Ecology and conservation of the Lesser White-fronted Goose Anser erythropus

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

University of Oulu, Linnanmaa IT115

Topic of the dissertation

Ecology and conservation of the Lesser White-fronted Goose Anser erythropus

Doctoral candidate

Master of Science Juha Markkola

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Ecology and Genetics

Subject of study

Ecology, conservation biology

Opponent

Professor Toni Laaksonen, University of Turku

Custos

Doctor of Philosophy, Docent, University teacher Seppo Rytkönen, University of Oulu, Faculty of Science, Ecology and Genetics Research Unit

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Ecology and conservation of the Lesser White-fronted Goose

I started field studies of the rare and threatened lesser white-fronted goose (Anser erythropus), abbreviated LWfG, in 1985 and have studied breeding biology and habitat selection of the LWfG in Lapland, phenology of spring migration and diet selection on the Bothnian Coast, and genetic structuring of the LWfG in its whole distribution area from Fennoscandia to East Asia. The LWfG is the most threatened original breeding bird species in Nordic countries. In early 20th century c. 1000 pairs bred in Finnish Lapland and the Fennoscandian spring population was at least 10 000 individuals. Breeding has not been confirmed in Finland after 1995, but LWfG are still breeding on the Norwegian side not very far from the border.

The studied LWfG subpopulation in sub-arctic Finnish Lapland consisted of 2-15 breeding pairs annually in 1989-1995. A total of 30 broods were observed with an average of 2.9 goslings per brood. The 1st year survival of satellite transmitter tagged and ringed 10 geese was low due to - in most countries illegal - hunting. Satellite locations, recoveries and re-sightings were received from NW Russia, Kazakhstan and north of the Black Sea. Cold spells had a negative, and warm early summers a positive influence on reproduction.

Habitat selection was studied in the same area. LWfG preferred the vicinity of water, flat close-range landscape, low forest height and intermediate relative altitudes. LWfG aggregated in the vicinity of conspecifics within the preferred habitats. The developed habitat selection model assigned observation points correctly with 83.4 % success, which enabled the model to be applied in the whole of sub-arctic Finnish Lapland. Locations of historical observations of LWfG matched the predicted distribution of breeding sites. The area of suitable LWfG environment covers 15 000 km2 in Finland and more in Norway and Sweden.

Spring migration patterns of LWfG on the Bothnian Bay coast were examined using observations published by Einari Merikallio for the years 1907-1916 and observations collected and made for this study in 1949-2014. Patterns of the taiga bean goose (Anser fabalis fabalis) migration were studied for the period 1975-2014. Arrival of the short-distance migrant, the bean goose, advanced more and the advance started earlier than the long-distance migrant, LWfG. In the bean goose, the advance was 10.9 days since late 1980’s vs. 5.3 days in LWfG since the beginning of the 2000’s.

In LWfG, the best model for explaining variation in timing included global and local temperatures, in the bean goose global and local temperatures and winter NAO (North Atlantic Oscillation, indicating a prevalence of westerly winds). Increasing global temperatures explained the advance in both.

In the spring staging places of the Bothnian Bay almost all dietary items determined in LWfG droppings were grasses growing in extensive sea-shore meadows. Only Phragmites australis, Festuca rubra and Triglochin palustris were preferred. As the feeding habitat, LWfG preferred extensive natural meadows. Mowing and livestock grazing benefit the restoration of habitats.

Genetic structuring of the LWfG was examined in its whole distribution area from Fennoscandia to East Asia using DNA samples of 110 individuals, sampled from individuals caught for tagging, from zoological museums etc. 15 mitochondrial DNA haplotypes were found and assigned to two mtDNA lineages. Molecular variance showed significant structuring among populations: the main western in western Russia – Central Siberia, the main eastern in East Asia and the Fennoscandian one, which earns a status as an independent management unit. Thus, it should be protected separately, and measures threatening the unit, e.g. restocking of individuals from other populations, should be avoided.
Last updated: 18.1.2022