L. Bakker et al., Exploitation of a new staging area in the Dutch Wadden Sea by Greylag Geese Anser anser: the importance of food-plant dynamics, ARDEA-T NED, 87(1), 1999, pp. 1-13
The colonisation by Greylag Geese Anser anser of a new autumn migration sta
ging area was studied on the island of Schiermonnikoog, The Netherlands. Ov
er 500 Greylag Geese first visited the island in 1991. During subsequent ye
ars, peak numbers rose to 700-900 birds. The geese most likely originated f
rom the neighbouring staging area on the mainland, the Lauwersmeer, where g
oose numbers had levelled off since 1985. Because of the time-lag between s
aturation of the source population and colonisation of the island, changes
on the island itself were investigated as a possible trigger for the arriva
l of the geese. Potential food availability on the island had increased for
the geese as a result of vegetation succession. Two food-plants, Sea Club-
rush Scirpus maritimus and Common Cord-grass Spartina anglica have increase
d over the last four decades. Greylag Geese fed mostly on Scirpus tubers an
d Spartina rhizomes. The soluble-carbohydrate content of the latter two foo
d items did not differ significantly, and was approximately 25% on a dry we
ight basis. Negative effects of grubbing by Greylag Geese on stands of both
Scirpus and Spartina appeared limited during the study period. Although Gr
eylag Geese now spend most of the year in agricultural areas, our study ind
icates that natural habitats are still of importance for migrating Greylag
Geese as staging areas.