The selection of grass swards by brent geese Branta b. bernicla: Interactions between food quality and quantity Original Research Article

Since the mid-1970s, brent geese Branta b. bernicla wintering in SE England have become an agricultural pest by grazing autumn-sown arable crops. The most satisfactory solution appears to be the creation of refuges (“Alternative Feeding Areas”), for which precise management guidelines are required. This paper describes a field experiment to investigate the interaction between food quality and quantity of grass swards, and how this influences their use by geese. Fertilizing swards increased their nitrogen content and made them much more attractive to geese. Throughout the winter, the main determinant of grazing intensity was whether or not a sward had been fertilized. Application of nitrogen fertilizer also reversed the traditional preference for short swards. On unfertilized plots, shorter swards were preferred at the beginning of winter but on fertilized plots, medium and longer swards were preferred. This can be attributed to the fertilizer application swamping the original relationship between sward height and nitrogen content. To maximize carrying capacity, nitrogen fertilizer should be combined with slightly longer swards (10–12 cm) than are at present recommended to farmers. If no fertilizer is to be applied, shorter swards are preferred. However, on heavily used sites, swards can be too short.