The swans had lived in the area for several years

The youths were seen throwing stones at the birds and hitting them with tree branches in Eastbourne, East Sussex.

The swans had nested at Langney pond for several years.

People living near the site, behind Langney shopping centre, saw the teenagers attacking the birds and called out East Sussex Wildlife Rescue.

By the time officers arrived the birds had gone and three of their eggs were found either smashed on the ground or thrown in the pond.

A fourth egg found undamaged could not be saved.

Spokesman Trevor Weeks said the attacks represented three offences under the Countryside and Wildlife Act.

The National Swan Sanctuary, which is based in Egham in Surrey, has offered a reward for information leading to the conviction of those responsible.