Fifty-year trends in UK hunting bags of birds and mammals, and calibrated estimation of national bag size, using GWCT’s National Gamebag Census

Viral pathogen detection in U.S. game-farm mallard (Anas platyrhynchos) flags spillover risk to wild birds

The threat posed by emerging infectious diseases is a major concern for global public health, animal health and food security, and the role of birds in transmission is increasingly under scrutiny. Each year, millions of mass-reared game-farm birds are released into the wild, presenting a unique and a poorly understood risk to wild and susceptible bird populations, and to human health. In particular, the shedding of enteric pathogens through excrement into bodies of water at shared migratory stop-over sites, and breeding and wintering grounds, could facilitate multi-species long-distance pathogen dispersal and infection of high numbers of naive endemic birds annually. The Mallard (Anas platyrhynchos) is the most abundant of all duck species, migratory across much of its range, and an important game species for pen-rearing and release. Major recent population declines along the US Atlantic coast has been attributed to game-farm and wild mallard interbreeding and the introduction maladaptive traits into wild populations. However, pathogen transmission and zoonosis among game-farms Mallard may also impact these populations, as well as wildlife and human health. Here, we screened 16 game-farm Mallard from Wisconsin, United States, for enteric viral pathogens using metatranscriptomic data. Four families of viral pathogens were identified - Picobirnaviridae (Genogroup I), Caliciviridae (Duck Nacovirus), Picornaviridae (Duck Aalivirus) and Sedoreoviridae (Duck Rotavirus G). To our knowledge, this is the first report of Aalivirus in the Americas, and the first report of Calicivirus outside domestic chicken and turkey flocks in the United States. Our findings highlight the risk of viral pathogen spillover from peri-domestically reared game birds to naive wild bird populations.

Evaluation of self-regulation by the hunting community: A case study on the voluntary restraint of woodcock hunting in the UK

Behaviour change through voluntary action can be an important approach to reducing human impacts on biodiversity. One example is self-regulation in hunting, potentially a vital contributory factor in improving the sustainability of wild bird harvest. There has been a growing realisation among woodcock Scolopax rusticola hunters, reinforced by advice from sector organisations, that components of the UK woodcock populations are declining and that some aspects of woodcock hunting, specifically timing of harvest, may contribute to these. This study utilised five qualitative and quantitative data sets, collected for different purposes, to assess the behaviour and attitudes of woodcock hunters, both currently and over the past century. In the UK, relatively few woodcock are harvested and few hunters or species-specific shoots target them. An estimated 26%-29% of lowland shoots advertise or harvest woodcock, with fewer than 5% of shoots or hunters participating in 'woodcock specific' shoot days. The number of birds harvested has fallen in recent years and is estimated to be between 62,000 and 140,000. Qualitative data suggests that over 90% of hunters now report shooting woodcock only after the recommended date of 1st December, or not at all. This is reflected in bag data which shows that, since 2018, fewer than 3%-13% of woodcock shot were harvested prior to 1st December. Around a third of hunters have reported stopping shooting woodcock and it is likely the harvest will decline in coming years due to voluntary restraint. This work demonstrates both through self-report data and independent harvest data that behaviour change among hunters can be effected. This provides a working example where self-regulation in response to a collective sector-led effort has the potential to conserve wild quarry.

Difference in concentration of lead (Pb) in meat from pheasants killed using lead and iron (Fe) shotgun ammunition

The use of lead shotgun ammunition for hunting has been banned in a few jurisdictions and habitats, principally to protect wild birds from poisoning by ingestion of spent lead shot. The EU and UK REACH processes have recently considered bans on lead ammunition throughout the European Union and United Kingdom, including assessments of possible health benefits from reduced human dietary exposure to lead from game meat. Comparisons of the mean lead concentrations in meat from gamebirds killed using lead and non‑lead shotgun ammunition have not been published. We compared lead concentrations in meat from wild-shot pheasants from which lead shotgun pellets were recovered (n = 27) with those from which iron pellets were recovered (n = 20), having removed all pellets from the meat before analysis. The mean concentration of lead in meat from pheasants killed using lead shot was 2.10 mg/kg w.w., which is >20 times the European Union's maximum permitted level for the lead concentration in meat from domesticated animals. For pheasants killed using iron shot the mean was 0.07 mg/kg w.w., which is below the maximum permitted level.

