Highland cattle are being used in Norfolk as an alternative to scything or spraying meadows with weedkiller.
The shaggy creatures have been released at Taverham Mill, near Norwich, to help restore the marshy meadows to their natural, wildflower-rich state.
A small herd of the cattle will chew down coarse grasses and other plants, allowing wildflowers to seed.
This should encourage insects, small mammals and then barn owls to the site, said Norfolk Wildlife Trust (NWT).
The project is part of an ongoing partnership between Anglian Water and NWT to restore 22 acres (nine hectares) of meadows close to the River Wensum.
NWT already has its own "flying flocks" of Highland cattle at other sites, where they have proved a success.
"Highland cattle are ideal for conservation grazing as they are hardy, well-adapted to wet sites like Taverham Mill, and thrive on coarse vegetation," said Norfolk Wildlife Trust conservation officer Andrina Walmsley.
"They happily eat tough plants such as sedges and thistles, which other breeds find unpalatable, and help to break up dead vegetation with their hooves. This provides bare ground where wildflower seeds can germinate and create habitat niches for many species.
"Over time the grazing cattle will encourage a wide range of marshy plant species including ragged robin, marsh marigold, orchids and cuckoo flower.
"A new range of insects should in turn help small mammal numbers and make the site a more suitable hunting ground for barn owls, which can detect their prey much more easily in shorter vegetation."