Wild hybrids of Lesser White-fronted Goose (Anser erythropus)×Greater White-fronted Goose (A. albifrons) (Aves: Anseriformes) from the European migratory flyway

The Lesser White-fronted Goose [Anser erythropus (Linnaeus, 1758)] is one of the most threatened Palearctic goose species, with the Fennoscandinavian subpopulation in particular having seen a drastic decline over the last century. In the 1990s, captive-bred Lesser White-fronted Geese were used successfully for reintroduction and restocking in Sweden and Finland. The discovery of Greater White-fronted Goose [Anser albifrons (Scopoli, 1769)] mtDNA haplotypes in some of these captive-bred birds (Ruokonen et al. 2000) suggested that hybridisation had occurred during captive propagation and led to the discontinuation of the release of captive goslings. Here we report two hybrids of Lesser×Greater White-fronted Geese that were collected on their wintering grounds in England in 1936 and Holland in 1966. Birds from western Russia normally do not migrate south to Western Europe. Hence, these birds most likely originated from the Fennoscandinavian subpopulation and were collected prior to the commencement of the captive-breeding programmes. Both specimens show a heterogeneous set of morphological characters, some of which shared with the putative parent species and others being intermediate between the two White-fronted Goose species. A Canonical Discriminant Function analysis positions both specimens between the two putative parent species, making their hybrid status likely. We show, thus, that hybridisation between Greater and Lesser White-fronted Geese does occur naturally, albeit perhaps infrequently, and argue that the presence of Greater White-fronted Goose mtDNA haplotypes in Lesser White-fronted Goose may be the result of this naturally occurring hybridisation. Our data provide additional information on the debate whether the restocking programmes were halted for the right reasons and whether it is desirable to re-commence with the reintroduction programme.     

Goose hybrids, captive breeding and restocking of the Fennoscandian populations of the Lesser White-fronted goose (Anser erythropus)

The lesser white-fronted goose (Anser erythropus) isthe most threatened of the Palearctic goose species with a decliningpopulation trend throughout its distributional range. The currentestimate of the Fennoscandian subpopulation size is 30–50 breedingpairs, whereas it still numbered more than 10000 individuals at thebeginning of the last century. Reintroduction and restocking have beencarried out in Sweden and Finland using captive lesser white-frontedgoose stock with unknown origins. We have carried out a study of thegenetic composition of captive-bred stock by sequencing a 221 bphypervariable fragment of the mitochondrial DNA (mtDNA) control regionfrom 15 individuals from the Hailuoto farm, Finland. Two out of thethree maternal lineages detected in the captive stock are also presentin wild populations. The third maternal lineage among the captive lesserwhite-fronted geese originates from the closely related greaterwhite-fronted goose (Anser albifrons). None of the investigatedwild lesser white-fronted goose individuals carried the mtDNA of thegreater white-fronted goose. The presence of greater white-fronted goosemtDNA in the lesser white-fronted goose captive stock suggests thathybridization has occurred during captive propagation.     

Circumpolar variation in morphological characteristics of Greater White-fronted Geese Anser albifrons

Capsule Greater White-fronted Geese show significant variation in body size from sampling locations throughout their circumpolar breeding range.

Aims To determine the degree of geographical variation in body size of Greater White-fronted Geese and identify factors contributing to any apparent patterns in variation.

Methods Structural measures of >3000 geese from 16 breeding areas throughout the Holarctic breeding range of the species were compared statistically.

Results Palearctic forms varied clinally, and increased in size from the smallest forms on the Kanin and Taimyr peninsulas in western Eurasia to the largest forms breeding in the Anadyr Lowlands of eastern Chukotka. Clinal variation was less apparent in the Nearctic, as both the smallest form in the Nearctic and the largest form overall (the Tule Goose) were from different breeding areas in Alaska. The Tule Goose was 25% larger than the smallest form. Birds from Greenland (A. a. flavirostris) were the second largest, although only slightly larger than geese from several North American populations. Body size was not correlated with breeding latitude but was positively correlated with temperature on the breeding grounds, breeding habitat, and migration distance. Body mass of Greater White-fronted Geese from all populations remained relatively constant during the period of wing moult. Morphological distinctness of eastern and western Palearctic forms concurs with earlier findings of complete range disjunction.

Conclusions Patterns of morphological variation in Greater White-fronted Geese across the Holarctic can be generally attributed to adaptation to variable breeding environments, migration requirements, and phylo-geographical histories.     

