Long-term studies (1990-2008) of Dark-bellied Brent Geese Branta b. bernicla breeding on the Taimyr Peninsula in the Russian high Arctic, revealed a three-year cycle in breeding success linked to Siberian Lemming Lemmus sibiricus and Collared Lemming Dicrostonyx torquatus dynamics. Peak lemming years provide abundant prey for Snowy Owls Nyctea scandiaca, Arctic Foxes Vulpes lag opus and Pomarine Skuas Stercorariuspomarinus, whose interactions coincidently facilitate Brent Goose nesting. Snowy Owls defend their own territories against Arctic Foxes, and Pomarine Skuas do the same against both Arctic Foxes and Snowy Owls, severely restricting foxes and owls from preying upon Brent Geese, their nests and their goslings. Brent clutch size varied from an average of five eggs in Snowy Owl territories, to four eggs in gull Larus sp. colonies in peak lemming years, and three eggs in gull colonies in non-lemming years. Following lemming crashes (for reasons not understood), predator abundance remains high and Brent completely fail to breed or skip reproduction, as foxes and owls switch to alternative prey and skuas are absent from the area. In the third year, with predator decline (through starvation or emigration) and lemming recovery, Brent Goose nesting success improves. A year later, the three-year cycle starts again. The key role of skuas in limiting the owls' ability to catch and carry larger prey, such as geese, creates fox-free areas where Brent are able to nest successfully, confirming their previously overlooked role in the interspecific predator-prey interactions shaping Brent Goose reproductive success in the high Arctic. This review of papers and reports from the long-term studies describes how complex predator-prey and interspecific interactions determine the annual variation in breeding outcomes for Dark-bellied Brent Geese.
Understanding variation in survival and reproduction is key for conservation and management of bird populations. By compiling and analysing data on hatching success (i.e. proportion of nests with at least one hatched egg) from Common Eider Somateria m. mollissima, Velvet Scoter Melanitta fusca and Red-breasted Merganser Mergus serrator, all breeding on a single island in the Baltic Sea, we demonstrate that species-specific variation can be distinct even when nests are found in the same habitat on a relatively small study site. A total of 3,316 nests was found, and hatching success was determined for 2,890 nests during a four-year study period (2021-2024). Both Common Eider and Velvet Scoter exhibited considerable interannual variation in hatching success. Hatching success for Common Eider was highest in the two last years, but in the first two years for Velvet Scoter. Red-breasted Merganser showed more stable and generally higher hatching success than the other two species. Lack of covariation between species over the years indicates that species-specific traits such as phenology and behaviour (e.g. defence-mechanisms to avoid nest predation) may override other local factors influencing breeding success. Our results suggest that knowledge of annual variation in hatching success cannot be applied to other closely related species, even when those species are found breeding in the same area and habitat and may even share nesting sites.
The behavioural ecology of urban Greylag Geese Anser anser was reviewed in relation to selective forces or bottlenecks - such as habitat, food availability, predators, disturbance, hunting, diseases and parasites, nest sites and brood rearing areas, and competition with other species - which may act on geese in the contemporary European city environment. Special consideration was given to behavioural changes during winter and moult. Studies to date indicate that urban geese have developed survival and reproduction strategies which sometimes differ from those of geese in other habitats. For instance, they must adapt to a more built-up environment, as additional mortality may arise from collisions caused by flying within confined urban spaces. They are also exposed to urbanised native, introduced and "domestic" predators, such as dogs, to which they show size-related escape responses. Most urban geese adapt to human disturbances, adjusting the intensity of their behavioural response to the perceived danger. Like their rural counterparts, urban geese are also highly selective in their choice of food plants and feeding habitat, although supplementary feeding by people may induce a change in behaviour. There was no evidence that disease or parasite loads are higher for geese in urban than in rural areas. Urban Greylag Geese use a broader range of physical structures for nesting in urban than in rural areas, with some also adopting colonial nesting. Some families moved to new brood-rearing areas immediately post-hatching, elevating reproductive success. Competition with other species was evident at some sites, with Greylag Goose breeding success being inversely related to the local abundance of Egyptian Goose Alopochen aegyptiaca breeding pairs. Although wintry conditions with snow and ice cover may limit food availability and frozen lakes may hinder the ability of largely sedentary urban geese to escape from predators, they appear able to cope with prolonged periods of cold. Urban geese have also demonstrated resilience during their flightless wing moult period. It is unlikely that urban goose populations will grow indefinitely, as density-dependent processes will lead to a stabilisation of the numbers which occur within the boundaries of a given city, although the geese may disperse into surrounding rural areas.
