Swans and cygnets rescued from Blenheim Palace

The levels of the Great Lake and Queen Pool were lowered by about half a metre to allow repairs to the Grand Cascade.

However, the timing of the work has caused the problem, with it taking place during the nesting season, although Blenheim says it was done during ‘low flow’ for the river, and was therefore safer.

The six adult birds and 13 cygnets are currently in emergency accommodation at the Swan Sanctuary in Shepperton, Middlesex.

See also: Rare wildlife in danger if ‘abhorrent’ warehouse plan is approved

David Barber is the Queen’s Swan Marker, a role that sees him advise organisations about swan welfare.

He said: “Several pairs of swans and cygnets were removed due to the low water level that left their nests rather exposed.

“The distance between the nests and the water’s edge posed a significant risk of death for the newly hatched cygnets who would be unable to reach the water in safety.

“Working closely with Roy Cox, director of Blenheim Estates, Wendy Hermon of Swan Support monitored the nests constantly.

Blenheim Estates director Roy Cox.

“As soon as the cygnets hatched, she was able to remove the adult pairs and their cygnets and take them to a safe location."

He added: "The problem arose when the lake was partially drained for major repair works, and this, combined with a dry spring, resulted in very low water levels.

“However, the flock of single swans that reside at Blenheim seem perfectly happy remaining on the water and they will continue to be monitored carefully.

“Once the repair works to the lake are complete, it will provide a marvellous habitat for wildlife once again.”

Read more: Cat loses leg in savage dog attack - as dog’s ‘owner’ chatted on mobile phone

The sanctuary in Shepperton has been caring for the birds since their arrival.

Stephen Knight, a trustee at the sanctuary, said: “Unfortunately Blenheim Palace has drained its main lake during nesting season leaving the waterfowl unnaturally vulnerable to predators.

“The rescues can be very dangerous due to the deep silt and no water, and one of the concerns in the decision to remove the birds was that a member of the public would see a cygnet or duckling struggling in the mud and put their own life at risk.”

Mr Knight said that following the swans’ stay at the sanctuary, which could last up to four months, they will not return to Blenheim, and three separate locations will need to be found – one for each of the three families.

Ecologists at Blenheim started clearing nesting habitat in December to deter wildlife from nesting, with most nesting successfully further downstream.

Ecologists visited the site prior to the work starting and for those animals that remained, they were happy for water levels to be lowered.

Mr Cox said: “We are proud to be home to many hundreds of swans and the work we’re doing over the next few years will ensure we are able to continue to provide a safe habitat for them for many hundreds of years to come.

“We did as much as could be reasonably expected earlier in the year to encourage the swans to nest elsewhere on the lake.”