Eileen Rees

Recent studies have suggested that protected areas often fail to conserve target species. However, the efficacy of terrestrial protected areas is difficult to measure, especially for highly vagile species like migratory birds that may move between protected and unprotected areas throughout their lives. Here, we use a 30-y dataset of detailed demographic data from a migratory waterbird, the Whooper swan ( Cygnus cygnus ), to assess the value of nature reserves (NRs). We assess how demographic rates vary at sites with varying levels of protection and how they are influenced by movements between sites. Swans had a lower breeding probability when wintering inside NRs than outside but better survival for all age classes, generating a 30-fold higher annual growth rate within NRs. There was also a net movement of individuals from NRs to non-NRs. By combining these demographic rates and estimates of movement (into and out of NRs) into population projection models, we show that the NRs should help to double the population of swans wintering in the United Kingdom by 2030. These results highlight the major effect that spatial management can have on species conservation, even when the areas protected are relatively small and only used during short periods of the life cycle.

This study aims to determine the level of movement of individuals between the Icelandic and Northwest Mainland European (NWME) Whooper Swan Cygnus cygnus populations, and to assess the extent to which this interchange affects total population estimates. Ringing, resighting and recovery data for Whooper Swans ringed across Europe since the early 1900s were compiled from the EURING Data Bank, national ringing schemes and individual ringers. Birds were assigned to the biogeographical population (Icelandic or NWME) in which they were ringed. Of >18 000 Whooper Swans ringed in 17 European countries, 172 individuals (0.94%) were later found outside the nominal range of their assigned biogeographical population. The proportion of ringed swans from the Icelandic population that were subsequently found ‘out of range’ did not differ significantly from the proportion recorded for the NWME population, indicating no directional bias in population interchange. Population switching by Whooper Swans in western Europe occurs consistently, but currently at very low levels. Our results reinforce the view that such levels of population interchange are unlikely to have caused major inaccuracies or biases in the total numbers recorded during the coordinated censuses used to estimate population size.

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.

Given their popularity with researchers and public alike, together with their welldocumented importance in aquatic and terrestrial ecosystems, fundamental and applied research on swans continues to develop in the 21st century. The 6th International Swan Symposium (6th ISS), was held at the Estonian University of Life Sciences in Tartu, Estonia, in October 2018. The symposium brought together 101 delegates from 17 countries, with presentations on a range of topics on Cygnus and Coscoroba species, including monitoring, habitat and resource use, demography, movements and migration, and threats and conservation. The proceedings of the 6th ISS in this special issue of Wildfowl include select papers on swan research presented at the 6th ISS, covering a wide range of species, systems and issues. This paper presents a synthesis of the 6th ISS and an overview of current trends and future directions in swan research. Despite progress on many topics, southern hemisphere swan species continue t...

Internationally coordinated censuses of Whooper Swans Cygnus cygnus across continental northwest Europe were undertaken in mid-winter 1995, 2000, 2005, 2010 and 2015. The estimate of 138,500 birds in 2015, the highest to date, represented a more than doubling of the population size (at an annual increase of 4.1%) since the first census total of 59,000 swans in 1995. The largest increase was in Denmark, where numbers almost trebled from 21,740 in 1995 to 62,620 in 2015. More than 97% of all swans were counted in just six countries. The percentage of total numbers increased significantly between 1995 and 2015 in Denmark (from 36.5% to 45.2%) and Germany (26.0% to 34.7%), but declined significantly in Sweden (14.2% to 8.4%), Norway (13.1% to 3.6%), Poland (6.2% to 4.0%) and the Netherlands (2.4% to 1.7%). The counts show an increasing discrepancy between national trends in abundance for Whooper Swans in Sweden and especially in Denmark in comparison with results obtained only from mid-...

Aim: Animal movement is an important determinant of individual survival, population dynamics, and ecosystem structure and function. Yet it is still unclear how local movements are related to resource availability and the spatial arrangement of resources. Using resident bird species and migratory bird species outside of the migratory period, we examined how the distribution of resources affect the movement patterns of both large terrestrial birds (e.g., raptors, bustards, hornbills) and waterbirds (e.g., cranes, storks, ducks, geese, flamingos). Location: Global Time Period: 2003 - 2015 Major taxa studied: Birds Methods: We compiled GPS tracking data for 386 individuals across 36 bird species. We calculated the straight-line distance between GPS locations of each individual at the 1-hour and 10-day timescales. For each individual and timescale, we calculated the median and 0.95 quantile of displacement. We used linear mixed-effects models to examine the effect of the spatial arrangement of resources, measured as Enhanced Vegetation Index (EVI) homogeneity, on avian movements while accounting for mean resource availability, body mass, diet, flight type, migratory status and taxonomy and spatial autocorrelation. Results: We found a significant effect of resource spatial arrangement at the 1-hour and 10-day timescales. On average, individual movements were seven times longer in environments with homogeneously distributed resources compared with areas of low resource homogeneity. Contrary to previous work, we found no significant effect of resource availability, diet, flight type, migratory status or body mass on the non-migratory movements of birds. Main conclusions: We suggest that longer movements in homogeneous environments may reflect the need for different habitat types associated with foraging and reproduction. This highlights the importance of landscape complementarity, where habitat patches within a landscape include a range of different, yet complimentary resources. As habitat homogenisation increases, it may force birds to travel increasingly longer distances to meet their diverse needs

