Spring grazing and the manipulation of food quality by barnacle geese.
The foraging activities of a large flock of barnacle geese (Branta leucopsis) wintering on the West Friesian island of Schiermonnikoog were monitored during the spring of 1978. On 14 sites distributed over the grazing area, grazing intensity, plant species presence and abundance, standing crop, herbage accumulation, and crude protein content of Festuca rubra, the primary food plant of barnacle geese, were estimated. Two of the sites had nitrogen fertilizer applied to them. Almost all the sites were grazed repeatedly, but barnacle geese utilized different areas with different intensities. In spite of this, the standing crops did not differ among sites, and the standing crop on all the sites remained relatively constant throughout the spring, including the sites that received N fertilizer. Areas with the highest rates of herbage accumulation were grazed most intensely. Barnacle geese displayed no consistent preference for other site characteristics. High levels of protein in Festuca rubra were a direct result of repeated grazing of sites by barnacle geese, and the consequent sustained regeneration of young, protein-rich plant tissues.