Bayesian areal disaggregation regression to predict wildlife distribution and relative density with low-resolution data

For species of conservation concern and human-wildlife conflict, it is imperative that spatial population data be available to design adaptive-management strategies and be prepared to meet challenges such as land use and climate change, disease outbreaks, and invasive species spread. This can be difficult, perhaps impossible, if spatially explicit wildlife data are not available. Low-resolution areal counts, however, are common in wildlife monitoring, that is, the number of animals reported for a region, usually corresponding to administrative subdivisions, for example, region, province, county, departments, or cantons. Bayesian areal disaggregation regression is a solution to exploit areal counts and provide conservation biologists with high-resolution species distribution predictive models. This method originated in epidemiology but lacks experimentation in ecology. It provides a plethora of applications to change the way we collect and analyze data for wildlife populations. Based on high-resolution environmental rasters, the disaggregation method disaggregates the number of individuals observed in a region and distributes them at the pixel level (e.g., 5 × 5 km or finer resolution), thereby converting low-resolution data into a high-resolution distribution and indices of relative density. In our demonstrative study, we disaggregated areal count data from hunting bag returns to disentangle the changing distribution and population dynamics of three deer species (red, sika, and fallow) in Ireland from 2000 to 2018. We show an application of the Bayesian areal disaggregation regression method and document marked increases in relative population density and extensive range expansion for each of the three deer species across Ireland. We challenged our disaggregated model predictions by correlating them with independent deer surveys carried out in field sites and alternative deer distribution models built using presence-only and presence-absence data. Finding a high correlation with both independent data sets, we highlighted the ability of Bayesian areal disaggregation regression to accurately capture fine-scale spatial patterns of animal distribution. This study uncovers new scenarios for wildlife managers and conservation biologists to reliably use regional count data disregarded so far in species distribution modeling. Thus, it represents a step forward in our ability to monitor wildlife population and meet challenges in our changing world.

Lead concentrations in commercial dogfood containing pheasant in the UK

UK and EU regulators are evaluating the potential health benefits of restricting the use of lead ammunition. Little information is available on exposure of pets to ammunition-derived dietary lead from petfood containing meat from wild-shot game animals. We found dogfood including wild-shot pheasant meat to be widely available in the UK. 77% of samples from three raw pheasant dogfood products exceeded the EU maximum residue level (MRL) for lead in animal feed, with mean concentrations approximately 245, 135 and 49 times above the MRL. Concentrations > MRL were also found in a dried food containing pheasant, but not in a processed food, nor in chicken-based products. Lead concentrations in raw pheasant dogfood considerably exceeded those in pheasant meat sold for human consumption, possibly because the dogfood mincing process further fragmented lead particles from shot. Dogs frequently consuming such high-lead food risk adverse health effects; this should be considered within decision-making processes about regulation.

Large-scale correlations between gamebird release and management and animal biodiversity metrics in lowland Great Britain

The ecological effects on populations of non-game species driven by the annual release and management of tens of millions of gamebirds for recreational shooting are complex and relatively poorly understood. We investigated these effects at a national scale, considering multiple taxa simultaneously. We used records from the UK National Biodiversity Network Atlas to compare animal species and diversity metrics previously suggested to be affected by behaviors of the released birds, or because resources or habitats are influenced by game management or both processes. We contrasted records from 1 km grid squares where gamebirds were reported released in Great Britain, and control squares with similar land cover but where no releases were reported. There were more records overall reported from release grid squares (RGS) compared with controls (CGS), perhaps due to greater reporting effort or greater biological richness. We found fewer foxes in RGS and fewest in grid squares with largest releases, but more carrion crows in RGS. We found no consistent effects for buzzards, ravens, jays, or magpies. There were more rodents and gray squirrels reported from RGS but no differences for reptiles. There were more butterflies but fewer beetles reported from RGS but no consistent patterns for Orthoptera or ground beetles considered common gamebird prey. Farmland and woodland birds exhibited higher abundance, richness, and diversity in RGS when considering absolute records, but woodland bird abundance and richness were lower when correcting for the relative number of records. These nationwide results, despite crude data resolution, reveal diverse effects of gamebird release and management at a national scale and across trophic levels, increasing some non-game animal populations while decreasing others. This should alert practitioners, opponents, and legislators that a focus on single taxa effects, either positive or negative, may obscure the simultaneous changes in other taxa.

