The annual census of the swan population on the River Thames is under way following a winter that saw some animals killed by bird flu.
David Barber, the Queen's Swan Marker, led his team as they carried out their count of new cygnets known as Swan Upping.
In February, around 20 swans from the Queen's Windsor flock were believed to have died from bird flu, but it is thought a significant number of cygnets were counted on the opening day of the week-long census.
The monarch, who technically owns all unmarked mute swans in open water in Britain, was kept informed about the development at the time.
Swan Upping is normally held on the third Monday of July and began with teams in rowing boats, known as Thames Skiffs, taking to the water.
The ceremony dates back to the 12th century when the ownership of all unmarked mute swans in open water in Britain was claimed by the Crown in order to ensure a ready supply for feasts.
Today, the Queen exercises this right only on certain stretches of the River Thames and surrounding tributaries.
The ownership is shared with the Worshipful Company of Vintners and the Worshipful Company of Dyers, who were granted rights of ownership by the Crown in the 15th century.
Swan Upping now serves as an annual health check when swans and cygnets are weighed and checked for signs of disease or injury.
Cygnets whose parents are Dyers or Vintners's birds are themselves ringed, while all others are left unmarked to denote they belong to the Queen.