Serological and virological survey and resighting of marked wild geese in Germany

In order to investigate the potential role of arctic geese in the epidemiology, the spatial and temporal spread of selected avian diseases, in autumn 2002, a virological and serological survey designed as capture-mark-resighting study was conducted in one of the most important coastal resting sites for migratory waterfowl in Germany. Oropharyngeal, cloacal swabs and blood samples were collected from a total of 147 birds comprising of three different arctic geese species including White-fronted Goose (Anser albifrons), Tundra Bean Goose (Anser fabalis rossicus), Pink-footed Goose (Anser brachyrhynchus) as well as from 29 non-migratory Canada Geese (Branta canadensis). Altogether, six adeno-like viruses (ALV; 95% CI, 1.74?C9.92%) and two avian paramyxoviruses (APMV-4; 95% CI, 0.19?C5.53%) were isolated mainly from juvenile White-fronted Geese. In addition, four Canada Geese were infected with lentogenic APMV-1 (95% CI, 3.89?C31.66%) at the date of sampling. No avian influenza viruses, reo-like viruses could be isolated despite serological evidence. Likewise, no evidence of current or previous infection by West Nile virus was found. Of the 147 birds tagged in the following years, 137 birds were re-sighted between 2002 and 2008 accumulating to 1925 sightings. About 90% of all sightings were reported from the main wintering and resting sites in Germany and The Netherlands. Eight of the resighted geese were virus positive (ALV and APMV-4) at the time point of sampling in 2002.     

Using historical captive stocks in conservation. The case of␣the␣lesser white-fronted goose

Many captive stocks of economically or otherwise valuable species were established before the decline of the wild population. These stocks are potentially valuable sources of genetic variability, but their taxonomic identity and actual value is often uncertain. We studied the genetics of captive stocks of the threatened lesser white-fronted goose Anser erythropus maintained in Sweden and elsewhere in Europe. Analyses of mtDNA and nuclear microsatellite markers revealed that 36% of the individuals had a hybrid ancestry. Because the parental species are closely related it is unlikely that our analyses detected all hybrid individuals in the material. Because no ancestral polymorphism or introgression was observed in samples of wild populations, it is likely that the observed hybridisation has occurred in captivity. As a consequence of founder effect, drift and hybridisation, captive stocks were genetically differentiated from the wild populations of the lesser white-fronted goose. The high level of genetic diversity in the captive stocks is explained at least partially by hybridisation. The present captive stocks of the lesser white-fronted goose are considered unsuitable for further reintroduction, or supplementation: hybridisation has involved three species, the number of hybrids is high, and all the investigated captive stocks are similarly affected. The results highlight the potential shortcomings of using captive-bred individuals in supplementation and reintroduction projects, when the captive stocks have not been pedigreed and bred according to conservation principles. Deceased 20 March 2004.     

长江中下游湿地大型水鸟种群动态和幼鸟比例研究

迁徙水鸟保护对生物多样性保护具有重要意义。开展水鸟种群数量和幼鸟比例监测,对科学评估其种群变化趋势、制定长期保护策略具有重要价值。长江中下游湿地是东亚-澳大利西亚迁徙路线上重要的水鸟越冬区之一。本研究采用野外同步调查等方法对该区域87个湿地的亟需保护和具有代表性的10种大型越冬水鸟,其中雁形目6种,分别是鸿雁Anser cygnoides、豆雁A.fabalis、灰雁A.grus、白额雁A.albifrons、小白额雁A.erythropus和小天鹅Cygnus columbianus;鹤形目4种,分别是白鹤Leucogeranus leucogeranus、白枕鹤Antigone vipio、灰鹤Grus grus和白头鹤G.monacha,进行了长期监测(2003—2019年冬季),并结合相关文献,评估其种群变化趋势、幼鸟比例和死亡率。研究结果如下：(1)2005—2019年3种水鸟(豆雁、灰雁和灰鹤)的种群数量呈上升趋势,7种水鸟(鸿雁、白额雁、小白额雁、小天鹅、白鹤、白枕鹤和白头鹤)种群数量呈下降趋势;(2)种群趋势下降组(N=7)和上升组(N=3)的幼鸟比例均值在2016—2...     