Regular spring and autumn observations of colour-ringed Eurasian Curlew Numenius a. arquata wintering on the River Severn estuary in Gloucestershire, UK, marked during 2010–2013 inclusive, were used to locate surviving ringed individuals (n = 147 birds resighted) and describe the timing of their annual arrivals and departures. Breeding locations reported for 18 birds were from Fennoscandia (5), the Netherlands or Germany (6) and Britain (7). Fennoscandian birds remained significantly later on the estuary each year than the 13 individuals known to breed in Britain, the Netherlands or Germany. Departure dates recorded for 109 Curlew during a more intensive survey in 2016 similarly found that onset of spring migration was significantly later for birds known (or thought because they remained on the estuary until April) to be of Fennoscandian origin. Curlew returned from breeding grounds to the Severn estuary from the first week of June onwards, sooner than reported in previous studies, ...

ABSTRACT The third coordinated international census of Whooper Swans in Iceland, Ireland and Britain was made in January 1995. Excellent coverage was achieved and 15,842 birds were counted or estimated, suggesting a decrease in the population of 2,193 birds (12.2% overall, or 3.0% per annum) since the previous census in January 1.991; 20.1% overall if only adult birds are considered. Average annual mortality was estimated at 1.9. 7%, compared with recruitment of 16.7%, over the four year period. Distribution was similar to 1991, however, with 5,016 (31.7%) recorded in Great Britain and the Isle of Man, 2, 783 (17.6%) in Northern Ireland, 7,072 (44.6%) in the Republic of Ireland and 971 (6.1%) in Iceland. Around 400 birds wintered on the continent, whilst an unknown but probably small number from the Scandinavian/Russian population wintered in Britain. It is recommended that the figure of 16,000 is adopted for the Icelandic Whooper Swan population. The 10,156 birds aged included 1,814 (17,9%) juveniles, indicating that 1994 was a good breeding year. Substantial variation in the distribution of juveniles in the wintering range emphasises the difficulty of obtaining accurate estimates of annual productivity from small or localised samples.

Conservationist, scientist, artist, author, broadcaster and sportsman, Sir Peter Scott was one of the leaders of the international conservation movement in the twentieth century. As founder of the Severn Wildfowl Trust (now the Wildfowl & Wetlands Trust) he and his team initiated research into the movements, ecology and behaviour of migratory populations of wildfowl (ducks, geese and swans), which were poorly known at the time, while also developing captive breeding programmes to save species such as the Hawaiian goose from extinction. As a co-founder of the World Wildlife Fund (later the Worldwide Fund for Nature), Scott worked tirelessly to raise money for programmes to save many globally endangered animals, with a particular interest in birds and cetaceans. As chairman of the Survival Service Commission (later the Species Survival Commission) of the International Union for the Conservation of Nature and Natural Resources (IUCN), Scott founded the IUCN red list , by which the leve...

This chapter describes the terminology, nomenclature, morphology, geographical distribution, diet, physiology, reproduction, behaviour, ecology, habitats, invasion patterns, environmental impact, control and human use of the mute swan (Cygnus olor).

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...

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 ...

The fifth international census of Whooper Swans in Britain, Ireland and Iceland was undertaken in January 2005 to determine the size and winter distribution of the Icelandic-breeding Whooper Swan population. A total of 26,366 Whooper Swans was counted, of which 37% were recorded in the Republic of Ireland (9,748 birds), 25% in England (6,480), 16% in Northern Ireland (4,331), 16% in Scotland (4,142), 6% in Iceland (1,556) and < 1% in Wales and the Isle of Man (109). A comparison with results of the previous international census made in January 2000 found that the numbers of swans counted had increased in all countries except Wales. There was also an increase in the proportion of swans wintering in England and Scotland, compared with numbers elsewhere in the range. The substantial increase in numbers of birds in England was not accompanied by a significant increase in the number of flocks recorded, and distribution remains concentrated at relatively few sites. In contrast, there w...