Nest sitting by males is rare in the Anserinae subfamily and has never previously been reported for the Greater White-fronted Goose Anser albifrons. Here one case of a male repeatedly sitting on a nest is described, based on recordings from automatic camera traps used to study the behaviour of breeding pairs. The male attended the nest during the female's absence, and there was a positive correlation between the time that the female spent away from the nest and the duration of nest sitting by the male. The female's absent periods and the time spent nest sitting by the male both increased as incubation progressed but then decreased during the last five days before hatching. The female tended to leave the nest more frequently during the day, whereas the male's nest sitting was not affected by the time of day. Further studies with larger sample sizes are needed to ascertain how common nest sitting behaviour is in male Greater White-fronted Geese.
The geographically discrete Caucasus breeding population of the Velvet Scoter Melanitta fusca has shown significant range contraction to its one last existing colony in Georgia. Despite active conservation efforts at this site, where numbers currently appear to be stable, there is an evident need to understand past and present pressures that have driven the species to the verge of extinction in the region. An assessment of the potential for recreating suitable conditions for restoring the species to its former range and abundance is also required. Here, we review historical information to determine potential factors (some of which may still be in place) that contributed to the decline and range contraction of the Velvet Scoter in Armenia, Georgia and T & uuml;rkiye. Breeding surveys conducted in all three countries since 2013 confirmed the species' absence from all sites except for the breeding colony at Lake Tabatskuri in Georgia, which supported 45-50 pairs in 2024. Of 13 lakes with documented observations of Velvet Scoters, seven were confirmed as former breeding sites, with < 150 pairs in the last 60 years. The remainder were either spring/autumn staging areas, or unconfirmed breeding sites. For some sites, reasons for the loss of breeding Velvet Scoter locally were evident; for instance, at Lake Sevan in Armenia, reductions in the water levels in the lake rendered nesting islands accessible to terrestrial predators. Elsewhere, it was not possible to identify the causes of declines and extinctions, but by using the IUCN-CMP classification of threats and stresses we identified interactions with native species, recreational activity, hunting/egg collecting and fishing as critical threats to the viability of Velvet Scoters in the Caucasus. Several sites are suffering water quality issues, which require management interventions to restore turbid water to clear aquatic systems before the sites would become suitable for the return of the species. More site-based research and management will be necessary to restore the Velvet Scoter to its former levels of abundance and distribution.
Scant consideration has been given to the ingestion of synthetic micro-particles (e.g. plastic particles such as micro-fibres and micro-fragments 0.5-5 mm in size) by non-marine waterbirds, such as geese, residing in coastal and inland areas. In the present study, we therefore assessed the occurrence of micro-particle ingestion for five goose species across multiple locations throughout the United Kingdom and Ireland. Micro-particle recovery was inclusive of synthetic micro-fibres and micro-fragments, as well as treated textile micro-fibres such as dyed cotton fibres. Goose faecal samples were collected opportunistically between May 2018 and October 2019. At least one micro-particle was detected in 46.5% of the samples (n = 809 samples in total; 0-21 micro-particles per sample), which were collected from Greater White-fronted Geese Anser albifrons (n = 31 samples; 41.9% yielded micro-particles), Greylag Geese A. anser (n = 256; 58.6%), Pink-footed Geese A. brachyrhynchus (n = 66; 42.4%), Canada Geese Branta canadensis (n = 298; 36.6%) and Barnacle Geese B. leucopsis (n = 158; 48.1%). Time of year and distance from the coast had significant partial effects on the abundance of micro-particles recovered, with fewer micro-particles recovered during winter months and from locations > 70 km from the coast. Overall, it appears that the ingestion of synthetic micro-particles is a widespread and frequent occurrence, albeit in low quantities, in different goose species. Further research is however needed to ascertain the extent of absorption and subsequent impacts of chemical contaminants derived from synthetic micro-particles and textile fibres, especially in relation to bird health and developmental life stages.
