This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Between 1988 and 2006, a total of 5,110 Whooper Swans Cygnus cygnus were caught and marked with p... more Between 1988 and 2006, a total of 5,110 Whooper Swans Cygnus cygnus were caught and marked with plastic leg-rings in four geographically discrete parts of Iceland. Of these, 53.6% were subsequently sighted at wintering sites, mainly in Britain and Ireland but with small numbers seen wintering in Iceland and elsewhere in Europe. Overall, the swans migrated on a broad front, had a predominantly northerly distribution in Britain and were widespread throughout many areas of Ireland, particularly in a belt stretching from the northeast to the southwest. Birds were distributed rather more evenly throughout Scotland. In England/Wales they were concentrated at relatively few sites, notably the Ouse Washes, Norfolk and Martin Mere/Ribble Estuary, Lancashire. Birds ringed in the more western parts of Iceland (in Skagafjör\ur) concentrated largely in more western parts of the wintering range (Ireland), whereas those ringed in east Iceland (Nor\ur-Múlasýsla) were more likely to occur in Scotland and in continental Europe. An overall southerly shift in distribution as the winter progressed was also detected.
Many species of large herbivore rely on agricultural land for their feeding habitats, but availab... more Many species of large herbivore rely on agricultural land for their feeding habitats, but available food resources are highly variable in space and time. The conservation and management of farmland-dependent herbivores would therefore benefit from predictions about how species will respond to changes in their environment. We developed an individualbased model (IBM) to provide such predictions for three overwintering avian herbivore Our findings suggest that the recent c.40% decline in Bewick's Swan numbers was unlikely to be linked to changes in winter food resources or competition.
A Microsoft Excel spreadsheet containing the raw and standardized values for all variables used i... more A Microsoft Excel spreadsheet containing the raw and standardized values for all variables used in the analysis of Bewick's Swan breeding success. The data cover the period 1988-2013. A legend describing the identity of each variable is also included. Further information on the data analysis is available in the published paper
Population declines among migratory Arctic-breeding birds are a growing concern for conservationi... more Population declines among migratory Arctic-breeding birds are a growing concern for conservationists. To inform the conservation of these declining populations, we need to understand how demographic rates such as breeding success are influenced by combinations of extrinsic and intrinsic factors. In this study we examined inter-annual variation and long-term trends in two aspects of the breeding success of a migratory herbivore, the Bewick's swan Cygnus columbianus bewickii, which is currently undergoing a population decline: 1) the percentage of young within the wintering population and 2) mean brood size. We used an information-theoretic approach to test how these two measures of productivity were influenced over a 26 yr period by 12 potential explanatory variables, encompassing both environmental (e.g. temperature) and intrinsic (e.g. pair-bond duration) factors. Swan productivity exhibited sensitivity to both types of explanatory variable. Fewer young were observed on the wintering grounds in years in which the breeding period (May to September) was colder and predator (Arctic fox) abundance was higher. The percentage of young within the wintering population also showed negative density-dependence. Inter-annual variance in mean swan brood size was best explained by a model comprised of the negative degree days during the swan breeding period, mean pair-bond duration of all paired swans (i.e. mean pair duration), and an interaction between these two variables. In particular, mean pair duration had a strong positive effect on mean brood size. However, we found no long-term directional trend in either measure of breeding success, despite the recent decline in the NW European population. Our results highlight that inter-annual variability in breeding success is sensitive to the combined effects of both intrinsic and extrinsic factors
Illegal killing of wildlife is a major conservation issue that, to be addressed effectively, requ... more Illegal killing of wildlife is a major conservation issue that, to be addressed effectively, requires insight into the drivers of human behaviour. Here we adapt an established socio-psychological model, the theory of planned behaviour, to explore reasons for hunting the Endangered Bewick's swan Cygnus columbianus bewickii in the European Russian Arctic, using responses from hunters to a questionnaire survey. Wider ecological, legal, recreational and economic motivations were also explored. Of 236 hunters who participated overall, 14% harboured intentions to hunt Bewick's swan. Behavioural intention was predicted by all components of the theory of planned behaviour, specifically: hunters' attitude towards the behaviour, perceived behavioural control (i.e. perceived capability of being able to perform the behaviour) and their subjective norms (perception of social expectations). The inclusion of attitude towards protective laws and descriptive norm (perception of whether o...