A particular aim of avian ecologists, especially those studying waterfowl Anatidae, in the 20th and early 21st centuries has been to elucidate how organisms use habitats and intrinsic resources to survive, reproduce and ultimately affect fitness. For much of the 20th century, research was mainly on studying species during the breeding season; however, by the 1970s, the focus had changed to understanding migratory waterfowl throughout their annual cycle and range in Europe and North America. Autumn and winter are considered the non-breeding seasons, but habitat and resource use through these seasons is crucial for completing spring migration and subsequent breeding. Here we review the literature on autumnal and winter habitat use by Nearctic and Palearctic waterfowl to determine characteristics of important landscapes and habitats for the birds during autumn migration and in winter. Selection of habitats and resources is discussed (when literature permits) in relation to Johnson'...

The seventh international census of Whooper Swans in Britain, Ireland, Iceland and the Isle of Man took place in January 2015, to update estimates of the size and midwinter distribution of the Icelandic Whooper Swan population. The 34,004 swans recorded represented a 16% increase in numbers compared to the previous census in 2010, a 155% increase on counts made in 1995, and was the highest census total to date. The drivers behind this increase have yet to be determined, but it seems that it is not solely attributable to an improvement in breeding success in recent years and that changes in survival rates and perhaps interchange with the Northwest Mainland Europe population may also be accountable for the trend. Overall, 35.5% of the population (12,083 birds) was recorded in England, 34.9% (11,852) in the Republic of Ireland, 11.1% (3,784) in Scotland, 10.4% (3,518) in Northern Ireland, 7.4% (2,520) in Iceland and < 1% (247) in Wales and the Isle of Man. There was a significant de...

This review considers data published on the effects of offshore and onshore windfarms on swans and geese and finds that the information available is patchy. Of 72 swans or geese reported as collision victims at 46 wind farms, most (39 birds) were reported at 23 wind farms in Germany where such data are collated. Post-construction monitoring was undertaken for ≤ 1 year at 67 % of 33 sites, making it difficult to test for cumulative effects or annual variation in collision rates. Site use by the birds was measured at only nine of 46 wind farms where collisions by swans and geese were monitored or recorded. Displacement distances of feeding birds at wintering sites ranged from 100–600 m, but preliminary evidence suggested that large-scale displacement also occurs, with fewer swans and geese returning to areas after wind farms were installed. Eight studies of flight behaviour all reported changes in flight-lines for swans or geese initially seen heading towards the turbines, at distance...

The dynamics and behaviour of the Northwest European population of Bewick's Swans Cygnus columbianus bewickii has been studied over several decades, yet relatively little is known about the more numerous Eastern population of the species.

The ability of a species to adapt to environmental change is ultimately reflected in its vital rates – i.e., survival and reproductive success of individuals. Together, vital rates determine trends in numbers, commonly monitored using counts of species abundance. Rapid changes in abundance can give rise to concern, leading to calls for research into the biological mechanisms underlying variations in demography. For the NW European population of Bewick's swan (Cygnus columbianus bewickii), there have been major changes in the population trends recorded during nearly five decades of monitoring (1970‐2016). The total number of birds increased to a maximum of c. 30,000 in 1995 and subsequently decreased to about 18,000 individuals in 2010. Such large fluctuation in population numbers is rare in long‐lived species and understanding the drivers of this population change is crucial for species management and conservation. Using the integrated population model (IPM) framework, we analys...

Coordinated international censuses of the Northwest European Bewick’s Swan  Cygnus columbianus bewickii population have been undertaken across the swans’ wintering range at c. 5-year intervals since 1984. During the early years of the study, numbers increased steadily to a peak of 29,780 individuals in January 1995, but then declined by 39.4% to 18,057 swans counted in January 2010 before showing a partial recovery to 20,149 recorded in January 2015. Changes in distribution across the wintering range were also recorded; a higher proportion of the population now remains in more easterly countries (notably Germany) in mid-winter, whilst only a handful of birds migrated to Ireland (at the western edge of the range) during the 2000s compared to >1,000 wintering there at the start of the study. Variation between censuses in the proportion of swans recorded in different parts of the range were attributable to weather conditions, with more swans wintering further north in warmer years. ...

This review considers data published on the effects of offshore and onshore windfarms on swans and geese and finds that the information available is patchy. Of 72 swans or geese reported as collision victims at 46 wind farms, most (39 birds) were reported at 23 wind farms in Germany where such data are collated. Post-construction monitoring was undertaken for ≤ 1 year at 67% of 33 sites, making it difficult to test for cumulative effects or annual variation in collision rates. Site use by the birds was measured at only nine of 46 wind farms where collisions by swans and geese were monitored or recorded. Displacement distances of feeding birds at wintering sites ranged from 100–600 m, but preliminary evidence suggested that large-scale displacement also occurs, with fewer swans and geese returning to areas after wind farms were installed. Eight studies of flight behaviour all reported changes in flight-lines for swans or geese initially seen heading towards the turbines, at distances...

