingestion of spent lead shot, was diagnosed in an adult female Pacific loon (Gavia pacifica) observed with partial paralysis on 13 June 2002 and found dead on 16 June 2002 on Kigigak Island, Yukon Delta National Wildlife Refuge, western Alaska, USA. A necropsy revealed three pellets of ingested lead shot in the loon's gizzard and a lead liver concentration of 31 ppm wet weight, which was consistent with metallic lead poisoning. This is the first report of lead poisoning in a Pacific loon and is the only account of lead toxicosis associated with ingestion of lead shot in any loon species breeding in Alaska.     

Occupancy Patterns of Breeding American Black Ducks

Occupancy patterns can assist with the determination of habitat limitation during breeding or wintering periods and can help guide population and habitat management efforts. American black ducks (Anas rubripes; black ducks) are thought to be limited by habitat and food availability during the winter, but breeding sites may also limit the size or growth potential of the population. The Canadian Wildlife Service conducts an annual breeding waterfowl survey that we used to explore the hypothesis that black duck carrying capacity is limited by wetlands available for breeding in Québec, Canada. We applied single-visit, multi-species occupancy models to the 1990–2015 population survey data to determine if there was evidence the black duck population was limited by breeding habitat. Using a dynamic (multi-season) occupancy modeling approach, we estimated latent occupancy (occupancy accounting for imperfect detection) of black ducks and then used latent occupancy estimates to derive occupancy, colonization, and extirpation rates. We jointly modeled the occupancy dynamics of black ducks and other duck species in wetlands where both species were present. Throughout the duration of the survey, 44% of wetlands were never observed to be occupied by black ducks. Occupancy models showed wetland size was positively associated with occupancy at the first time step (initial occupancy) and colonization. All 2-species models indicated initial black duck occupancy, persistence (continued occupancy), and colonization were positively associated with the presence of a second species. Colonization rate over the 26-year period ranged from 7% to 27% across all models. Extirpation rates were similar and were constant through time within each model. Low occupancy rates, combined with approximately equal colonization and extirpation rates, suggest there are available wetlands for breeding black ducks in their core breeding area. If breeding habitats are not saturated, this suggests migration or wintering areas may be more limiting to black duck population abundance. © 2019 The Wildlife Society.     

Evidence of High Tolerance to Ecologically Relevant Lead Shot Pellet Exposures by an Upland Bird

Upland birds that display grit ingestion behavior are potentially at risk of detrimental effects and death from lead poisoning at trap and skeet ranges and other areas where vast quantities of spent lead shot pellets abound. Because commonly cited force-feeding pellet exposure studies deviate from true field conditions, their results may not reflect true risks faced by upland birds. In particular, studies that use new shot pellets and administer more pellets than would be reasonably ingested, critically interfere with the understanding of actualized pellet exposures. In this study, northern bobwhites (Colinus virginianus), a frequent test species in shot pellet research, were dosed in an ecologically-relevant manner (i.e., with spent shot and with no more than three pellets). Notably, the 56-day post-dosing observation period, during which a battery of physiological measures were recorded, exceeded that of related studies. Despite a sustained suppression of a lead poisoning indicator, the data suggest upland birds can withstand spent shot pellet exposures. Data detected a survivorship ≥95%, absence of illness, demonstrated tolerance for extremely high blood lead concentrations, and unaffected blood parameters. In conjunction with ecological considerations (e.g., spatial scale and animal behavior), concern about bird population losses from the incidental ingestion of spent shot pellets is potentially overstated.     

Potential Hazard to Human Health from Exposure to Fragments of Lead Bullets and Shot in the Tissues of Game Animals

Background

Lead is highly toxic to animals. Humans eating game killed using lead ammunition generally avoid swallowing shot or bullets and dietary lead exposure from this source has been considered low. Recent evidence illustrates that lead bullets fragment on impact, leaving small lead particles widely distributed in game tissues. Our paper asks whether lead gunshot pellets also fragment upon impact, and whether lead derived from spent gunshot and bullets in the tissues of game animals could pose a threat to human health.

