NEARLY 200 swans have died as a result of a severe winter and the worst outbreak of a virus for years, a Royal official says.

And many young birds are being shot in vandal attacks, causing “horrific” injuries and slow deaths, it has been revealed, ahead of the traditional Swan Upping on the River Thames.

The annual 12th century tradition is set to take place next month and this year's census of the white water bird's population will assess just how great the death toll has been.

Marlow will be one of the stops along the way as the Queen's Swan Marker counts the number of young cygnets.

Assisted by the Queen’s Swan Warden, Professor Christopher Perrins of the University of Oxford, the swans and young cygnets are also assessed for injury and disease.

David Barber, The Queen’s Swan Marker said: “Another winter of severe weather has contributed to the death of many swans.

“Furthermore, a virus known as duck virus enteritis was discovered within the mute swan population on the River Thames.

“Unfortunately, more than 180 swans were found either dying or dead on the river between Reading and Windsor, with over 115 deaths being reported in the Windsor area alone.

He said the virus is not uncommon in swans but added: “this was the worst outbreak on the Thames we have seen in many years.”

Mr Barber said:“The dead swans included many of the Thames’ breeding pairs and we anticipate that fewer cygnets will be born this year as a result of the outbreak.

“We will have a greater understanding of the impact of the virus in July when Swan Upping takes place.”

He added a prime cause of death is “vandalism”.

“The number of vandal attacks has continued to increase over the past year which is extremely disappointing,” he said.

“Shootings by youths with air rifles and catapults cause horrific injuries, unnecessary suffering and slow deaths.”

The Swan Uppers will be in Marlow on July 20 at the Compleat Angler, with schoolchildren attending to witness it and learn about the tradition.

Dating back to the 12th century, the monarch claimed ownership of any unmarked mute swans swimming in open water.

The first written record of the swan as a royal bird dates back to around 1186. Cygnets were highly valued for food and were often served at banquets.

Unmarked swans were rounded up by the King or Queen's servants and lifted up into their boats. Anyone caught stealing the birds was severely punished.

Schools seeking further information should contact the Swan Marker's office on +44 (0)1628 523030 or email info@royalswan.co.uk.