Mute swan grazing on winter crops: evaluation of three grazing deterrents on oilseed rape

摘要: The population of mute swans Cygnus olor (Gmelin) in the UK has increased since 1986 to >25 000 birds, leading complaints damage winter crops, and need for cost-effective management measures. Using a randomized block design split-field experiment, effectiveness three licensed grazing deterrents was evaluated feeding on oil-seed rape: (1) ziram-based chemical repellent (AAprotect TM at 10 kg ha -1 ), (2) white flags (25 (3) hazard warning tape (1000 m ) with twine (400 ). Deterrents control (no treatment) were assigned one four plots (approximately 1 ha) each fields. From 4 December 1998 26 March 1999, intensity estimated by counting swan droppings approximately 2-week intervals. Over entire study (10 - 15 weeks depending field), total numbers did not differ significantly between treatments. initial 8 weeks, however, significan...