The shift from a ‘reader pays’ to an ‘author pays’ model of scientific publishing presents a fina... more The shift from a ‘reader pays’ to an ‘author pays’ model of scientific publishing presents a financial threat to environmental nongovernmental organizations (eNGOs). Many of these support, conduct and publish applied research on real-world solutions to the planet’s most pressing challenges. Funded mainly by donations, eNGOs must now choose between taking conservation action and publishing more research papers. A more equitable publishing system is needed. Platinum and diamond open access (see L. Barnes Open Book Publishers https://doi.org/g3tb; 2018), financed by a third party such as a scientific society, avoid article-processing charges (APCs) for authors and paywalls for readers, and can offer the lowest-cost option for eNGOs. Alternatively, journals could offer APC waivers for authors at eNGOs. Discussions at this year’s United Nations biodiversity conference (COP15) and climate-change conference (COP26) are informed by eNGO research. Mandatory APCs risk pricing eNGOs out of scientific publishing at a time when their research output is most urgently needed.
Background Winter numbers of the northwest European population of Bewick’s Swans (Cygnus columbia... more Background Winter numbers of the northwest European population of Bewick’s Swans (Cygnus columbianus bewickii) declined recently by c. 40%. During the same period, numbers of two sympatric and ecologically-similar congeners, the Mute Swan (Cygnus olor) and Whooper Swan (Cygnus cygnus) showed increases or stability. It has been suggested that these opposing population trends could have a causal relationship, as Mute and Whooper Swans are larger and competitively dominant to Bewick’s Swans in foraging situations. If so, effects of competition of Mute and Whooper Swans on Bewick’s Swans should be detectable as measurable impacts on behaviour and energetics. Methods Here, we studied the diurnal behaviour and energetics of 1083 focal adults and first-winter juveniles (“cygnets”) of the three swan species on their winter grounds in eastern England. We analysed video recordings to derive time-activity budgets and these, together with estimates of energy gain and expenditure, were analysed ...
Our understanding of how energy shapes animal behavioural decisions has been limited by the diffi... more Our understanding of how energy shapes animal behavioural decisions has been limited by the difficulty of measuring directly the energy gain and expenditure in free-living animals. Mechanistic models that simulate energy gain and expenditure from estimable parameters can overcome these limitations and hence could help scientists to gain a predictive understanding of animal behaviour. Such models could be used to test mechanistic explanations of observed patterns of resource use within a landscape, such as behavioural decisions to switch among food resources. Here, we developed mechanistic models of the instantaneous and daily rates of net energy gain for two species of migratory swans, the Bewick's swan (Cygnus columbianus bewickii) and whooper swan (Cygnus cygnus), that feed on root and cereal crops within an agricultural landscape in eastern England. Field data show that both species shift from using predominantly root crops (e.g. sugar beet and potatoes) in early winter to using mostly cereals (e.g. wheat) in late winter. Our models correspondingly predicted that swans could achieve the greatest rates of net energy gain on root crops in early winter and on cereal crops in late winter. The change from root crops to cereal crops providing the greatest net rates of energy gain was predicted to occur at the same time as the birds' switch from feeding predominantly on root crops to predominantly cereal crops (between December and January). We used Monte Carlo simulations to account for variance in model parameters on predictions of energy gain and profitability. A sensitivity analysis indicated that predictions of net energy gain were most sensitive to variance in the intake rate and food quantity parameters. The agreement between our model estimates of energy gain and the observed shifts in resource use observed among the overwintering swans suggests that maximising net rates of energy gain is an important resource selection strategy among overwintering birds. A mechanistic understanding of where and when birds will use food resources can inform the conservation management of key feeding areas for species of conservation concern, as well as the deployment of crop protection strategies.
If the multiple negative health impacts associated with lead ammunition are to be mitigated, a tr... more If the multiple negative health impacts associated with lead ammunition are to be mitigated, a transition to the non-toxic alternatives is needed. This paper aims to map out the pathways to such a transition via a modification of Kotter's eight step theory of change, identifying key stakeholders, exploring options for those of us advocating change and the relationships between policy and persuasion. The focus is primarily on the UK, but it is of direct relevance to the rest of Europe and beyond. The theory of change model involves (1) creating urgency, (2) building coalitions, (3) creating a vision for change, (4) communicating that vision, (5) removing barriers to enable action, (6) creating short-term or geospatial wins, (7) building on the change and (8) embedding change in culture and regulation. The paper reflects on good progress to date in initial steps, but throughout subsequent steps creative engagement and other disciplines which appreciate the human dimensions such as mediation and psychology of behaviour change have been lacking. Although significant barriers remain for Step 5, the paper identifies the central vision of sustainability of hunting as a shared value around which most stakeholders can engage. The paper concludes that, given the growing momentum surrounding this issue in recent years, the phasing out of lead ammunition is at a tipping point.