Methodology/Principal Findings

Wild-shot gamebirds (6 species) obtained in the UK were X-rayed to determine the number of shot and shot fragments present, and cooked using typical methods. Shot were then removed to simulate realistic practice before consumption, and lead concentrations determined. Data from the Veterinary Medicines Directorate Statutory Surveillance Programme documenting lead levels in raw tissues of wild gamebirds and deer, without shot being removed, are also presented. Gamebirds containing ≥5 shot had high tissue lead concentrations, but some with fewer or no shot also had high lead concentrations, confirming X-ray results indicating that small lead fragments remain in the flesh of birds even when the shot exits the body. A high proportion of samples from both surveys had lead concentrations exceeding the European Union Maximum Level of 100 ppb w.w. (0.1 mg kg⁻¹ w.w.) for meat from bovine animals, sheep, pigs and poultry (no level is set for game meat), some by several orders of magnitude. High, but feasible, levels of consumption of some species could result in the current FAO/WHO Provisional Weekly Tolerable Intake of lead being exceeded.

Conclusions/Significance

The potential health hazard from lead ingested in the meat of game animals may be larger than previous risk assessments indicated, especially for vulnerable groups, such as children, and those consuming large amounts of game.     

Genetic studies facilitated management decisions on the invasion of the ruddy duck in Europe

The ruddy duck (Oxyura jamaicensis), a stifftail native to the Americas, was introduced to the UK in the 1950s and has since been recorded in 22 western Palearctic countries. By 2000, the UK population peaked at nearly 6,000 individuals. In 1991, hybridisation with the native and globally threatened (IUCN Endangered) white-headed duck (Oxyura leucocephala), a stifftail restricted to the Mediterranean and Asia, was recorded in Spain and culling of hybrids and ruddy ducks began. Here we report on a series of genetic studies that have enabled and supported management decisions to the benefit of the white-headed duck. First, genetic data confirmed that these are two distinct species, each of which is more closely related to other stifftail species. Second, molecular studies indicated that ruddy ducks in Spain, Iceland and elsewhere in Europe were of captive origin and not descendants from vagrants from their native North America. Third, genetic methods were used to distinguish among different hybrid generations in Spain and detected no ruddy duck introgression in birds identified morphologically as white-headed ducks. Collectively, these results supported management decisions to eradicate ruddy ducks from Europe. Subsequently, a control programme reduced the UK population by over 95 % by 2010, and the arrival of ruddy ducks to Spain decreased from 21 birds in 2003 to two sightings in 2010–2011. However, increased efforts to control small ruddy duck populations elsewhere in Europe and Morocco are still required to ensure conservation of the white-headed duck. This case of invasion by hybridization demonstrates that successful control is feasible given early detection followed by a rapid response plan; it also shows the contribution of research to management and that to guarantee the conservation of an endangered native species action may be required in countries outside its distribution range.     

Microsatellite markers for two stifftail ducks: the white‐headed duck,Oxyura leucocephala,and the ruddy duck,O. jamaicensis

Hybridization with a close relative, the North American ruddy duck (Oxyura jamaicensis), is a major problem for the conservation of the endangered white‐headed duck (Oxyura leucocephala). We report the development of 11 microsatellite markers that can facilitate the identification of hybrids as well as the study of the population structure of both species across their distributions. These markers were tested in 63 white‐headed ducks and 50 ruddy ducks and show a larger diversity in the latter species.     

Lead poisoning in swans and sources of contamination in Ireland

A study of blood levels in mute swans Cygnus olor in Ireland has revealed that ingested lead pellets are responsible for acute lead poisoning. Forty-two percent of blood samples from 890 live birds at one site showed elevated lead levels. X-ray examination of live birds revealed the source of contamination to be ingested lead pellets. Urban birds were shown to have higher ( P 0001) lead levels than rural birds, the blood lead levels of which were presumed to reflect natural background levels. Urban grass was shown to have elevated lead but this did not cause lead poisoning in Canada geese Branta canadensis . Post-mortem examination has shown that 68% ( n = 101) of all mute swans examined from a number of sites died from lead poisoning. Two sources of poisoning were identified; spent gunshot from a claypigeon shooting site at Lough Neagh, Northern Ireland, and lost or discarded anglers' weights at Cork Lough and at a fishing pond in Belfast, N.I. The first known case of lead poisoning in whooper swans Cygnus cygnus in Ireland is recorded which resulted from the ingestion of gunshot used almost two decades earlier. Aspects of the pathology of lead poisoned swans is discussed.     