Goose parental behaviour is costly and represents a compromise between an individual's need to spend time and resources maintaining its own body condition and survival with that required to successfully rear young. Geese are long-term monogamous species, with pair members cooperating to maximise their fitness outcomes by contributing differentially in time and function to the success of breeding attempts. For instance, enhanced male alertness during the reproductive season contributes to predator detection, whilst defending territories and broods from conspecifics also helps increase reproductive success. Such behaviour supports the female, which faces the high energy demands involved in producing and incubating eggs, by enabling her to spend more time foraging before, during and after the nesting period. Males also need to rebuild body stores after spending less time foraging during a period of heightened alertness, but this will be less marked than for the female following incubation. Hence, the time spent feeding and alert by parents would be expected to be more similar during autumn migration than during the breeding season, although both parents would be predicted to be more alert and to feed less than goslings, so that the still-growing young could maximise their food intake. To test these hypotheses, we observed the behaviour of individual Pink-footed Geese Anser brachyrhynchus, which were autumn-staging on spilt grain in stubble fields in central Norway. As predicted, there were no significant differences between female and male parents in the time spent foraging, alert or being aggressive towards conspecifics. Time spent by the parents on preening and sleeping were also similar for both sexes. Goslings and adult geese without young spent significantly more time foraging and less time alert than parental geese. On considering behaviour patterns in relation to the time of day, all geese were found to spend significantly more time foraging during the evening. We conclude that the behaviour of Pink-footed Geese at an autumn staging site, on their way to their wintering areas, reflects their age and breeding status, which may have positive fitness consequences.
Management of exploited populations needs to account for hunting pressure, yet estimating this parameter remains challenging. The study presented here compares the geographic distribution of dead recovery sites between the mid-20th century (1953-1983) and early 21st century (2002-2025), for birds all ringed in the same initial area (the Camargue in southern France) and proposes that this approach be used as a method for evaluating changes in relative hunting pressure over time. Analysis of ring recovery data from Common Teal Anas crecca, used as an example, suggests that hunting pressure on these birds has become increasingly concentrated in France in the 21st century, highlighting the responsibility of the country for hunting management of this species.
The 39.4% decline in numbers in the Northeast/Northwest European population of Bewick's Swan Cygnus columbianus bewickii between 1995 (29,780 birds) and 2010 (18,057 birds) was of major conservation concern, alleviated by a partial recovery to 20,149 recorded in the January 2015 census. The most recent census, in January 2020, however found that the recovery was not sustained. The results described in this paper found a further 29.7% decline between 2015 and 2020, with 12,702 individuals counted in 2020 and the population estimated at 12,930 birds. This represents a 56.7% decrease over the 25-year period from 1995-2020; an annual average decrease of 3.3% per year, with a higher rate of decline (8.5%/year) over the most recent 5year period. Changes in the Bewick's Swans distribution were evident, with a significant increase in the proportion of the population recorded in countries in the northeastern part of the wintering range compared with those further south and west. More sites of international importance for Bewick's Swans in mid-winter (i.e. with >= 1% of the total population) consequently were found in Germany during the 2020 census than in previous censuses. Moreover, the swans were found to be more widely dispersed, rather than being concentrated at key sites, in 2015 and 2020. Annual productivity data, based on the percentage of cygnets (first-winter birds) recorded in wintering flocks, indicate that the recruitment to the population was consistently lower than estimated survival rates between 2010 and 2020, and moreover this has continued up to and including winter 2024/25. A population model predicts that a further reduction in population size to an estimated 11,068 Bewick's Swans will be found during the next census scheduled for January 2026, unless the swans have a good breeding season in summer 2025, which would represent a decrease of 14.4% since 2020.