Long-term changes in numbers of geese stopping over and wintering in south-western Poland

South-western Poland belongs to the key staging areas for geese in Europe, supporting some 100000 birds in recent years. We compared goose counts conducted in the 1970s, 1990s and during 2009–2011 in this region, and linked the findings to the recent assessments of trends in the flyway-populations. Numbers increased several dozen times between the first two counts and have stabilized to the present. More than 14% of the flyway Tundra Bean Goose (Anser fabalis rossicus) stopped over in SW Poland on passage. Smaller numbers of White-fronted Goose (A. albifrons), Greylag Goose (A. anser), and four other rarer species, have all increased since the 1970s. The likely factors responsible for these changes are mild weather conditions, increased availability of large water bodies and shifts in winter ranges of particular species. Temporal mismatch between SW Poland and the total flyways in Bean and White-fronted Geese was recorded when we compared the long-term and the short-term population trends. Increasing reports of other species in SW Poland match the general tendencies in Europe. These data document that regional trends are not a simple reflection of those in flyways as a whole. To understand changes in goose populations a re-established international count network is desired.     

Food constraints explain the restricted distribution of wintering Lesser White‐fronted Geese Anser erythropus in China

More than 90% of the Lesser White‐fronted Geese Anser erythropus in the Eastern Palearctic flyway population winter at East Dongting Lake, China. To explain this restricted distribution and to understand better the winter feeding ecology and habitat requirements of this poorly known species, we assessed their food availability, diet and energy budgets at this site through two winters. Lesser White‐fronted Geese maintained a positive energy budget when feeding on above‐ground green production of Eleocharis and Alopecurus in recessional grasslands in autumn and spring to accumulate fat stores. Such food was severely depleted by late November and showed no growth in mid‐winter. Geese fed on more extensive old‐growth Carex sedge meadows in mid‐winter where they were in energy deficit and depleted endogenous fat stores. Geese failed to accumulate autumn fat stores in one year when high water levels prevented the Geese from using recessional grassland feeding areas. Fat stores remained lower throughout that winter and Geese left for breeding areas later in spring than in the previous year, perhaps reflecting the need to gain threshold fat stores for migration. Sedge meadows are widespread at other Yangtze River floodplain wetlands, but recessional grasslands are rare and perhaps restricted to parts of East Dongting Lake, which would explain the highly localized distribution of Lesser White‐fronted Geese in China and their heavy use of these habitats at this site. Sympathetic management of water tables is essential to maintain the recessional grasslands in the best condition for Geese. Regular depletion of fat stores whilst grazing sedge meadows in mid‐winter also underlines the need to protect the species from unnecessary anthropogenic disturbances that enhance energy expenditure. The specialized diet of the Lesser White‐fronted Goose may explain its highly restricted winter distribution and global rarity.     

Amphibians: suitable candidates for breeding-release programmes

Zoological parks are playing an increasingly important role in the management of threatened species through education, the maintenance of captive gene banks and the reintroduction of captive-bred animals into the wild. This paper discusses the suitability of amphibian species for reintroduction. The important features of amphibians for these programmes are highlighted, i.e., their high fecundity to allow rapid build-up of captive populations coupled with few behavioural problems with captive-bred animals, as well as the low cost of maintenance. The potential problems of inbreeding, poor retention of innate behavioural repertoires after multiple generation captive breeding, and the introduction of alien pathogens into wild populations are considered. Release programmes for two species, the Mallorcan midwife toad Alytes muletensis and the Puerto Rican crested toad Peltophryne lemur, are reviewed.     

On the occurrence of the Lesser White-fronted GooseAnser erythropus in Greece

Summary Since 1859, wintering Lesser White-fronted Geese have been recorded 25 times in Greece. Of the records obtained in the second half of the 19th century only two, based on museum specimens, are valid. There were four records in the first half of the present century, while all the others come from the second half due to increased coverage mostly during IWRB midwinter censuses. Their distribution had been more southerly in the past, but in recent years only northern Greek wetlands hold the bulk of the wintering population, with the Evros Delta being the most important area (12, or 48% of all records). The wintering population of the species in the Evros Delta is threatened by habitat destruction and shooting.

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Zum Vorkommen der Zwerggans in Griechenland

Zusammenfassung Seit 1859 wurden in Griechenland 25mal Zwerggänse festgestellt; aus dem 19. Jh. liegen nur 2 sichere Nachweise vor. 4 Nachweise fallen in die erste Hälfte des 20. Jh., die restlichen alle in die zweite Hälfte, Die Verteilung der Funde scheint in der Vergangenheit weiter nach Süden gereicht zu haben; heute liegen nur aus dem Norden Beobachtungen vor. Der wichtigste Platz ist das Evros-Delta (12 von 25 Nachweisen; einmal 1630 Ind. im Februar 1963). Die Winterpopulation ist durch Biotopzerstörung und Abschuß bedroht.

