A motorist has allegedly driven on to a colony of 3000 endangered birds, squashing nests and eggs.
The colony of black-billed gulls, one of the most endangered gull species in the world, has been nesting at the Ashburton River.
Environment Canterbury senior biodiversity adviser Frances Schmechel said she understood that the Conservation Department was investigating.
Disturbing protected birds and destroying nests are offences under the Wildlife Act that can result in imprisonment or a fine of $100,000.
"We would strongly support such a move. This sort of behaviour is totally unacceptable," she said.
"Unfortunately, it's not the first time a motorist has driven on to the riverbed and destroyed nests and eggs of a very vulnerable species, which tends to desert its nest if disturbed early in incubation. This is despite prominent ‘endangered bird' signs at a number of locations along the river, including the access point apparently used in this instance."
In 2007, the colony was attacked by vandals who killed more than 100 birds.