Greylag Geese Anser anser usually nest on the ground, close to water. In Hamburg, northern Germany, a pair of urban Greylag Geese was first seen nesting on a roof terrace of a building, 25 m above ground level, in 2013. Since then, the number of breeding pairs showing this unusual behaviour has steadily increased to 21 pairs nesting on roofs in the city in 2024. Hatchlings appeared unable to leave leave these new nesting locations on their own and required human intervention to reach ground level. This type of nesting behaviour now seems to have become established in Hamburg's Greylag Geese. As far as we know, there have been no previous reports of this behaviour in other towns or cities, and it therefore represents a new aspect in the species' urban ecology.
Individual marking is an essential method in avian ecological research, yet the potential ecological effects of tagging remain a concern. In this study, we investigated whether the presence of neckbands on Greater White-fronted Geese Anser albifrons affected the probability an individual was paired to another at a spring migratory stopover. Videos (15-30 min in duration) were recorded for 25 neck-banded and 25 randomly selected unmarked geese. From visual assessment of the behaviour of focal birds, pairing status (single or paired) was assessed for each. Our results found that over 70% of the neck-banded Greater White-fronted Geese were paired, and that there was no significant difference in pairing status between neck-banded and unmarked geese. Further studies with bigger sample sizes and using more advanced methods are needed to assess potential impacts of neckbands on the pairing status of Greater White-fronted Geese in greater detail.
Detailed studies of swans Cygnus sp. have been undertaken since the mid-20th century, with results of research programmes presented periodically at international symposia since the 1st International Swan Symposium was held in the UK in 1971. Here, we introduce the proceedings of the 7th International Swan Symposium (7th ISS) of the IUCN SSC Swan Specialist Group, held at Jackson, Wyoming in October 2022, by providing an overview of the latest information on swan populations presented at the meeting, published as papers in this issue and in other journals. The symposium was held in conjunction with the 26th Conference of the Trumpeter Swan Society and was hosted and co-organised by the Ricketts Conservation Foundation. Presentations covered a range of topics including population monitoring, movements and flyway delineation, habitat use, demographic rates, climate change, threats and conservation management of the species. As for the 6th ISS, held in Estonia in 2018, Southern Hemisphere swans were under-represented at the 7th ISS, but greater efforts will be made to cover these species more effectively, along with continued monitoring and assessment of swan populations in the Northern Hemisphere, ahead of the next International Swan Symposium in c. 2-3 years' time.
Trumpeter Swans Cygnus buccinator, North America's largest waterfowl, breed at high latitudes where they construct unusually large nest mounds and incubate from the top of the mound while experiencing daily ambient temperature fluctuations of 25 degrees C or more, as well as substantial exposure to solar radiation, high winds, rain and snow. This study investigates how incubating swans accommodate the thermal flux in their environment. Swan incubation dynamics were measured at Red Rock Lakes National Wildlife Refuge in southwestern Montana, USA, a federally protected high-elevation marsh complex where the last breeding population of Trumpeter Swans in the contiguous United States persisted during the early 20th century, a period when they neared extinction. Using around-the-clock digital video imaging, environmental monitoring devices and thermal recording devices, which were placed within clutches and also within and upon nest mound material, thermal dynamics were modelled in relation to swan incubation behaviour. Swans maintained a mean (+/- s.e.) egg temperature of 35.7 +/- 0.27 degrees C during active incubation. Linear mixed models of thermal covariates evaluated using AICc values and model weights (omega) revealed an interactive association between nest attendance and: (1) deviation of ambient environmental temperature from average egg incubation temperature, (2) solar radiation and (3) vapour density. Ambient temperature deviations above and below average egg incubation temperature, elevated solar radiation and declining vapour density were interactively associated with swan presence on the nest. Egg temperature per se was associated with both ambient temperature (positive) and vapour density (positive). Nest mound temperature was positively associated with ambient temperature, solar radiation and vapour density. The nest mound acted as a thermal mass, moderating thermal flux. Nesting success depended on swans shielding their eggs from excessive daytime warming and desiccation, and on contact incubation when ambient temperature was below the average egg incubation temperature.
