Svenska fjällgäss födoval - Svenska Jägareförbundet
bakgrund

Ibland besöker svenska fjällgäss jordbruksmark. På fotot, från höstflyttningen 2015, ses två fjällgäss på en betesmark för hästar utanför Hudiksvall. Att fjällgäss besöker jordbruksmark anses av BirdLife Norge vara onaturligt och ett hot.

Svenska fjällgäss födoval


Ett argument om används av BirdLife Norge är att svenska fjällgäss sägs ha övergått till att söka föda på jordbruksmark vilket anses vara onaturligt, eftersom fjällgäss ska vara habitatspecialister och bara födosöka på naturliga gräsmarker. Det finns, idag, inga jämförande studier på födosöksbeteende hos svenska och norska fjällgäss.

Enligt BirdLife Norge finns det en risk att det svenska beteendet kan sprida sig till det norska beståndet om populationerna skulle mötas och kontakt utgör därför ett hot. Projekt Fjällgås anser att denna teori saknar vetenskaplig grund och delvis grundar sig i att BirdLife Norge har en felaktig bild av var svenska fjällgäss födosöker. Svenska fjällgäss återfinns oftast i habitat som starkt påminner om miljöer som beskrivits för den norska populationen. I den vetenskapliga litteraturen finns också flera exempel som visar att fjällgåsen, på samma sätt som andra gåsarter, är mycket anpassningsbar i sitt födosök (sa tabellen nedan), men visar en stark preferens för en viss typ av habitat. I den aktuella rapportens inledande stycke finns dock en nyansering av budskapet som inte funnits tidigare. Nu anges att även andra fjällgåspopulationer besöker jordbruksmark i form av stubbåkrar (…”although at times cereal stubbles” (sidan 9)). Uppenbarligen återfinns det ”onaturliga beteendet” även bland andra fjällgåspopulationer och man ställer sig lätt frågan var gränsen för naturligt och onaturligt beteende finns.

Den starka preferensen för naturliga och semi-naturliga gräsmarker är en stor och gemensam utmaning för projekten i Sverige och Norge.

Projekt Fjällgås anser att om skillnader verkligen skulle finnas mellan populationerna så är inte detta inte en betydelsefull fråga, utan möjligheterna för fåglar att hitta mat är viktigare än valet av föda. Högsta prioritet bör därför vara att skapa så stora möjligheter som går för fjällgäss att hitta bästa tänkbara habitat. Målbilden för det svenska och norska projektet borde inte skilja sig åt i denna fråga, då vi eftersträvar samma habitat. Att kartlägga och återskapa, eller nyskapa, denna typ av gräsmarker för de förhoppningsvis växande fjällgåspopulationerna utmed deras respektive flyttvägar, är en viktig utmaning för ett långsiktigt bevarandearbete i båda länderna.

Enligt BirdLife Norge finns det en stor risk för att svenska fjällgäss genom sitt födoval kommer att bli betraktade som en problemart ”pest species” på grund av uppkomna skador i jordbruket. Det svenska fjällgåsprojektet menar att ett sådant påstående är extremt långsökt och helt saknar vetenskapligt grund.

Feeding of Swedish LWfG

LWfG on agricultur crops

You may find Swedish LWfG feeding on agricultur fields. On the photo, from autumn migration 2015, two LWfG feeding in a pasture for horses outside Hudiksvall. Accordning to BirdLife Norway, feeding on agricultur fields isa unnatural trait fro LWfG and a threat.

One reason for the Norwegian criticism is said to be the transition to feed on cultural habitats/farmland made by Swedish LWfG. This is regarded unnatural, as LWfG are said to be habitat specialists. But there are no comparative studies regarding differences in habitat choice between Swedish and Norwegian LWfG.

According to BirdLife Norway, the mixing of birds from Sweden and Norway poses a risk and could lead to a change in choice of feeding habitat and contact between the populations therefore constitutes a threat. The Swedish LWfG Project consider this theory to lack scientific ground and partly depend on an erroneous conception regarding the feeding preferences among Swedish birds. These birds are frequently found in habitats strongly reminding about those described to be typical for Norwegian birds. In the scientific literature there are a number of examples showing that LWfG, like other goose species, easily adapts their feeding habits (cf Table below), at the same time as they demonstrate a clear preference to a certain type of habitat. In the introduction of the present report we find that not only the Swedish LWfG-population feed on agriculture crops (…”although at times cereal stubbles”… at p. 9). Accordingly, the “unnatural” trait for the Swedish population is also found in other populations and as a consequence it is hard to understand where the defined limit for “natural” and “unnatural” feeding grounds for the species is found

The strong preference to natural and semi-natural grassland is a great and common challenge for both LWfG project in Sweden and Norway.

