Background

Until early 20th century the Lesser White-fronted Goose was a rather common breeding bird in the mountainous area of Scandinavia and all the way to far east Russia.

The population then suffered a dramatic decline. In 1970 there was only a small part of the Swedish population left. As a reaction to the population decrease, Lambart von Essen at the Swedish Association for Hunting and Wildlife Management together with his colleagues initiated a conservation project for the Lesser White-fronted Goose (hereafter LWfG) in 1975. The first years after the Project start, they put a lot of effort into locating wild LWfG still breeding in Sweden. They also tried to investigate what had happen to the population by interviewing local inhabitants in the area.

In 1981 the first release of young LWfG, bred in captivity, was done in the mountains of Arjeplog, Sweden. This, as an attempt to reinforce the wild LWfG population that was still breeding in Sweden.    

The major cause of the drastic population decline was detected as high hunting pressure and environmental changes along the migration route and in the wintering areas in Western Asia and Eastern Europe. Having this in mind, the Project decided to use Barnacle geese as foster parents as they spend their winters mainly in western Europe. The young LWfG then learned to migrate to wintering areas in western Europe, primarily The Netherlands where no hunting was allowed, and the habitat offered a good quality of grasslands. LWfG has a strong philopatry, which means that they will return and breed in the area where they grew up and learnt to fly. So, in springtime the released LWfG returned to the mountains in Swedish Arjeplog, where they were released and learnt to fly. This conservation action was very successful, and the population was saved from extinction by the combination of reinforcement releases and an altered migration route.  

In 1999, the work with breeding and releasing LWfG with Barnacle geese as foster parents went into a sudden freeze. A genetic study had discovered introgressive hybridisation from Greater White-fronted Goose among the captive breeding population. The result was that the whole breeding program was terminated.

2020, Diez-del-Molino D et al. published a scientific paper that determined that it is highly unlikely that the reinforcement releases that was done during 1981-1999 caused any element of foreign DNA to be spread into the wild population.

To be able to continue the work with reinforcement releases of LWfG to strengthen the population, young Russian LWfG was caught in the wild and imported to Sweden. These Russian birds became the foundation of a new breeding stock. In 2010 the releases of LWfG could continue but now with Russian descendent birds and without foster parents.

The release of young LWfG and the altering of the migration route in combination worked out well and today the Swedish Lesser White-fronted Goose population is the only breeding population within the European Union.

The Swedish Hunting Association has been the head of Project LWfG since the beginning. Today, Nordens Ark Zoo and Norrbottens Ornithological Association is cooperators within the project, and it runs according to the Swedish Conservation plan for the species. The project has been running since 1975 and the focus has been on breeding and releasing LWfG. Today the project works widely with different actions, national and international, as an attempt to save the Swedish population of LWfG.

Facts

Lesser White -fronted Goose (Answer erythropus) is classified as a critically endangered species CR in SLU artdatabankens redlist 2020. The species is classified as vulnerable VU, globally and in the rest of Europe.

Foto: Niklas Liljebäck

Exterior description

The Lesser White -fronted Goose is a small and delicate dark grey goose with a tall white facial blaze and a yellow eye ring. It has a short, pink beak and the belly is striated with black bars. It’s hard to tell the difference between the sexes. In springtime however when the LWfG appears in couples it’s possible to tell who’s male and who’s female by looking at their behavior. The characteristic appearance of a LWfG doesn’t show in a young bird but by the time they reach one year of age both the eye ring and the belly spots usually has appeared.  

The Lesser White -fronted Goose is easily mistaken for the Greater White -fronted Goose. Although the GWfG is, as the name indicate, a much larger goose which lack the yellow eye ring and has more and thicker black bars on the belly. At distance, also other relatives in the Anser family like Greylag goose, Pink-footed goose and Bean goose can be hard to tell from the LWfG, especially in a hunting situation.

The Lesser White- fronted Goose makes a high -pitched, melodic almost whistling sound, cackling “kikyi-kikyi”. In the mountain area this cackling can be heard miles away. The sound is very different from the rougher cackling that comes from a Greater White -fronted Goose.      

In early 20^th century the LWfG population was spread throughout the most northern part of the palearctic area, so from Scandinavia to far east Russia. Today only a few fragmented parts of the population exist.

Ecology- Swedish population

The LWfG usually commit to their partner for life. It takes until two years of age before a female LWfG breed for the first time, but it is not unusual that she waits another year as well. Adult LWfG is very committed to previous breeding sites and juvenile birds are committed to the place where they learnt to fly. Especially young female LWfG is very committed to the place where they learnt to fly, while young males can pair with females from other populations at the winter staging ground.