Legal regulation of human activities is a key mechanism for alleviating anthropogenic impacts on ... more Legal regulation of human activities is a key mechanism for alleviating anthropogenic impacts on wildlife populations. Conservationists frequently request the regulation of toxic substances such as lead, which can be harmful to animals even at low levels of exposure. However, without assessments of the effectiveness of legislation, such regulations may be undermined or revoked and opportunities to make amendments to improve the legislation may be missed. Here we carried out a population-level study of the effectiveness of regulating the use of lead. We show that the increase in population size of a charismatic waterbird (the mute swan Cygnus olor) in Great Britain over 39 years was best explained by the regulation of lead fishing weights, rather than by changes in food supplies, habitat quality, or winter temperature. The proportion of individuals dying of lead poisoning dropped following regulation, from 0.34 to 0.06, suggesting that higher survival rates were the demographic driver of increased population size. Legal restriction therefore succeeded in alleviating, although not eliminating, the impact of poisoning on mute swans. Restrictions on the use of toxic substances, and their release into the environment, would provide an effective conservation mechanism for reducing negative effects of human activities on wildlife populations. At a time when many policy makers prefer to rely on voluntary actions or market forces to achieve change, our study highlights that legal regulations on human activities can be an effective means of alleviating anthropogenic impacts on wildlife.
SummaryThe north-west European population of Bewick’s Swan Cygnus columbianus bewickii declined b... more SummaryThe north-west European population of Bewick’s Swan Cygnus columbianus bewickii declined by 38% between 1995 and 2010 and is listed as ‘Endangered’ on the European Red List of birds. Here, we combined information on food resources within the landscape with long-term data on swan numbers, habitat use, behaviour and two complementary measures of body condition, to examine whether changes in food type and availability have influenced the Bewick’s Swan’s use of their main wintering site in the UK, the Ouse Washes and surrounding fens. Maximum number of Bewick’s Swans rose from 620 in winter 1958/59 to a high of 7,491 in winter 2004/05, before falling to 1,073 birds in winter 2013/14. Between winters 1958/59 and 2014/15 the Ouse Washes supported between 0.5 and 37.9 % of the total population wintering in north-west Europe (mean ± 95 % CI = 18.1 ± 2.4 %). Swans fed on agricultural crops, shifting from post-harvest remains of root crops (e.g. sugar beet and potatoes) in November and...
The northwest European population of Bewick's Swan Cygnus columbianus bewickii declined by 38% be... more The northwest European population of Bewick's Swan Cygnus columbianus bewickii declined by 38% between 1995 and 2010 and is listed as 'Endangered' on the European Red List of birds. Here, we combined information on food resources within the landscape with long-term data on swan numbers, habitat use, behaviour and two complementary measures of body condition, to examine whether changes in food type and availability have influenced the Bewick's Swan's use of their main wintering site in the UK, the Ouse Washes and surrounding fens. Maximum number of Bewick's Swans rose from 620 in winter 1958/59 to a high of 7,491 in winter 2004/05, before falling to 1,073 birds in winter 2013/14. Between winters 1958/59 and 2014/15 the Ouse Washes supported between 0.5 and 37.9 % of the total population wintering in northwest Europe (mean ± 95 % CI = 18.1 ± 2.4 %). Swans fed on agricultural crops, shifting from post-harvest remains of root crops (e.g. sugar beet and potatoes) in November and December to winter-sown cereals (e.g. wheat) in January and February. Inter-annual variation in the area cultivated for these crops did not result in changes in the peak numbers of swans occurring on the Ouse Washes. Behavioural and body condition data indicated that food supplies on the Ouse Washes and surrounding fens remain adequate to allow the birds to gain and maintain good body condition throughout winter with no increase in foraging effort. Our findings suggest that the recent decline in numbers of Bewick's Swans at this internationally important site was not linked to inadequate food resources.