The Swedish LWfG Project regards possible differences regarding habitat choice between the two populations not to be an overriding issue. The feasibility to find food is more important than the selection of diet. Priority number one therefore should be to create as many alternatives as possible to find the most suitable habitat. This objective should be the same for conservation efforts in Sweden and Norway, as the same habitat is aimed at. To map and recreate or create this type of grassland benefitting the hopefully increasing LWfG populations along their respective flyway is an important task for the long-term conservation activities in both countries.

According to BirdLife Norway there is a genuine risk that the Swedish population will be regarded as pest species due to damages caused in agricultural areas. The Swedish LWfG Project consider this statement extremely farfetched and totally devoid of any scientific support.

Scientific framework with references for interested readers.

No scientific studies including comparisons between the feeding preferences among LWfG populations in Sweden and Norway have been made. Hence any statement regarding any differences is based on as best anecdotal information or personal opinions.

Lesser White-fronted Geese are known to feed in a variety of habitats spanning from Russian forested areas (AEWA 2008), saltmarshes in Greece (AEWA 2008) to agriculture fields in Hungary (Bogyó et.al. 2013).
The studies made on LWfG feeding show that the birds may feed on a variety of plant species ranging from reed shots on spring staging site in Finland (Markkola et.al. 2003), wheat and barley in western Asia (Lorentsen et.al. in Madsen et al. 1999) and under certain conditions even on Carex on winter sites in China (Wang et.al. 2013b).

Table 1. Studies on LWfG diet or food preference.

Reference

Plant family or corresponding that LWfG are observed to feed on.

Locality of study

Lorentsen & Spjotvoll 1990

Equisettacea, Poacea,Cyperacea, Polygonacae, Astaraceae

Breeding area Norway

Niemelä & Markkola 1997

Poaceae, Juncaceae, Other monocotyledons, dicotyledons

Spring staging site in Finland

In Madsen et.al. (1999), Lorentsen et.al.

Various, including:  ”wheat and barley”

Reference to “wheat and barley from stopover/winter sites in Azerbaijan and Bulgaria

Markkola et.al. 2003

Poaceae, Rushes and Cyperaceae, Monocotyledonae sp.

Spring staging site in Finland

Cong et. al. 2012

Eleocharis, Alopecurus, Carex

Wintering area in China

Bogyó et.al. 2013

Various  including non-specified “Agriculture crops”

Hungary

Wang et.al. 2013a

 

Alopecurus, Cynodon, Eleocharis

Wintering area in China

Karmiris et.al. 2014

Graminoids, aquatic plants and

halophytes

Wintering areas.  Lake Kerkini, Evros Delta, Greece

 

During migration, Lesser White-fronted Geese are mainly feeding on natural and semi-natural grasslands, like saltmarshes, seashore and floodplain grasslands, as well as on steppe vegetation, but also on artificial grasslands and arable land, e.g. in Azerbaijan, Bulgaria, Finland, Hungary and southern Russia (Lorentsen et al. in Madsen et.al. 1999)

In Germany and the Netherlands, Lesser White-fronted Geese are mainly observed on grasslands, often with low management intensity. The two major sites in the Netherlands are former marine areas, now embanked, but still partly having the old soil structure with hummocks, intersected with old creek systems (Ouweneel et.al. 2008).

Many goose species have changed feeding from more “natural habitats” to more energy-rich agriculture crops, which has been beneficial for the population (e.g. Eerden et.al. 1996, Fox et.al. 2005).

Greater White-fronted Goose, a closely related species to LWfG, made this shift in feeding preference to adopt to changes in food availability, showing that such shifts in diet may be beneficial for a species (see Madsen et.al. 1999).