The breeding area of the LWfG in Sweden is located where the birch forest meets the lower alpine area. They prefer mountain lakes with a mosaic of islands and a lot of birch and willow for protection. Egg laying starts in the middle of May when snow free patches appears and the ice on the lakes are beginning to break. A delay in spring can result in LWfG giving up their breeding attempt. This contributes to big fluctuations in the number of young produced yearly.

The female LWfG incubate her eggs in 25-28 days while the male partner is guarding. After the eggs are hatched, both female and male LWfG helps their young throughout the mountain area by foot. After a bit more than a month the young LWfG are able to fly and in the turn of the month August- September family groups gather for a joint flight south. Families then stick together throughout the entire autumn, winter, and the beginning of spring. That way young LWfG learn migration routes and staging sites from their parents.     

Couples of Lesser White- fronted Goose that was successful in breeding, molt at the breeding area after the eggs have been hatched. Those who has not bred usually gathers in big groups and travels to other sites to molt. Lately in Sweden we have seen big groups of LWfG molting in Lillfjärden Hudiksvall. Studies show that LWfG sometimes chose to fly long distances to find a good molting place. When geese molt, they lose all their wing pens at the same time and are therefore not able to fly. It takes a lot of energy to grow back the feathers so a molting place with good forage and few predators are extremely important.

In the end of March, the first reports of sighted LWfG in Skåne, south of Sweden usually occurs. In the beginning of April, you usually find LWfG in Svartåmynningen in Östergötland. How long they stay there before continuing their journey north usually depends on the weather.

In May, a major part of the Swedish population of LWfG is located in the mountain area but still below the breeding area. They then do flights to probe the breeding area until its snow free and it’s time to start a breeding attempt. In the end of August, they leave the breeding area and stage for a longer time in middle Sweden. In the beginning of October, they usually migrate straight to their wintering sites, mainly in the Netherlands and Germany.   

 

The Swedish population of Lesser White-fronted Goose

The Swedish population of Lesser White- fronted Goose (LWfG) has steadily been increasing since the population declined in 2012-2013 and this is primarily due to the reinforcement releases of LWfG that has been done.

Foto: Projekt fjällgås

In 2023 the population size was estimated to 130-140 birds. Previous survival estimations shows that the breeding success for the Swedish population is not high enough to compensate for the losses of adult birds during summer. Even though breeding success has been relatively good during the four last years (2021,2022,2023,2024) were totally more than 100 young LWfG has been fledged, it is still a very small and fragile population. Reinforcement releases of captive bred birds is still needed to avoid a population decline. Sweden holds the only breeding population of LWfG within the European Union and with that comes a big responsibility for the species survival.

A major part of the Swedish LWfG population is today observed and reported at the pre-breeding site in Västerbotten. An estimation of the population size is then made with the numbers counted in Västerbotten together with the readings of color rings in other places in Sweden and abroad. The Swedish population of LWfG migrates to the southwest and flocks are regularly seen in the southern parts of the country, primarily in Hudiksvall, Hjälstaviken (Uppland), and Svartåmynningens nature reserve (Östergötland).  

To monitor LWfG in the field is hard work and it requires a lot of knowledge and patience from the observer. The Swedish Lesser White-fronted Goose Project is dependent on our devoted volunteers that spend hours of their free time to observe and report LWfG appearing in their local area.

Lesser White-fronted Geese has a strong philopatry and especially females tend to return and breed at the site where they learned to fly. The Swedish population of LWfG has only one known breeding site in Sweden. This makes the population vulnerable since a site-specific threat then can become a threat to the entire population. This is the main reason why the Swedish Lesser White-fronted Goose Project in 2020 started up a new pilot project which aims to establish a new breeding population in a different geographic area in the Swedish mountains. Hopefully this action will help the Swedish population of LWfG to reclaim new breeding sites outside the main breeding area.

Threats and measures

Project LWfG wants to act against as many threats towards the LWfG population as possible. During the years that Project LWfG have been active some threats has been averted while others has increased.

Photo: Project LWfG

Major population decrease during 20th century

Project LWfG started their work with releasing captive bred birds when the population was nearly extinct. Through this hard work, for several years, the population went from decreasing rapidly to slowly increasing.

High mortality during migration

When the project started their work, the LWfG in Sweden migrated southeast through Russia towards western Asia and eastern Europe. During this migration route the mortality was high, mainly because of high hunting pressure and environmental changes. So, in the beginning of the project, captive bred LWfG was released with Barnacle geese as foster parents. Barnacle geese migrates to The Netherlands and did then imprint this behavior on the LWfG. The result of this is that the population of LWfG today migrates mainly to The Netherlands and the mortality during migration and wintering is minimal.

Predation in the breeding area

All land breeding bird species is vulnerable to predation and the LWfG is no exception. Even though this is a natural element, the Swedish population of LWfG is still so small so that every individual is important. The advances of the Red Fox in the Swedish mountainous area have been a hard blow for both LWfG and other artic specialists as the Artic Fox. Project LWfG and the municipality has during the years put in a lot of effort in hunting Red Fox in the breeding area of LWfG.

