The annual count of Queen Elizabeth II's mute swans has begun amid fears that dog attacks may have taken their toll on the monarch's waterfowl in the River Thames.

The queen is the traditional owner of unmarked mute swans and royal tradition requires they be counted each year.

The tally began Monday when royal Swan Uppers rowed up the River Thames outside London to count and examine cygnets, or young swans, for disease and injuries.

The group fears that a recent spate of fatal dog attacks may affect the final tally. In 2015, they only marked 83 cygnets, down from 120 the previous year.

The Queen's Swan Marker, David Barker, hopes the number has grown to 100, but they won't know until the end of the week.