Following increases in numbers during the second half of the 20th century, several Arcticbreeding... more Following increases in numbers during the second half of the 20th century, several Arcticbreeding migrant bird species are now undergoing sustained population declines. These include the northwest European population of Bewick's Swan Cygnus columbianus bewickii, which declined from c. 29 000 birds on the wintering grounds in 1995 to 18 000 in 2010. It is unclear whether this decrease reflects reduced survival, emigration to a different area, or a combination of both. Furthermore, the environmental drivers of any demographic changes are also unknown. We therefore used an information-theoretic approach in RMark to analyse a data set of 3929 individually marked and resighted Bewick's Swans to assess temporal trends and drivers of survival between winters 1970/71 and 2014/2015, while accounting for effects of age, sex and different marker types. The temporal trend in apparent survival rates over our study period was best explained by different survival rates for each decade, with geometric mean survival rates highest in the 1980s (leg ring marked birds = 0.853, 95% confidence interval (CI) = 0.830-0.873) and lowest in the 2010s (leg ring = 0.773, CI = 0.738-0.805; neck-collar = 0.725, CI = 0.681-0.764). Mean (± 95% CI) resighting probabilities over the study period were higher for birds marked with neck-collars (0.91 ± 0.01) than for those marked with leg-rings (0.70 ± 0.02). Weather conditions in different areas across the flyway, Accepted Article This article is protected by copyright. All rights reserved. food resources on the winter grounds, density-dependence and the growth of numbers at a relatively new wintering site (the Evros Delta in Greece) all performed poorly as explanatory variables of apparent survival. None of our 18 covariates accounted for more than 7.2% of the deviance associated with our survival models, with a mean of only 2.2% of deviance explained. Our results provide long-term demographic information needed to help conservationists understand the population dynamics of Bewick's Swans in northwest Europe.
Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity... more Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity and mortality in waterbirds globally, but the thresholds at which blood levels begin to affect the physiology of birds in the wild are less well known. Here we determine the prevalence of lead exposure in whooper swans and, for the first time, identify the level of blood lead associated with initial reductions in body condition. Blood lead elevated above background levels (i.e. >20 μg dL(-1)) was found in 41.7% (125/300) of swans tested. Blood lead was significantly negatively associated with winter body condition when levels were ≥44 μg dL(-1) (27/260 = 10%). Our findings indicating that sub-lethal impacts of lead on body condition occur at the lower end of previously established clinical thresholds and that a relatively high proportion of individuals in this population may be affected, reaffirm the importance of reducing contamination of the environment with lead shot.
Population declines among migratory Arctic-breeding birds are a growing concern for conservationi... more Population declines among migratory Arctic-breeding birds are a growing concern for conservationists. To inform the conservation of these declining populations, we need to understand how demographic rates such as breeding success are infl uenced by combinations of extrinsic and intrinsic factors. In this study we examined inter-annual variation and long-term trends in two aspects of the breeding success of a migratory herbivore, the Bewick ' s swan Cygnus columbianus bewickii , which is currently undergoing a population decline: 1) the percentage of young within the wintering population and 2) mean brood size. We used an information-theoretic approach to test how these two measures of productivity were infl uenced over a 26 yr period by 12 potential explanatory variables, encompassing both environmental (e.g. temperature) and intrinsic (e.g. pair-bond duration) factors. Swan productivity exhibited sensitivity to both types of explanatory variable. Fewer young were observed on the wintering grounds in years in which the breeding period (May to September) was colder and predator (Arctic fox) abundance was higher. Th e percentage of young within the wintering population also showed negative density-dependence. Inter-annual variance in mean swan brood size was best explained by a model comprised of the negative degree days during the swan breeding period, mean pair-bond duration of all paired swans (i.e. mean pair duration), and an interaction between these two variables. In particular, mean pair duration had a strong positive eff ect on mean brood size. However, we found no long-term directional trend in either measure of breeding success, despite the recent decline in the NW European population. Our results highlight that inter-annual variability in breeding success is sensitive to the combined eff ects of both intrinsic and extrinsic factors.
This Manual is intended to provide the reader with an overview of the principles and practicaliti... more This Manual is intended to provide the reader with an overview of the principles and practicalities of managing animal diseases at wetland sites. The Manual highlights the importance of including disease prevention and control in wetland management plans and provides guidelines on how to do so. It should be used in conjunction with Ramsar Handbook No. 18 on Managing Wetlands.
