Contractors working with Bracknell Forest Council's parks and countryside team are set to take away the concrete island in the South Lake, behind the arts centre in Ringmead, before March.
But Birch Hill resident Jo Machin, of the South Hill Park Wildlife Protection Group, was dismayed by the news and claims the island is crucial for ducks and other wildlife - and in ensuring these feathered friends remain at the site.
She said: "It has been part of the lake for decades and provided an ideal nesting site, as well as a sanctuary for the more vulnerable birds.
"The previous owners of the centre cared enough about wildlife to install the island, as well as wooden duck-houses and information boards, but it appears no-one was prepared to maintain them once the property passed to its present keepers - with the result that the island became overgrown and the duck-houses fell into disrepair."
Mrs Machin said several injured ducks have made the island their home over the years, as well as moorhens, which she says use the land to hide from geese. She was concerned about the welfare of the birds and the threat the change would have on their habitat.
"The birds are used to the island being there and would have to make their own area to nest if it goes," she said. "It simply does not make sense to go to the expense of destroying the island when all it requires is a little management.
"Nature trails are very popular in other parks across the country and the centre could play a big part in educating children by providing information about their environment and the wildlife within it.
"Who knows, perhaps the swans and the more exotic birds may return to South Lake if provision were made for them? That could only be beneficial to all."
Richard Walton, head of parks and countryside at Bracknell Forest Council, said a fountain will be installed to replace the old concrete island, as well as a floating island with aquatic planting.
He said: "Ecological assessment has been carried out by independent experts prior to instructing this work. Surveys indicate this artificial island is of limited ecological value and the work will not have an adverse impact on biodiversity. Wildlife value of the south lake has previously been improved by clearing silt and biodiversity will be further enhanced by installing a new island, proposed for installation in the spring."
The works are part of the restoration of South Hill Park's grounds, which has been financed by a combination of Lottery and council funding.