The UK's royal swan census

King Charles III is, among many of his royal titles, the Seigneur of the Swans. He has the right to claim ownership of any unmarked mute swan in the country. But with great power comes great responsibility - that of keeping track of them. That's why the King's Swan Marker, David Barber, is charged with counting all of the swans on the River Thames every summer. That census is underway this week. Host Marco Werman explains the history behind this tradition, and why it's also known as "swan upping."