Variability in the duration of the breeding season and the mean number of annual breeding attempts recorded for Black Swans Cygnus atratus in southeast Queensland, Australia, were evaluated in relation to environmental variables. There was a significant correlation between the extent of the breeding season (measured as the number of months in which eggs were hatched) with both the number of breeding attempts made by paired birds in that year and also the number of territorial pairs recorded. This may reflect changes in the timing of breeding by individual pairs to reduce competition for favoured breeding and foraging locations. The number of breeding attempts per territorial pair in any one year was influenced primarily by summer rainfall and the Southern Oscillation Index (SOI), with higher values for both of these environmental variables being associated with more breeding attempts and increasing numbers of breeding pairs. We therefore suggest that the increasing numbers of breeding pairs, and also the increasing numbers of breeding attempts associated with more favourable weather conditions, may have led to the longer breeding seasons recorded for Black Swans in southeast Queensland in recent years.
Trends in abundance and changes in the distribution of the Northeast Europe/ Northwest Europe Bewick's Swan Cygnus columbianus bewickii population have been studied in detail since the second half of the 20th century, but much less is known about the Northwestern Siberia/Caspian population which was estimated at 1,000- 1,500 individuals at the turn of the century. Here, we describe the results of the first species-specific mid-winter International Bewick's Swan Census (IBSC) covering the East Mediterranean to Central Asia, made in January 2020. We also use longer-term data collated by Wetlands International through the annual International Waterbird Census (IWC) programme to construct trends in wintering numbers in the region. Results from the IBSC and IWC both showed a marked increase in population size for the Northwestern Siberia/Caspian Bewick's Swans over the past two decades. A total of 6,819 was recorded during the IBSC and there was a five-year mean of 9,111 +/- 4,300 swans reported to the IWC (for the years 2018-2022) with a peak count of 13,775 in 2019. An aerial survey of the Volga Delta in the northern Caspian Sea in 2020, rarely covered because of the logistical difficulties of carrying out midwinter counts in the region, found an estimated 551 Bewick's Swans wintering at the site. There was marked annual variation in the IWC counts recorded from 2017 onwards, although the reasons for these fluctuations remain unknown. Trends analysis suggested a slow increase over time from 2000-2015, followed by a period of rapid increase during 2015-2017, then a weak decline in 2017-2022. Given that the IBSC and the IWC have provided totals of > 6,000 Bewick's Swans in five of the last six years, however, we propose that the new population estimate should be increased to 6,000-13,000 birds, pending further comprehensive surveys of the whole region.
Variation in the abundance and habitat use recorded for three swan species - the Bewick's Swan Cygnus columbianus bewickii, Whooper Swan Cygnus cygnus and Mute Swan Cygnus olor - at their main spring staging areas in the coastal waters of Neva Bay, Gulf of Finland, were studied from 2018-2022. The count sites were grouped into two distinct habitat types: "traditional" (defined as natural shallow coastal water areas with low levels of anthropogenic disturbance, supporting a range of emergent vegetation), and "reclaimed" (defined as the shallow waters created behind artificial sand embankments during and following their creation). The numbers of swans using traditional sites varied widely, but never exceeded 121 Bewick's Swans and 292 Whooper Swans at any one site. At the reclaimed sites, numbers of the two yellow-billed swans increased progressively following completion of the reclamation work, with peak counts ranging from 0-442 Bewick's Swan and up to 160 Whooper Swans. In contrast, Mute Swans in any one area never exceeded two individuals. Surveys of potential food plants used by swans in summers 2021 and 2022 demonstrated the prevalence of Perfoliate Pondweed Potamogeton perfoliatus at the main stopover sites close to reclaimed areas, together with Hairlike Pondweed Potamogeton trichoides and the green algae Cladophoraglomerata. These results suggest that, with the continued gradual colonisation by aquatic vegetation of shallow waters formed near reclaimed areas, there is potential for the number of swans feeding in these areas to increase, provided that the sites are protected (e.g. from disturbance by human activity) and continue to provide suitable habitats for the swans.
