Species of beach-nesting terns and gulls, beach-nesting shorebirds, large wading birds, marsh birds and ocean-dwelling birds are also at risk, along with migratory shorebirds and songbirds, the Initiative said.

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"We hope the clearing of a lot of bracken and re-seeding of heather will bring back ground-nesting birds as well as more cuckoos, " she added.

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Now their appetite for the eggs and chicks of ground-nesting birds such as the South Georgia pipit and pintail is threatening the survival of these endemic species.

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Nick Hazlitt, a forester with the Forestry Commission, said they were also hoping to promote wildlife on the site, which is important for ground-nesting birds, dragonflies and damselflies.

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For ground-nesting birds like the South Georgia pipit and South Georgia pintail, both of which are unique to the island, the rat explosion spells disaster because the rats feed on chicks and eggs.

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The mammals are not native to the isles and have been blamed for preying on the eggs of ground-nesting wading birds.

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Established in 1929 by President Hoover to protect a breeding ground for migratory birds, the sanctuary still ranks as one of the largest nesting areas in north Florida, for birds such as ibises, pelicans, egrets and double-crested cormorants.

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