Population Genetics of a Translocated Population of Mottled Ducks and Allies

Translocating species is an important management tool to establish or expand the range of species. Success of translocations requires an understanding of potential consequences, including whether a sufficient number of individuals were used to minimize founder effects and if interspecific hybridization poses a threat. We provide an updated and comprehensive genetic assessment of a 1970s–1980s translocation and now established mottled duck (Anas fulvigula) population in South Carolina, USA. In addition to examining the population genetics of these mottled ducks, we simulated expected genetic assignments for generational hybrids (F1–F10), permitting formal purity assignment across samples to identify true hybrids and establish hybridization rates. In addition to wild mallards (A. platyrhynchos), we tested for presence of hybrids with migrant American black ducks (A. rubripes) and released domestic game-farm mallards (A. p. domesticus). We used wild reference populations of North American mallard-like ducks and sampled game-farm mallards from 2 sites in South Carolina that could potentially interbreed with mottled ducks. Despite 2 different subspecies of mottled duck (Florida [A. f. fulvigula] and the Western Gulf Coast [A. f. maculatlus]) used in original translocations, we determined the gene pool of the Western Gulf Coast mottled duck was overwhelmingly represented in South Carolina's current population. We found no evidence of founder effects or inbreeding and concluded the original translocation of 1,285 mottled ducks was sufficient to maintain current genetic diversity. We identified 7 hybrids, including an F1 and 3 late-staged (i.e., F2–F3 backcrosses) mottled duck × black duck hybrids, 1 F2-mottled duck backcrossed with a wild mallard, and 2 F3-mottled ducks introgressed with game-farm mallard. We estimated a 15% hybridization rate in our mottled duck dataset; however, the general lack of F1 and intermediate hybrids were inconsistent with scenarios of high hybridization rates or presence of a hybrid swarm. Instead, our results suggested a scenario of infrequent interspecific hybridization between South Carolina's mottled ducks and congeners. We concluded that South Carolina's mottled duck population is sufficiently large now to absorb current hybridization rates because 85% of sampled mottled ducks were pure. These results demonstrate the importance in managing and maintaining large parental populations to counter hybridization. As such, future population management of mottled ducks in South Carolina will benefit from increased geographical and continued sampling to monitor hybridization rates with closely related congeners. We also suggest that any future translocations of mottled ducks to coastal South Carolina should originate from the Western Gulf Coast. © 2021 The Wildlife Society.     

Fish–duck interactions in boreal lakes in Finland as reflected by abundance correlations

We studied the hypothesis that fish play an important role in lake use by ducks (pairs and broods) in boreal lakes. The study was based on densities of different duck and fish species in 28 boreal lakes in southern Finland. We focused on the three most common duck species (mallard Anas platyrhynchos, green-winged teal A. crecca and common goldeneye Bucephala clangula) and on the three most common fish species (perch Perca fluviatilis, roach Rutilus rutilus and pike Esox lucius) in the region. We considered both competitive and predatory interactions between ducks and fish, the perch and roach being potential competitors with ducks and the pike a potential predator of ducks. We found a negative association between green-winged teal brood density and total fish density, the other duck species having only a weak association with total fish density. When the three fish species were considered separately, a negative association, suggesting food competition, was found between perch, green-winged teal and goldeneye, whereas the role of roach as a food competitor seemed to be of minor importance. We did not find any clear signs of predatory effects of pike on ducks. Our results suggest that food competition is a more important factor than pike predation in affecting lake use by ducks in oligotrophic boreal environments in southern Finland.     

Lead shot ingestion by mourning doves on a disked field

Previous field studies of hunter-harvested mourning doves (Zenaida macroura) have reported the percentage of birds with ingested lead shot as 0.2–6.5%. To reduce the uncertainty concerning the number of doves that ingest shot, we conducted an experiment to test the proportion of mourning doves that ingested lead shot on the bare soil of a disked field (typical of a managed dove field) to simulate more natural feeding conditions. In each of 3 treatment groups of 80 birds, we exposed 35 birds to low-density lead shot (1.5 million shot/ha), and35 birds to high-density lead shot (29.5 million shot/ha), and 10 birds served as controls (no shot). We dosed 5 positive control birds with 2 lead shot each in trials 2 and 3. We scattered lead shot and mixed seed on the loosely packed soil of treatment cages and after 4 days of exposure, 2.9% of doves voluntarily ingested ≥1 lead shot. The proportion of birds that ingested shot when exposed to the high-density shot treatment (4.9%) was not different (P = 0.098) from that of the low-density shot treatment (1.0%). Lead concentrations in liver, kidneys, and blood reached maxima of 94.402 ppm, 346.033 ppm, and 13.883 ppm wet mass, respectively. Differences in delta-aminolevulinic acid dehydratase (ALAD) activity, packed cell volume, and heterophil:lymphocyte ratio (H:L) were greater posttreatment in doves that had ingested shot than in those that did not. The risk posed to mourning doves from lead shot ingestion can be reduced by banning lead shot on management areas or dove fields or disking fields after hunting season to reduce shot availability. © 2011 The Wildlife Society.     

