Queen's Swan Marker David Barber prepares a swan for its release back to the river during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

A swan is released during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Queen's Swan Marker David Barber holds a swan during the annual census of the Queen's swans, known as "Swan Upping", near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Queen's Swan Marker David Barber checks a swan next to the River Thames during the annual census of the Queen's swans, known as "Swan Upping", near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

An official carries a swan to record measures, during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Queen's Swan Marker David Barber holds a swan during the annual census of the Queen's swans, known as "Swan Upping", in Maidenhead near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials record the measures of a cygnet during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials gather the boats to capture cygnets and swans during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, in Maidenhead near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials record and examine cygnets and swans during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Queen's Swan Marker David Barber secures the feet of a swan before the disembark to measure the animal, during the annual census of the Queen's swans, known as "Swan Upping", in Maidenhead near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Swans and cygnets swim along the River Thames, before being caught during the annual census of the Queen's swans, known as "Swan Upping", in Maidenhead near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials secure a swan before disembarking it during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials examine a cygnet during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls 

Officials clear ducks away before they catch cygnets and swans to measure them, during the annual census of the Queen's swans, known as "Swan Upping", along the River Thames, near London, Britain, July 20, 2021. REUTERS/Peter Nicholls