New hit for COAT's lesser white-fronted goose forecast
Published on: 3. November 2025
COAT Finnmark and Birdlife Norway have had a fruitful research collaboration for several years on the factors that control the population development of the critically endangered lesser white-fronted goose in Finnmark. Since 2024, we have used new knowledge about the close connection between the small rodent population cycle and the goose's reproductive success to make model-based forecasts one year ahead.
Foto: Thomas Aarvak
The predictions were well-targeted in 2024, but actually even better for 2025 (see graphs below). Birdlife Norway's monitoring showed that only 3 little goose broods fledged this year - which is very close to the forecast of 4 broods. The ongoing low phase in the small rodent cycle (see the grey-sided vole graph) has obviously led to extensive predation on goose nests and chicks. This also corresponds with the extensive nest predation COAT documented on other bird species this summer.
COAT's forecast model for willow ptarmigan in Finnmark also predicted a marked decline in the ptarmigan population this year, largely driven by the ongoing low phase in the small rodent cycle. This forecast did not correspond well with results from FeFo's ptarmigan survey in August which indicated that the population was at the same level as the previous year. One reason for the difference in the accuracy of the predictions for lesser white-fronted goose and willow ptarmigan may be that the survey data that goes into the models is less precise for grouse than for geese. It may also be easier to predict chick production (goose) than population changes (ptarmigan) since the latter is determined by a combination of adult survival and chick production.
Time series graphs based on the number of captured grey-sided voles (top) and the number of observed lesser white-fronted goose broods (bottom) shown as black points connected by solid black lines for the period 1998–2025. The model forecasts for 2024 and 2025 are shown as colored points with uncertainty margins (90 % confidence intervals).