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Between 1988 and 2006, a total of 5,110 Whooper Swans Cygnus cygnus were caught and marked with p... more Between 1988 and 2006, a total of 5,110 Whooper Swans Cygnus cygnus were caught and marked with plastic leg-rings in four geographically discrete parts of Iceland. Of these, 53.6% were subsequently sighted at wintering sites, mainly in Britain and Ireland but with small numbers seen wintering in Iceland and elsewhere in Europe. Overall, the swans migrated on a broad front, had a predominantly northerly distribution in Britain and were widespread throughout many areas of Ireland, particularly in a belt stretching from the northeast to the southwest. Birds were distributed rather more evenly throughout Scotland. In England/Wales they were concentrated at relatively few sites, notably the Ouse Washes, Norfolk and Martin Mere/Ribble Estuary, Lancashire. Birds ringed in the more western parts of Iceland (in Skagafjör\ur) concentrated largely in more western parts of the wintering range (Ireland), whereas those ringed in east Iceland (Nor\ur-Múlasýsla) were more likely to occur in Scotland and in continental Europe. An overall southerly shift in distribution as the winter progressed was also detected.
Many species of large herbivore rely on agricultural land for their feeding habitats, but availab... more Many species of large herbivore rely on agricultural land for their feeding habitats, but available food resources are highly variable in space and time. The conservation and management of farmland-dependent herbivores would therefore benefit from predictions about how species will respond to changes in their environment. We developed an individualbased model (IBM) to provide such predictions for three overwintering avian herbivore Our findings suggest that the recent c.40% decline in Bewick's Swan numbers was unlikely to be linked to changes in winter food resources or competition.
A Microsoft Excel spreadsheet containing the raw and standardized values for all variables used i... more A Microsoft Excel spreadsheet containing the raw and standardized values for all variables used in the analysis of Bewick's Swan breeding success. The data cover the period 1988-2013. A legend describing the identity of each variable is also included. Further information on the data analysis is available in the published paper
Population declines among migratory Arctic-breeding birds are a growing concern for conservationi... more Population declines among migratory Arctic-breeding birds are a growing concern for conservationists. To inform the conservation of these declining populations, we need to understand how demographic rates such as breeding success are influenced by combinations of extrinsic and intrinsic factors. In this study we examined inter-annual variation and long-term trends in two aspects of the breeding success of a migratory herbivore, the Bewick's swan Cygnus columbianus bewickii, which is currently undergoing a population decline: 1) the percentage of young within the wintering population and 2) mean brood size. We used an information-theoretic approach to test how these two measures of productivity were influenced over a 26 yr period by 12 potential explanatory variables, encompassing both environmental (e.g. temperature) and intrinsic (e.g. pair-bond duration) factors. Swan productivity exhibited sensitivity to both types of explanatory variable. Fewer young were observed on the wintering grounds in years in which the breeding period (May to September) was colder and predator (Arctic fox) abundance was higher. The percentage of young within the wintering population also showed negative density-dependence. Inter-annual variance in mean swan brood size was best explained by a model comprised of the negative degree days during the swan breeding period, mean pair-bond duration of all paired swans (i.e. mean pair duration), and an interaction between these two variables. In particular, mean pair duration had a strong positive effect on mean brood size. However, we found no long-term directional trend in either measure of breeding success, despite the recent decline in the NW European population. Our results highlight that inter-annual variability in breeding success is sensitive to the combined effects of both intrinsic and extrinsic factors
Illegal killing of wildlife is a major conservation issue that, to be addressed effectively, requ... more Illegal killing of wildlife is a major conservation issue that, to be addressed effectively, requires insight into the drivers of human behaviour. Here we adapt an established socio-psychological model, the theory of planned behaviour, to explore reasons for hunting the Endangered Bewick's swan Cygnus columbianus bewickii in the European Russian Arctic, using responses from hunters to a questionnaire survey. Wider ecological, legal, recreational and economic motivations were also explored. Of 236 hunters who participated overall, 14% harboured intentions to hunt Bewick's swan. Behavioural intention was predicted by all components of the theory of planned behaviour, specifically: hunters' attitude towards the behaviour, perceived behavioural control (i.e. perceived capability of being able to perform the behaviour) and their subjective norms (perception of social expectations). The inclusion of attitude towards protective laws and descriptive norm (perception of whether o...