Predation from White tailed eagle on molting adult geese is still a big problem at the breeding site. It is hard to solve since this individual eagle that has specialized on predating on LWfG also is a protected species.

The Swedish Association for Hunting and Wildlife Management has initiated a project which aims to eradicate the alien invasive species Mink (Neovison vison) in the breeding area of the LWfG. Mink turned out to be much more abundant in the area than we previously thought. Hopefully we will be able to see positive effects of this in the coming years.

Public interference

Disturbance from fishers walking alongside mountain lakes where the LWfG is breeding can be a big problem. Sometimes it only takes one disturbance for a couple to abandon their nest. The project is keeping a dialog with the municipality to set up protection areas around the breeding sites.

Increasing hunting pressure at wintering sites

One of the reasons why the migration route for the Swedish LWfG was altered to The Netherlands to begin with was that geese hunting was almost nonexistent there. Although resent years the costs of damage caused by geese has increased enormously in The Netherlands and therefore, they have set up for protective hunting of geese. The project is, through dialog with authorities, hunters and bird watchers’ organizations in The Netherlands acting for decisions that will make these hunting actions interfere with the LWfG as little as possible. For example, to only allow hunting during periods of the year when LWfG do not appear at these locations. Hunting at wintering site is not considered a threat to the Swedish LWfG population today.

Molting sites

A good molting site is extremely important for geese since they shed all their wing pens at the same time and therefore temporarily loses their ability to fly. A molting site needs to have a high qualitative forage and a low predation pressure. The project LWfG has started to map out the molting places of LWfG. One important molting site for the Swedish population of LWfG is in Lillfjärden, Hudiksvall. This place is very special since it consists of a lake and a city park which attracts a lot of wild birds. The pasturage is limited because of high grazing pressure from all the wild graylag geese choosing to molt here. Efforts have been made, trying to disturb the graylag geese. This, with the purpose of getting them to choose a different molting site, thus the efforts only had a limited effect. The project is having a dialog with the authorities on further actions to favor those LWfG whom choose this molting site.

Resting Sites

There are well-known staging sites in Sweden that are frequently used by LWfG on their spring- and autumn migration. A majority of these sites are already protected and managed in a way that favors LWfG. But still there are some staging sites that are unknown to the project. To find, protect and manage these sites are prioritized actions for the Swedish Lesser White-fronted Goose Project. One important tool in this investigative work is LWfG equipped with GPS-transmitters.   

A scientific report regarding the Swedish population of LWfG was published in 2023. The study was based on GPS-data from wild caught Swedish LWfG and it revealed an unexpected wide network of migration corridors and staging sites.  So far unknown key stopover sites were discovered in Denmark, northern Germany, and Sweden (Kruckenberg, H. et al. 2023). This gives us valuable information in the work with site protection and management.  

Kruckenberg, H., Moonen, S., Kölzsch A., Liljebäck, N. & Müskens, G.J.D.M. 2023. Migration routes and steppingstones along the western flyway of Lesser White-fronted Geese (Anser erythropus). Bird Conservation International, 33, e42, 1–8.      

Scientific publications

A short summary of some of the latest Scientific publications regarding the Swedish population of Lesser White-fronted Goose.

Based on all data collected from ringed released LWfG since the start of the reinforcement project in Sweden a comparison was made of the fate of individual birds being released with foster parents, as in the 'old' project and birds released without support of foster parents as has been done from 2010 onwards. The article is published in the journal Restoration Ecology, with the title: Reinforcement of an endangered goose population: the effect of age and interspecific fostering on survival of released birds has open access and can be retrieved via: https://onlinelibrary.wiley.com/doi/10.1111/rec.14286?af=R

Many thanks go to all contributing to the project during the years by fieldwork, and all people providing resightings of ringed birds in the past 40 years.

Short summary of main results:
1. Our analysis include data from 646 birds, released 1984-2017, including two different age classes, divided in two distinct periods. In the years 2000-2010 no birds were released.

2. LWfG released the same year as they were born were released with foster parents of Barnacle Geese in the first period and without support of foster parenting in the second period. Analysis show that use of foster parents enhanced survival rates, but these differences were detectable only in the first year of life. The higher survival can likely be explained by the fact that foster parents learned the released bird crucial behaviors (e.g. feeding, anti-predator and migration). Such transfer of knowledge between generations, so called social learning, has been described for many goose species.

3. Birds born the year before they were released, without foster parents in both periods, showed significantly lower survival than birds released the first year of life. But this difference between age classes was not so big when both age classes were released without foster parents in the second period. Likely the birds released as one-year olds, had several weeks to finalize the moulting, that is when they change feathers in the wing and cannot fly, making them highly vulnerable for up to a month.