Poisoning from lead gunshot: still a threat to wild waterbirds in Britain

Lead is a highly toxic metal known to be an important cause of morbidity and mortality in waterbirds and terrestrial birds worldwide. The risk to birds of poisoning from lead has resulted in the introduction of legislation in many countries, such as UK restrictions on the use of lead in angling weights and lead gunshot. In this study, we examined data on current and historical trends in lead poisoning in British waterbirds and related these to the introduction of legislation restricting the use of lead. Our results indicate that lead poisoning has continued to affect a wide range of British waterbirds long after legal restrictions were introduced. Elevated levels of lead (i.e. >20.0 μg/dL) were found in the blood of 34 % (n?=?285) of waterbirds tested at four sites in Britain during the 2010/2011 winter and accounted for the deaths of at least 10.6 % (n?=?2,365) of waterbirds recovered across Britain between 1971 and 2010 and 8.1 % (n?=?1,051) between 2000 and 2010, with lead gunshot being the most likely source of poisoning. The proportion of birds dying from lead poisoning in England did not vary significantly after the introduction of legislation, accounting for 13.7 % of non-infectious causes of death between 1971 and 1987 (n?=?204), 20.8 % (n?=?360) between 1988 and 1999 and 11.8 % (n?=?423) between 2000 and 2010, despite a significant change in lead-related mortality in mute swans found during the same time period, 25 % (n?=?12) between 1971 and 1987, 4.6 % (n?=?65) between 1988 and 1999 and 2 % (n?=?100) between 2000 and 2010. Existing legislation needs review and extension to ensure the delivery of international commitments and a broad-scale transition to the use of non-toxic shot and angling materials in all environments.     

PCK1 expression is correlated with the plasma glucose level in the duck

Phosphoenolpyruvate carboxykinase 1 (soluble) (PCK1) is a key gene in gluconeogenesis and glyceroneogenesis. Although its functions have been extensively studied in mice, bats and humans, little is known in ducks. Here, PCK1 functions were studied using a duck domestication model and a 48‐h fasting experiment. We found PCK1 expression significantly decreased in two breeds of domestic ducks (Jinyun Pockmark ducks and Cherry Valley ducks) as compared with wild ducks (Anas platyrhynchos). Simultaneously, plasma levels of glucose, triglycerides and free fatty acid in domestic ducks were lower than in wild ducks. When compared with fed ducks, the plasma triglyceride level was observed to be significantly decreased, while the glucose and free fatty acid levels remained constant in 48‐h fasting ducks. The expression analysis of gluconeogenic genes revealed that fructose‐1,6‐bisphosphatase genes (FBP1 and FBP2) and the glucose‐6‐phosphatase gene (G6PC2) were not changed, whereas PCK1 was significantly upregulated. In addition, the reported regulators of PCK1, including forkhead box A2 (FOXA2) gene and orphan nuclear receptor NR4A family genes (NR4A1, NR4A2 and NR4A3), exhibited similar expression levels between 48‐h fasting ducks and fed ducks, suggesting that PCK1 is not regulated by these genes in the duck under fasting conditions. In conclusion, PCK1 expression may affect plasma levels of glucose, triglycerides and free fatty acid during the duck domestication process. This work demonstrates for the first time in duck that PCK1 is a key gene in maintaining plasma glucose homeostasis during fasting and that the upregulated expression of PCK1 may be responsible for constant plasma free fatty acid level by the glyceroneogenesis process.     