The shift from a ‘reader pays’ to an ‘author pays’ model of scientific publishing presents a fina... more The shift from a ‘reader pays’ to an ‘author pays’ model of scientific publishing presents a financial threat to environmental nongovernmental organizations (eNGOs). Many of these support, conduct and publish applied research on real-world solutions to the planet’s most pressing challenges. Funded mainly by donations, eNGOs must now choose between taking conservation action and publishing more research papers. A more equitable publishing system is needed. Platinum and diamond open access (see L. Barnes Open Book Publishers https://doi.org/g3tb; 2018), financed by a third party such as a scientific society, avoid article-processing charges (APCs) for authors and paywalls for readers, and can offer the lowest-cost option for eNGOs. Alternatively, journals could offer APC waivers for authors at eNGOs. Discussions at this year’s United Nations biodiversity conference (COP15) and climate-change conference (COP26) are informed by eNGO research. Mandatory APCs risk pricing eNGOs out of scientific publishing at a time when their research output is most urgently needed.
Background Winter numbers of the northwest European population of Bewick’s Swans (Cygnus columbia... more Background Winter numbers of the northwest European population of Bewick’s Swans (Cygnus columbianus bewickii) declined recently by c. 40%. During the same period, numbers of two sympatric and ecologically-similar congeners, the Mute Swan (Cygnus olor) and Whooper Swan (Cygnus cygnus) showed increases or stability. It has been suggested that these opposing population trends could have a causal relationship, as Mute and Whooper Swans are larger and competitively dominant to Bewick’s Swans in foraging situations. If so, effects of competition of Mute and Whooper Swans on Bewick’s Swans should be detectable as measurable impacts on behaviour and energetics. Methods Here, we studied the diurnal behaviour and energetics of 1083 focal adults and first-winter juveniles (“cygnets”) of the three swan species on their winter grounds in eastern England. We analysed video recordings to derive time-activity budgets and these, together with estimates of energy gain and expenditure, were analysed ...
Our understanding of how energy shapes animal behavioural decisions has been limited by the diffi... more Our understanding of how energy shapes animal behavioural decisions has been limited by the difficulty of measuring directly the energy gain and expenditure in free-living animals. Mechanistic models that simulate energy gain and expenditure from estimable parameters can overcome these limitations and hence could help scientists to gain a predictive understanding of animal behaviour. Such models could be used to test mechanistic explanations of observed patterns of resource use within a landscape, such as behavioural decisions to switch among food resources. Here, we developed mechanistic models of the instantaneous and daily rates of net energy gain for two species of migratory swans, the Bewick's swan (Cygnus columbianus bewickii) and whooper swan (Cygnus cygnus), that feed on root and cereal crops within an agricultural landscape in eastern England. Field data show that both species shift from using predominantly root crops (e.g. sugar beet and potatoes) in early winter to using mostly cereals (e.g. wheat) in late winter. Our models correspondingly predicted that swans could achieve the greatest rates of net energy gain on root crops in early winter and on cereal crops in late winter. The change from root crops to cereal crops providing the greatest net rates of energy gain was predicted to occur at the same time as the birds' switch from feeding predominantly on root crops to predominantly cereal crops (between December and January). We used Monte Carlo simulations to account for variance in model parameters on predictions of energy gain and profitability. A sensitivity analysis indicated that predictions of net energy gain were most sensitive to variance in the intake rate and food quantity parameters. The agreement between our model estimates of energy gain and the observed shifts in resource use observed among the overwintering swans suggests that maximising net rates of energy gain is an important resource selection strategy among overwintering birds. A mechanistic understanding of where and when birds will use food resources can inform the conservation management of key feeding areas for species of conservation concern, as well as the deployment of crop protection strategies.
If the multiple negative health impacts associated with lead ammunition are to be mitigated, a tr... more If the multiple negative health impacts associated with lead ammunition are to be mitigated, a transition to the non-toxic alternatives is needed. This paper aims to map out the pathways to such a transition via a modification of Kotter's eight step theory of change, identifying key stakeholders, exploring options for those of us advocating change and the relationships between policy and persuasion. The focus is primarily on the UK, but it is of direct relevance to the rest of Europe and beyond. The theory of change model involves (1) creating urgency, (2) building coalitions, (3) creating a vision for change, (4) communicating that vision, (5) removing barriers to enable action, (6) creating short-term or geospatial wins, (7) building on the change and (8) embedding change in culture and regulation. The paper reflects on good progress to date in initial steps, but throughout subsequent steps creative engagement and other disciplines which appreciate the human dimensions such as mediation and psychology of behaviour change have been lacking. Although significant barriers remain for Step 5, the paper identifies the central vision of sustainability of hunting as a shared value around which most stakeholders can engage. The paper concludes that, given the growing momentum surrounding this issue in recent years, the phasing out of lead ammunition is at a tipping point.
