The official behind the annual count of swans on part of the River Thames claims the number of injuries caused by fishing tackle is on the rise.
The Upping sees swans ringed and checked for injuries
David Barber, the Queen's Swan Marker, has announced this year's Swan Upping - the traditional count of cygnets - will take place from 16 July until 20 July.
The Upping, which takes place from Sunbury to Abingdon, sees swans weighed and ringed and checked for injuries.
Mr Barber said the number of injuries already known about was "regrettable".
Mr Barber said: "Although the reported incidence of vandalism has decreased in the last year, it is regrettable that the number of injuries caused to mute swans by fishing tackle continue to rise.
"There has also been an increase in treatment required for incidents involving diesel oil.
"Birds whose feathers are impregnated with oil require washing and further treatment if they have ingested any of the oil."
The ceremony itself dates from the 12th Century when the Crown claimed all unowned mute swans in Britain to ensure a ready supply for banquets and feasts.
Nowadays, the Queen retains the right to ownership on some stretches of the River Thames and tributaries.
Local schoolchildren are being invited to join the "uppers" at various locations during the week to learn more about the count.