Habitat selection by wintering tufted ducks with special reference to their digestive organ and to possible segregation between neighboring populations

Habitat selection by tufted ducks (Aythya fuligula), a diving duck which swallows benthic prey organisms, was studied during winter at two neighboring lagoons (Lakes Nakaumi and Shinji, Honshu, Japan) which differ strongly in their benthic fauna and in their diving duck densities. The ducks fed overwhelmingly on the dominant bivalve found in each of the two lagoons, the mussel Musculista senhousia in L. Nakaumi and the clam Corbicula japonica in L. Shinji. In general, however, the ducks probably preferred the mussels to the clams because of: (i) their high (2.9 times) calorific content for their weight; (ii) their high digestibility; (iii) their greater accessibility; and (iv) their shorter handling time. An average tufted duck (850 g) was estimated to require 1.3 kg of mussels or 3.8 kg of clams to meet their daily energy requirements. As a result, the two wintering populations were estimated to consume 4970 t mussels and 4770 t clams during a single wintering season, amounting to some 20% of the standing clam crop. Throughout the winter the average gizzard weight (37 g), and gizzard–body mass ratio (4.2%) of the Lake Nakaumi population were half those of the Lake Shinji population (73 g, 8.1%, respectively), despite their significantly similar nutritive body condition (% body lipid > 12%). The need to maintain a specialized gizzard mass in order to be able to cope with the different prey species results in little opportunity for sampling movements of birds between lakes/prey types and as a result two subpopulations of ducks are indicated to be segregated.     

Genome‐wide association studies reveal genetic loci associated with plasma cholinesterase activity in ducks

Plasma cholinesterase (PCHE) activity is an important auxiliary test in human clinical medicine. It can distinguish liver diseases from non‐liver diseases and help detect organophosphorus poisoning. Animal experiments have confirmed that PCHE activity is associated with obesity and hypertension and changes with physiological changes in an animal's body. The objective of this study was to locate the genetic loci responsible for PCHE activity variation in ducks. PCHE activity of Pekin duck × mallard F2 ducks at 3 and 8 weeks of age were analyzed, and genome‐wide association studies were conducted. A region of about 1.5 Mb (21.8–23.3 Mb) on duck chromosome 9 was found to be associated with PCHE activity at both 3 and 8 weeks of age. The top SNP, g.22643979C>T in the butyrylcholinesterase (BCHE) gene, was most highly associated with PCHE activity at 3 weeks (?logP = 21.45) and 8 weeks (?logP = 27.60) of age. For the top SNP, the strong associations of CC and CT genotypes with low PCHE activity and the TT genotype with high PCHE activity indicates the dominant inheritance of low PCHE activity. Problems with block inheritance or linkage exist in this region. This study supports that BCHE is a functional gene for determining PCHE levels in ducks and that the genetic variations around this gene can cause phenotypic variations of PCHE activity.     

Breeding Ecology of Mottled Ducks: A Review

Mottled ducks (Anas fulvigula) are endemic to the Gulf Coast of North America, and their range stretches from Alabama to the Laguna Madre of Mexico, with a distinct population in peninsular Florida and an introduced population in South Carolina. As one of the few non-migratory ducks in North America, mottled ducks depend on a variety of locally available habitat throughout the annual cycle, and threats to these landscapes may affect mottled ducks more acutely than migratory species. Annual population monitoring has revealed declines in mottled duck populations in Texas and Louisiana since 2008, and the genetic integrity of the Florida population has been muddled by the presence of large numbers of feral mallards (Anas platyrhynchos) resulting in hybridization. Similar to other closely related dabbling ducks, mottled duck populations are influenced by recruitment and breeding season survival, so changes in these factors may contribute to population decline. Accordingly, researchers have attempted to address various aspects of mottled duck breeding season ecology and population dynamics since the 1950s. We conducted a literature review on this topic by searching a combination of key terms using Google Scholar, including mottled duck, nesting ecology, habitat use, breeding incidence, nest success, brood, and breeding season survival, and followed citation trees to eventually aggregate information from nearly 50 publications on mottled duck breeding ecology. Our review concluded that mottled ducks use brackish and intermediate coastal marsh, including managed impoundments, and agricultural land during the breeding season. Their nests can be found in pastures, levees, dry cordgrass marsh, cutgrass marsh, spoil banks, and small islands. Nesting propensity and nest success estimates are often lower than other waterfowl species that are characterized by stable or increasing populations. Broods use wetlands composed of a mix of open water with submerged and emergent vegetation. Breeding season survival is higher for the Florida population than the western Gulf Coast population, but adult survival in both geographies is comparable to (or higher than) that of other dabbling duck species. Breeding habitat use, breeding season survival, and nest-site selection and success have been studied extensively in mottled ducks, whereas information on nesting propensity, renesting intensity, and post-hatch ecology is lacking. © 2021 The Wildlife Society.     

