Approximately 30.000 non-breeding Greylag geese visit the Oostvaardersplassen each year. Throughout the year, there are three periods in which the numbers of geese in the reserve are at their highest: during May geese travel from Germany and Sweden to the Oostvaardersplassen to moult; and during spring and autumn, geese travel from Denmark and Sweden to feed in the grassy areas.

Non-breeding Greylag geese perform a moulting migration to well defined moulting areas, where they moult their primaries simultaneously and are flightless for about 28 days. The Oostvaardersplassen has become the most important moulting site for Greylag Geese in Europe.

The majority of those moulting in the Oostvaardersplassen are non-breeding birds. However, the number of breeding pairs that have been sited in the Oostvaardersplassen is steadily increasing.
The timing of moult influences the moment at which a goose can start building up its body reserves needed for autumn migration, effecting their survival and future breeding performance.
During the moulting period in June they live for a few weeks in the reeds eating reed mace, reed leaves and root stocks (Phragmites australis) and stay in the thick reeds for protection during this vulnerable stage.
Prior to and immediately after wing moult, the geese spend a short time feeding on adjacent grassy fields.

This intensive reed grazing and grubbing has radical consequences, it creates a less dense marshland and keeps the ponds open, benefiting many plant, animal and bird species that prefer this type of habitat.

source: oostvaardersplassen.biofaan.nl