     

The Genetic Integrity of the Ex Situ Population of the European Wildcat (Felis silvestris silvestris) Is Seriously Threatened by Introgression from Domestic Cats (Felis silvestris catus)

Studies on the genetic diversity and relatedness of zoo populations are crucial for implementing successful breeding programmes. The European wildcat, Felis s. silvestris, is subject to intensive conservation measures, including captive breeding and reintroduction. We here present the first systematic genetic analysis of the captive population of Felis s. silvestris in comparison with a natural wild population. We used microsatellites and mtDNA sequencing to assess genetic diversity, structure and integrity of the ex situ population. Our results show that the ex situ population of the European wildcat is highly structured and that it has a higher genetic diversity than the studied wild population. Some genetic clusters matched the breeding lines of certain zoos or groups of zoos that often exchanged individuals. Two mitochondrial haplotype groups were detected in the in situ populations, one of which was closely related to the most common haplotype found in domestic cats, suggesting past introgression in the wild. Although native haplotypes were also found in the captive population, the majority (68%) of captive individuals shared a common mtDNA haplotype with the domestic cat (Felis s. catus). Only six captive individuals (7.7%) were assigned as wildcats in the STRUCTURE analysis (at K = 2), two of which had domestic cat mtDNA haplotypes and only two captive individuals were assigned as purebred wildcats by NewHybrids. These results suggest that the high genetic diversity of the captive population has been caused by admixture with domestic cats. Therefore, the captive population cannot be recommended for further breeding and reintroduction.     

SUMMER RECORDS FROM WEST-SPITSBERGEN, 1964

An expedition studying geese spent six weeks in the summer of 1964 on the west coast of West-Spitsbergen, Svalbard. The topography of the area is described. Observations were made on 28 species of birds and details of numbers and distribution are given for each. Counts were made over a period of a week of the numbers of Common Eider Somateria mollissima which began nesting in a small colony as the snow cleared from the ground. Weights and measurements were taken of Purple Sandpipers Calidris maritima and Glaucous Gulls Larus hyperboreus. One species new to Svalbard was seen, a Black-headed Gull Larus ridibundus. Previously unrecorded breeding sites of Pink-footed Geese Anser brachyrhynchus, and Barnacle Geese Branta leucopsis were found, and it is concluded that the further spread of the Barnacle Goose is probable. New sea-bird colonies were also located.     

Characteristics, abundance and fertility of orphan eggs of the Lesser Rhea ( Pterocnemia-Rhea-pennata pennata ): implications for conservation

The Lesser Rhea (Pterocnemia-Rhea-pennata pennata) has a complex reproductive system that combines polygyny with sequential polyandry, in which males build the nest, fully incubate the eggs and care for the young. As occurs with the Greater Rhea (Rhea americana), Lesser Rhea females sporadically lay eggs outside the nest (‘orphan’ eggs), which are not incubated and thus fail to hatch. We have examined the orphan eggs of Lesser Rhea over two separate breeding seasons to determine their abundance and fertility status. During 2004 and 2005, weekly ground searches for orphan eggs were conducted in a wild population of Lesser Rhea in northwestern Patagonia, Argentina. During these searches the total number of nests, eggs in each nest and orphan eggs laid outside the nests was recorded. Orphan eggs represented approximately 7% of the total eggs laid in a breeding season. Six fresh orphan eggs were artificially incubated, four of them being fertile. Orphan eggs seemed to have two origins: some were laid near deserted nests in the early to mid-reproductive season; others were probably laid by first-time breeders and were found later in the reproductive season. Given the near-threatened status of the Lesser Rhea, harvesting and artificial incubation of orphan eggs, which otherwise would be unproductive, may contribute significantly to the conservation of this species, i.e., ‘recovered’ birds could be used for reintroduction or reinforcement of wild Lesser Rhea populations.     

Staging site fidelity of Greenland White-fronted Geese Anser albifrons flavirostris in Iceland

Capsule Based upon resighting histories of marked individuals, a high level of site loyalty was found for Greenland White-fronted Geese staging in Icelandic stopover areas in spring and autumn.