Legal regulation of human activities is a key mechanism for alleviating anthropogenic impacts on ... more Legal regulation of human activities is a key mechanism for alleviating anthropogenic impacts on wildlife populations. Conservationists frequently request the regulation of toxic substances such as lead, which can be harmful to animals even at low levels of exposure. However, without assessments of the effectiveness of legislation, such regulations may be undermined or revoked and opportunities to make amendments to improve the legislation may be missed. Here we carried out a population-level study of the effectiveness of regulating the use of lead. We show that the increase in population size of a charismatic waterbird (the mute swan Cygnus olor) in Great Britain over 39 years was best explained by the regulation of lead fishing weights, rather than by changes in food supplies, habitat quality, or winter temperature. The proportion of individuals dying of lead poisoning dropped following regulation, from 0.34 to 0.06, suggesting that higher survival rates were the demographic driver of increased population size. Legal restriction therefore succeeded in alleviating, although not eliminating, the impact of poisoning on mute swans. Restrictions on the use of toxic substances, and their release into the environment, would provide an effective conservation mechanism for reducing negative effects of human activities on wildlife populations. At a time when many policy makers prefer to rely on voluntary actions or market forces to achieve change, our study highlights that legal regulations on human activities can be an effective means of alleviating anthropogenic impacts on wildlife.
SummaryThe north-west European population of Bewick’s Swan Cygnus columbianus bewickii declined b... more SummaryThe north-west European population of Bewick’s Swan Cygnus columbianus bewickii declined by 38% between 1995 and 2010 and is listed as ‘Endangered’ on the European Red List of birds. Here, we combined information on food resources within the landscape with long-term data on swan numbers, habitat use, behaviour and two complementary measures of body condition, to examine whether changes in food type and availability have influenced the Bewick’s Swan’s use of their main wintering site in the UK, the Ouse Washes and surrounding fens. Maximum number of Bewick’s Swans rose from 620 in winter 1958/59 to a high of 7,491 in winter 2004/05, before falling to 1,073 birds in winter 2013/14. Between winters 1958/59 and 2014/15 the Ouse Washes supported between 0.5 and 37.9 % of the total population wintering in north-west Europe (mean ± 95 % CI = 18.1 ± 2.4 %). Swans fed on agricultural crops, shifting from post-harvest remains of root crops (e.g. sugar beet and potatoes) in November and...
The northwest European population of Bewick's Swan Cygnus columbianus bewickii declined by 38% be... more The northwest European population of Bewick's Swan Cygnus columbianus bewickii declined by 38% between 1995 and 2010 and is listed as 'Endangered' on the European Red List of birds. Here, we combined information on food resources within the landscape with long-term data on swan numbers, habitat use, behaviour and two complementary measures of body condition, to examine whether changes in food type and availability have influenced the Bewick's Swan's use of their main wintering site in the UK, the Ouse Washes and surrounding fens. Maximum number of Bewick's Swans rose from 620 in winter 1958/59 to a high of 7,491 in winter 2004/05, before falling to 1,073 birds in winter 2013/14. Between winters 1958/59 and 2014/15 the Ouse Washes supported between 0.5 and 37.9 % of the total population wintering in northwest Europe (mean ± 95 % CI = 18.1 ± 2.4 %). Swans fed on agricultural crops, shifting from post-harvest remains of root crops (e.g. sugar beet and potatoes) in November and December to winter-sown cereals (e.g. wheat) in January and February. Inter-annual variation in the area cultivated for these crops did not result in changes in the peak numbers of swans occurring on the Ouse Washes. Behavioural and body condition data indicated that food supplies on the Ouse Washes and surrounding fens remain adequate to allow the birds to gain and maintain good body condition throughout winter with no increase in foraging effort. Our findings suggest that the recent decline in numbers of Bewick's Swans at this internationally important site was not linked to inadequate food resources.
