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Managing predation on ground-nesting birds
Many ground-nesting farmland bird species have decreased in numbers drastically in
recent years mainly due to loss and fragmentation of their habitats. Therefore,
management of declining species has often focussed on protection and restoration of
their habitats, but this is not always enough. High rates of nest predation may also
threaten bird populations and both lethal and non-lethal predator control has
therefore been employed to decrease the predation pressure on threatened groundnesting birds. Lethal predator control is often used to reduce nest predation, but it is
problematic since it must be continuous as otherwise culled predators might be
replaced through immigration from nearby areas, and there may be negative attitudes
towards lethal predator control among the general public.
Several non-lethal techniques have been proposed and implemented as
management tools for threatened species, but few have been properly evaluated.
We evaluated the use of nest exclosures as a non-lethal means of reducing nest
predation on ground-nesting waders. We tested exclosures on two common and
widespread shorebirds: lapwing and redshank. In both species, hatching success
was much higher for protected than for unprotected nests. In redshanks, however,
mortality increased on incubating birds in protected nests while no such effect was
found in lapwings. Therefore, caution should be exercised in the use of nest
exclosures on redshanks or species with similar incubation behaviour. However, nest
exclosures should be considered as a management tool for shorebirds that leave
their nest early when approached by a predator.