The Trumpeter Swan Cygnus buccinator is a charismatic species, important to many North Americans, and estimating demographic parameters - including abundance and distribution - is a basic requisite for the conservation and management of its populations. From 1968 to 2015, the primary population survey for Trumpeter Swans useful for determining trends in abundance and range expansion following nearextirpation of the species in the first half of the 20th century. The NATSS also had some shortcomings, however, which limited its utility as an index of the swans' status, and the NATSS has been suspended indefinitely. To help inform decisions as to whether the NATSS should be reinstated, or an alternative monitoring programme developed, we here review the strengths and drawbacks of the NATSS as well as those of other operational surveys and monitoring programmes. For instance, the Waterfowl Breeding Population and Habitat Survey, the Mid-Winter Waterfowl Survey, the Breeding Bird Survey, the Christmas Bird Count, and eBird data also cover large areas of the Trumpeter Swans' range during certain (albeit different) periods of the year, and several have been mentioned as possible alternatives to the NATSS for assessing the status of Trumpeter Swan populations in North America, but each also has some limitations. We discuss the types of data that each of these monitoring efforts generate, and whether any might provide information sufficiently useful for managing Trumpeter Swan populations and their habitats effectively. We hope that this critique will not only be useful to federal, state and provincial agencies as they develop monitoring programmes for revision of management objectives, but that it will help to stimulate the development of updated strategies for Trumpeter Swan conservation.
A total count of 940 swans was recorded for the U.S. Breeding Segment of the Rocky Mountain Population (RMP) of Trumpeter Swans Cygnus buccinator during autumn 2022, a 1.8% increase on the 923 swans counted the previous year. The number of white birds (i.e. adults and yearlings) in the Greater Yellowstone Area (473) was 8.2% higher than the 437 recorded in 2021, but the total number of grey birds (cygnets) decreased by 8.8%, from 91 in 2021 to 83 in 2022. There was some regional variation in breeding success. The cygnet count decreased by 74.1% in Montana (where only seven cygnets fledged; the lowest number recorded since 2008) and cygnet production in Wyoming also decreased, by 17.0%, but conversely it increased by 191% in Idaho. In Oregon, 27 white birds were observed at the Summer Lake Wildlife Management Area (WMA) and vicinity (a 10% decrease on last year's count of 30), and two white birds were observed at Malheur National Wildlife Refuge (NWR). There were no white birds recorded at Ruby Lake NWR, Nevada. Precipitation throughout most of the Greater Yellowstone Area was 40%-80% of normal during winter 2021-2022. During the summer months, temperatures were within the normal average whereas precipitation was 75-130% of normal, especially during June-August. Palmer Drought Indices for areas within the Greater Yellowstone area also suggested wetter conditions for 2022 in comparison with 2021. The 2022 survey results are described in relation to longer-term monitoring of the U.S. Breeding Segment of the RMP, which found no evidence for a trend in total numbers over the period 2015-2021, but a decrease in the proportion of cygnets recorded during this time.
The influence of winter temperature and spring ice melt on Mute Swan Cygnus olor abundance and productivity in a northern part of its breeding range was studied using data from 831 nests on the Kurgalsky Peninsula, in the Russian part of the Gulf of Finland, during 2006-2021. There was marked annual variation in the numbers of breeding pairs, which ranged from 17-95 per year over the 16-year study, with greatest numbers observed in years with early ice melt in the gulf. Birds nested either territorially or in colonies. Nest sites were categorised as being occupied for either short-term or long-term periods, with the latter considered likely to include cases of the same pairs nesting at the same sites over several years. Clutch sizes and hatching success were greater for territorial pairs and for those on long-term sites compared to pairs on short-term and colonial nests. Overall hatching success decreased in years with later ice melt.
In recent years the number of breeding Whooper Swans in Latvia and Estonia combined has increased from one pair in 1973 to 900-1,200 pairs in 2021, with a similar growth rate in both countries. Sixty-nine percent of confirmed Latvian breeding sites were located in western Latvia during 2018-2021, a stronghold for the species, while in Estonia breeding sites were more widely distributed across the country. In Estonia, Whooper Swans preferred bogs, lakes and coastal waters whereas the vast majority of pairs in Latvia occurred on fish-pond complexes, natural lakes and ponds created by the Eurasian Beaver Castorfiber ("beaver dams").
