Nest predation on artificial blackgrouse clutches in the high Rhoen mountains of Hesse (Germany)
2000
Mueller, F. (Vonderau-Museum Fulda, Gersfeld (Germany))
The research area is in the Nature Reserve "Rotes Moor" and its immediate vicinity (approx. 500 ha) in the High Rhoen Mountains of Hesse. The experiments were done only in years when greyhens were absent from this area. This was in order to avoid disturbance and to prevent any ®extra supply¯ of clutches from encouraging predators to intensify their search for nests. Artificial nest can give indications as to the local influence of predators on real nest of groundnesting birds. It is unfortunately not possible to simulate the breeding bird and its nest protection behaviour, i.e. distraction display or feigning of injuries. In order to conduct experiments under near-natural circumstances, the following factors were taken into account. The total number or density of artificial nests was appropriate to the habitat capacity, i.e. not any higher than had been the case previously with regard to natural clutches of Greyhen eggs in this area. The nest were placed in structurally the same vegetation which preciously contained Greyhen nests. As a rule, they were protected from view from above. Number, dimensions and colour were kept similar to Greyhensi eggs (6 bantam hensi eggs per nest, light brown with dark spots). The artificial clutches were laid out during the typical laying and breeding period of Greyhens in the High Rhoen Mountains (15/5 to 30/6). The artificial nests had to be visible with binoculars at a distance of the least 10 m from an elevated point (e.g. rock, tree, high seat) to allow checking them every seven days without introducing any further man-made changes to the terrain. Each artificial clutch was complemented by an egg made of a non-hardening plasticine material to get information on the type of predator by means of bite, scratch or peck marks. The identified predators were: Martes martes, Vulpes vulpes, Sus scrofa, Corvus corone
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