Aims To determine levels of within- and between-season staging site fidelity, to assess whether offspring adopt the staging areas of their parents and to determine relationships between Icelandic staging areas and winter provenance of individuals.

Methods Sequential resighting histories and recoveries (2658 observations) of 415 different individually marked geese were analysed from the period 1986–99.

Results In spring, > 90% of goslings associated with parents and siblings and all goslings were subsequently seen <4 km from where they were first sighted with parents in spring. Ninety-six percent of all multiple within-spring resightings of 192 marked individuals were within 4 km of each other; three geese moved 88 km from the southern to the western staging areas. Four percent of the 45 marked geese seen in two consecutive springs and none of the 27 birds seen in consecutive autumns moved more than 4 km between years. By contrast, significantly more (12%) moved greater than 4 km in subsequent seasons between spring/autumn (n = 56) and autumn/spring (n = 49). All these individuals shifted to Hvanneyri Agricultural College in autumn, the only declared hunting-free area for Greenland White-fronted Geese. Based upon resighting histories and recoveries of shot birds, Scottish wintering birds were more likely to use southern staging areas, and Wexford (Ireland) wintering birds were generally more likely to be seen staging in the western lowlands in Iceland.

Conclusions Given the apparent cultural reinforcement of patterns of use of staging areas in Iceland, the high levels of site loyalty and the relatively limited exchange between southern and western staging areas, we argue for strategic refuge designation throughout both staging areas to protect the population.     

Rise in human activities on the mudflats and Brent Geese (Branta bernicla) wintering distribution in relation to Zostera spp. beds: a 30-year study

Human activities may restrict access of wintering birds to their food resources, but habitat destruction and fragmentation may interact with disturbance to reduce carrying capacity. We analysed the abundance and distribution of wintering Brent Geese (Branta bernicla) in a major French wintering site from 1970 to 2000, when they experienced increases in human foreshore activities. We used mixed-effects models to test whether spatial extent of two Zostera species, Z. noltii and Z. marina, influenced the distribution of Brent Geese. The number of geese increased significantly with the area of both Zostera species beds. However, the relationship changed in the period after the increase in human activities. More specifically, fragmentation of the most accessible food resource, Z. noltii, negatively affected Brent Goose distribution. This fragmentation was in turn increased by human activities and reduced by the protection of Z. noltii (by banning human access). This implies that direct disturbance, although not excluded, might not have been the major cause of changes in Brent Goose distribution, but rather the effects of human activities on food resources. Thus, our results show that establishment of resource protection areas are efficient as conservation measures, and they underline the need for studies of impacts of human activities on resources, in addition to disturbance effects.     

Detecting hybridization between willow grouse (<Emphasis Type="Italic">Lagopus lagopus</Emphasis>) and rock ptarmigan (<Emphasis Type="Italic">L. muta</Emphasis>) in Central Sweden through Bayesian admixture analyses and mtDNA screening

Willow grouse (L. lagopus) and rock ptarmigan (L. muta) are sibling species with similar phenotypic and life histories that coexist sympatrically in wide areas of their distribution range. These grouse are amongst the most popular game birds in Scandinavia but contrary to other quarry species, no restocking with captive-bred animals has ever been performed. The discovery of two individuals with intermediate plumage features evoked the question of possible hybridization events between both species, an idea that did not seem too unlikely on the basis of habitat overlap. Thus, to assess whether any genetic exchange is occurring, we used different Bayesian-based admixture analyses of multilocus genotypes determined at twelve microsatellite loci. We also obtained mitochondrial COI-sequences from a selected number of individuals to infer the maternal geneflow and potential introgression. The capacity of our panel of microsatellite markers to detect hybridization was verified using assignments of simulated genotypes. We then evaluated the extent of hybridization in an actual sample of 111 individuals collected in a 100-km² area in the Scandinavian mountain range. An admixed condition was verified in one of the suspected hybrids, that seemed to carry a L. muta genotype with partial L. lagopus introgression. In addition, more than 4% of L. lagopus showed signs of hybridization under the most conservative scenario with respect to discrepancies between population assignment methods. This was unexpected, given that no L. lagopus displayed any apparent intermediate plumage features. Furthermore, interspecific geneflow of mtDNA haplotypes was lower than expected; which suggests that Haldane’s rule might apply for these two grouse species. Hence, plumage identification of hybrid ancestry is not always reliable and might lead to biases in the estimation of hybridization rates. Hybridisation may be expected to increase if the climate gets warmer as the habitat overlap between the species will become more extensive. We discuss whether hybridisation is a threat to the long-term survival of any of the two species.     