β-Lactam resistance genes present in UK pheasants and red-legged partridges

BACKGROUND

Despite considerable recent reductions in antimicrobial use, the UK gamebird industry continues to struggle with production diseases during the rearing season, necessitating significant antibiotic use. This observational study investigated the presence of genes conferring resistance to β-lactam antibiotics within industry-reared pheasants and red-legged partridges in the UK.

METHODS

DNA was extracted from 60 pooled caecal samples collected from gamebirds at routine postmortem examinations during the rearing season. Genes encoding extended-spectrum β-lactamases (ESBL) were detected by PCR and the corresponding alleles were determined.

RESULTS

Over half (53%) of the samples harboured genes encoding blaTEM resistance, with blaSHV identified in 20% of samples. The blaTEM gene was more common on sites with higher antibiotic use, whereas blaSHV was predominantly found in birds younger than 5 weeks. Genotyping of the identified resistance genes revealed the presence of blaTEM-1 , blaSHV-1 and blaSHV-11 alleles.

LIMITATIONS

This was a small-scale study conducted at four sites in southern England.

CONCLUSION

This is the first report of the presence of ESBL genes in gamebirds, highlighting the need for further research into antimicrobial resistance in UK gamebirds.

Spatial and temporal heterogeneity of the density of Borrelia burgdorferi-infected Ixodes ricinus ticks across a landscape: A 5-year study in southern England

The density of Borrelia burgdorferi-infected Ixodes ricinus nymphs (DIN) was investigated during 2013-2017 across a Lyme disease-endemic landscape in southern England. The density of nymphs (DON), nymph infection prevalence (NIP), and DIN varied across five different natural habitats, with the highest DIN in woodland edge and high biodiversity woodlands. DIN was significantly lower in scrub grassland compared to the woodland edge, with low DON and no evidence of infection in ticks in non-scrub grassland. Over the 5 years, DON, NIP and DIN were comparable within habitats, except in 2014, with NIP varying three-fold and DIN significantly lower compared to 2015-2017. Borrelia garinii was most common, with bird-associated Borrelia (B. garinii/valaisiana) accounting for ~70% of all typed sequences. Borrelia burgdorferi sensu stricto was more common than B. afzelii. Borrelia afzelii was more common in scrub grassland than woodland and absent in some years. The possible impact of scrub on grazed grassland, management of ecotonal woodland margins with public access, and the possible role of birds/gamebirds impacting NIP are discussed. Mean NIP was 7.6%, highlighting the potential risk posed by B. burgdorferi in this endemic area. There is a need for continued research to understand its complex ecology and identify strategies for minimizing risk to public health, through habitat/game management and public awareness.

Highest densities of mountain hares (Lepus timidus) associated with ecologically restored bog but not grouse moorland management

Over the last 20 years, ecological restoration of degraded habitats has become common in conservation practice. Mountain hares (Lepus timidus scoticus) were surveyed during 2017-2021 using 830 km of line transects in the Peak District National Park, England. Historically degraded bog areas were previously reported having low hare numbers. Following bog restoration, we found hare densities of 32.6 individuals km-2, notably higher than neighboring degraded (unrestored) bog with 24.4 hares km-2. Hare density on restored peatland was 2.7 times higher than on bogs managed for grouse shooting at 12.2 hares km-2 and 3.3 times higher than on heather moorland managed for grouse shooting at 10.0 hares km-2. Yearly estimates varied most on habitats managed for grouse, perhaps indicative of the impact of habitat management, for example, heather burning and/or possible hare culling to control potential tick-borne louping ill virus in gamebirds. Acid grassland used for sheep farming had a similar density to grouse moorland at 11.8 hares km-2. Unmanaged dwarf shrub heath had the lowest density at 4.8 hares km-2. Hare populations are characterized by significant yearly fluctuations, those in the study area increasing by 60% between 2017 and 2018 before declining by ca. 15% by 2020 and remaining stable to 2021. During an earlier survey in 2002, total abundance throughout the Peak District National Park was estimated at 3361 (95% CI: 2431-4612) hares. The present study estimated 3562 (2291-5624) hares suggesting a stable population over the last two decades despite fluctuations likely influenced by weather and anthropogenic factors. Mountain hares in the Peak District favored bog habitats and were associated with restored peatland habitat. Wildlife management should be cognizant of hare density variation between habitats, which may have implications for local extinction risk.

