THE SELECTION OF GRASS SWARDS BY BRENT GEESE BRANTA-B-BERNICLA - INTERACTIONS BETWEEN FOOD QUALITY AND QUANTITY

Since the mid-1970s, brent geese Branta b. bernicla wintering in SE En gland have become an agricultural pest by grazing autumn-sown arable c rops. The most satisfactory solution appears to be the creation of ref uges (''Alternative Feeding Areas''), for which precise management gui delines are required. This paper describes a field experiment to inves tigate the interaction between food quality and quantity of grass swar ds, and how this influences their use by geese. Fertilizing swards inc reased their nitrogen content and made them much more attractive to ge ese. Throughout the winter, the main determinant of grazing intensity was whether or not a sward had been fertilized. Application of nitroge n fertilizer also reversed the traditional preference for short swards . On unfertilized plots, shorter swards were preferred at the beginnin g of winter but on fertilized plots, medium and longer swards were pre ferred. This can be attributed to the fertilizer application swamping the original relationship between sward height and nitrogen content. T o maximize carrying capacity, nitrogen fertilizer should be combined w ith slightly longer swards (10-12 cm) than are at present recommended to farmers. If no fertilizer is to be applied, shorter swards are pref erred. However, on heavily used sites, swards can be too short. (C) 19 96 Published by Elsevier Science Ltd.