Staff and volunteers help during the biennial round-up of swans at Abbotsbury Swannary on July 20, 2019 in Abbotsbury, Dorset, UK. /VCG Photo

Held every two years, the Abbotsbury swan round-up is timed to coincide with the annual wing-moult of the swans, as this renders them flightless for several weeks each summer. /VCG Photo

Over 800 swans were checked, weighed, ringed and vaccinated before being released back to the water this year./VCG Photo

The University of Oxford has used the measured information for research into global warming with the birds acting as a good indicator of environmental changes in weather patterns and temperature changes. /VCG Photo