Successful Deer Management in Scotland Requires Less Conflict Not More

What would successful deer management look like in Scotland? To some, flourishing populations of native wild deer represent success. But to others, negative impacts such as damage to woodlands and peatlands, agricultural and forestry losses, deer-vehicle collisions, and facilitating Lyme disease spread represent failure. Conflicting interests and incentives among people involved in deer management mean a common definition of success, and therefore clear management targets, remain elusive. While some environmental groups urgently call for an increase in the number of deer culled (shot) each year, other stakeholders aim to maximize deer numbers. Overcoming this governance failure will require clearly articulated, scientifically valid, and socially acceptable socio-ecological objectives to be co-produced by a broad range of stakeholders. Systematic monitoring of deer impacts will also be needed to evaluate the ability of specific management interventions to achieve defined objectives. Reintroducing Eurasian lynx (Lynx lynx) has been suggested as a means to reduce deer numbers and their negative ecological and socioeconomic impacts. However, evidence of lynx impacts on deer numbers, deer impacts, and social conflicts over deer suggest lynx reintroduction alone would not effectively reduce negative impacts of deer in Scotland, though it could be part of a broader solution. In the short-term, achieving sustainable numbers of deer in Scotland will require a substantial increase in the number of deer culled and effective changes to the way deer management is incentivized, regulated, implemented, and monitored.

How many gamebirds are released in the UK each year?

Large numbers of gamebirds (pheasants Phasianus colchicus, red-legged partridges Alectoris rufa and mallard Anus platyrhynchos) are released annually in the UK to support recreational shooting. It is important to know how many of these birds are being released because their release and management has ecological effects on the wildlife and habitats of the UK. There is little regulation governing their release, and consequently, an accurate figure for the numbers being released is unknown. I took 12 different approaches, totalling 4329 estimates of the numbers of birds being released annually, based on a series of datasets that described numbers of birds being held for breeding, rearing or release, being released, managed or shot on game shoots, being shot by individual guns or being recorded during breeding bird surveys. These 12 approaches produced estimates ranging from 14.7 to 106.1 million with a mean of 43.2 million (95% CI 29.0–57.3 million). This suggests that 31.5 million pheasants (range 29.8–33.7 million), 9.1 million red-legged partridges (range 5.6–12.5 million) and 2.6 million mallard (range 0.9–6.0 million) are released annually in the UK. These figures differ substantially from both official records of gamebirds and previous published estimates, and I discuss why such differences may occur. I set these figures in the context of the number and behaviour of shoots operating in the UK. Improved estimates of numbers of gamebird being released are critical if we are to better understand the ecological effects occurring in areas where they are released and managed.

Contribution of non-native galliforms to annual variation in biomass of British birds

Millions of individuals of two species of non-native galliform birds, the Common Pheasant (Phasianus colchicus) and Red-legged Partridge (Alectoris rufa) are released into the British countryside annually in late summer, supplementing established breeding populations of these two species. The biomass of birds involved in these releases has been compared to the British breeding bird biomass. However, the validity of this comparison is compromised because the biomass of wild birds varies across the year due to reproduction, mortality and migration. How the biomass of Common Pheasants and Red-legged Partridges compares to that of other British bird species in late summer, or across the whole year, is currently unknown. Here, we produce estimates of how British bird biomass varies across the year, to assess the contribution of the two non-native galliforms to this variation. We show that overall British bird biomass is probably lowest around the start of the breeding season in April, and peaks in late summer and autumn. We estimate that around a quarter of British bird biomass annually is contributed by Common Pheasants and Red-legged Partridges, and that at their peak in August these two species represent about half of all wild bird biomass in Britain.

Estimating hunting harvest from partial reporting: a Bayesian approach

Quantifying hunting harvest is essential for numerous ecological topics, necessitating reliable estimates. We here propose novel analytical tools for this purpose. Using a hierarchical Bayesian framework, we introduce models for hunting reports that accounts for different structures of the data. Focusing on Swedish harvest reports of red fox (Vulpes vulpes), wild boar (Sus scrofa), European pine marten (Martes martes), and Eurasian beaver (Castor fiber), we evaluated predictive performance through training and validation sets as well as Leave One Out Cross Validation. The analyses revealed that to provide reliable harvest estimates, analyses must account for both random variability among hunting teams and the effect of hunting area per team on the harvest rate. Disregarding the former underestimated the uncertainty, especially at finer spatial resolutions (county and hunting management precincts). Disregarding the latter imposed a bias that overestimated total harvest. We also found support for association between average harvest rate and variability, yet the direction of the association varied among species. However, this feature proved less important for predictive purposes. Importantly, the hierarchical Bayesian framework improved previously used point estimates by reducing sensitivity to low reporting and presenting inherent uncertainties.

