The Interaction of Brent Geese Branta Bernicla and Sea Plantain Plantago Maritima During Spring Staging: Field Observations and Experiments

In spring, migrating Brent Geese (Branta bernicla) stage on the salt-marsh of Schiermonnikoog, a Dutch island in the Wadden Sea. During May, their principal food plants on the marsh are Puccinellia maritima and Plantago maritima. The Brent graze in large groups, and regraze the same places every four days. This interval seems to be related to the rate of regrowth of their food plants. A close study of the grazing of Plantago by the Brent revealed that the bite size is about 14 mm and is almost exclusively confined to the youngest leaves. Each time the geese harvest about 30 % of the rosette's leaf material. A clipping experiment on the salt-marsh with Plantago, showed that a regime of harvesting about 30 % of the rosette once every four days, like the geese do, gave the highest regrowth of new plant tissue, compared with no clipping, or with other clipping treatments. The selective advantage to the individual in taking part in flock grazing movements is discussed in relation to the effects of Brent grazing on the vegetation.