References

AEWA. 2008. International Single Species Action Plan for the Conservation of the Lesser White-fronted Goose (Western Palearctic population). Technical series

Bogyó, D., Ecsedi, Z., Tar, J. & Zalai, T. 2013. Hungarian National Action Plan for Lesser White-fronted Goose (Anser erythropus). Ministry of Rural Development, State Secretariat for Environmental Affairs. 93pp. (In Hungarian with English summary)

Cong. P., Wang X., Cao L. & A.D. Fox. 2012. Within-winter shifts in Lesser Whitefronted Goose distribution at east Dongting lake, China. Ardea. 100(1): pp 5-11.

Eerden, M.R. van, M. Zijlstra, M. van Roomen & A. Timmerman, 1996. The response of Anatidae to changes in agricultural practise: long-term shifts in the carrying capacity for wintering waterfowl. Gibier Faune Sauvage 13: 681-706.

Fox, A.D., J. Madsen, H. Boyd, E. Kuijken, D.W. Norris, I.M. Tombre & D.A. Stroud, 2005. Effects of agricultural change on abundance, fitness components and distribution of two arctic-nesting goose populations. Global Change Biology 11: 881-893.

Karmiris, I., Papachristou, T., Platis, P. & Kazantzidis, S. 2014. The diet of the wintering Lesser White-fronted Goose (Anser erythropus L., 1758) in two wetlands in Greece. Final Rep., action A5, LIFE10NAT/GR/000638 project “Safeguarding the Lesser White–fronted goose Fennoscandian population in key wintering and staging sites within the European flyway». Hellenic Agr. Org. “DEMETER”/Forest Res. Inst., Thessaloniki, Greece.

Koffijberg, K. & van Winden, E. 2013. Lesser White-fronted Geese in The Netherlands: a review of trends, phenology, distribtuion patterns and origin. Sovon-rapport 2013/48. Sovon Vogelonderzoek Nederland, Nijmegen

Lorentsen, S-H. & Spjøtvoll, Ø. 1990. Notes on the food choice of breeding Lesser White-fronted Goose Anser erythropus. Fauna Norv. Ser. C., Cinclus. 13: 87-88

Lorentsen, S.-H., Øien, I.J., Aarvak, T., Markkola, J., von Essen, L., Farago, S., Morozov, V., Syroechkovsky Jr., E. & Tolvanen, P. 1999. Lesser White-fronted Goose Anser erythropus. Pp.: 144-161 in: Madsen, J., Cracknell, G. & Fox, A.D. (Eds.) Goose populations of the Western Palearctic. A review of status and distribution. Wetlands International Publ. No. 48, Wetlands International, Wageningen, The Netherlands.
Madsen, J., Cracknell G. & Fox T. 1999. Goose Populations of the Western Palearctic. A review of status and distribution. Wetlands International Publication 48, NERI, Wageningen/Kalø.

Markkola, J., Niemela, M., & Rytkonen, S. 2003. Diet selection of lesser white-fronted geese Anser erythropus at a spring staging-area. Ecography

Niemelä, M. & Markkola, J. 1997. Diet selection of the Lesser White-fronted Goose Anser erythropus in the spring staging area of Tömppä seashore meadow, Hailuoto, Finland. In: Tolvanen, P., Ruokolainen, K., Markkola, J. & Karvonen, R. (eds). Finnish Lesser White-fronted Goose conservation project. Annual report 1997. WWF Finland Report No 9: pp. 43-44.

Ouweneel, G., van der Linden, L, van der Linden, A. & Koffijberg, K. 2008. Terreingebruik van Dwergganzen in het Oude Land van Strijen. Limosa 81: 17-23. [in Dutch with english summary)

Wang X., Fox A.D., Cong P.&Cao L.2013 a. Food constraints explain the restricted distribution of wintering Lesser White-fronted Geese in China. Ibis 155: 576-592.

Wang X., Zhang Y., Zhao M., Cao L.& Fox A.D. 2013 b. The benefits of being big: effects of body size on energy budgets of three wintering goose species grazing Carex beds in the Yangtze river floodplain, China. J. Ornithol. 154:1095-1103.

Wang, X, Fox, A.D., Zhuang, X., Cao, L., Meng, F. & Cong, P. 2014. Shifting to an energy-poor diet for nitrogen? Not the case for wintering herbivorous Lesser White-fronted Geese in China Journal of Ornithology 155

 


  • Dela med e-mail
  • Skriv ut
2017-01-11 2017-01-18