Predatie door vossen Vulpes vulpes op broedende Grauwe Kiekendieven Circus pygargus

Montagu’s Harriers nests in The Netherlands are routinely located and marked in order to prevent losses during harvest of a variety of crops (mainly alfalfa and wheat). During 1990-2000, 196 nests were thus checked, of which 83 failed. Predation was indicated 13 times, i.e. by red fox (9x), Carrion Crow (2x) and Common Buzzard or Marsh Harrier (2x). Other mortality causes included adverse weather (5x) and deliberate destruction by man (9x). Adult Montagu’s Harriers were rarely predated, once in 1999 (away from the nest, presumably taken by surprise in high vegetation, Lauwersmeer) and twice in 2000. In both latter cases, the female was taken on the nest in alfalfa by red foxes. This situation may have been unusual, as the fields had flattened after a prolonged period with rain and high winds. Precautionary steps to prevent nest destruction during harvest and by ground predators after harvest are explained. Each nest is located and staked out (11x11 m) before harvest and farmers/contract workers are informed of the precise nest position. After harvest, the spared blocks of vegetation containing the nest are protected with an electric fence for the duration of the nestling and fledging stage. This turned out to be an effective protection device against red foxes (although it may attract people with malicious intent). The few cases of predation of adult breeding birds by red foxes occurred before harvest in wind-flattened crops and before electric fences were erected.