Following increases in numbers during the second half of the 20th century, several Arcticbreeding... more Following increases in numbers during the second half of the 20th century, several Arcticbreeding migrant bird species are now undergoing sustained population declines. These include the northwest European population of Bewick's Swan Cygnus columbianus bewickii, which declined from c. 29 000 birds on the wintering grounds in 1995 to 18 000 in 2010. It is unclear whether this decrease reflects reduced survival, emigration to a different area, or a combination of both. Furthermore, the environmental drivers of any demographic changes are also unknown. We therefore used an information-theoretic approach in RMark to analyse a data set of 3929 individually marked and resighted Bewick's Swans to assess temporal trends and drivers of survival between winters 1970/71 and 2014/2015, while accounting for effects of age, sex and different marker types. The temporal trend in apparent survival rates over our study period was best explained by different survival rates for each decade, with geometric mean survival rates highest in the 1980s (leg ring marked birds = 0.853, 95% confidence interval (CI) = 0.830-0.873) and lowest in the 2010s (leg ring = 0.773, CI = 0.738-0.805; neck-collar = 0.725, CI = 0.681-0.764). Mean (± 95% CI) resighting probabilities over the study period were higher for birds marked with neck-collars (0.91 ± 0.01) than for those marked with leg-rings (0.70 ± 0.02). Weather conditions in different areas across the flyway, Accepted Article This article is protected by copyright. All rights reserved. food resources on the winter grounds, density-dependence and the growth of numbers at a relatively new wintering site (the Evros Delta in Greece) all performed poorly as explanatory variables of apparent survival. None of our 18 covariates accounted for more than 7.2% of the deviance associated with our survival models, with a mean of only 2.2% of deviance explained. Our results provide long-term demographic information needed to help conservationists understand the population dynamics of Bewick's Swans in northwest Europe.
Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity... more Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity and mortality in waterbirds globally, but the thresholds at which blood levels begin to affect the physiology of birds in the wild are less well known. Here we determine the prevalence of lead exposure in whooper swans and, for the first time, identify the level of blood lead associated with initial reductions in body condition. Blood lead elevated above background levels (i.e. >20 μg dL(-1)) was found in 41.7% (125/300) of swans tested. Blood lead was significantly negatively associated with winter body condition when levels were ≥44 μg dL(-1) (27/260 = 10%). Our findings indicating that sub-lethal impacts of lead on body condition occur at the lower end of previously established clinical thresholds and that a relatively high proportion of individuals in this population may be affected, reaffirm the importance of reducing contamination of the environment with lead shot.
Population declines among migratory Arctic-breeding birds are a growing concern for conservationi... more Population declines among migratory Arctic-breeding birds are a growing concern for conservationists. To inform the conservation of these declining populations, we need to understand how demographic rates such as breeding success are infl uenced by combinations of extrinsic and intrinsic factors. In this study we examined inter-annual variation and long-term trends in two aspects of the breeding success of a migratory herbivore, the Bewick ' s swan Cygnus columbianus bewickii , which is currently undergoing a population decline: 1) the percentage of young within the wintering population and 2) mean brood size. We used an information-theoretic approach to test how these two measures of productivity were infl uenced over a 26 yr period by 12 potential explanatory variables, encompassing both environmental (e.g. temperature) and intrinsic (e.g. pair-bond duration) factors. Swan productivity exhibited sensitivity to both types of explanatory variable. Fewer young were observed on the wintering grounds in years in which the breeding period (May to September) was colder and predator (Arctic fox) abundance was higher. Th e percentage of young within the wintering population also showed negative density-dependence. Inter-annual variance in mean swan brood size was best explained by a model comprised of the negative degree days during the swan breeding period, mean pair-bond duration of all paired swans (i.e. mean pair duration), and an interaction between these two variables. In particular, mean pair duration had a strong positive eff ect on mean brood size. However, we found no long-term directional trend in either measure of breeding success, despite the recent decline in the NW European population. Our results highlight that inter-annual variability in breeding success is sensitive to the combined eff ects of both intrinsic and extrinsic factors.
This Manual is intended to provide the reader with an overview of the principles and practicaliti... more This Manual is intended to provide the reader with an overview of the principles and practicalities of managing animal diseases at wetland sites. The Manual highlights the importance of including disease prevention and control in wetland management plans and provides guidelines on how to do so. It should be used in conjunction with Ramsar Handbook No. 18 on Managing Wetlands.
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