I went back to where I had encountered the boisterous herd of calves on Tuesday this afternoon, and can confirm that they are indeed bull calves. Today they were on the other side of the river munching grass, and gazed across at me blankly.
They had churned up the pathway so badly that with all the rain it was quite impassable and I had to scrabble into the nature reserve where the old canal used to be in order to make my way. It was while doing that that I caught this pair of mallards flying across the low sun.
Looks more gooder Large
Calves on the other bank: Never Mind The Bullocks