Mutual benefits of associations between breeding and non-breeding White-fronted Geese Anser albifrons

The relationships between yearlings and adult pairs of White-fronted Geese Anser albifrons were studied during pre-nesting, laying and early incubation in the central Canadian Arctic. Prior to nesting, females of lone pairs spent 75–81% of their time feeding, while males spent only 42–47% of time feeding and 46–50% alert. In pairs with one or more associated yearlings, both females and males fed significantly more and spent less time vigilant. Yearlings spent significantly less time (59%) feeding when alone compared with 71–76% when with pairs. Associations between yearlings and paired adults were most frequent before adult females began prospecting for nest sites. No prospecting pairs were associated with yearlings. After the egg-laying period, groups of geese, predominantly yearlings, made distraction flights over humans and terrestrial predators approaching nests, in contrast to the more cryptic behaviour of nesting pairs. The presence of groups of geese associated with some nest sites suggests that continuing parent-offspring relationships may involve assistance with nest defence.     

Comparing the genetics of wild and captive populations of White‐headed Ducks Oxyura leucocephala: consequences for recovery programmes

The White‐headed Duck is a globally threatened species historically recorded from Spain in the west to China in the east. It has suffered major population declines, local extinctions and range fragmentation. Several projects have attempted to reintroduce captive‐bred birds into parts of the former range in Europe, but with little success. Two captive stocks currently exist, one originating from Pakistan in 1968 and the other originating from Spain in 1982. This study compares the suitability of these captive stocks for specific reintroduction projects by using 11 microsatellite markers and mtDNA control region sequences to assess genetic differences between captive populations and wild birds from Spain and Greece. No significant population structure was found and all microsatellite alleles recorded in captive birds originating from Pakistan were also observed in the wild Spanish population. A higher diversity of alleles was observed in wild birds from Greece than from Spain, probably due to the effects of a strong bottleneck experienced in Spain in the 1970s. Compared with wild populations, both captive stocks have suffered a significant loss of diversity in microsatellites and mitochondrial DNA owing to founder effects and/or genetic drift, and therefore may not be well suited for release programmes. We recommend the development of a more diverse captive breeding programme based on birds taken from different areas of the range, in particular by supplementing the Spanish population with birds from North Africa. Our study shows the value of molecular tools in developing conservation programmes for threatened bird species and has implications for the design of recovery programmes.     

Assortative mating among animals of captive and wild origin following experimental conservation releases

Captive breeding is a high profile management tool used for conserving threatened species. However, the inevitable consequence of generations in captivity is broad scale and often-rapid phenotypic divergence between captive and wild individuals, through environmental differences and genetic processes. Although poorly understood, mate choice preference is one of the changes that may occur in captivity that could have important implications for the reintroduction success of captive-bred animals. We bred wild-caught house mice for three generations to examine mating patterns and reproductive outcomes when these animals were simultaneously released into multiple outdoor enclosures with wild conspecifics. At release, there were significant differences in phenotypic (e.g. body mass) and genetic measures (e.g. G_st and F) between captive-bred and wild adult mice. Furthermore, 83% of offspring produced post-release were of same source parentage, inferring pronounced assortative mating. Our findings suggest that captive breeding may affect mating preferences, with potentially adverse implications for the success of threatened species reintroduction programmes.     

Barnacle Goose (Branta leucopsis) feeding ecology and trophic relationships on Kolguev Island: The usage patterns of nutritional resources in tundra and seashore habitats

Insight into colonization of new areas by invasive species and their relationships with aboriginal species is a major challenge in ecology, allowing for prediction of the outcome of biological invasions. In this context, the current expansion of the Barnacle Goose (Branta leucopsis) is of great interest. The seasonal dynamics of Barnacle Goose feeding and the structure of its diet on Kolguev Island during the nesting and postnesting periods (May 27–July 29) have been examined. The diet structures of the invasive Barnacle Goose and the aboriginal species White-fronted goose (Anser albifrons) and Bean goose (A. fabalis) have been compared. The probability of interspecific competition and the ecological advantages in the diet patterns of these species have been estimated. If the Barnacle Goose population on Kolguev Island continues to increase, this may led to a decline in the population of aboriginal species of geese on the island.