Mottled ducks,feral mallards,and their hybrids in Florida

The nonmigratory and endemic Florida mottled duck (Anas fulvigula fulvigula) is facing conservation threats from the combined effects of urbanization and introgressive hybridization with feral mallards (Anas platyrhynchos) and mallard x mottled duck hybrids. In the past, the status of the Florida mottled duck population was assessed during annual aerial surveys and most brown ducks (mottled ducks, mallards, and hybrids of them) detected during the survey would have been mottled ducks. But the release of domesticated mallards for aesthetic purposes has led to increases in the prevalence of mallards-hybrids (mallards or mallard x mottled duck hybrids) throughout peninsular Florida, USA, and because it is impossible to differentiate among mottled ducks, female mallards, and hybrids during aerial surveys, helicopter surveys were halted in 2009 until state researchers could conduct a range-wide study to determine what proportion of brown ducks are mottled ducks versus mallards-hybrids. We used plumage keys and high-resolution photography to categorize brown ducks from 557 wetland grid points as either mottled ducks or mallards-hybrids. Of the 5,179 brown ducks categorized, 40.1% were mottled ducks and 59.9% were mallards-hybrids. We used logistic regression analysis to model the interactive effect of a site's latitude and level of urbanization (urban gradient value within a 2-km buffer) to generate a predictive raster surface (1-km resolution) of the study area with values corresponding to the probability that a brown duck observed within a cell is a pure mottled duck. Predicted values will be used as correction factors when estimating final mottled duck population abundance from brown-duck survey data. Additionally, the predictive raster surface will be used to identify wetlands where mottled ducks remain predominant so that these sites can be targeted for preservation. Overall, mallards-hybrids outnumbered mottled ducks throughout most of peninsular Florida, especially in more urbanized regions, and their current prevalence rate presents a serious conservation threat, via hybridization, to extant mottled duck populations.     

Feeding ecology of the diving ducks pochard (Aythya ferina), tufted duck (A. fuligula), scaup (A. mania) and goldeneye (Bucephala clangula) overwintering on Lough Neagh, Northern Ireland

1. The diets of pochard (Aythya ferina), scaup (A. marila) and goldeneye (Bucephala clangula) overwintering on Lough Neagh are dominated by chironomid larvae, while molluscs are more important in that of tufted duck (A. fuligula). 2. Inshore areas of Lough Neagh offer poor feeding conditions for these diving ducks because chironomid larvae and molluscs are of small individual body size or low abundance. These factors lead to all four ducks foraging at least in part at depths greater than those usually exploited. 3. Due to their common consumption of molluscs, the diet of tufted duck shows a higher overlap with that of an introduced roach (Rutilus rutilus) population than with any other duck or fish species. 4. The feeding ecology of tufted duck and roach in Lough Neagh may form an example of distant competition and be at least partly responsible for recent fluctuations in the numbers of tufted duck.     

Stepwise colonization of the Andes by Ruddy Ducks and the evolution of novel β‐globin variants

Andean uplift played a key role in Neotropical bird diversification, yet past dispersal and genetic adaptation to high‐altitude environments remain little understood. Here we use multilocus population genetics to study population history and historical demographic processes in the ruddy duck (Oxyura jamaicensis), a stiff‐tailed diving duck comprising three subspecies distributed from Canada to Tierra del Fuego and inhabiting wetlands from sea level to 4500 m in the Andes. We sequenced the mitochondrial DNA, four autosomal introns and three haemoglobin genes (α^A, α^D, β^A) and used isolation‐with‐migration (IM) models to study gene flow between North America and South America, and between the tropical and southern Andes. Our analyses indicated that ruddy ducks dispersed first from North America to the tropical Andes, then from the tropical Andes to the southern Andes. While no nonsynonymous substitutions were found in either α globin gene, three amino acid substitutions were observed in the β^A globin. Based on phylogenetic reconstruction and power analysis, the first β^A substitution, found in all Andean individuals, was acquired when ruddy ducks dispersed from low altitude in North America to high altitude in the tropical Andes, whereas the two additional substitutions occurred more recently, when ruddy ducks dispersed from high altitude in the tropical Andes to low altitude in the southern Andes. This stepwise colonization pattern accompanied by polarized β^A globin amino acid replacements suggest that ruddy ducks first acclimatized or adapted to the Andean highlands and then again to the lowlands. In addition, ruddy ducks colonized the Andean highlands via a less common route as compared to other waterbird species that colonized the Andes northwards from the southern cone of South America.