High prevalence of the neonicotinoid clothianidin in liver and plasma samples collected from gamebirds during autumn sowing

Since neonicotinoid insecticides were introduced to the agricultural market, evidence of the negative impacts of these systemic compounds on non-target species has accumulated. Birds are one of the largest groups of species to inhabit farmland, but the extent of neonicotinoid exposure in avian communities is poorly understood and very little is known about how any exposure may affect wild birds. Here, free-living gamebirds were used as a model group to measure the extent of avian exposure to the neonicotinoid clothianidin via seed treatment. During a typical sowing period of winter cereals treated with clothianidin, blood and liver samples were collected simultaneously from individual hunted gamebird carcasses, both pre- (n = 18) and post-sowing (n = 57) and were analysed for clothianidin via LC/MS-MS. Body weight, fat score and faecal parasite load were also quantified in the birds to ascertain whether any of these health parameters were associated with clothianidin exposure under field conditions. Clothianidin was detected in 6% of individuals sampled pre-sowing and 89% of individuals sampled post-sowing. The frequency of clothianidin detection in plasma samples and the concentration of clothianidin in liver and plasma samples decreased significantly between the first week and 2-4 weeks post-sowing. Faecal parasite load was positively associated with concentrations of clothianidin in the liver (but not plasma) of partridge species, but there was no association between clothianidin concentration and fat score or body weight, for either sample type. This study provides clear evidence that treated seed is a source of pesticide exposure for gamebirds following autumn sowing. These findings have implications for gamebirds worldwide where seed treatments are in use, and will aid the design of any future avian biomonitoring studies for agrochemical compounds.

Moose Management Strategies under Changing Legal and Institutional Frameworks

Moose (Alces alces) management strategies in Lithuania, East Europe, were analyzed. The study was intended to show the (un)sustainability of the current management approach in relation to changes in hunting rules, hunting organization and development of the responsible administrative bodies. Moose population and bag dynamics were analyzed using I index in connected scatterplots and compound annual growth rates (CAGR). In 1962–2020, the CAGR of the moose population was 3.84%, resulting in a population size increase of nearly 10 times. The seesaw principle in moose management was confirmed, showing three periods of population decrease (1973–1977, 1989–1995, 2000–2005), and two periods of hunting bag decrease (1976–1978 and 1990–1993). All decline phases were related to legal and administrative issues in the country. Since 2006, population growth has not been controlled. Lithuania has no long-term strategy of the moose population management at any administrative level. The current management approach is not sustainable, as it has not ensured long-term stability of the moose population. The current continuous growth of population, followed by only a moderate increase in the hunting bag, is related to the possibility for owners to adopt long-term planning of the hunting plot units.

Diets of European polecat Mustela putorius in Great Britain during fifty years of population recovery

Following nineteenth-century declines, polecats Mustela putorius are recolonising Great Britain. Polecat diet relates to two potential risks to recovery. First, rabbits Oryctolagus cuniculus, which are important prey for polecats, have experienced extreme population fluctuations, with near extirpation due to myxomatosis in the 1950s, recovery in 1960s–1990s and declines in 1990s–2010s. Second, polecats are secondarily exposed to anticoagulant rodenticides by eating contaminated rodents, and the frequency of polecat exposure to rodenticides is increasing. We analysed stomach contents from 99 polecats collected in 2012–2016 and compared results with earlier studies. Lagomorphs were the most abundant prey (66% frequency of occurrence, 95% confidence interval 53–74%), followed by other mammals (12%, 4–18%), amphibians (10%, 3–16%) and birds (7%, 1–13%). Diet varied seasonally; lagomorph occurrence was highest in spring and summer and lowest in autumn. Dietary niche breadth was greater in the 1960s, when rabbits were scarce, than in other decades, but did not differ between the 1990s and 2010s, indicating that diets have not diversified with recent rabbit declines. This may be because rabbit abundance is not yet low enough to cause dietary diversification or because polecats were collected in areas where rabbits were still abundant. Rodents did not increase in diet between the 1990s and 2010s and still occur with < 10% frequency, indicating that rodents need not contribute much to diet to expose polecats to rodenticides. This potentially limits the effectiveness of management actions designed to minimise polecat exposure to contaminated rodent prey.