Effect of Bird Refuges on the Greifensee (canton of Zurich) on the Breeding Behaviour of Great Crested Grebe Podiceps Cristatus, the Breeding Population of Birds in Reedbeds and Waterbirds in Winter

27 Mar Effect of Bird Refuges on the Greifensee (canton of Zurich) on the Breeding Behaviour of Great Crested Grebe Podiceps Cristatus, the Breeding Population of Birds in Reedbeds and Waterbirds in Winter

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Abstract

English Abstract

We evaluated the effectiveness of refuges for waterbirds on the Greifensee intended to mitigate the effects of disturbance from water-based recreational activities on birds, before (1994–1997) and after the marking (1998–2009) of the bird refuges. Adult Great Crested Grebes preferably moved into protected zones during the breeding season, the number of young per family increased in protected zones and they preferred protected lakesides during the moulting season. Furthermore, the temporal pattern of the onset of breeding during years with high nest densities suggested that protected areas were high-quality habitats of primary quality for Great Crested Grebes. However, the establishment of refuges did not affect the position of their likely nest sites. The population size of important reedbed birds (Little Bittern Ixobrychus minutus, Savi’s Warbler Locustella luscinioides) increased simultaneously with the implementation of protected areas, whereas other species showed no change. Moreover, the bird refuges enabled species conservation measures i.e. for Common Tern Sterna hirundo or Common Black-headed Gull Larus ridibundus. In contrast to expectations, waterbird numbers in winter were higher outside than inside the refuges, probably because Great Crested Grebes increased in numbers and progressively rested in the open water. Based on these findings the authors list several recommendations for the establishment of protected zones on lakes.