TIJSEN W & KOFFIJBERG K (2015) Thirty years of goose and swan counts in the north of the province of Noord-Holland. LIMOSA 88 (2): 83-95.

In the northern part of the province Noord-Holland, close to the western Wadden Sea and Lake IJsselmeer, large numbers of geese and swans roost in the polders of Wieringermeer and on the former island of Wieringen and the adjacent Balgzand area. The area is mainly in agricultural use (Fig. 1).
Swans and geese predominantly feed on harvest remains of sugar beet and potatoes, on Wieringen mainly on grassland. The area is highly attractive to swans and geese as the feeding areas are well in reach of suitable night-roosts (Fig. 2 & 3). This paper describes the occurrence of geese and swans in the area in the past decades and tries to explain some observed trends with known changes in land-use.
Both from a national perspective as well as in an international flyway context, Bewick's Swan Cygnus bewickii and Tundra Bean Goose Anser serrirostris are the most important species occurring in the region. For Bewick's Swan numbers amounted to up to 11% of the flyway population (Tab 1.). Numbers in this species initially remained on a high level, while the size of the flyway population and the numbers in The Netherlands started to decline in the mid-1990s (Fig. 4). After 2006/07 also in the Wieringermeer a sharp decline occurred (Fig. 4). Nowadays, only small numbers are observed. Although a separate study showed a local impact of the establishment of a new windpark, it is unlikely that establishment of a large windpark in 2006 caused the decline of the swans. Changing migration and wintering strategies (indicating an eastward movement of the winter range) are more likely drivers for the observed patterns. Numbers of Tundra Bean Geese have continued to increase (Fig. 6), even at a higher rate than the national trend, and in contrast to a decline at other sites in the Wadden Sea area, which has rendered the Wieringermeer (together with the island of Texel) a rather isolated staging area in the northwestern part of The Netherlands. Numbers peak in December (Fig. 7), after which at least part of the geese leave for staging areas in the northeastern part of The Netherlands, or even in the eastern part of Germany (as shown by individually marked geese). The increase of Tundra Bean Goose occurred in a period where food availability declined (Fig. 1), but obviously not to an extent that affected the numbers of geese.
Brent Geese, mainly Dark-bellied Brent Goose Branta bernicla, occur mainly on the former island of Wieringen. Their distribution on the island has changed slightly in the past decades, possibly linked to the strong increase in yearround present Greylag Geese Anser anser, which compete with Brent Geese, but also facilitate Brent Geese in spring by keeping the sward of the grasslands suitable for them. During influxes in cold winters, Wieringen also becomes one of the most important winter roosts of Light-bellied Brent Geese B. hrota in The Netherlands. In 2009/10 up to 3% of the flyway population was observed in the area. Occurrence of Light-bellied Brent Geese on Wieringen has also been documented in the past (1920-1930), both in cold and normal winters.

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