Background Installation of wind farms has increased rapidly across Europe over the last two decades, as governments seek to reduce the greenhouse gas emissions associated with climate change and secure energy supplies through greater use of renewable resources. Although there is increasing evidence for climate change having a deleterious effect on avian populations (Bright et al. 2006), there is also concern that wind farms may have direct negative effects on the birds through collision mortality, decreased landscape function (barrier effects) and displacement from feeding areas (Drewitt & Langston 2006). Accurate assessment of potential cumulative impacts from multiple wind farms along a flyway is a major challenge as it requires detailed information on the birds’ migration routes. Where there is evidence of potential risk at one or more sites, specific research projects should be undertaken in order to support conclusions made within Environmental Impact Assessments (EIAs) for eac...

Recent estimates of the world’s swan Cygnus sp. populations indicate that there are currently between 1.5–1.6 million birds in 8 species, including the Coscoroba Swan Coscoroba coscoroba as an honorary swan. Monitoring programmes in Europe and North America indicate that most populations increased following the introduction of national and international legislation to protect the species during the early- to mid-20th century. A switch from feeding primarily on aquatic vegetation to foraging on farmland (especially high-energy arable crops) in winter during the second half of the 20th century, is also considered a contributing factor. Trumpeter Swans Cygnus buccinator famously increased from just 69 individuals known to exist in 1935 (although small numbers were missed) to c. 76,000 at the present time, and most of the northern hemisphere swan populations have continued to show increasing/stable trends over the last 20 years. The exception to this pattern is a decline since 1995 in t...

The seventh international census of Whooper Swans in Britain, Ireland, Iceland and the Isle of Man took place in January 2015, to update estimates of the size and midwinter distribution of the Icelandic Whooper Swan population. The 34,004 swans recorded represented a 16% increase in numbers compared to the previous census in 2010, a 155% increase on counts made in 1995, and was the highest census total to date. The drivers behind this increase have yet to be determined, but it seems that it is not solely attributable to an improvement in breeding success in recent years and that changes in survival rates and perhaps interchange with the Northwest Mainland Europe population may also be accountable for the trend. Overall, 35.5% of the population (12,083 birds) was recorded in England, 34.9% (11,852) in the Republic of Ireland, 11.1% (3,784) in Scotland, 10.4% (3,518) in Northern Ireland, 7.4% (2,520) in Iceland and < 1% (247) in Wales and the Isle of Man. There was a significant de...

The Wildfowl & Wetlands Trust (WWT) has contributed to the conservation of swan species by establishing refuges for the birds in winter, through its research programmes, and by advising others on site management. This paper describes an increase in the number of migratory swans wintering at Slimbridge, Caerlaverock, the Ouse Washes and Martin Mere following the development of WWT Centres at these sites. The build-up in numbers may be due to changing population levels, and to conditions created by WWT. We describe changes in feeding site selection in the last 50 years, and consider the potential for inter-specific competition between Bewick's and Whooper Swans in areas where the two species co-exist. WWT's long-term studies of individual birds, which have provided detailed insight into the swans' life-cycles, are reviewed. The importance of international collaboration for the effective conservation of migratory waterbirds is again emphasised.

Range shifts and phenological change are two processes by which organisms respond to environmental warming. Understanding the mechanisms that drive these changes is key for optimal conservation and management. Here we study both processes in the migratory Bewick's swan (Cygnus columbianus bewickii) using different methods, analysing nearly 50 years of resighting data (1970-2017). In this period the wintering area of the Bewick's swans shifted eastwards ('short-stopping') at a rate of ~13 km/year, thereby shortening individual migration distance on an average by 353 km. Concurrently, the time spent at the wintering grounds has reduced ('short-staying') by ~38 days since 1989. We show that individuals are consistent in their migratory timing in winter, indicating that the frequency of individuals with different migratory schedules has changed over time (a generational shift). In contrast, for short-stopping we found evidence for both individual plasticity (individuals decrease their migration distances over their lifetime) and generational shift. Additional analysis of swan resightings with temperature data showed that, throughout the winter, Bewick's swans frequent areas where air temperatures are c. 5.5°C. These areas have also shifted eastwards over time, hinting that climate warming is a contributing factor behind the observed changes in the swans' distribution. The occurrence of winter short-stopping and short-staying suggests that this species is to some extent able to adjust to climate warming, but benefits or repercussions at other times of the annual cycle need to be assessed. Furthermore, these phenomena could lead to changes in abundance in certain areas, with resulting monitoring and conservation implications. Understanding the processes and driving mechanisms behind population changes therefore is important for population management , both locally and across the species range.