4. Data suggest that most losses occurred during the acclimation period i.e. the weeks following the release, most likely due to predation of the released birds.

5. In conclusion the conservation benefits of using foster parents of other species must be balanced in relation to the risk of undesired behaviors such as hybridization and high costs. The authors advise other, future, conservation projects to carefully consider foster parenting as one method to improve survival probability, especially if capacity to produce individuals to be released is a limiting factor for conservation objectives.

Population genomics reveals lack of greater white-fronted goose introgression into the Swedish lesser white-fronted goose.

The complete genomes of 21 birds from the Swedish, Russian and Norwegian LWfG populations were sequenced, and compared with genomes from other goose species, including the GWfG. No evidence of interspecific introgression into the wild Swedish LWfG population in either nuclear genomic or mitochondrial data were found. Therefore, it is highly unlikely that the reinforcement programme between 1981 and 1999 led to the introduction of introgressed genes into the wild Swedish population.

Swedish LWfG birds are genetically distinct from the Russian and Norwegian populations and display comparatively low genomic diversity and high levels of inbreeding. The comparatively lower diversity in the population indicates a reduced potential to adapt to changes in the environment, but the second release programme 2010 may have resulted in a restoration of genetic diversity and mitigation of inbreeding in the population.

Diez-del-Molino D, von Seth, J., Gyllenstrand, N., Widemo, F., Liljebäck, N., Svensson, M., Sjögrem-Gulve, P., & Dalén, L. 2020. Population genomics reveals lack of greater white-fronted goose introgression into the Swedish lesser white-fronted goose. Scientific Reports Volume 10.

Use of foster parents in species conservation may cause conflicting objectives: hybridization between Lesser White-fronted Goose Anser erythropus and Barnacle Goose Branta leucopsis.

An LWfG conservation programme launched in the late 1970s used Barnacle Geese Branta leucopsis as foster parents. Starting in 2003, mixed pairs LWfG x BG produced at least 49 free-flying hybrid offspring until 2013.  In total 1.7 % of all released young males with foster parents were observed to produce hybrid offspring with Barnacle Goose females. As a response, the conservation program decided to remove LWfG males in mixed pairs and their offspring in the wild.

In the Netherlands, hybrids were reported annually from 2003/2004 onwards. The highest numbers were recorded between 2008/2009 and 2013/2014 (maximum of 8–15 birds per year). Only one observation was reported from Finland and none from Norway. In the breeding area (and release site) of LWfG in the mountains of Arjeplog, no hybrids or mixed pairs were ever found.

No evidence that the hybrids ever posed a serious threat to LWfG breeding in Fennoscandia was found, but any translocation program using foster parents should seriously take into account the risk that hybrids between the target and foster species may be produced.

Liljebäck, N., Koffijberg, K., Kowallik, C., Månsson, J. & Andersson, Å. 2021. Use of foster parents in species conservation may cause conflicting objectives: hybridization between Lesser White-fronted Goose Anser erythropus and Barnacle Goose Branta leucopsis. Ornis Svecica, 31, 125–138.

Migration routes and stepping stones along the western flyway of Lesser White-fronted Geese (Anser erythropus).

This article is based on transmitter data from four Lesser White-fronted Geese which was caught and provided with a transmitter in Hudiksvall in 2015 and 2016. All four tracked LWfG visited the core breeding area in Swedish Lapland and migrated to winter in the Netherlands. The transmitter data was processed and statistically examined and the final result revealed several, so far unknown, stopover sites in Sweden, Denmark and northern Germany.

Of new sites identified, Roden Fed in Danish Lolland was pinpointed as a site of great importance since the LWfG was staging there for about four weeks annually.  Of the in total 22 identified sites, 7 were not listed as SPAs and of the 14 sites that was listed, 6 of them lacked LWfG in the list of species special importance. The article spotlight the fact that from a species protection perspective mapping all sites used during migration and wintering is essential for a small and vulnerable population, like the Lesser White-fronted Goose in Western Europe. An effective protection regime for the mapped sites could prohibit threats regarding hunting or degradation of foraging areas. A complete chart of all the staging sites and their SPA status can be found in the article.

All tracked autumn migrations started from the same site (Lake Hjälstaviken, Sweden). In most years all birds also left this site on the same night, indicating coordinated departure of flocks for autumn migration. Data also describe that migration routes and strategies differed between spring and autumn which is in accordance with previous research on other goose species. 

The study found little evidence of geographically overlap of migration routes described for the Norwegian and Russian LWfG populations. Therefore, the authors suggest the Swedish population can be viewed as a separate conservation unit.

Kruckenberg, H., Moonen, S., Kölzsch, A., Liljebäck, N., Müskens, G.J.D.M. 2023. Migration routes and stepping stones along the western flyway of Lesser White-fronted Geese (Anser erythropus). Bird Conservation International, 33, e42, 1–8.